Browsing by Author "Premila, K S"

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Bio-ecology and management of perianth infesting mealy bugs dysmicoccus brevipes(Cockerell) and Pseudococcus Longispinus (Targioni-Tozzetti) on coconut
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2003) Bindu Radhakrishnan; Premila, K S
A study was conducted at the College of Agriculture, Vellayani from January 2001 to December 2001 to study the biology, species composition and symptomatology of perianth infesting mealybugs, D. brevipes and P. longispinus infesting the coconut palm and to assess the yield losses caused by the pest and to evolve management measures. The biology of the two species was studied after reanng them on pumpkin fruits. The mean larval period and adult longevity of D. brevipes and P. longispinus when reared on pumpkin were 36 and 103.3 and 26 and 57 days respectively. The mean sex ratio of D. brevipes was 3.17 and of P. longispinus was 3.54. Pumpkin appeared to be a good host material for mass rearing PMBs. Studies on the yield loss assessment revealed an annual yield loss of Rs 139.20/ palm in the highly susceptible palms whereas in the medium and low susceptible palms the yield losses were Rs. 85.80/palm and Rs. 40.80/ palm respectively. When the influence of bunch age on the extent of damage by mealybugs was studied, highest mean per cent damage was observed in the fifth bunch followed by fourth and sixth bunches. Maximum population of PMBs were observed in the fifth nutlet. The mean population of D. brevipes was maximum during May (1.31) whereas the mean population of P. longispinus was maximum during March (1.13). Studies on the susceptibility of stage of bunch to mealybug damage indicated that the peak level of damage was in the fifth bunch. Consequently the maximum damage was observed in the month of June. Rainfall was observed to be the most important factor adversely affecting mealybug population. Development of symptoms as a consequence of feeding injury by PMBs include drying of nut without drying of calyx, stunting, deformities in the buttons such as development of cavities in place of embryo and gummy exudation. The mean population of other perianth infesting arthropods found associated with highly infested category of palms was low when compared to medium and low category palms. A positive relation between number of flowers per spikelet and susceptibility to mealybugs was observed. A study on the reaction of nutlets of WC'T variety to PMBs in terms of tepal colour revealed that orange and green coloured tepals were the most preferred by PMBs. Ant species C. nuda, T. albipis and A. longipes were seen closely associated with PMBs. Among the various pesticides evaluated against PMBs, triazophos (0.05) and profenofos (0.05) were found to be effective in controlling the pest.
Chemical control of thrips stenchaetothrips biformis Bagnall using synthetic pyrethroids in rice nursery
(Kerala Agricultural University, 1988) Reghunath, P; Premila, K S; Thomas Biju Mathew; Nandakumar, C
Documentation and predatory potential of spiders in rice ecosystem and impact of insecticides on spiders
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2007) Anis Joseph, R; Premila, K S
The survey conducted to document the spiders in the paddy fields of Thiruvananthapuram district during the Virippu and Mundakan seasons of 2005-’06, brought out sixty five species of spiders, which fall into two major groups, hunters and web builders and belonged to eleven families and seven foraging guilds. The species composition of hunters was more than the web building spiders, although the latter was numerically dominant. The dominant guild was orb web weavers. Araneidae was the family with more species composition, followed by Tetragnathidae and Salticidae. The predominant genus being Tetragnatha, and species, Tetragnatha mandibulata Walckenaer. The other dominant species were Tetragnatha maxillosa Thorell, Argiope anasuja Thorell, Neoscona rumpfi Tikader & Biswas, Telamonia dimidiata Simon, Bianor carli Reimoser, Oxyopes javanus Thorell, Peucetia viridana Stoliczka, Pardosa pseudoannulata Böesenberg & Strand and Thomisus projectus Tikader. Seventeen species of spiders were reported for the first time from the rice fields of Kerala, and it included the three dominant spiders, viz., N. rumpfi, B. carli and T. projectus. Spiders were also observed in the field bunds and border weeds, and from the webs built among plants, in between the plants and on individual leaves. The seasonal occurrence of spiders during the Virippu and Mundakan seasons did not show any remarkable difference. Among the eleven families, six were more populated viz., Tetragnathidae, Araneidae, Salticidae, Lycosidae, Oxyopidae and Thomisidae. The predominant family was Tetragnathidae. The vegetative and reproductive stages of the crop harboured more spiders and the highest population was recorded during the reproductive stage. The crop growth stages had significant influence over the spider population, where as the weather parameters had no correlation. The ten spiders showed a definite preference for the different hoppers, bugs and lepidopterans when evaluated for their prey preference. The spiders A. anasuja, P. viridana, T. dimidiata and T. projectus broadened their preference to the orthopteran and coleopteran pests. The predatory potential of the spiders showed that the spiders which consumed more number of prey insects per day in a mixed diet took comparatively lower numbers when the prey insects were provided individually. A. anasuja was the most potential predator and P. viridana was the spider with highest rate of hyper predation and the most cross predated insect predator was C. lividipennis. The parasitoids were not consumed by the spiders. The topical application of chemicals recorded higher mortality of spiders than when released on the treated plants. Among the chemicals, imidacloprid 0.005 per cent proved to be safer and triazophos 0.05 per cent more toxic. Azadirachtin 0.004 per cent had more toxicity among the neem formulations. In the field, better recolonization of spiders was noticed in the neem products treated plots than the synthetic pesticides, imidacloprid proved to be the safest chemical for the spiders and all the insect natural enemies and was quite promising for the pests. From the results obtained, it can be concluded that pest management will be effectively executed in the field by these potential predators, which are abundant and had specific adaptations which overpowered the other natural enemies in the rice fields. In a naturally balanced rice ecosystem, in a pesticide free environment, these carnivores can survive and when assembled into groups, they could contribute to significant reductions in pest numbers, which have a positive effect on crop production and is beneficial to farmers. Imidacloprid 0.005 per cent could be utilized for pest control when infestation is severe without harming the spider fauna. Hence, conservation biological control could be practiced along with spider mediated IPM.
Major predators in rice ecosystems and their potential in rice pest management
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2003) Premila, K S; Nalinakumari, T
Survey conducted in three heterogeneous rice ecosystems of Kerala viz., Kuttanadu rice fields of Alappuzha district with high load of pesticide, double cropped rice fields of Thiruvananthapuram district with moderate level of pesticide and Pokkali rice fields of Ernakulam district with no pesticide during two consecutive seasons at the vegetative, tillering and reproductive stages of the crop revealed a distinct change in the composition and status of natural enemies and pests in rice ecosystem. While pests dominated in Kuttanadu and double cropped rice fields of Thiruvananthapuram, natural enerm es dominated In Pokkali ecosystem. Among the natural enemies, population of predators was signi ficantly higher 111 all the three ecosystems. Population of pnr as lt o i d s was very low. Among the predators, insect predators dominated the predator fauna followed by the spiders in the three ecosystems. The important insect predators observed were the mirid bug Cyrtorhinus livi dipennis Reuter and the coccinellid beetle Micraspis di scol or (Fabricius) and the major spider predators recorded were Tetragnatho maxillosa Thorell and Lycosa pseudoannulata (Boesenberg et Strand). Among the pests seen in th~ three ecosystems, the sucking pests were dominant followed by the defoliators. Stage specific sucking pests like the ricebug Lept ocorisa acut a (Thunb) and earhead thrips Hapl ot hrips ganglb aueri Schmutz too were seen infesting the crop during the respective crop stages. Hoppers were the predominant sucking pests in all the three rice ecosystems. Population of other sucking pests was very low. Among the hoppers Nephot ettix sp. and Sogatella furcifera (Horvath) were predominant. Comparatively, population of the brown planthopper, Nilaparvata lugens (Stal) was low. Population of other pests considered as major ones in the State like yellow stem borer Scirpophaga incertulas (Walker), gall fly Orseolia oryzae (Wood-Mason), case worm Parapoynx stagnalis Zeller etc. was negligible. The population of neutrals was low in all the three rice ecosystems. On the other hand, high population of these 'other insects' was seen in the adjoining vegetation. Greater diversity of arthropod spec ies was observed in the insecticide-free Pokkali rice ecosystem and insecticide-rationally-used double cropped rice ecosystem of Thiruvananthapuram. Less diversity of species was seen in Kuttanadu rice ecosystem where insecticides were applied indiscriminately. Studies on the suitability of different prey for mass culturing C. l ivi dip enni s, M. discolor, T. maxillosa and L. pseudoannulata under controlled conditions indicated that the best prey for C. lividipennis was the first instar nymphs of N. I ugens ,for M. discol or its eggs, for T. maxillosa, Nephotettix sp. and for L. pseudoannul at a, N. lugens. Efficiency of the predators 111 suppressing hopper pests when assessed in terms of searching capacity, feeding potential, prey preference and hyperpredation revealed that the insect predators C. lividipennis and M. discolor showed better ability to search for plant hoppers, especially N. lugens and S. furcifera. Comparatively, the searching capacity of the spiders for hoppers was low. The feeding potential and prey preference of C. livi dipenni s was significantly high for first instar nymphs of N. l ugens . Similarly, M. discolor preferred more of its own eggs than the other prey tested. The spider, L. ps eu do annul at a was observed to be a significantly better predator of hoppers than T. maxill os a. None of the predators tested showed cannibalism. Hyperpredatory activity was observed in Crocothemis sp., Agri ocne mis sp., Polytoxus fuscovitt at us (Stal), T. maxillosa, Oxyopes sp. and L. pseudoannulata. The mirid bug C. lividipennis was a highly preferred prey for hyperpredation. The commonly used insecticides for nee pest control viz., carbaryl, phosphamidon, monocrotophos, quinalphos and methyl parathion caused 80 to 100 per cent mortality of predators at the dose normally recommended for pest control. The results of the study emphasized the need for periodical assessment of the arthropod community Jl1 nee ecosystems as agro- ecological conditions tend to shift the status of phytophages and entomophages from time to time. Based on the results, growing of varieties tolerant to major pests and regulation of incident pests by conserving naturally occurring predators through optimal habitat modification and use of predator-friendly insecticides when absolutely needed will go a long way in sustainable production of rice in Kerala.
Management of the leaf roller complex on rice Oryza sativa L
(Division of Agricultural Entomology, College of Agriculture, Vellayani, 2003) Lekha, M; Premila, K S
The magnitude and intensity of leaf roller complex and natural enemies at different growth stages of the rice crop were assessed in a survey conducted during Mundakan season of 2002, adopting random sampling technique in Kalliyoor panchayat of Thiruvananthapuram district. The survey revealed the occurrence of two different species of leaf roller viz., Cnaphalocrocis medinalis (Guenee) and Marasmia patnafis (Bradley). The distribution pattern of these two species in the n ce ecosystem varied. C. medinalis had a population peak during the vegetative stage and showed a gradual decline as the crop growth progressed, whereas, M. patnalis had a population peak during the early reproductive stage compared to vegetative and late reproductive stage. The natural enemies recorded from the rice ecosystem incl ude three parasites and ten predators. The distribution of natural enemies in the rice ecosystem revealed that the population of parasites and predators showed a gradual increase from vegetative to reproductive phase. From the field experiment, it was evident that the synthetic insecticides alone and botanicals + half dose synthetic insecticides were efficient in suppressing the pbpulation of rice leaf roller. The treatments with botanicals alone did not show any significant reduction in the population of leaf roller compared to control. G. tr iangulifer, a specific larval parasite of rice leaf roller, was unaffected by the botanicals, synthetic insecticides and their combinations at 30 OAT. In the case of X flavolineata and Cot esia sp., only an initial suppression was noticed in insecticide included treatments. Later it was found to be safe. All these treatments were found to be relatively safe to predatory beetles. But Agriocnemis sp., spiders, predatory bugs and Conocephalus sp. was adversely affected by the insecticide included treatments. Botanicals were safe to all the natural enemies observed but they were ineffective against rice leaf roller. The yield obtained was also the highest in synthetic insecticides alone and botanicals + half dose of synthetic insecticide treatments and were on par. Overall assessment of the results obtained revealed that synthetic insecticides alone and botanicals + half dose of synthetic insecticides were equally effective in controlling rice leaf roller and safe to its specific parasites and predators. For other natural enemies, it showed a varying trend. In some cases there was an initial suppression and then recolonization occurred. From this result, it was clear that botanicals + half dose synthetic insecticides were as equally effective as full dose of synthetic insecticides in suppressing the pest and in protecting natural enemies. Hence we can substitute the full dose of synthetic insecticides with combination of botanicals (either NSO three per cent or azadirachtin 0.004 per cent) and half dose of synthetic insecticides (either quinalphos 0.0025 per cent or imidacloprid 0.0025 per cent) for an ecofriendly management of rice leaf roller.
Pests and diseases of stingless bees Trigona iridipennis Smith (Meliponinae: Apidae)
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2015) Jayalekshmi, C R; Premila, K S
Safety of new generation insecticides to bee pollinators
(Department of agricultural entomology, College of agriculture, Vellayani, 2013) Ravi Boli; Premila, K S
The investigation on “Safety of new generation insecticides to bee pollinators” was conducted at the AICRP on Honey bee and Pollinators, Department of Agricultural Entomology, College of Agriculture, Vellayani during 2012- 2013. The objectives were to determine the safety of newer molecules of insecticides to bee pollinators mainly Apis cerana indica F., Apis mellifera L. and Trigona iridipennis Smith. under laboratory and field conditions. New generation insecticides with label claim, suggested for pest management recommended against defoliators and sucking pests in vegetable ecosystems were chosen for the study. The insecticides selected were chlorantraniliprole 18.5 SC @ 30 g a.i. ha-1, flubendiamide 480 SC @ 75 g a.i. ha-1, emamectin benzoate 5 SG @ 10 g a.i. ha-1, spinosad 45 SC @ 75 g a.i. ha-1, indoxacarb 15.8 SC @ 75 g a.i. ha-1, thiodicarb 75 WP @ 750 g a.i. ha-1, fipronil 5 SC @ 50 g a.i. ha-1 and cartap hydrochloride 50 SP @ 500 g a.i. ha-1 (against defoliators). Acetamiprid 20 SP @ 10 g a.i. ha-1, thiacloprid 21.7 SC @ 30 g a.i. ha-1, imidacloprid 17.8 SL @ 20 g a.i. ha-1, clothianidin 50 WDG @ 20 g a.i. ha-1, buprofezin 25 SC @ 250 g a.i. ha-1, acephate 25 SC @ 292 g a.i. ha-1 were chosen (against sucking pests) with dimethoate 30 EC @ 200 g a.i. ha-1 as insecticidal check and untreated check. Laboratory evaluation of the two sets of new generation insecticides showed that chlorantraniliprole 18.5 SC @ 30 g a.i. ha-1, emamectin benzoate 75 g a.i. ha-1 and spinosad 45 SC @ 75 g a.i. ha-1 recorded low mortality of bees ranging from 9.40 to 20.00 per cent and acetamiprid 20 SP @ 10 g a.i. ha-1, imidacloprid 20 g a.i. ha-1 and buprofezin 250 g a.i. ha-1 recorded the per cent mortality ranging between 17.23 and 34.60 per cent. These new generation insecticides along with cartap hydrochloride 50 SP @ 500 g a.i. ha-1 and dimethoate 30 EC @ 200 g a.i. ha-1 were selected for field evaluation in culinary melon (C. melo var. acidulus). Prior to the evaluation of new generation insecticides, the number of flower visitors/ pollinators recorded on culinary melon was found to be 15. Of these, the important groups were hymenoptera (40 per cent), coleoptera (20 per cent), lepidoptera (16 per cent), diptera (16 per cent) and hemiptera (8 per cent). Highest activity of insect pollinators were recorded under pesticide free condition. Maximum foraging activity of bee pollinators was recorded during 10 AM to 11 AM. A. c. indica was the dominant bee pollinator in culinary melon. Foliar application of the selected new generation insecticides done at 10 per cent flowering showed that chlorantraniliprole 18.5 SC @ 30 g a.i. ha-1 and buprofezin 250 g a.i. ha-1 were safe to bee pollinators compared to other insecticides. The foraging activity of bee pollinators observed in terms of their relative abundance and foraging time revealed that there was no significant difference between treatments and untreated check. To conclude, among the new generation insecticides evaluated for their safety to bee pollinators like A. c. indica, A. mellifera and T. iridipennis, chlorantraniliprole 18.5 SC @ 30 g a.i. ha-1 was safe when sprayed against defoliators and buprofezin 25 SC @ 250 g a.i. ha-1 was safe when sprayed against sucking pests of culinary melon (C. melo var. acidulus).