Browsing by Author "Mani Chellappan"

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Antifeedant and growth regulatory activity of Sphagneticola trilobata(L) Pruski on tobacco caterpiller, Spodoptera litura (Fab)(Lepidoptera: noctuidae)
(Department of Agricultural Entomology, College of Agriculture, Vellanikkara, 2021) Rahul Raj, M; Mani Chellappan
One of the most important aspects of agriculture is pest management. Pesticides used in the past produced a variety of environmental problems, including ecological imbalances, soil fertility loss, and marine life degradation. Conventional pesticides have also been linked to a number of significant and detrimental effects on human and animal health, including severe malignancies, neurological diseases, hormone disruptions, and reproductive troubles. Botanical pesticides are found to be an effective alternative to conventional pesticides for pest management. Sphagneticola trilobata (L.) Pruski, is an herb included in the Asteraceae and is well known for its medicinal properties, information about its bioactivity against insects is very less. Hence, in this study we evaluated the antifeedant and growth regulatory activity of various extract of Sphagneticola trilobata against Spodoptera litura. Dried and powdered S. trilobata plant materials were sequentially extracted with hexane and methanol followed by concentrated in vacuo in a rotary evaporator at a lower temperature to obtain crude extracts of S. trilobata. Hexane extracts of aerial parts and roots were named as SP1 and SP3 and methanol extract of aerial parts and roots were named as SP2 and SP4. The yield of methanol extract of aerial parts (5.67% w/w) was higher followed by methanol extract of roots (2.32% w/w), hexane extract of aerial parts (1.96% w/w) and hexane extract of roots (1.23% w/w) The antifeedant activity of various extracts of Sphagneticola trilobata tested in nochoice leaf disc bioassay revealed that methanol extract of aerial parts of S. trilobata had the maximum antifeedant activity of 52.10 per cent at 0.1 per cent of the extract against S. litura after 24h of feeding. Compared to aerial extracts, root extracts were less active against S. litura. At lower concentrations, the antifeedant activity of all the extract were not much prominent and are not statistically significant. The antifeedant activity of all the extract increased in 48h experiment except for 0.1 per cent concentration. The decreasing order of antifeedancy of four extracts was SP2>SP1>SP4>SP3. ii Similar results were recorded in the choice method of bioassay of extracts against S. litura. Maximum antifeedant activity of 46.65 per cent was obtained for methanol extract of aerial parts (SP2) after 24h of feeding. At lowest concentrations of 0.005, 0.01 and 0.03 per cent none of the extracts exhibited significant difference in activity. Increasing concentration beyond 0.03 per cent had a significant effect on antifeedancy in the choice method. As similar to the no-choice method, reduced activity was recorded after 48h of feeding. Maximum antifeedant activity of 38.81 per cent was recorded for SP2 after 48h of feeding. Similar to the no-choice method, root extracts exhibited a low level of activity against S. litura. Insect growth regulatory activity of various extracts was evaluated by diet incorporation method against five-day old larvae of S. litura. A maximum larval weight reduction of 31.4 per cent was recorded for SP4 at 0.1 per cent of the extract. A significant increase in larval duration compared to control was recorded for SP2 extracts at higher concentrations. Similar to larval weight reduction, a dose-dependent pupal weight reduction was recorded for SP1 (29.57 per cent at 0.1 per cent of the extract). Compared to the other three extracts, pupal weight reduction was very less for SP3. Pupal duration increased to a maximum period of 13.54 days at 0.1 per cent of SP4. Observations on abnormal pupae were not significant for any of the extracts. No larval mortality could be obtained with any of the treatments. A maximum of 16.7 per cent larval pupal intermediates was recorded for SP4 at the highest dose, but it was not significantly different from other treatments. Similar to larval mortality, no pupal adult intermediates were recorded for any of the extracts. Maximum pupal mortality of 41.00 per cent was recorded at 0.1 per cent of SP1, and it was significantly different from other treatments. For all the extracts, pupal mortality was dose-dependent. Minimum adult emergence was noticed for SP1 at 0.1 per cent of the extract. GC-MS/MS and LC-MS/MS analysis of active fractions revealed that more phytochemicals are present in aerial parts than roots. The higher activity of aerial parts might be due to the presence bioactive compounds like andrographolide, artemisin, iii genistein and taxifolin. Most of the chemicals identified were derivatives of steroids, terpenoids and flavonoids. The study results indicate that methanol extract of aerial parts of S. trilobata has strong antifeedant activity against S. litura. All other extracts were relatively less active against S. litura. Insect growth regulatory activity was maximum for hexane extract of aerial parts. All the extracts adversely affected the growth and devolvement of S. litura. The absence of larval mortality indicates that all the extracts have less contact toxicity.
Bio efficacy of newer isecticides against leaf hopper, empoasca motti pruthi in bitter gourd
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2003) Karthikeyan, K; Mani Chellappan
Bio efficacy of newer insecticides was evaluated by two field experiments at the College of Horticulture, Vellanikkara during rabi, 2001 and summer, 2002.against major pests of bitter gourd. Imidacloprid (2 g a.i.kg") and acetamiprid (1.5 g a.i.kg") were used as a seed dressers .The newer molecules namely acetamiprid, ethofenprox and imidacloprid were sprayed at different crop stages viz., early vegetative (30 DAS), pre flowering (50 DAS) and fruiting stage (64 DAS) as separate treatments. Acephate was used as a standard check. The present investigation revealed that acetamiprid (1.5 g a. i. kg") was the most effective insecticide as seed dressers against sap feeders viz., leaf hoppers and aphids. Foliar spray application revealed that both imidacloprid (20 g a.i.ha") and acetamiprid (10 g a.i. ha") consistently effective in reducing the sucking pests viz., leaf hopper and aphids followed by ethofenprox (50 g a.i.ha") in both the season. Fruiting stage spray by acetamiprid and imidacloprid had registered the lowest fruitfly infestation .The fruit borer infestation was less in the plots, which received the preflowering and fruiting stage insecticide sprays. The highest yield of bitter gourd was recorded in the imidacloprid (pre flowering stage spray) treated plots in both rabi (1 o 1. 66'fruits/Sm2) and summer (1 02. 66fruits/Sm2) seasons. Seed treatment of newer insecticides had no harmful effect 'on soil micro flora (fungi, bacteria and actinomycetes). Population of natural enemies was unaffected by the insecticide applied along with the seed compared to the foliar applications. Studies on the residues of imidacloprid by high performance liquid chromatography indicated that imidacloprid applied at different stage of the crop viz., sowing, early vegetative, preflowering and fruiting stage to bitter gourd resulted no detectable residue in the harvested fruits.
Biology and insecticide sensitivity of rice white backed planthopper, Sogatella furcifera (Horvath) (Hemiptera:Delphacidae) in Kerala
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2006) Prathibha, P S; Mani Chellappan
Among planthoppers infesting rice, white backed planthopper (WBPH), Sogatella furcifera (Horvath) (Hemiptera: Delphacidae) has become a menace to rice growers recently. Biology of the S. furcifera studied during winter (December) and summer months (March) showed a shorter incubation period and nymphal duration in summer when compared to the winter. The developmental cycle was longer in December. The fecundity of S. furcifera was more during March. But the per cent hatchability was higher in December. However, there was no significant difference in the per cent survival of WBPH over two seasons. The sex ratio exhibited significant difference in two seasons with more number of males during March than that in December. Population build up studied under laboratory condition recorded a reduction in fecundity of WBPH in the second generation. Feeding study conducted by honeydew test revealed that adult females produced more feeding damage than the adult males and any other stages of WBPH. The insect excreted two amino acids (glutamic acid and aspartic acid) along with the honeydew. The important natural enemies recorded were spiders (Argeops sp., Lycosa pseudoannulaata, Oxyopus spp., Thomisus spp. and Salticus spp.) and mirid predator, Cyrtorhinus lividipennis (Reut.). Two entomopathogenic fungi isolated from WBPH were identified as Aspergillus flavus (Dirk.) and Penicillium oxalicum (Currie & Thomb). This is the first report of above mentioned entomopathogenic fungal infection on WBPH. Imidacloprid and lambda cyhalothrin were more toxic to WBPH nymphs and recorded lower LC50 values. Among the tested insecticides, higher relative toxicity (compared to imidacloprid) was exhibited by lambda cyhalothrin. Under laboratory condition, phosphamidon and monocrotophos were more persistent insecticides which persisted for seven days while the DDVP persisted only for three days. There was a slight reduction in total protein content in insecticide treated samples compared to the untreated ones.
Biology and management of cassava mealybug Phenacoccus manihoti Matile -Ferrero (Hemiptera : Pseudococcidae)
(Department of Agricultural Entomology, College of Agriculture, Vellanikkara, 2025-08-29) Jasti Sri Vishnu Murthy; Mani Chellappan
Cassava is one of the most important crops that ensures food security and supports the livelihoods of millions of farmers across tropical and subtropical regions. One of the major threats to the productivity and sustainability of cassava is the cassava mealybug, Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae), a highly destructive, sap-sucking insect capable of causing substantial yield losses under severe infestations. In India, this invasive pest was first reported in 2020 at the Kerala Agricultural University, Vellanikkara campus, Thrissur and currently poses a significant threat to cassava cultivation in India. However, research on its biology, distribution, and management within the Indian context remains limited. The present study aimed to address this gap by investigating the biology, population dynamics, and genetic diversity of P. manihoti, characterizing its endosymbionts, and developing effective management strategies. A preliminary survey was conducted across Kerala on cassava to record the population density of P. manihoti, associated mealybug complex, symptoms, alternative hosts, natural enemies, and ant species associated with P. manihoti. The invasive pest P. manihoti exhibited a sparse, patchy distribution, with epicentres of infestation identified in the districts of Thrissur, Kannur, Kottayam, and Alappuzha. This scattered distribution reflects its limited natural dispersal capacity. During the survey, five mealybug species associated with cassava were identified using both morphological and molecular methods. Damage symptoms on cassava caused by P. manihoti include leaf curling, bunchy top, shortened internodes, and stunted growth. Nine alternative hosts belonging to seven different plant families were identified. Natural enemies associated with P. manihoti colonies included seven species of coccinellid beetles, one lepidopteran predator (Spalgis epius), and five species of spiders. During the study, three entomopathogenic fungal isolates were obtained from P. manihoti cadavers. Additionally, seven ant species were recorded in association with P. manihoti, suggesting potential mutualistic interactions. A survey was conducted at two selected locations, Madakkathara (Thrissur, 2023) and Krishnapuram (Alappuzha, 2024), to study the population dynamics of P. manihoti. In Madakkathara, maximum temperature showed a strong positive correlation with mealybug abundance (r = 0.806, p < 0.01), while minimum relative humidity showed a moderate negative effect (r = -0.478, p < 0.05). In Krishnapuram, maximum and minimum relative humidity, as well as the number of rainy days, exhibited strong negative correlations with mealybug density (r = -0.915 to -0.675, p < 0.01), indicating suppression under humid conditions. Biology studies of P. manihoti reared on the M4 cassava variety revealed that the egg, first, second, and third instar nymphs lasted 6.8, 6.4, 4.6, and 5.3 days, respectively, with the adult stage lasting 20.9 days. The complete life cycle averaged 44.2 days, and with an average of 259 eggs were produced per female. Morphometric measurements indicated progressive increase across stages. The genetic diversity of P. manihoti was analyzed based on mitochondrial cytochrome oxidase I (mtCOI) and the nuclear internal transcribed spacer 1 (ITS1) gene sequences across fourteen populations of Kerala. DNA sequence polymorphism analysis of the mtCOI sequences revealed one segregating site and two haplotypes, with an overall haplotype diversity of 0.143 and a nucleotide diversity of 0.00029, indicating a genetically homogeneous population with minimal variation. In contrast, analysis of the ITS1 region showed moderate genetic variation, with nine haplotypes and 17 segregating sites were identified, resulting in a haplotype diversity of 0.879. Metagenomic DNA from two P. manihoti samples, Thrissur (CMBT) and Kannur (CMBK), was analyzed to profile the gut-associated microbiota. Using Illumina MiSeq sequencing targeting the V3–V4 region of the 16S rRNA gene, a diverse bacterial community was identified. A total of 192 genera were detected in the CMBK sample, while 169 genera were recorded in the CMBT sample. Taxonomic classification based on the Kraken SILVA database revealed Candidatus Tremblaya as the dominant genus, accounting for 97.48 and 99.06 per cent of the bacterial community in CMBK and CMBT, respectively. This study assessed the functional response of Anagyrus lopezi to second and third-instar P. manihoti nymphs at varying host densities. Logistic regression analysis revealed a negative linear and a positive quadratic coefficient of host density (No) on the proportion parasitized (Na/No), which confirmed a Type II functional response. Further, Holling’s disc equation revealed a higher searching rate (a = 0.033 h⁻¹) and shorter handling time (Th = 1.17 h) for third instars when compared to second instars (a = 0.025 h⁻¹; Th = 1.72 h), respectively. Varying densities of A. lopezi (1–8 individuals) were tested against 25 and 100 P. manihoti nymphs. At the higher host density (100 nymphs), per capita searching efficiency declined significantly (from 0.006043 to 0.002454), indicating mutual interference (m = 0.44316). At the lower host density (25 nymphs), searching efficiency remained relatively stable (m = 0.15655), reflecting reduced interference due to limited host availability. The functional response of A. lopezi to varying host densities, along with the effect of different densities of A. lopezi on P. manihoti, significantly influenced the reproductive strategies and foraging efficiency of A. lopezi. The efficacy of various treatments against P. manihoti, viz., entomopathogenic fungi (Purpureocillium lilacinum, Lecanicillium lecanii @ 1×108 spores ml-1), horticultural mineral oil (HMO @ 2%), botanicals (neem oil and karanj oil @ 2%), insecticidal soap combined with eco-neem plus (@ 2%) were evaluated along with the biological control agent, Anagyrus lopezi De Santis (Hymenoptera: Encyrtidae) and an untreated control. Under polyhouse conditions, A. lopezi achieved the highest suppression (69.36%), followed by insecticidal soap combined with eco-neem plus (55.85%), neem oil (50.34%), karanj oil (49.57%), P. lilacinum (46.35%), L. lecanii (42.35%), and HMO (40.88%). A subsequent field trial with two applications at 15 day intervals showed insecticidal soap + eco-neem plus as the most effective (94.33% reduction), followed by karanj oil (92.68%), neem oil (92.26%), HMO (82.13%), P. lilacinum (75.46%), A. lopezi (75.39%), and L. lecanii (62.06%). The integration of fast-acting botanical treatments with the sustained efficacy of biological control agents, notably A. lopezi and P. lilacinum, provides a balanced and ecologically sustainable management strategy. This study provided comprehensive insights into the distribution, biology, endosymbionts, genetic diversity, and management of P. manihoti. Field surveys across Kerala revealed a patchy distribution of P. manihoti with localized infestations and association with multiple mealybug species, natural enemies, and mutualistic ants. Population dynamics showed that high humidity and rainfall play a significant role in suppressing infestations. Genetic analysis of P. manihoti populations across Kerala revealed low diversity in the mtCOI gene but high variability in the ITS1 region, indicating differential evolutionary patterns within these markers. Metagenomic profiling confirmed Ca. Tremblaya as the dominant endosymbiont in P. manihoti, highlighting its key role in the host’s microbiome. Field trials demonstrated that insecticidal soap with eco-neem plus, neem oil, and karanj oil were effective for short term suppression. However, the incorporation of A. lopezi as a principal component of the biological control strategy in this study underscores its critical role in the sustainable management of P. manihoti. Together, these findings laid a strong foundation for developing integrated, eco-friendly, and sustainable management strategies for P. manihoti in India.
Characterization of Bemisia tabaci (Gennadius) (hemiptera: aleyrodidae), for genetic variability, endosymbionts and vector-virus interactions in cassava
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2018) Harish, E R; Mani Chellappan
Cassava is one of the important tuber crops cultivated all over the World. Cassava Mosaic Disease (CMD) is the most important limiting factor in its production. Silverleaf whitefly, Bemisia tabaci (Gennadius) is the vector responsible for the transmission of Cassava mosaic virus in cassava, which causes CMD. Genetic variation among the members of B. tabaci, makes them very difficult to manage. Endosymbionts present in the whitefly system could be a factor responsible for making them a successful sucking pest. There are various kinds of interactions existing between whitefly and the CMV. Studying these interactions precisely will help to understand the behavioural and physiological variations in whiteflies. In this background the present study, “Characterization of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), for genetic variability, endosymbionts and vector-virus interactions in cassava” was proposed and carried out at the Department of Agricultural Entomology, College of Horticulture, Vellanikkara, during Mrch 2014 to April 2016, with the objectives to analyse the genetic variability in cassava whitefly, characterization of its endosymbionts and elucidation of cassava whitefly - cassava mosaic virus interactions. Various life stages of B. tabaci were collected from different cassava growing agro ecological zones of Kerala and reared in laboratory as well as in polyhouse at optimum conditions. Genetic variability study was conducted with 10 selected ISSR primers which had shown polymorphism in their banding pattern; with amplicon size ranged between 200bp to 2900bp. Phylogenetic analysis using NTsys software revealed the presence of two major clusters with Sultan Bathery population as out group. Similarity matrix had shown up to 49 per cent variation between the samples. Polymerase chain reaction using mitochondrial cytochrome oxidase1 primers, C1-J2195 and L2-N-3014 had given amplicon of 850bp. Nucleotide sequences had shown variation up to 16.5 per cent and dendrogram generated out of the sequences using MEGA-6 (Neighbor Joining Method) gave two clusters and one out group. Sequence similarity check using reference sequences from NCBI data base indicated the presence of two biotypes, AsiaI and AsiaII5 in cassava plants of Kerala. Morphometric studies were conducted to assess the variations in different pupal and adult characters of thirteen whitefly populations. Significant variations were found in pupal length and pupal width of the biotypes. Pupal length varied between 0.746 mm to 0.668 mm and pupal width varied between 0.539 mm to 0.468 mm in female pupa. Out of 14 characters of pupa studied, variations in length and width were found to be significant. Among seven characters of adults studied, variations in wing, antennal length, body length and width were significant. AsiaI biotype was found to have lesser body length, but more width compared to AsiaII5. AsiaII5 was found to be an important biotype of B. tabaci infesting cassava in 12 out of the 13 locations surveyed. Endosymbiont characterization from whitefly using Next Generation Sequencing (NGS) - Illumina platform revealed the variations in microbiota. At phylum level, Proteobacteria was found at 87.57 per cent in whitefly populations collected from plains. The populations from high ranges contained Firmicutes at 82.67 per cent. Arsenophonus, an ‘indirect helper’ for virus spread by protecting viral coat protein from degradation in insect system with their GroEL chaperones were found at 24. 69 per cent in B. tabaci populations collected from plains. Behavioural and life cycle variation study of B. tabaci using six cassava genotypes had shown that virus infection in B. tabaci altered the dispersal and settling. Speed of movement observed to be maximum at 16.25 cm/s in non- virulent female whiteflies on the genotype CMR-9. Life cycle of virulent and non-virulent whiteflies was found to vary between 19.57 days to 30.77 days. A thorough understanding of genetic variations, endosymbiont diversity and behavioural response to virus could help the researchers in planning proper management strategies for B. tabaci. In future, information generated of such kinds could also help the researchers and policy makers to foresee and manage any possible outbreak of the pest and avoid any havoc caused by them.
Characterization of microbiota associated with stingless bee Tetragonula travancorica Shanas and Faseeh(Hymenoptera:Apidae:Meliponinae) and its pollen
(Department of Agricultural Entomology, College of Agriculture,Vellanikkara, 2024-09-12) Bindu,G R.; Mani Chellappan
Stingless bees are small to medium-sized eusocial insects belonging to the tribe Meliponini (Hymenoptera: Apidae). They are one of the potential pollinators in the tropics and adapted to varied climatic conditions than other pollinators such as honey bees and bumble bees. There are over 600 species of stingless bees worldwide, with India recording three genera viz., Tetragonula Moure, Lisotrigona Moure, and Lepidotrigona Schwarz. Tetragonula is the most complex and widely distributed genus with more than 30 and 17 species worldwide and in India, respectively. A new species was discovered in Kerala, Tetragonula travancorica Shanas and Faseeh, and found to be the widespread species of stingless bee in peninsular India. Stingless bees and their products host symbiotic microbes, which play a prominent role in metabolism, hormonal signaling, behaviour, gut physio-chemical conditions, growth and development, protection against pathogens, and the immune response of bees. However, the microbial communities associated with stingless bees and their pollen remain poorly understood. Hence, the present research programme was proposed to study the pollen sources, and microbiota associated with stingless bees, hive-stored pollen, and flower pollen. A survey was carried out to collect stingless bees (T. travancorica) and their hive-stored pollen from all districts of Kerala for palynological and microbial diversity analysis. Palynological studies conducted through light microscopy and scanning electron microscopy revealed the presence of 102 pollen types from 38 plant families. Eight predominant pollen types were found across Kerala, viz., Mimosa pudica, Mangifera indica, Coffea arabica, Bauhinia purpurea, Alternanthera sessilis, Pennisetum polystachion, Artocarpus heterophyllus, and Cocos nucifera. The hivestored pollen analysis of stingless bee T. travancorica recorded the highest number of pollen types from the family Fabaceae (14) followed by Asteraceae (9) and Euphorbiaceae (6). The maximum pollen types belonged to the trees followed by weeds, ornamentals, and horticultural crops. Absolute pollen count was the highest in Kannur district (11,01,000 pollen grains/mL) and lowest in Idukki district (1,28,500 pollen grains/mL). The microbial diversity analysis of hive-stored pollen revealed the presence of bacteria and fungi, whereas, yeast and actinomycetes were not detected across Kerala. A total of 24 bacterial and 20 fungal isolates were identified in the hive-stored pollen and their morphological, and cultural characteristics were recorded. Among them, distinct bacterial isolates were subjected to biochemical characterization, which revealed that all bacterial isolates showed positive for the catalase test, while six isolates were positive for the oxidase test. All the isolates except one isolate were negative for the methyl red test and five isolates were positive for the Voges Proskauer test. Seven isolates showed positive reactions for sucrose and fructose fermentation, which helps in identifying bacterial isolates. Molecular characterization of bacterial isolates revealed that Bacillus spp., B. cereus, B. acanthi, B. velezensis, B. subtilis, B. megaterium, Priesta aryabhattai, Pseudomonas spp., P. aeruginosa, Klebsiella pneumonia, and Acinetobacter spp., were recorded in the hive-stored pollen of stingless bee. Fungal isolates viz., Aspergillus flavus, A. aculeatus, Penicillium spp., and P. chrysogenum were identified in the hive-stored pollen of stingless bees. The microbial load to pollen grain ratio was highest in Idukki (1:30.5) and lowest in Kollam (1:25750). The highest total bacterial and fungal population was observed in Idukki (4160 cfu g-1 of pollen), Pathanamthitta, and Thrissur (90 cfu g-1 of pollen). The lowest bacterial and fungal population was recorded in Kollam and Alappuzha (10 cfu g-1 of pollen), respectively. The predominant pollen and secondary pollen obtained from the various districts of Kerala were selected to study flower microbial diversity. The microbial analysis of flower pollen revealed the presence of bacteria and fungi, whereas yeast and actinomycetes were not detected in the flower pollen. A total of 19 bacterial and 21 fungal isolates were recorded in the flower pollen and identified with morphological and cultural characteristics. Biochemical tests revealed that all the isolates were catalase-positive and four being oxidase-positive. Six bacterial isolates tested positive for the methyl red test, while five were positive for the Voges- Proskauer test. Eight isolates showed sucrose utilization, indicated by a color change from red to yellow without air bubbles in the durum tube. Molecular characterization of the bacterial isolates revealed that Priesta aryabhattai, Bacillus megaterium, B. safensis, B. pumilis, Pseudomonas aeruginosa, Pantoea spp., P. dispersa, and Serratia marcescens were present in the flower pollen. Similarly, molecular characterization of fungal isolates revealed that Penicillium spp., P. chrysogenum, P. citrinum, Curvularia warraberensis, C. clavata, Aspergillus spp., A. niger, A. aculeatus, A. flavus, Pestalotiopsis spp., Fusarium incarnatum, and Mucor irregularis were present in the flower pollen. The microbial load-to-pollen grain ratio was highest for Pennisetum polystachion (1: 0.84), and the lowest ratio for Mimosa pudica flower pollen(1:8.8), Alternanthera sessilis had the highest total bacterial population (63,000 cfu g-1 of pollen), while Mimosa pudica had the lowest (5000 cfu g-1 of pollen). Similarly, Areca catechu had the highest total fungal population (90 cfu g-1 of pollen), while Pennisetum polystachion had the lowest (30 cfu g-1 of pollen). The gut microbiota of stingless bees, T. travancorica, and their hive-stored pollen were investigated and compared through metagenomic analysis under a nextgeneration sequencing platform. The sequence analysis revealed that Lactobacillus (41.57 %) was the dominant symbiont in the gut of T. travancorica, while Bacillus (28.11 %) was the predominant genus in the pollen of T. travancorica. Similarly, the fungal symbionts associated with the gut of T. travancorica revealed that Rhodosporidiobolus (15.46 %) was the dominant fungal symbiont in the gut, while Saccharomycopsis (27.67 %) was dominant in the pollen. Characterization of the microbiota associated with the stingless bees and their pollen unveils the complex relationship between bees and their microbial symbionts. Bee and its products are potential sources of beneficial microorganisms that have wide applications in various fields. The specific microbiota associated with the bees helps to enhance beekeeping practices, reducing colony losses and aiding in the conservation of these crucial pollinators. Harnessing these bees and their symbionts has an immense scope in agriculture, food, and probiotic industries
Characterization of proteins and trehalose as heat shock regulators in insect system
(Centre for Plant Biotechnology and Molecular Biology, College of Horticulture, Vellanikkara, 2008) Swetaleena Tripathy; Mani Chellappan
Diversity and ecology of the blue banded bees, Amegilla spp (Hymenoptera:Apidae)
(Department of Agricultural Entomology, College of Agriculture , Vellanikkara, 2024-01-11) Thanu, C N.; Mani Chellappan
Insects play a crucial role in pollination with around 75 per cent of crop plants relying on insects, especially bees. However, due to the prevalent use of managed bee pollinators, the significance of wild pollinator’s service in agriculture is often unnoticed. Wild bees play a crucial role in delivering essential pollination services to wild plants and crops in agricultural ecosystems. Among wild bees, the blue banded bees, Amegilla spp. have been identified as an effective pollinator of various horticultural crops such as capsicum, tomato, and brinjal. In Kerala, studies on the blue banded bees are scanty. Therefore, this study was undertaken to explore the diversity, palynology, nesting architecture and behaviour of blue banded bees. Purposive surveys were conducted to collect the blue banded bees in central and northern districts of Kerala viz., Thrissur and Wayanad, respectively. Morphological and molecular characterization of the collected specimens revealed nine species of blue banded bees namely, Amegilla calceifera, A. zonata, A. cingulata, A. cingulifera, A. dizona, Amegilla (Zonamegilla) sp., Amegilla sp.1, Amegilla sp.2, and Amegilla sp.3. Palynological studies of pollen loads collected from Thrissur and Wayanad districts revealed the presence of 12 pollen types under eight plant families and eight pollen types under six plant families, respectively. Floral hosts of the family Fabaceae were the most preferred pollen source for the blue banded bees in both the districts. Melastoma malabathricum, Solanum melongena, and Ocimum sp. were the predominant pollen types in Thrissur and Mimosa pudica was the predominant pollen type in Wayanad. Natural nesting locations of blue banded bees were identified in inaccessible places. Female bees were found digging soil under stones, near shaded areas and at the base of buildings in search of suitable nesting sites. Blue banded bees did not form nests in the artificial nesting sites provided with various nesting substrates viz., red soil, laterite soil, potting mixture and clay soil. During summer months, foraging bout started at around 6.15 am and continued until 6.35 pm. The peak foraging activity of bees was observed from 10.00 to 11.00 am. In partly cloudy to sunny weather, foraging was observed when the temperature ranged between 280C and 350C. However, the foraging period ranged between 6.50 am and 6.10 pm during the rainy season. The number of bees visited on Asystasia gangetica from 10.00 to 11.00 am was significantly higher (15.38) than all other hosts on all different timings and the lowest was on M. malabathricum (1.74) from 4.00 to 5.00 pm. The number of flowers visited by the bees were statistically highest (28.16) on Duranta plumieri from 10.00 to 11.00 am and the least number of visits was on M. malabathricum from 4.00 to 5.00 pm (4.64). Significantly more time per flower spent by the bees on M. malabathricum (12.01 sec) between 10.00 to 11.00 am and the minimum time was spent on D. plumieri flowers from 2.00 to 3.00 pm as well as 4.00 to 5.00 pm. Fourty six host plants under 25 different families were identified as the floral resources for blue banded bees. They preferred to forage mostly on the plant species of family Lamiaceae, Verbenaceae, Acanthaceae, Rubiaceae and Bignonaceae; bees were found attracted more to white flowers, followed by purple-coloured flowers. Male biased and intraspecific sleeping cluster of A. zonata was found on the dried twig of Alternanthera sp. in Thrissur. Isolated roosting of A. zonata female was also seen on the dried stem of Panicum sp. In Wayanad, two male biased and interspecific sleeping clusters composed of two species viz., A. zonata and A. calceifera were found on Emilia sonchifolia. The time of sleeping cluster formation was between 6.12 to 6.58 pm and the departure time in the morning was between 6.02 am and 6.25 am. The number of bees forming the cluster varied every day. Understanding the mutualistic relation between crops and pollinator species is essential. Their spatial and temporal fluctuations, foraging habits and effectiveness in pollination are the factors influencing the success of pollination. Currently, there is very less studies regarding the involvement of wild pollinators in the pollination of crops. The genus Amegilla serves as an example, highlighting the presence of potential pollinators of agricultural crops. Additional research to explore the potential of Amegilla as a viable and significant pollinator within agricultural systems is crucial.
Eco-friendly management of pineapple mealybug, Dysmicoccus brevipes (Cockerell) (Hemiptera: Pseudococcidae)
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2016) Manjushree, G; Mani Chellappan
Pineapple mealybug (Dysmicoccus brevipes) causes severe damage to pineapple crop in Kerala. Apart from the direct damage and it also transmits Pineapple Mealybug Wilt Disease (PMWD). This is a polyphagous pest and its host includes banana, coffee, citrus, palm, sugarcane etc. Use of broad spectrum synthetic insecticides to manage the mealybug has been restricted owing to the residual problem in the fruit and other environmental concerns.
Identification of larval morphotypes of helicoverpa armigera (Hiibner) (Lepidoptera: noctuidae) and their characterization using molecular markers
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2015) Ranjith, M T; Mani Chellappan
Infestation induced reactions of papaya mealybug, Paracoccus marginatus Williams and Granara de willink, (Hemiptera : Pseudococcidae) on papaya and amaranthus
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2013) Jimcymaria, T; Mani Chellappan
Insecticide tolerance in stingless bee, Tetragonula iridipennis Smith(Hymenoptera: Apidae: Meliponini)
(Department of Agricultural Entomology, College of Agriculture ,Vellanikkara, 2023-12-08) Vineetha, V.; Mani Chellappan
Bees are the most ecologically and economically important group of insects. Many cross-pollinated crops rely on bees for pollination services. Among the bees, stingless bees (Apidae: Meliponini) form the largest group with over 50 genera and more than 505 known species. Stingless bees play a prominent role in the pollination of many food crops. They are recognized as viable pollinators in cucurbits due to their remarkable biological traits that make them suitable for supervised pollination. Stingless bees regularly visit a wide range of flowering crops and often encounter various agrochemicals while foraging in agro-ecosystems. Continuous exposure to insecticides in crop ecosystems can lead to insecticide tolerance in bee populations, much like in pestiferous insects. However, the different mechanisms underlying pesticide detoxification in stingless bees have gained little attention so far. In this context, the present study was undertaken with the objectives of assessing the toxicity of different insecticides to stingless bees, detecting insecticide residues in pollen, determining the activity of metabolic enzymes and investigating the role of gut endosymbionts in insecticide detoxification. Purposive surveys were carried out to document the information on insecticide use in cucurbits from four districts of Kerala viz., Malappuram, Palakkad, Thrissur and Ernakulam. Survey among 120 farmers in four districts recorded the use of 26 different insecticides in cucurbits on an average of 5 to 7 sprays per season at an interval of 12 to 15 days. Based on the survey, the most widely used insecticides viz., chlorantraniliprole, thiamethoxam, malathion, flubendiamide and dimethoate were selected for further toxicological bioassays. Toxicological assays were carried out in two populations of stingless bees collected from a feral colony and an agro-ecosystem using a new protocol standardized as part of the study. The results of bioassay showed that stingless bees from the feral colony had low toxicity to chlorantraniliprole (LC50 of 12.53 ppm) followed by flubendiamide (11.50 ppm), dimethoate (5.28 ppm), malathion (1.20 ppm) and thiamethoxam (0.37 ppm). In comparison, the insecticide flubendiamide was least toxic (LC50 of 20.58 ppm) to stingless bees from the agro-ecosystem followed by chlorantraniliprole (15.59 ppm), dimethoate (9.52 ppm), malathion (4.02 ppm) and thiamethoxam (0.78 ppm). A field experiment was conducted to investigate the presence of insecticide residues in bee pollen by raising bitter gourd plants and fixing stingless bee hives in each treatment plot. Insecticides were sprayed onto the treatment plots and bee pollen samples were collected for residue analysis. The LCMS/ MS and GC analysis of pollen samples detected residues of fipronil and chlorantraniliprole at concentrations of 0.596 mg/kg and 0.108 mg/kg, respectively. The biochemical analyses of stingless bees collected from different treatment plots on 0, 1, 3, 5 and 7 days after spraying insecticides revealed that the total protein content in stingless bees ranged between 2.307 mg/ml for bees in the control plot and 2.565 mg/ml in bees from the dimethoate-treated plot. Highest protein concentration was observed on the third day after treatment application. The highest activity of the detoxifying enzyme, carboxyl esterase was observed in bees collected from the dimethoate-treated plot (83.024 μMol min-1 mg protein-1) and the least in bees from the control plot (26.599 μMol min-1 mg protein-1). The production of carboxyl esterase was found to be highest on the 5th day after spraying. The treatment-wise comparison of the detoxifying enzyme, cytochrome P450 in stingless bees revealed that the enzyme activity was significantly higher in bees collected from chlorantraniliprole treated plot (383.960 pMol min-1 mg protein-1) compared to the control (4.926 pMol min-1 mg protein-1). The cytochrome level was significantly higher on 3rd day after spraying of insecticides. Higher glutathione Stransferase (GST) was induced in bees when sprayed with dimethoate (382.206 μMol min-1 mg protein-1), whereas the level of GST in bees in the control plot was very low (3.164 μMol min-1 mg protein-1). The highest GST activity was observed one day after treatment application which differed noticeably among other days. Investigation and comparison of the gut microbiota of stingless bees collected from the forest and agro-ecosystem were done through metagenomic DNA isolation and next-generation sequencing (NGS) technology. The metagenomic sequencing results showed the presence of 103763 microbes belonging to 123 species and 41080 microbes from 272 species in the gut of stingless bees from the forest and agricultural ecosystems respectively. The predominant microbial species recorded in the bee gut of forest ecosystem was Klebsiella sp. (70.26 %) and in agro-ecosystem was Pantoea agglomerans (84.68 %), which are reported to be involved in insecticide degradation followed by chlorantraniliprole (15.59 ppm), dimethoate (9.52 ppm), malathion (4.02 ppm) and thiamethoxam (0.78 ppm). A field experiment was conducted to investigate the presence of insecticide residues in bee pollen by raising bitter gourd plants and fixing stingless bee hives in each treatment plot. Insecticides were sprayed onto the treatment plots and bee pollen samples were collected for residue analysis. The LCMS/ MS and GC analysis of pollen samples detected residues of fipronil and chlorantraniliprole at concentrations of 0.596 mg/kg and 0.108 mg/kg, respectively. The biochemical analyses of stingless bees collected from different treatment plots on 0, 1, 3, 5 and 7 days after spraying insecticides revealed that the total protein content in stingless bees ranged between 2.307 mg/ml for bees in the control plot and 2.565 mg/ml in bees from the dimethoate-treated plot. Highest protein concentration was observed on the third day after treatment application. The highest activity of the detoxifying enzyme, carboxyl esterase was observed in bees collected from the dimethoate-treated plot (83.024 μMol min-1 mg protein-1) and the least in bees from the control plot (26.599 μMol min-1 mg protein-1). The production of carboxyl esterase was found to be highest on the 5th day after spraying. The treatment-wise comparison of the detoxifying enzyme, cytochrome P450 in stingless bees revealed that the enzyme activity was significantly higher in bees collected from chlorantraniliprole treated plot (383.960 pMol min-1 mg protein-1) compared to the control (4.926 pMol min-1 mg protein-1). The cytochrome level was significantly higher on 3rd day after spraying of insecticides. Higher glutathione Stransferase (GST) was induced in bees when sprayed with dimethoate (382.206 μMol min-1 mg protein-1), whereas the level of GST in bees in the control plot was very low (3.164 μMol min-1 mg protein-1). The highest GST activity was observed one day after treatment application which differed noticeably among other days. Investigation and comparison of the gut microbiota of stingless bees collected from the forest and agro-ecosystem were done through metagenomic DNA isolation and next-generation sequencing (NGS) technology. The metagenomic sequencing results showed the presence of 103763 microbes belonging to 123 species and 41080 microbes from 272 species in the gut of stingless bees from the forest and agricultural ecosystems respectively. The predominant microbial species recorded in the bee gut of forest ecosystem was Klebsiella sp. (70.26 %) and in agro-ecosystem was Pantoea agglomerans (84.68 %), which are reported to be involved in insecticide degradation
Microbial diversity in hive-stored pollen of indian honey bee, Apis cerana indica (Fabricius)
(Department of Agricultural Entomology, College of Agriculture, Vellanikkara, 2021) Abhishek, V; Mani Chellappan
Honey bees are eusocial flying insects. Among all insects that pollinate, honeybees are considered to be one of the crucial pollinators. Honey bees represent only a small fraction of the roughly 20,000 known species of bees. Honey bees obtain all of their nutritional requirements from a diverse combination of pollen and nectar. Pollen grains referred to as 'bee bread' or 'bee meat' are the natural sources of proteins, vitamins, fats, lipids and minerals, of which proteins are very much essential for building the body tissues of the bees, especially during the early embryonic growth. Worker bees of Apis cerana indica help in the fermentation of pollen which releases additional nutrients that are used in the production of antibiotics and fatty acids which inhibit spoilage. Pollen analysis of samples provides the information regarding the plants preferred by bees for nectar, as the pollen grains dispersed are mostly collected by bees along with nectar. Honey has two sources of contamination, primary one being the hive stored pollen. Thus, it is very essential to study the microbial diversity of pollen, which may lead to spoilage of pollen and nectar. The present investigation on “Microbial diversity in hive-stored pollen of Indian honey bee, Apis cerana indica (Fabricius)” was conducted at Department of Agricultural Entomology, College of Agriculture, Vellanikkara, Kerala Agricultural University during 2020-2021 in order to study the diversity of hive-stored pollen and associated microbes in A. cerana indica (Fabricius) colonies. Purposive surveys were conducted in six locations at Palakkad and Wayanad district viz., Mannarkkad, Nellipuzha, Nottaamala, Kenichira, Kayakunnu and Cheengode. Hive stored pollen collected were maintained in refrigerated conditions after assigning unique accession numbers as PKD-1, PKD-2, PKD-3, WYD-1, WYD2, WYD-3. Microbial diversity, microbial load of hive stored pollen, identification and characterization of pollen with respect to its nature, size, shape, aperture, exine pattern along with physicochemical properties viz., moisture content, water activity, pH, ash content, total acidity and protein content were studied. Palynological identification plays a crucial role in beekeeping industry. Pollen aids as a food supplement to honeybees for their growth and development. It assists in the identification of geographical and botanical origin of pollen. A total of 21 plants were recorded as pollen sources by bees from the study area (six locations) of two districts. Ten pollen types were identified based on its nature, size, shape, aperture, exine pattern using PalDAT software. Identified plant species were Sphagneticola trilobata (Asteraceae), Caesalpinia pulcherrima (Fabaceae), Zinnia elegans (Asteraceae), Ocimum sanctum (Lamiaceae), Clitoria ternatea (Fabaceae), Biophytum sensitivum (Oxalidaceae), Bauhinia acuminata (Fabaceae), Mimosa pudica (Fabaceae), Tecoma stans (Bignoniaceae), Portulaca grandiflora (Portulacaceae). Characterization of pollen revealed that ten plant species belonging to seven families serve as pollen sources in respective survey locations. Physicochemical properties of hive stored pollen of A. cerana indica collected from six locations were investigated by estimating the moisture content, water activity, pH values, ash content, total acidity and protein content. Moisture content varied from 15.29-15.38 (g/100g). Water activity varied from 0.73 to 0.74 (aw) and the pH varied between 3.77 and 3.83. Ash content varied from 1.87-2.01 (g/100g). Total acidity varied from 9.64-10.13 (mmol/g). Protein content varied from 3.46-3.69 (%). Parameters like moisture content, water activity, protein content were more in the Wayanad sample, it may be because of high humidity and temperature variations. Parameters like pH, total acidity and ash content were more in Palakkad sample, which infers that mineral content might be more. Microbial diversity of hive stored pollen of Apis cerana indica collected from six locations was investigated by identifying the microbes through their morphological, cultural, molecular characterization. Other parameters like microbial diversity, microbial load, microbial load to pollen grain ratio, microbial population were also observed. In total, four bacteria and three fungal species were identified. However, colonies of actinomycetes and yeast were not obtained. Out of four bacteria, B2, B3, B4 – gram positive while B1- gram negative. The shape of all bacterial isolates was rod with change in their colony colour.16s rRNA sequencing of bacterial isolates revealed that B1 as Pseudomonas aeruginosa, B2 as Bacillus megaterium, B3 as Bacillus aryabhattai and B4 as Bacillus megaterium respectively. Out of the three fungi, colony colour of T1 colony colour was green, W1 colony colour was white and A1 colony colour was orange. All isolates have flat elevation with an entire margin. ITS sequencing of fungal isolates revealed that T1 as Trichoderma reesei, W1 as Westerdykella multispora and A1 as Neurospora crassa. Microbial diversity was more in sample collected Wayanad with two fungal and two bacterial colonies whereas, one fungal and two bacterial colonies in sample collected from Palakkad. Microbial load was more in samples from Wayanad (6.6x104 cfu/g) when compared with Palakkad sample (3.3x104 cfu/g). Comparison of microbial load to pollen grain ratio revealed that Wayanad sample recorded highest with 6.6x104 cfu/g to Palakkad sample with 3.3x104 cfu/g. Bacterial and fungal populations were observed more in Wayanad sample when compared to Palakkad sample. The study recorded the pollen sources of different localities in and around the Palakkad and Wayanad districts of Kerala. Moisture content plays a significant role which might be the reason for high microbial diversity and microbial load in Wayanad. The present study demands the investigations of other physicochemical properties like EC, starch content, amino acid composition, microbial spores present in pollen which could be useful for the food preservation industry or potentially hazardous in due course of time.
Pollination ecology of solitary pollen bees
(Department of Agriculture Entomology, College of Agriculture, Vellanikkara, 2023-04-24) Anusree Padmanabhan P S.; Mani Chellappan
Bees are often considered to be effective pollinators in both agricultural and natural ecosystems. The recent declines in feral and domesticated social bee populations have raised serious concerns about their impact on the productivity of ecosystems and this urges the need to explore potential alternate bee pollinators for the future. There are 20,000 known species of bees in seven recognised biological families and more than 90 per cent of them are solitary. Unlike social bees, solitary pollen bees establish and provision nests on their own with no assistance from other individuals. Solitary bees play an immensely important role in the pollination of crop plants as well as wild plants. In India, little attempt has been made in documenting solitary bee species. This study was therefore undertaken to document the diversity of solitary pollen bees in selected cucurbitaceous ecosystems with a major emphasis on determining their peak foraging time, nesting preferences, palynology, and the effect of plant protection practices on pollination.
Population dynamics, biology and management of mealybug, phenacoccus solenopsis tinsley (Hemiptera: pseudococcidae) on okra
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2017) Anusree Padmanabhan, P S; Mani Chellappan