Browsing by Author "Haseena Bhaskar"

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Acaricide resistance in spider mites (Acari: Tetranychidae) Infesting major crops of Central Kerala
(Agricultural Entomology, College of Agriculture, Vellanikkara,, 2025-08-18) Penuballi Swathi; Haseena Bhaskar
Spider mites (Acari) inhabit a wide array of environments and pose significant threat to a variety of commercially grown vegetable crops and ornamental plants. Chemical management measures using synthetic acaricides remains the primary means of mite management, globally. However, the repeated use of chemical pesticides has led to the development of resistance in mite populations, including resistance to acaricides with novel modes of action, resulting in control failures. TetranychustruncatusEhara and Tetranychusgloveri Banks are the predominant spider mite pests on vegetable crops and ornamental plants in Kerala. Mite management in vegetable fields and horticultural nurseries of Kerala primarily relies on synthetic acaricides like spiromesifen, fenazaquin and diafenthiuron. Increased instances of control failures, despite the application of recommended doses of these acaricides, have recently been reported by the farmers and nursery owners. Sole dependence on acaricides for a prolonged period might have resulted in the reduced susceptibility of mite populations to commonly used acaricides. Hence, a study was carried out to investigate the susceptibility of the field populations of T. truncatus and T. gloveri to commonly used acaricides, the possible development of cross /multiple resistance and to elucidate the underlying mechanisms of resistance. Purposive sampling surveys were conducted across commercial horticultural nurseries, vegetable fields and tissue culture (TC) hardening units in central Kerala (Thrissur, Ernakulam, Palakkad and Malappuram) to collect spider mite populations. Isoline cultures of eight T. truncatus populations collected on marigold (Mg1Tr) and vegetable crops (Cp1Pt, Cu1Pt, Ok1Pt, Am2Pt, Am3Vt, Cp2Tv and Am4Tv), and nine T. gloveri populations collected on adenium (Ad1Rg and Ad2Sd), gerbera (Gr1Pt), dahlia (Da1Vt), anthurium (An1Bv) and tissue culture banana (Bn3Tr, Bn2Kn, Bn1Gn and Bn4Ak) were maintained in the laboratory with unique accession numbers. The laboratory maintained populations of T. truncatus (SST) for more than 10 years (>300 generations) and T. gloveri (SSO) for more than six years (>180 generations), without exposure to acaricides were designated as susceptible reference populations. The laboratory bioassay of T. truncatus with fenazaquin showed moderate levels of resistance in the populations on amaranthus (Am2Tr- 39.70 folds) and marigold (Mg1Tr- 25.60 folds) populations from Thrissur, cucumber from Pattambi (Cu1Pt- 12.90 folds) and amaranthus from Vyttila (Am3Vt- 10.50 folds). The other populations collected on amaranthus from Tavanur (Am4Tv) and on okra (Ok1Pt), and cowpea (Cp1Pt) from Pattambi, recorded low levels of resistance (RR 3.70- 7.90 folds). Among the T. gloveri populations, adenium population from National Rose Garden, Thrissur (Ad1Rg- 57.20 folds) and TC banana population from Kannara (Bn2Kn- 41.04 folds) recorded high levels of resistance to fenazaquin, while the mite populations collected on TC banana plants from Vyttila (Bn1Gn- 15.72 folds) and Thrissur (Bn3Tr- 15.80 folds), and on dahlia from Vyttila (Da1Vt- 13.31 folds) recorded moderate level of resistance. Other T. gloveri populations collected on gerbera, anthurium and adenium showed only low levels of resistance. Tetranychustruncatus collected on marigold (81.90 folds) and amaranthus (79.75 folds) from Thrissur recorded very high levels of spiromesifen resistance. The amaranthus population from Vyttila (Am3Vt- 33.41 folds); cowpea (Cp1Pt-25.16 folds) and okra (Ok1Pt- 25.83 folds) populations from Pattambi, showed moderate levels of resistance, while populations on cowpea (RR 07.08) and amaranthus (RR 05.90) collected from Tavanur recorded low levels of resistance. Susceptibility studies of T. gloveri with spiromesifen showed that the population on adenium from National Rose Garden (76.33 folds) and on TC banana from Kannara (71.33 folds) exhibited high levels of resistance. Populations collected on TC banana from Vyttila (30.33 folds), Thrissur (28.17 folds) and Anakkayam (13.79 folds) recorded moderate levels of resistance. The populations collected on the ornamental plants viz., dahlia (24.33 folds), anthurium (19.08 folds) and adenium (17.25 folds) also recorded moderate levels of resistance to spiromesifen. Low to moderate levels of resistance to diafenthiuron were recorded in T. truncatus (1.94- 17.56 folds) and T. gloveri (1.95- 15.57 folds), where marigold population from Thrissur (17.56 folds) and adenium population from National Rose Garden (15.57 folds) recorded significantly higher levels of resistance, respectively. Tetranychustruncatus and T. gloveri populations with resistance to fenpyroximate showed moderate levels of cross-resistance to fenazaquin and the propargite resistant populations showed cross resistance to diafenthiuron. However, the field populations recorded only low levels of multiple resistance to chlorfenapyr and hexythiazox (acaricides with different modes of action) in T. truncatus (1.20- 5.40 folds; 1.00- 1.50 folds) and T. gloveri (1.10- 2.35 folds; 2.08- 12.00 folds). Assay of detoxification enzymes in T. truncatus and T. gloveri showed significantly elevated activities of carboxylesterase (CarE) (1.27-2.27fold; 1.59-2.10 folds), cytochrome P450 monooxygenase (CytP450) (1.36- 4.98 folds; 1.08-3.10 folds), and glutathione S-transferase (GST) (1.00- 2.12 folds; 1.09- 1.98 folds) in resistant populations. The highest activity of detoxifying enzyme was recorded in T. truncatus population on marigold for CytP450. The study on differential gene expression and sequence variation of the CYP392E10 gene (encodes CytP450 enzyme) in the spiromesifen and fenazaquin resistant marigold population of T. truncatus showed a lower CT value with 7.61 folds higher gene expression than the susceptible population. Sequence analysis of CYP392E10 gene in the resistant population showed four single nucleotide polymorphisms (SNPs), where T is substituted by A (256th, 676th and 1356th) and A is replaced with G (708th position). The alignment of amino acid sequences of the susceptible and resistant T. truncatus populations showed substitution of Lleucine with methionine at 86th position and phenylalanine with isoleucine and lysine at 226th and 452nd positions, respectively. This study reports alarming levels of acaricide resistance in the spider mites, T. truncatus and T. gloveri in central Kerala, to commonly used acaricides. The mite species were also found to have developed significant levels of cross resistance to many unexposed acaricides. However, significantly low level of multiple resistance to the acaricides, chlorfenapyr and hexythiazox suggests their suitability as alternatives to commonly used acaricides in mite management. The study highlights the role of detoxifying enzymes and the overexpression of the related gene, particularly CytP450 in the development of resistance against commonly used acaricides (fenazaquin, spiromesifen and diafenthiuron). The study also provides new insights into the resistance mechanisms in the mite species in response to sustained acaricide pressure, exhibiting metabolic and target-site insensitivity, which further needs functional validation.
Behavioural ecology of cowpea aphid,aphis craccivora koch (aphididae:hemiptera)mediated by tri-trophic interactions
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2008) Jaba Jagdish; Haseena Bhaskar
The study entitled “Behavioural ecology of cowpea aphid, Aphis craccivora Koch (Aphididae: Hemiptera) mediated by tri-trophic interactions” was carried out in the farmer’s fields and Department of Agricultural Entomology, College of Horticulture, Vellanikkara. The objectives of the study include evaluation of temporal and spatial dynamics of population of A. craccivora and associated natural enemy fauna, monitoring the patterns of dispersal, polymorphic transition and phenological relationship of A. craccivora in cowpea and assessing the role of plant, pest and natural enemy mediated semiochemicals in the population build up of A. craccivora and natural enemy fauna in cowpea. Field survey was carried out in the cowpea fields and glyricidia, a major alternate host of A. craccivora during May, 2007 – March, 2008 to study the population dynamics of A. craccivora (Koch) and its predators. The population of A. craccivora in cowpea was significantly high in November sown crop with the population reaching its peak in the first fortnight of December. In the field, the highest population was recorded from the East direction followed by North. Among the different plant parts, a significantly higher population of the aphid was recorded on leaves followed by pods. The aphid population showed a significant positive correlation with sunshine hours and wind speed whereas; the correlation with relative humidity though significant was negative. The predatory complex of A. craccivora on cowpea comprised of the coccinellids Cheilomenes sexmaculata (Fabricius), Coccinella transversalis (Fabricius), Scymnus latemaculatus (Motschulsky), Scymnus pyrocheilus (Mulsant), Psedaspidimerus trinotatus (Thunberg), Micraspis discolor (Fabricius), 9Harmonia octomaculata Fabricius) and Brumoides suturalis (Fabricius) and the syrphids Dideopsis aegrota (Fabricius) and Ischiodon scutellaris (Fabricius). C. sexmaculata was the most abundant predator on A. craccivora in cowpea. The populations of C. sexmaculata, C. transversalis, and the total population of the syrphids had shown a significant positive correlation with the prey population suggesting their density dependant relationship with the prey. In glyricidia, a higher population of A. craccivora was recorded during the second fortnight of December. The most abundant predator of A. craccivora in glyricidia was S. pyrocheilus. Correlations between the population of the aphid on glyricidia and weather parameters were not significant. However, temperature showed a significant correlation with the populations of the predators, C. sexmaculata, M. discolor and S. latemaculatus. C. sexmaculata and M. discolor also showed a significant negative correlation with relative humidity. Pot culture experiment was conducted to study the population buildup of A. craccivora and development of alate morphs. Higher population build up of the alates was recorded on leaves followed by pods that coincided with 48th day after sowing. Studies on the dispersal pattern of the alate morphs using yellow sticky trap showed maximum dispersal of the alates during day compared to night. More dispersal was found to occur during the crop season, June – July than February-March. Maximum alates were caught in the sticky traps installed in the north direction of the field. Trap installed at 1m distance from the potted plants caught more dispersing alates. The role of semichemicals originating from the host plant, the aphid and predators were studied using a four arm olfactometer. While A.craccivora responded more towards the water extracts of cowpea, the predatory coccinellids, C. sexamculata responded more to the hexane extract. Cowpea was found to be the most preferred host plant to A. craccivora in the olfactometer. Though the aphid showed more attraction towards the leaf of cowpea, it preferred the shoot tip to other plant parts in glyricidia. While A. craccivora prefered low density of conspecific population, C. sexmaculata showed more attraction towards high aphid population density in the olfactometer. The coccinellid predators C. sexamculata and C. transversalis responded more to the olfaction cues of aphid infested leaves of the host plants than the uninfested leaves. The predators showed a negative response towards the eggs of these predators in aphid colonies. In response to host plant odour, antennal and leg movements were observed in the aphid, the leg movement becoming faster as they reached closer. On locating the host plant, the antennal movement stopped in the aphid. The coccinellids also responded to prey odour by walking towards the prey. On reaching the prey, the predators tapped the aphid before they started feeding on it.
Biocontrol efficiency of Neoseiulus longispinosus evans (Mesostigmata:Phytoseiidae) against Tetranychus gloveri banks (Prostigmata:Tetranychidae) on Adenium obsesum (Forssk.) roem. & schult.
(Department of Agricultural Entomology, College of Agriculture,Vellanikkara, 2025-02-04) Subiksha, T S.; Haseena Bhaskar
Adenium obesum (Forssk.) Roem. & Schult. is a highly demanded ornamental plant in the floriculture industry. As this plant requires low maintenance, the popularity of this ornamental is widely increasing. Recently, the spider mite species, Tetranychus gloveri Banks has emerged as a serious pest on adenium in the ornamental nurseries of Kerala. The mite species has developed a significant level of resistance to commonly used synthetic acaricides, making mite management difficult in commercial horticultural nurseries. This demands the search for more viable alternative control strategies. Biological control offers a safer substitute for chemical acaricides to manage mite pests. The predatory mites of the family Phytoseiidae constitute a sizeable proportion of effective natural enemies commercially used as biocontrol agents. Among phytoseiid mite species, Neoseiulus longispinosus Evans, has been reported as a potential biocontrol agent against several spider mite species. A study was carried out in the Insectary and the Acarology Laboratory, Department of Agricultural Entomology, College of Agriculture, Vellanikkara, during the period 2022 2024 to investigate the biology of T. gloveri on adenium, the biology of N. longispinosus on T. gloveri, the predatory potential of N. longispinosus against T. gloveri, and the field efficacy of N. longispinosus for the management of T. gloveri on adenium. The life stages of T. gloveri consist of egg, larva, protonymph, deutonymph, and adult. The inactive stages that occur between the larva and protonymph, protonymph and deutonymph, and deutonymph and adult stage were nymphochrysalis, deutochrysalis, and teliochrysalis, respectively. The total developmental duration from egg to adult lasted 7.62 days for male and 8. 71 days for female. The adult male survived for 11.30 days after emergence. The mated and unmated female lived for 14.50 and 17.10 days after emergence, respectively. The mean oviposition period for mated and unmated female was 10.70 days and 11.20 days, respectively. The average fecundity of mated and unmated female was 36.04 and 17.20 eggs, respectively. The unmated female exhibited arrhenotokous parthenogenesis, whereas mated females produced both male and female progenies in a male-to-female ratio of 1:4.7. The development of N. longispinosus recorded egg, larva, protonymph, deutonymph, and adult stages. There were no quiescent stages observed between the active stages up to adult, unlike T. gloveri. The average total development duration from egg to adult lasted 4.20 and 4.86 days, respectively, for male and female. The adult male lived for 15.00 days, whereas the adult female lived for 16.50 days on average, with an oviposition period of 12.90 days. Unmated female did not lay eggs. The female recorded a mean fecundity of 33.40 eggs with both male and female in a male-to-female ratio of 1:2.04. The study on the functional response of N. longispinosus on all life stages of T. gloveri provided evidence for a Type-II response, with no indication of a Type-III response. The present study found that N. longispinosus consumed all stages of T. gloveri and exhibited a high preference for the eggs of T. gloveri. The attack rate was observed to be highest for T. gloveri eggs (1.976), and the least was observed for adult females of T. gloveri (0.471). The predator took the longest handling time for adult T. gloveri (0.166 day) and the least for T. gloveri egg (0.055 day). The study on the numerical response of N. longispinosus to different densities of T. gloveri female showed an increase in prey consumption and oviposition, with the increase in prey density. The highest oviposition (3.05 eggs/day) was observed at a prey density of 12. The polyhouse study to evaluate the field efficacy was carried out with different predator-prey ratios of 1:25, 1:50, 1:75, 1:100, and 1:125. The study identified that the narrow predator-prey ratios of 1:25 and 1:50 were efficient in suppressing the mite population on adenium, under polyhouse conditions. During the study, a single release of the predatory mite could not suppress the prey population, so a second release of the predator was carried out. After ten days of the second release, the reduction in prey population was 94.50, 61.95, and 28.98 per cent in treatments 1:25, 1:50, and 1:75, respectively. All other treatments were found to be inferior. The control treatment recorded about a 3.36-times increase in prey population. The findings on the investigation of the biological traits, predatory potential, and field efficacy indicate that the phytosiied predator, N. longispinosus, can be an effective biocontrol agent against T. gloveri on adenium plants as an eco-friendly and sustainable alternative to synthetic acaricides. However, there is a need for continued research, for standardising technologies to scale up the mass production, as well as for field release of the predator. Studies are to be carried out to evaluate the safety of acaricides and botanicals to the predator for ensuring the successful incorporation of N. longispinosus in integrated pest management programs.The mite species has developed a significant level of resistance to commonly used synthetic acaricides, making mite management difficult in commercial horticultural nurseries. This demands the search for more viable alternative control strategies. Biological control offers a safer substitute for chemical acaricides to manage mite pests. The predatory mites of the family Phytoseiidae constitute a sizeable proportion of effective natural enemies commercially used as biocontrol agents. Among phytoseiid mite species, Neoseiulus longispinosus Evans, has been reported as a potential biocontrol agent against several spider mite species. A study was carried out in the Insectary and the Acarology Laboratory, Department of Agricultural Entomology, College of Agriculture, Vellanikkara, during the period 2022 2024 to investigate the biology of T. gloveri on adenium, the biology of N. longispinosus on T. gloveri, the predatory potential of N. longispinosus against T. gloveri, and the field efficacy of N. longispinosus for the management of T. gloveri on adenium. The life stages of T. gloveri consist of egg, larva, protonymph, deutonymph, and adult. The inactive stages that occur between the larva and protonymph, protonymph and deutonymph, and deutonymph and adult stage were nymphochrysalis, deutochrysalis, and teliochrysalis, respectively. The total developmental duration from egg to adult lasted 7.62 days for male and 8. 71 days for female. The adult male survived for 11.30 days after emergence. The mated and unmated female lived for 14.50 and 17.10 days after emergence, respectively. The mean oviposition period for mated and unmated female was 10.70 days and 11.20 days, respectively. The average fecundity of mated and unmated female was 36.04 and 17.20 eggs, respectively. The unmated female exhibited arrhenotokous parthenogenesis, whereas mated females produced both male and female progenies in a male-to-female ratio of 1:4.7. The development of N. longispinosus recorded egg, larva, protonymph, deutonymph, and adult stages. There were no quiescent stages observed between the active stages up to adult, unlike T. gloveri. The average total development duration from egg to adult lasted 4.20 and 4.86 days, respectively, for male and female. The adult male lived for 15.00 days, whereas the adult female lived for 16.50 days on average, with an oviposition period of 12.90 days. Unmated female did not lay eggs. The female recorded a mean fecundity of 33.40 eggs with both male and female in a male-to-female ratio of 1:2.04. The study on the functional response of N. longispinosus on all life stages of T. gloveri provided evidence for a Type-II response, with no indication of a Type-III response. The present study found that N. longispinosus consumed all stages of T. gloveri and exhibited a high preference for the eggs of T. gloveri. The attack rate was observed to be highest for T. gloveri eggs (1.976), and the least was observed for adult females of T. gloveri (0.471). The predator took the longest handling time for adult T. gloveri (0.166 day) and the least for T. gloveri egg (0.055 day). The study on the numerical response of N. longispinosus to different densities of T. gloveri female showed an increase in prey consumption and oviposition, with the increase in prey density. The highest oviposition (3.05 eggs/day) was observed at a prey density of 12. The polyhouse study to evaluate the field efficacy was carried out with different predator-prey ratios of 1:25, 1:50, 1:75, 1:100, and 1:125. The study identified that the narrow predator-prey ratios of 1:25 and 1:50 were efficient in suppressing the mite population on adenium, under polyhouse conditions. During the study, a single release of the predatory mite could not suppress the prey population, so a second release of the predator was carried out. After ten days of the second release, the reduction in prey population was 94.50, 61.95, and 28.98 per cent in treatments 1:25, 1:50, and 1:75, respectively. All other treatments were found to be inferior. The control treatment recorded about a 3.36-times increase in prey population. The findings on the investigation of the biological traits, predatory potential, and field efficacy indicate that the phytosiied predator, N. longispinosus, can be an effective biocontrol agent against T. gloveri on adenium plants as an eco-friendly and sustainable alternative to synthetic acaricides. However, there is a need for continued research, for standardising technologies to scale up the mass production, as well as for field release of the predator. Studies are to be carried out to evaluate the safety of acaricides and botanicals to the predator for ensuring the successful incorporation of N. longispinosus in integrated pest management programs.
Bioefficacy of botanicals against the spider mite tetranychus truncatus ehara (Postigmata: Tetranychidae)
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2020) Laya, A C; Haseena Bhaskar
Bioefficacy of horticultural mineral oil aganist the spider mite, tetranychus truncatus (Prostigmata: tetranychidae) on okra
(Department of Agricultural Entomology, College of Horticulture, 2018) Kavya Yadhav, G A; Haseena Bhaskar
Bioefficacy of the acaropathogen, acremonium zeylanicum (petch) gams and evans against the spider mite, tetranychus truncatus ehara (acari: tetranychidae)
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2017) Alka Sherief; Haseena Bhaskar
Biology and management of rice leaf mite, Oligonychus oryzae (hirst) (acari: tetranychidae)
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2015) Aswin, T; Haseena Bhaskar
Mites have emerged as serious pest of rice, particularly in South India in the recent years. The rice leaf mite, Oligonychus oryzae Hirst (Acari: Tetranychidae) is reported to cause a reduction in yield of 25 per cent in rice. Sporadic incidence of the leaf mite has been reported recently from many rice growing tracts of Kerala as well. Yet, hardly any study has been conducted either on biology or management of this important pest. The present study entitled “Biology and management of the rice leaf mite, Oligonychus oryzae (Acari: Tetranychidae) was undertaken at Department of Agricultural Entomology, College of Horticulture, Vellanikkara during 2014-15. The objectives of the study were to elucidate the biology of O. oryzae on rice and to evaluate four new acaricide molecules namely, spiromesifen 240 SC, fenazaquin 10 EC, fenpyroximate 5 SC, propargite 57 SC, two botanicals (neem oil 2 per cent and azadirachtin 0.005 per cent) and wettable sulphur 80 WP against O. oryzae on rice. The study on the biology of O. oryzae was conducted in the Acarology laboratory during July-August, 2014 at 27+ 3 0 C and 70.2 + 7 per cent RH, following leaf bit method. The life cycle of O. oryzae consisted of egg, larva, protonymph, deutonymph and adult. The immature stages were followed by short quiescent intervals called nymhochrysalis, deutochrysalis and teleiochrysalis. The mite recorded an incubation period of 3.80 days. Larval period of 1.37 and 1.40 days, protonymphal period of 0.91 and 1.04 days and deutonymphal period of 0.98 and 1.30 days were recorded in males and females of O. oryzae respectively. The total development period from egg to adult was shorter for male (9.87 days) as compared to female (10.47 days). O. oryzae exhibited both sexual and parthenogenetic reproduction. Mated female’s progeny consisted of both males and females in the ratio 1: 3, whereas, unmated female produced only males. Pre-oviposition, oviposition and post-oviposition periods lasted for 0.89, 6.27 and 2.08 days in case of mated female, and 1.02, 7.31 and 2.12 days in unmated female respectively. Mated and unmated females on an average produced 21 and 17 eggs respectively. The adult mite recorded longevity of 8.00, 10.34 and 12.1 days for male, mated female and unmated female, respectively. The new acaricide molecules namely, fenazaquin 10 EC, spiromesifen 240 SC and propargite 57 SC evaluated in the laboratory resulted in significantly higher mortality of eggs and gravid females, 72 h after treatment application. In the pot culture experiment, all the four novel acaricide molecules tested, namely fenazaquin, spiromesifen, fenpyroximate and propargite succeeded in reducing the population of O. oryzae significantly. Efficacy of these molecules in reducing the mite population was pronounced from 3 rd day after spray application. Wettable sulphur also showed high efficacy against O. oryzae and 14 days after treatment application, its efficacy was on par with novel acaricide molecules. The botanicals tested significantly reduced mite population over untreated control, though were found to be inferior to all other treatments. The study has for the first time, documented the biology of O. oryzae in Kerala, which could form the basis for future investigation into ecological and management aspects of the mite. It has also succeeded in identifying a number of novel molecules for further, field level evaluation.
Biology and Management of the two spotted spider mite, Tetranychus urticae Koch (Prostigmata : Tetranychidae) on okra (Abelmoschus esculentus (L) Moench
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2013) Aswathi Krishna, R; Haseena Bhaskar
Diversity of phytophagous mites and their natural enemies in vegetables
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2012) Binisha, K V; Haseena Bhaskar
Vegetable crops are subjected to attack by a number of mite species leading to heavy economic loss. However, information on the diversity of phytophagous mites affecting major vegetable crops in Kerala is limited. Considering this, the proposed study entitled ‘Diversity of phytophagous mites and their natural enemies in vegetables’ was undertaken to develop a database on the important acarine species associated with major vegetable crops in Thrissur district, Kerala. The study was carried out in the Department of Agricultural Entomology, College of Horticulture, Vellanikkara during 2011-2012. The main objectives of the study were to identify the species composition of phytophagous and predatory mites associated with brinjal, okra, amaranthus, cowpea, chilli and bitter gourd from various localities of Thrissur district and also to study the spatial and temporal dynamics of population of phytophagous mites in these vegetable crops. A total of 19 species of phytophagous and predatory mites belonging to eight families in two suborders were identified. Tetranychidae, Tenuipalpidae and Tarsonemidae were the major phytophagous mite families recorded in the study. Tetranychus was found to be the dominant phytophagous mite in brinjal, bhindi, amaranthus and cowpea, whereas in chilli and bitter gourd, the tarsonemid mite, Polyphagotarsonemus latus (Banks) was the predominant one. The predatory mites associated with vegetables belonged to five families viz., Phytoseiidae, Stigmaeidae, Tydeidae, Cunaxidae and Bdellidae, among which Phytoseiidae predominated. The important phytoseiid predators observed in the survey included Amblyseius paraaerialis Muma, Paraphytoseius orientalis Narayanan, Neoseiulus longispinosus (Evans), Phytoseius sp., Euseius macrospatulatus Gupta, Typhlodromips sp. and Scapulaseius sp. The predatory mite Tydeus sp. of the family Tydeidae, Cunaxa sp. of the family Cunaxidae and Bdella sp. of the family Bdellidae were found in chilli. The Stigmaeid mite of the genus Agistemus was found in brinjal, bhindi and chilli. The comparison of different diversity indices in various crop ecosystems revealed that brinjal had highest genus richness. The value of Simpson-Yule Diversity index (D) was highest for brinjal which indicated that brinjal supported maximum genera of mites. The minimum value of D was in bitter gourd suggesting that it was least favoured by mites. Similarly the value of Shannon – Weaver Diversity index was found to be highest in brinjal and the least in bitter gourd. This shows that brinjal is favoured by a large number of mite species as compared to bitter gourd. The Berger – Parker dominance index (d) was worked out for the most dominant genus in the respective ecosystem and it was found that Tetranychus was the most dominant genus in brinjal, bhindi, cowpea and amaranthus where as P.latus was the dominant one in chilli and bitter gourd. The study on the population dynamics of mites in vegetables revealed that the mite population increased during hot summer months. The mite population was at their lowest from June to September as they were washed off due to heavy and consistent rainfall. After the cessation of rainfall, the mite incidence increased again and attained a second peak during December to January. The distribution pattern of mites on the plants varied with the canopy level and it was found that tetranychid mites preferred matured leaves of middle canopy in brinjal and amaranthus but bottom canopy in cowpea. In bhindi, there was no significant difference in the distribution of mites at the three canopy levels. The distribution of P.latus in chilli and bitter gourd was restricted to the top canopy leaves alone. Weather factors such as rainfall and evening relative humidity showed highly significant negative correlation with mite population, whereas maximum temperature showed highly significant positive effect on the population of mites. Hence it is evident from the study that increase in temperature coupled with decrease in relative humidity favoured an increase of mite population.
Diversity of predatory mite fauna in vegetable ecosystem
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2015) Maheswary, J; Haseena Bhaskar
Mites constitute the most important group of non-insect pests in agriculture. Vegetable crops in particular, are subjected to infestation by a number of mite species, leading to heavy economic loss. The average yield loss in vegetable crops due to mite pests in India has been estimated to be around 25 per cent (Gupta, 1991). Predatory mites play a major role in reducing the populations of phytophagous mites and are able to feed on alternate sources of food and can survive in the absence of prey mites. The present study was undertaken at the Acarology Laboratory, Department of Agricultural Entomology, College of Horiculture, Vellanikkara during 2014 – 2015 to explore the diversity of predatory mite fauna in the vegetable ecosystems of Thrissur district, Kerala. The objectives of the study were to document the species diversity of predatory mites associated with phytophagous mites in vegetable ecosystems in Thrissur and also to develop a taxonomic key for the identification of predatory mite fauna in vegetable ecosystems. A purposive survey was undertaken to explore the mite fauna associated with the vegetable crops viz. amaranthus, brinjal, bhindi, bittergourd, chilli, cowpea, coccinia, cucumber, snakegourd and snap melon in major vegetable growing tracts of Thrissur district, Kerala. The taxonomic characters of the collected mite specimens were studied and were classified upto species level. Based on the characters studied and the species identity established, a detailed dichotomous key to the identification of the predatory mites studied was prepared. A total of 18 species of predatory mites belonging to six families were encountered in the study. The predatory mite families included Phytoseiidae, Stigmaeidae, Cunaxidae, Bdellidae, Tydeidae, and Acaridae represented by the genera Neoseiulus, Amblyseius, Typhlodromips, Euseius, Paraphytoseius, Phytoseius, Scapulaseius, Agistemus, Cunaxa, Bdella, Tydeus and Pronematus. The associated phytophagous prey mite families recorded were Tetranychidae, Tenuipalpidae and Tarsonemidae represented by the genera Tetranychus, Eutetranychus, Brevipalpus and Polyphagotarsonemus. Faunal studies in ten vegetable crops revealed highest species richness of predatory mites in brinjal, with a total of 18 species belonging to five different families. Mites in the family Phytoseiidae were found to be the most common predators in the vegetable fields of Thrissur district. Among the phytoseiid mites, Neoseiulus longispinosus was identified as the major species, associated with phytophagous mites in all the vegetable fields surveyed. Other species were Amblyseius paraaerialis, Amblyseius largoensis, Euseius macrospatulatus, Euseius sp. nr. prasadi, Typhlodromips syzygii, Paraphytoseius orientalis, Phytoseius intermedius and Scapulaseius sp. Occurence of Euseius sp. nr. prasadi and Phytoseius intermedius are new reports for Kerala. Predatory mites, Cunaxa sp. of the family Cunaxidae and Bdella khasyana of the family Bdellidae were recorded in chilli, cowpea and snap melon. Bdella khasyana is a new report for Kerala. Four species of mites belonging to the family Stigmaeidae viz., Agistemus gamblei, A. fleschneri, A. garrulus and A. macrommatus were recorded on bhindi, bitter gourd, brinjal, chilli and snake gourd. Occurence of A. fleschneri, A. garrulus and A. macrommatus are new reports for Kerala. The predatory mites Tydeus gossabaensis and Pronematus anconai of the family Tydeidae recorded in amaranthus, bhindi, brinjal, chilli, cowpea and snake gourd are new reports from Kerala. One species of astigmatid mite in the family Acaridae was also collected from brinjal and cowpea during the study.
DNA barcoding of spider mites (Prostigmata:Tetranychidae) associated with ornamental plants
(Centre for Plant Biotechnology and Molecular Biology, College of Horticulture, Vellanikkara, 2019) Jayalakshmi Prakash; Haseena Bhaskar
Total area under floriculture in India is estimated to be 0.31 million hectares with a production of 2.08 million tonnes loose flowers and 0.82 million tonnes cut flowers in 2018-19. In Kerala, Thrissur district is considered as the centre of floriculture nursery business. Majority of nurseries in the area do not maintain their own sources of mother plants and hence import planting materials from other countries. Trade of commercial ornamentals has been recognized worldwide as an important invasion pathway for non-native pests, especially insects and mites. Though mites are reported as major pests of commercial ornamental plants from different parts of India, no systematic study has been conducted so far to document the diversity of mites associated with ornamental plants in Kerala. Considering this, the present study, ‘DNA barcoding of spider mites (Prostigmata: Tetranychidae) associated with ornamental plants’ was undertaken with the objectives to generate DNA barcodes for different species of spider mites infesting commercial ornamental plants of central Kerala and to find the genetic variability among them. The study included collection and culturing of spider mites, morphology based identification and molecular characterization of selected accessions. Purposive sampling surveys were carried out in commercial ornamental nurseries and homestead gardens of Thrissur and Ernakulam districts, covering 12 ornamental plants. Mite infested leaf samples were collected, brought to the laboratory and maintained separately as isoline cultures by assigning unique accession numbers. Morphological characterization of 26 isoline cultures revealed the occurrence of six species of spider mites under two genera viz., Tetranychus and Oligonychus. The genus Tetranychus was more diverse with five species viz., Tetranychus truncatus, T. urticae, T. okinawanus, T. neocaledonicus and T. marianae. The genus Oligonychus was represented by only one species, Oligonychus biharensis Hirst. Rose recorded the highest diversity of spider mites with five species. The mite species, T. okinawanus recorded wider host range with eight host plants viz., Adenium, rose, Gerbera, chrysanthemum, orchid, cairo morning glory, marigold and balsam. All the host plants except Adenium are new host records of T. okinawanus from India. The study recorded three new host plants for T. truncatus from India viz., rose, cock’s comb and marigold. In this study, T. marianae was recorded for the first time from Kerala. For molecular characterization, DNA was isolated and COI locus of 868 bp length was amplified using universal primer, specific to COI. Polymerase chain reaction (PCR) products of 12 accessions representing five species were sequenced and in-silico analysis was carried out. Homology analysis of sequences of 11 accessions showed 90-99 per cent similarity with sequences in NCBI database, which were in consensus with morphological identification. The sequence of the accession, Ros1vk (T. marianae) did not show significant similarity with any of the sequences in the NCBI database. In this study, COI sequence of T. marianae was submitted for the first time in GenBank. Barcode gaps among the species were examined by aligning the COI sequences using Clustal Omega tool and species-specific barcodes were identified at different nucleotide positions. Pairwise distance analysis of the sequences showed intraspecific divergence ranging from 0.00 to 0.036 and interspecific divergence ranging from 0.070-0.217. Phylogenetic analysis revealed the monophyly of T. truncatus and T. urticae and the close relationship of T. marianae with T. okinawanus. The study has shown that rose harbours many species of spider mites, indicating the need for imposing strict quarantine regulations for movement of planting materials of rose to avoid entry and invasion of mites into newer areas. The potential of T. okinawanus and T. truncatus to turn invasive in Kerala’s ecosystems is also brought out. The study establishes the reliability of COI locus as a marker for species discrimination in spider mites.
DNA barcoding of spider mites (Prostigmata:Tetranychidae) on major crop plants of Kerala
(Centre for Plant Biotechnology and Molecular Biology, College of Horticulture, Vellanikkara, 2017) Arunima, V; Haseena Bhaskar
Efficacy of Neoseiulus longispinosus (Evans) (Mesostigmata: Phytoseiidae) for the management of Tetranychus urticae Koch (Prostigmata: Tetranychidae) on cucumber under protected cultivation
(Department of Agricultural Entomology, College of Horticulture,Vellanikkara, 2017) Neena Lenin; Haseena Bhaskar
A study was undertaken at the Acarology laboratory, Department of Agricultural Entomology, College of Horticulture, Vellanikkara during 2013-2016, to investigate the biology, incidence, crop phenology relationship and natural enemies of the two spotted spider mite, Tetranychus urticae Koch infesting cucumber in polyhouse as well as to study the biology, efficacy and prey stage preference of the predator, Neoseiulus ongispinosus (Evans) on T. urticae and standardize the optimum predator: prey ratio of N. longispinosus for biological control of T. urticae in polyhouse. Purposive surveys, conducted in fifteen polyhouses in four districts of Kerala viz., Thrissur, Palakkad, Wayanad and Thiruvananthapuram, revealed the occurrence of four species of tetranychid mites, namely, Tetranychus truncatus Ehara, T. urticae Koch, T. okinawanus Ehara, Eutetranychus orientalis (Klein) and one species of tarsonemid mite, Polyphagotarsonemus latus (Banks) on cucumber. The occurrence of T. truncatus and T. okinawanus is a new report on cucumber in polyhouse. Hence, DNA barcoding was carried out to confirm the species identity of T. truncatus (TOCRF001-15) and T. okinawanus (TOIR001-15). Studies on the relationship of crop stage and mite incidence on cucumber revealed that the population of spider mites was significantly higher during the late fruiting stage of the crop, followed by early vegetative stage. Relatively lower population was recorded at flowering stage and early fruiting stage.Four species of insect predators and six species of mite predators were recorded in association with spider mites on cucumber. The insect predators were Stethorus pauperculus (Weise), Oligota sp., Scolothrips sp. and an unidentified species of Cecidomyiidae. The predatory mite fauna included Agistemus garrulus Chaudhari, Amblyseius paraaerialis (Muma), Cunaxa sp., Cheyletus sp., Neoseiulus longispinosus (Evans) and Tydeus gossabaensis Gupta.Neoseiulus longispinosus was found to be the predominant species of predatory mite on spider mites infesting cucumber. Tetranychus urticae recorded a developmental period of 6.75 days in male and 7.15 days in female. Adult male lived for 8.95 days while mated and unmated female lived for 11.59 days and 13.04 days, respectively. Mated and unmated females recorded a fecundity of 47.91 and 36.08 eggs, respectively. The sex ratio was female biased (1:4.6) in T. urticae. Total developmental period of N. longispinosus was 3.91 and 4.27 days for male and female, respectively. Adult male lived for 19.66 days and the female, for 22.75 days. On an average, a single female laid 31.33 eggs and the progeny consisted of both males and females in the ratio 1:3.31. Parthenogenesis was not observed in N. longispinosus. The adult of N. longispinosus recorded significantly higher predation compared to the nymph. Both nymph and adult, showed preference towards egg compared to active stages of the prey. The time needed to eliminate the available prey population was found to increase with increase in prey density. Studies conducted to identify the optimum predator: prey ratio required for field release of N. longispinosus against T. urticae on cucumber in the laboratory showed that, at ratios of 1:5 and 1:10, the prey population was completely eliminated by tenth day. The prey population recorded in the ratios, 1:20, 1:25 and 1:33 were on par with this. In the polyhouse, the predator: prey ratios of 1:20 and 1:25 were found to significantly reduce the population of T. urticae on cucumber. The present study has revealed the potential of the predatory mite, N. longispinosus as a biocontrol agent of the spider mites. The short life cycle, longer life span of adults, female biased sex ratio and preference for egg stages and above all, the density dependant nature of the prey predator relationship, brought out in the present study could provide a platform for viable biocontrol strategy based on N. longispinosus for management of spider mites under protected cultivation in Kerala.
Insect pest natural enemy- host plant interaction studies with special reference to the brown planthoper nilaparvata lugens(Stal.)
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1999) Haseena Bhaskar; Joy, P J
Field surveys were conducted in Kole land and Kuttanad to assess the population of rice BPH, Nilaparvata lugens (Stal) and its natural enemies. Field investigations on the population dynamics of BPH and its natural enemies were carried out on susceptible (Jaya), moderately resistant (Jyothi) and resistant (Kanakom) rice varieties at the rice fields of Rice Research Station, Moncompu during 1997-98. The influence of these varieties on the biology of the pest, the biocontrol efficiency of the major natural enemies and the biology of the mirid predator Cyrtorhinus lividipennis Reuter was studied in the laboratory. Histological and chemical investigations were undertaken to evaluate the factors that contribute to the resistance/susceptibility in them. Results of field survey in Kole land revealed that the population of BPH was far below the economic threshold level (ETL). In Kuttanad, in kayal area during Rabi season and in karappadam tract during Kharif season outbreaks of BPH occurred in some localities due to the indiscriminate use of insecticides resulting in the mortality of natural enemies. The results of the study on population dynamics revealed that the BPH population was significantly high on the susceptible J aya and low on the resistant Kanakom with the population reaching a peak from February to March. The predatory complex of the BPH comprised of the rnirid Cyrtorhinus lividipennis, Lycosa pseudoannulata, Tetragnatha maxillosa, Atypena formosana, Microvelia douglasi atrolineata, Pseudogonatopus sp. and Ophionea nigrofasciata. C. lividipennis was the most predominant predator regulating the hopper population and there exists a density dependent host-predator relationship. The population of the mirid predator on Jaya and Kanakom did not differ significantly. The prey-predator ratio was lowest on the resistant variety and highest on the susceptible variety. Of the weather parameters studied, the minimum -. temperature showed a highly significant negative correlation with the population of N. lugens in all the varieties. BPH reared on the resistant variety recorded longer nymphal duration, decreased nymphal survival and shorter adult longevity indicating the prevalence of antibiosis in the variety. Lesser number of eggs laid, longer pre-oviposition period and shorter oviposition period recorded on Kanakom indicate the antixenosis factor in it. Macrpterous forms of BPH did not develop on the variety . The predator C. lividipennis and Micraspis sp. fed more BPH when reared on the resistant variety. The veliid bug M. d. atrolineata, the spider L. pseudoannulata and the dryinid Pseudogonatopus sp. predated significantly more BPH nymphs on resistant variety at a higher prey density only. However, the dryinid parasitoid consumed significantly fewer number of hoppers on Kanakom at the higher host density. C. lividipennis recorded longer nymphal duration, shorter adult longevity and low fecundity when fed on BPH reared on Kanakom which can be attributed to the low fecundity of N. lugens on Kanakom leading to less availability of food to the mirid. Nymphal duration and adult longevity of C. lividipennis did not vary between the varieties Jaya and Jyothi. Well developed bundle sheath with more frequently distributed schlerenchyma tissue in the culm of the resistant variety seemed to impart resistance in Kanakom along with thicker cuticle. Higher amounts of silica, Zn and Mn and lower amounts of N, K, Ca and Mg were recorded in the culm of the resistant variety compared to moderately resistant and susceptible varieties. The findings strongly suggest the mechanism of antibiosis and antixenosis in the resistant variety Kanakom.
Molecular basis of acaricide resistance in tetranychus truncatus ehara (prostigmata: tetranychidae) infesting vegetable crops
(Department of Plant Biotechnology, College of Horticulture, Vellanikkara, 2018) Anushree Bachhar; Haseena Bhaskar
Spider mites of the family Tetranychidae are considered as one of the most serious sucking pests of vegetable crops worldwide. Intensive use of conventional acaricides had lead to the development of resistance in many mite species around the globe. In view of this, several novel acaricides with unique chemical structure and mode of action were introduced and commercialized for mite management. In Kerala, mite management in vegetable crops solely depends on the use of novel acaricides. Of late, several farmers have raised concern over their poor efficacy against mite pests. Spider mites have the ability to develop resistance quickly on continuous exposure to a pesticide. In this context, the present study was undertaken to investigate the status, biochemical and molecular bases of acaricide resistance in Tetranychus truncatus Ehara, the predominant species of spider mite infesting vegetable crops of Kerala. Purposive surveys were conducted in the vegetable fields of Vellanikkara, Thrissur and spider mites were collected and reared in the laboratory by assigning accession numbers. Three accessions/strains viz., VkOk1 (okra), VkAm3 (amaranthus) and VkPm3 (pumpkin) which were identified as T. truncatus were used for the study. Susceptibility of the three field strains to three commonly used acaricides, viz., spiromesifen, fenazaquin and diafenthiuron was evaluated in the laboratory following leaf dip bioassay in comparison with a laboratory maintained susceptible strain (SS). Bioassay study revealed that the strain VkOk1 recorded highest LC50 value and has developed 8, 13 and 10 fold resistance to spiromesifen, fenazaquin and diafenthiuron, respectively. This was followed by VkAm3 which showed 7.0, 5.53 and 1.67 fold resistance, while VkPm3 recorded 1.35, 1.13 and 1.03 fold resistance. The activity of the detoxifying enzymes viz., cytochrome P450 and carboxylesterase, was significantly higher in VkOk1strain followed by VkAm3. The strains VkOk1, VkAm3 and VkPm3 showed 2.69, 1.24 and 1.09 fold enhanced activity of Cytochrome P450, respectively compared to SS, while carboxylesterase in VkOk1 and VkAm3 showed an increased activity by 2.59 and 1.18 fold. However, the strain VkPm3 recorded a decrease in activity of carboxyleasterase by 0.78 fold compared to the susceptible strain. DNA isolated from the two resistant strains (VkOk1 and VkAm3) and the susceptible strain (SS) was amplified with the help of gene specific primers for cytochrome P450 and carboxylesterase. The results of PCR for cytochrome P450 gene showed that there was no amplification in the case of SS, whereas there were distinct markers in the resistant strains, okra and amaranthus at 1300 bp size. However, PCR amplification showed distinct markers for carboxyl esterase in all the three strains. The strains VkOk1 and SS showed markers at 1500 bp and 1300bp size respectively, while VkAm3 strain showed both the markers. The sequence homology search by BLASTn analysis showed that the sequences of cytochrome P450 of T. truncatus has similarities with cytochrome P450 sequences from different species of spider mites with an identity match ranging from 81 to 97 per cent, while carboxylesterase sequences showed similarity with two mRNA sequences of carboxylesterase of T. urticae. Further, the translated sequences of cytochrome P450 and carboxylesterase aminoacids from T. truncatus when analysed by BLAST P showed similarity with the amino acid sequences from other spider mites. The sequences of carboxylesterase genes from the resistant and susceptible strains did not align together, showing that there are two different caboxylesterase genes controlling the resistance to acaricides in T. truncatus. The study recorded resistance in T. truncatus to three novel acaricide molecules, for the first time from India. This is the first report of cytochrome P450 and carboxylesterase genes conferring resistance to acaricides in T. truncatus. The study also developed standard markers for discriminating the resistant and susceptible population in T. truncatus.
Molecular mechanism of virulence in the bacterium, Photorhabdus luminescens (Thomas and Poinar) against Tetranychus truncatus Ehara (Prostigmata: Tetranychidae)
(Department of Plant Biotechnology, College of Agriculture, Vellanikkara, 2021) Ashwini, M N; Haseena Bhaskar
Spider mites (Tetranychidae) are a major group of sucking pests of many agricultural and horticultural crops worldwide. Tetranychus truncatus Ehara is the predominant mite species infesting economically important crops of Kerala. Novel acaricides are being extensively used for managing mite infestation, which has led to development of significant level of resistance in mite populations to these acaricides. This, along with other adverse effects of synthetic acaricides to the environment, calls for alternative strategies in mite pest management. The entomopathogenic bacteria Photorhabdus luminescens (Thomas and Poinar), a natural symbiont of the entomopathogenic nematode, Heterorhabditis spp. has potential virulent properties and the ability to infect a wide range of insect pests and a few mite pests. An array of toxins produced by the bacteria are responsible for this appreciable insecticidal activity. Most of the orally active toxins are encoded by tca and tcd loci of TC genes. These toxins might also be responsible for the acaricidal activity of the bacterium. In this context, the present study was undertaken to identify the virulent strain of P. luminescens against T. truncatus and to elucidate the molecular mechanism of virulence against T. truncatus. Eleven bacterial isolates associated with the entomopathogenic nematodes, Heterorhabditis spp. were isolated in the study. Cultural characterization of the bacterial isolates showed that the bacterial colonies were circular to irregular, entire, opaque, smooth colonies on NBTA medium. All the isolates were found to be Gram negative and rod shaped. For molecular characterization, the 16S rRNA gene of the isolates was amplified, sequenced and subjected to BLASTn for homology search. One species of EPN symbiotic bacteria, P. luminescens and eight nonsymbiotic/ associated bacteria namely, two isolates of Pseudomonas aeruginosa, five isolates of Ochrobactrum and one isolate of Stenotrophomonas maltophila were identified. Phylogenetic tree was constructed based on the gene sequences of 16S rRNA to validate the bacterial identification.Laboratory bioassays were carried out to evaluate the efficacy of the both cell suspension and cell free supernatant (CFS) of five bacterial isolates (1 isolate of P. luminescens, 2 isolates of P. aeruginosa, and 2 isolates of Ochrobactrum sp.) separately against the eggs and adults of T. truncatus. Though the isolates did not show any significant ovicidal action, they recorded significant adulticidal action against the mite. The P. luminescens isolate was superior over other isolates recording 64.67 and 60.67 per cent mortality for CFS and cell suspension, respectively at 96 h of treatment The virulent P. luminescens isolate was subjected to characterization of the toxin complex (TcdA gene). The full length gene (7.5 kb) was split into eight regions and the primers were designed to amplify each regions separately. Among the eight regions, only six got amplified and were sequenced. Toxin gene sequence of the isolated P. luminescens bacteria involved in the virulence against T. truncatus was partially sequenced and the variations in the sequence were analyzed. The study identified a potential isolate of P. luminescens with significant adulticidal action against T. truncatus and the major gene TcdA encoding the toxin complexes which possess appreciable insecticidal activity was sequenced and characterized. The P. luminescens isolate obtained in the study can be evaluated for efficacy against major insect pests in the region in order to identify the potential in pest management.
Susceptibility of Tetranychus okinawanus Ehara (Prostigmata: Tetranychidae) infesting ornamental plants to novel acaricides
(Department of Agricultural Entomology, College of Agriculture, Vellanikkara, 2021) Sreshma, M; Haseena Bhaskar
Spider mites of the family Tetranychidae are well-known agricultural and horticultural pests that feed on a wide variety of plants, including vegetables, fruit trees, and ornamentals. Many traditional insecticides and acaricides have been used to manage mite pests for several decades. The widespread usage of acaricides around the world has facilitated development of resistance in different mite species, making mite management challenging. As a result, many novel acaricides with distinct chemical structures and modes of action have been developed and marketed for mite control. However, after a few years of use, mite populations developed resistance to these newly introduced compounds too. The spider mite species, Tetranychus okinawanus, recently recorded on an ornamental plant Adenium in Thrissur district, for the first time in India, has now emerged as the predominant species of mite infesting ornamental plants in Kerala. Recently, several growers reported inefficacy of the commonly used novel acaricides against mite pests in many ornamental crops, suggesting that the mite populations might have developed resistance to acaricides. Hence a study was carried out to investigate the status of acaricide resistance in Tetranychus okinawanus infesting Adenium in horticultural nurseries and also to elucidate the biochemical mechanism involved in development of resistance. Purposive surveys were conducted in six commercial horticultural nurseries in Thrissur district viz., National Rose Garden, Mangadan Botanical Garden, Ayyappa Nursery, Saranamayyappa Nursery, Pooja Gardens and Nursery, and Manalur Adenium Garden and samples of spider mite infesting Adenium were collected. Mites were maintained as separate isoline cultures assigning unique accession numbers as NrAd1, MgAd2, AyAd3, SyAd4, PjAd5 and MnAd6. Morphological characterisation of the slide mounted mite specimens from the isoline cultures was carried out to confirm the species identity as T. okinawanus. Susceptibility of the six field populations to three acaricides viz., spiromesifen, fenazaquin and dicofol was evaluated in the laboratory, in comparison with the reference susceptible population maintained without exposure to any acaricides in the laboratory, following toxicological bioassay. Susceptibility studies with fenazaquin revealed that the accession NrAd1 recorded the highest LC50 value (27.85 ppm) and has developed moderate level of resistance (14.38-fold) to fenazaquin. This was followed by PjAd5 (9.70-fold), AyAd3 (4.06-fold), MnAd6 (3.78-fold), and SyAd4 (3.23-fold). The lowest resistance ratio was recorded by the accession MgAd2 (1.66). The toxicity studies of spiromesifen also recorded low to moderate levels of resistance in different populations of T. okinawanus. The accession NrAd1 recorded highest resistance ratio of 27.31 followed by PjAd5 (7.18), MnAd6 (3.94), AyAd3 (1.78), MgAd2 (1.42) and SyAd4 (1.06). However, the mite populations showed only low level of resistance to dicofol, recording resistance ratios in the range of 3.65 to 1.22. Biochemical basis of acaricide resistance in different populations of T. okinawanus was investigated by estimating the activity of detoxifying enzymes such as carboxyl-esterase, cytochrome P450 and glutathione S- transferase. Carboxyl-esterase enzyme showed an enhanced activity of 1.03 to 3.52-fold, while cytochrome P450 monooxygenases recorded 1.01 to 2.08-fold higher activity in the field collected populations, compared to the susceptible population. The level of these detoxifying enzymes was found to be higher in the accession NrAd1, which also recorded the highest resistance ratio in the study. However, the activity of glutathione S-transferase (GST) did not differ significantly among the field populations and also with susceptible population, indicating that GST is not a contributing factor in the development of resistance in T. okinawanus against spiromesifen, fenazaquin and dicofol. The study recorded development of resistance in the spider mite, T. okinawanus on Adenium to spiromesifen and fenazaquin, in the horticultural nurseries in Thrissur district, Kerala for the first time in the world. The significant role of the detoxifying enzymes, carboxyl-esterases and cytochrome P450 monooxygenases in imparting resistance in T. okinawanus to the two novel acaricides, fenazaquin and spiromesifen was also confirmed in the study. The study demands formulation of a suitable resistance management strategy in horticultural nurseries in the state for suppressing or delaying resistance development in mite populations.
Systematics of the subfamily aphidinae (Hemiptera :aphididae) from south India
(Department of agricultural entomology, college of agriculture, Vellanikkara, 2023-09-18) Sharanabasappa M Ganganallil; Haseena Bhaskar
Aphids (Hemiptera: Aphididae) are one of the major groups of economically important sucking pests of crops worldwide. They are remarkable for their role as the largest group of insect vectors of plant viral diseases. The family Aphididae is composed of 24 subfamilies that globally include 5109 species under 527 genera. In India, only 16 subfamilies are recognized,comprising of 794 species under 208 genera. Aphidinae, is the largest subfamily under Aphididae, which includes highly polyphagous aphids with 431 species distributed in India. In spite of the diversity and potential as crop pests, the fauna of aphids from South India is poorly studied.
Systematics of the tribes scymnini and stethorini (coleoptera: coccinellidae) from South India
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2018) Vidya, C V; Haseena Bhaskar
Family Coccinellidae, the lady beetles, belong to the superfamily Coccinelloidea of the order Coleoptera and comprises approximately 6000 described species worldwide. Tribes Scymnini and Stethorini of the subfamily Scymninae of Coccinellidae are economically important predators successfully used in the biological control programmes of sucking pests of crops. Members of Scymnini are mainly predators of aphids, mealybugs, whiteflies and scales, whereas Stethorini are specific to mites. Though the fauna of Scymnini and Stethorini in India is species rich, it is poorly studied. The present investigation on “Systematics of the tribes Scymnini and Stethorini (Coleoptera: Coccinellidae) from south India” was carried out during 2015-17. The objectives include the following: (1) taxonomy of the tribes Scymnini and Stethorini associated with sucking pests in different agricultural ecosystems of south India, (2) prepare a key to the species of Scymnini and Stethorini and (3) generate DNA barcode for different species of Stethorini. Purposive surveys were undertaken across different districts of Kerala, Karnataka and Tamil Nadu covering 47 locations and 64 crops under different agricultural ecosystems. Beetles and immature stages of Scymnini and Stethorini were collected along with the associated prey. Immature stages of Scymnini and Stethorini were reared to adults. The specimens were then mounted, labeled and preserved as per standard procedures. The beetles were dissected and the taxonomic characters viz., antenna, mouth parts, prosternum, tarsus, post coxal line, male and female genitalia were studied and illustrated. The specimens were identified up to species level. Descriptions, illustrations and key to genera and species of Scymnini and Stethorini of southern India were prepared. The study encompasses 28 species of Scymnini of which six are putative new species. Two species are recorded for the first time in India and two species each from south India and Kerala are new records. Scymnini include Axinoscymnus, The genera treated under Cryptolaemus, Horniolus, Nephus, Sasajiscymnus and Scymnus. The genus Scymnus, represented by 20 species, of which 18 species are placed in three subgenera viz., Scymnus, Neopullus and Pullus. Two species are treated separately, as these differ distinctly from the known subgenera. The genus Nephus is represented by three species, Axinoscymnus with two species and Cryptolaemus, Horniolus and Sasajiscymnus with one species each. Stethorini are represented by 10 species in two genera: Stethorus and Parastethorus. Two putative new species of the tribe are described. Six species of Stethorini are new reports for Kerala. Two subgenera recognized under the genus Stethorus are Stethorus and Allostethorus. represented by four species each. Stethorus keralicus, one of the most common species, has been treated separately in this study, as its characters are not in agreement with the known subgenera. The genus Parastethorus is represented by only one species. The prey ranges of Scymnini and Stethorini were documented. Species distribution map were prepared for the species studied. Twenty one species of prey in four families viz., Aphididae, Pseudococcidae, Aleyrodidae and Diaspididae were recorded in association with the tribe Scymnini. Two new prey records for Scymnini are Toxoptera odinae for Scymnus pyrocheilus and Saccharicoccus sacchari for Nephus tagiapatus. Among Scymnini, Scymnus coccivora and S. saciformis are widely distributed with wider host range of six species as prey, while species of Axinoscymnus, though widely distributed, is specific to whiteflies. Among Stethorini, Stethorus pauperculus was found to be the predominant species with wider host range, while Stethorus keralicus was specific to Raoiella indica. New prey records for Stethorini includes Tetranychus okinawanus and T. truncatus for Stethorus forficatus; T. macfarlanei for S. pauperculus and Eutetranychus orientalis for Parastethorus indira. For barcoding the species of Stethorini, DNA was isolated using Qiagen DNeasy blood and tissue kit and the COI locus was amplified and sequenced. The sequences were aligned and characteristic barcode gaps were identified for Parastethorus indira, Stethorus forficatus, S. pauperculus, S. rani, S. keralicus, S. (Allostethorus) sp. 1 and S. (Stethorus) sp.1. Pairwise distances between the sequences were analysed which showed that intraspecific divergence ranged between 0.00 to 0.03, while the interspecific distance ranged between 0.14 to 0.24. A phylogenetic tree was constructed with 21 sequences in MEGA 7 using the maximum likelihood tree method. The sequences were submitted to GenBank (NCBI) and to BOLD for the generation of species specific barcodes. The study identified 38 species of predatory coccinellids in the tribe Scymnini and Stethorini in association with aphids, mealybugs, whiteflies, scales and mites, which are serious pests of crops. Knowledge on the taxonomy of these predators and their prey range throws light on the potential of the above groups in biocontrol of sucking pests.
Taxonomy of predatory coccinellid beetles (Coccinellidae:coleoptera) in rice and vegetables
(Department of Agricultural Entomology, College of Horticulture,Vellanikkara, 2003) Queno Jose; Haseena Bhaskar
Members of the family Coccinellidae, commonly called as lady bird beetles and are predatory on a wide variety of pests. The grubs and adults of the beetle are voracious feeders of many sucking pests and effect natural control of pests in our crop fields. The diversity and abundance of predatory coccinellids in field crops are very much dependent on species and number of prey available. The present investigation entitled "Taxonomy of predatory coccinellid beetles (Coccinellidae : Coleoptera) in rice and vegetables was undertaken to study the taxonomy, species composition and diversity of coccinellid predators in rice and vegetable fields of Vellanikkara and to develop an up to date key for identifying them. Survey was conducted at vegetable fields of College of Horticulture and farmers fields, Vellanikkara and rice fields at Agricultural Research Station, Mannuthy. From the various fields surveyed, sixteen species of coccinellids were collected. Associated with the aphid, Aphis craccivora, ten species of coccinellids were recorded from cowpea fields. Four species of coccineIlids each were reported from coccinia and bittergourd fields. In brinjal, three species of coccineIlids were recorded on mealy bug C. insolitus. Only one species was recorded in bhindi feeding on Aphis gossypii. They were included in four subfamilies, viz., Sticholotidinae, Coccirrellinae, Chilocorinae and Scyrnninae in five tribes and ten genera Taxonomic characters of 11 species collected were studied, namely, Jauravia soror of the subfamily Sticholotidinae, Coccinella transversalis, Q Cheilomenes sexmaculata, Micraspis discolor, Harmonia octomaculata and Anegleis cardoni of the subfamily Coccinellinae, Brumoides suturalis of Chilocorinae and Scymnus (Pullus) coccivora, S. (P) pyrocheilus, S. (P) latemaculatus and Pseudaspidimerus trinolatus of the subfamily Scymninae. A detailed key for all the species studied is prepared by the author. J dorsalis and J pallidula of tribe• Sticholotidinae, s. (P.) coccivora and Pseudoscymnus sp. of Scyrnninae are new records from Kerala. The present study I has also revealed new prey records from Kerala: S. (P.) pyrocheilus and S. (P.) latemaculatus on A. gossypii and A. craccivora; J. dorsalis, J. pallidula. on A. gossypii; P. trinotatus on C. insolitus and A. gossypii . . ' Of the total 400 species of coccinellids reported from India only 16 species were recorded in the present study from rice and vegetable fields. With the diverse flora and fauna characteristic to Kerala, there is wider scope to explore the species diversity of coccinellids in this region,: