Theses

Browse

Search Results

Now showing 1 - 9 of 15

Open Access
Diversity of predatory mite fauna in vegetable ecosystem
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2015) Maheswary, J; KAU; 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.
Open Access
Management of pests of cowpea using red ant, oecophylla smaragdina (fab.)
(Department of agricultural entomology, College of agriculture, Padannakkad, 2015) Amida, Saparya; KAU; Sreekumar, K M
The experiment entitled “Management of pests of cowpea using red ant, Oecophylla smaragdina (Fab.)” was undertaken at the College of Agriculture, Padannakkad during the period from March 2014 to June 2015. The seasonal variation in population of red ant was measured by counting the number of live nests over one year and the ant activity was measured during 3 seasons for a period of 30 days in each. The interaction was measured by colonizing red ant on plants dominated by other ants. The effect of food provisioning was studied by counting the live nests constructed on host plants provided with and without artificial food. The experiment on the eradication of competitive ants was done on cashew and cowpea. Pest management efficacy and impact of commonly used pesticides on red ant were also studied. In the study on seasonal variation in red ant population, it was observed that there was a general tendency of decrease in the number of nests during monsoon period. The mean ant activity, temperature and relative humidity in each season show that relation between ant activity and temperature was positively correlated. The ant activity was found less during morning hours when temperature was less. The interaction between O. smaragdina and Tetraponera nigra and Paratrchina longicornis was found submissive and they coexist. The yellow crazy ant Anoplolepis gracileps was found dominant over O. smaragdina and severely affected red ant colony establishment. On an average, the number of nests on cashew trees provisioned with food increased 10 times where as it was only 1.35 times when food was not provided over a period of 33 days. In the competitive ant eradication experiment, Azadirachtin 0.1 % sprayed on the entire crop was observed as best on cashew and DDVP 76 EC @ 0.076 % sprayed on entire crop in cowpea. In the pest management efficacy study, maximum number of pods and leaves were attacked by aphids in control and red ant harboured plants and POP treated plants were on par. The result on yield parameters shows that there is no significant difference between the treatments in the case of pod number and pod length. Fresh weights of the pods were significantly low in control but POP treated and red ant colonized plants were on par. In the study on the impact of pesticides on red ant, DDVP 0.076 % treatment most adversely affected the red ant nest building and activity followed by Azadirachtin 0.03 % and Bordeaux mixture 1 % and least by Tobacco decoction 2.5 %
Open Access
Taxonomic studies on indian belonnotus (coleoptera: curculionidae: ceutorhynchinae)
(Department of agricultural entomology, College of agriculture, Padannakkad, 2015) Shruthi, C; KAU; Ramesha, B
The study entitled “Taxonomic studies on Indian Belonnotus (Coleoptera: Curculionidae: Ceutorhynchinae)” was undertaken in the Department of Entomology, College of Agriculture, Padannakkad during 2013-2015. The members of the tribe Mecysmoderini of the subfamily Ceutorhynchinae are one of the very large, diversely represented group of weevils in India, compared to other geographical regions of the world. Amongst the diverse genera representing of this tribe in India, genera Belonnotus and Mecysmoderes are important as it is distributed in Oriental region. A total of eighteen species are reported worldwide, out of which ten species are known from India in genus Belonnotus, whereas 26 species are known to be reported from worldwide in genus Mecysmoderes, of which five are known from India. Some of these species are major pests on economically important crops such as cucurbitaceous and cruciferous vegetables, as they cause pitting on the leaves and fruits. Some ceutorhynchine species feed on weeds and therefore are considered as biological control agents. The only substantial work on these weevil groups had come from Pajni and Kohli (1982). The available information is limited and lacking in essential diagnostics especially genitalia and morphometric observations. Hence, the present study was undertaken with objectives of survey and collection, study of morphological characters, redescription of species and formulation of taxonomic keys for the identification of the species. The present study was based on the collections from Malabar Insect Repository, College of Agriculture, Kerala Agricultural University, Padannakkad, Kerala and the specimens loaned from National Pusa Collection, Indian Agricultural Research Institute, New Delhi. Collections were also made through surveys from different parts of Kerala and Karnataka. The study constitutes five species belonging to two genera. All the species known so far under genera Belonnotus and Mecysmoderes have been taxonomically described. The descriptions of all the species studied are supplemented with taxonomic characters of genitalia and morphometric observations. An annotated checklist of the world Ceutorhynchinae had been prepared and these covered a total of 1316 species in worldwide distributed under 90 genera while the number of species reported from India is 45 distributed under 5 tribe and 13 genera. The geographic distribution of these species had been documented by taking up to date literature. The discrepancies in the description of the genera and species had been corrected and descriptions standardized to a uniform format loaded with morphometric ratios. Taxonomic keys to the species of all these two genera have been formulated and augmented with valid characters. Thus the present study fulfills to bridge a glaring lacuna of knowledge on these weevils and to keep its taxonomy on International standards.
Open Access
Nematode association in cabbage, brassics oleracea L. var. capitata and its management using botanicals
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2015) Annie, P Varghese; KAU; Nisha, M S
An investigation entitled „Nematode association in cabbage, Brassica oleracea L. var. capitata and its management using botanicals‟ was carried out at College of Agriculture, Vellayani during 2012-2014 with an objective to study the nematode fauna in rhizosphere of cabbage and to evolve an eco-friendly management strategy using plant products. A survey was conducted in major cabbage growing tracts of the state viz., Idukki, Kollam and Thiruvananthapuram districts. Result of the survey revealed the presence of Meloidogyne incognita (Kofoid & White) Chitwood., Rotylenchulus reniformis Linford and Oliveira, Helicotylenchus sp., Tylenchorhynchus sp., Radopholus similis (Cobb) Thorne and Xiphinema sp. The population of M. incognita ranged from 0-118, 0-247, 0-310 and 0-262 per 200 g soil in Vattavada (Idukki district), Kanthalloor (Idukki district), Kollam and Thiruvananthapuram respectively. The average and frequency of occurrence of M. incognita in these areas ranged from 29 to 104 and 38.5 to 61.5 respectively. The population of Helicotylenchus sp. ranged from 0-752 and was the dominant nematode in cabbage growing areas surveyed. The population of R. reniformis ranged from 0-374 with an average of 94 and frequency of occurrence of 67.3 in these areas. In the case of Tylenchorhynchus sp. the population ranged from 0-238 per 200 g soil with an average of 45 and frequency of occurrence of 48.73 in the above four areas. Xiphinema sp. and R. similis was observed in soil samples collected from Kollam and Thiruvananthapuram districts respectively. Community analysis of nematodes was also done. Aqueous leaf extracts of Tithonia diversifolia (Hemsl.) Gray, Lantana camara L., Eichhornia crassipes (Mart.) Solms and root extract of Chromolaena odorata L. were screened for ovicidal and larvicidal effect against M. incognita under in vitro condition. T. diversifolia 100 % recorded minimum egg hatching (1 to 1.5 %) three to eight days after treatment. The bio efficacy of fresh leaf extracts of T. diversifolia, L. camara, E. crassipes and C. odorata on mortality of M. incognita juveniles revealed that T.diversifolia 100, 50, 33.3 and 25 % were effective in increasing the mortality of M. incognita juveniles at 24, 48 and 72 hours after treatment (63 to 100 %). C. odorata 50 and 100% also showed significant superiority over other treatments giving a mortality of 56 to 98 % at 48 and 72 hours after treatment. Pot culture study was conducted to find out efficacy of different preparations of T. diversifolia and appropriate method of application. T. diversifolia dried powder @100 and 50 g(kg soil)-1 were effective in decreasing the nematode population in soil and root (98 to 99 %) and improving the plant growth (31 to 87 %). Results of field study revealed that highest reduction of nematode population in soil was observed in thiamethoxam followed by Paecilomyces lilacinus (Thom)Samson enriched neem cake and nematode population in these treatments was significantly lower than T. diversifolia dried powder.T. diversifolia dried powder @ 50 and 100 g plant-1 was statistically on par in reducing the nematode population (85 % reduction over untreated) in cabbage rhizosphere.
Open Access
Biology and management of rice leaf mite, Oligonychus oryzae (hirst) (acari: tetranychidae)
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2015) Aswin, T; KAU; 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.
Open Access
Bioecology and management of ginger rhizome maggots
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2015) Sandhya, P T; KAU; Madhu, Subramanian
A study entitled “Bioecology and management of ginger rhizome maggots” was carried out at College of Horticulture, Vellanikkara during 2013-2014, with the objective to identify the major species of rhizome maggots on ginger; to study the bioecology of major species of rhizome maggots and to evaluate eco-friendly management measures against the rhizome maggots. Surveys were conducted in farmers’ fields at Vellanikkara and Madakathara panchayats of Thrissur district as well as Pattencheri and Perumatty panchayats of Palakkad district during August, September and October months of 2013, for identification of the major species of ginger rhizome maggots. Three species of rhizome maggots were obtained in all the four locations surveyed which were identified as Mimegralla sp. nr coeruleifrons (Macquart, 1843), Eumerus figurans (Walker, 1859) and Elassogaster sp. nr linearis (Walker, 1849). This is the first report of the incidence of E. figurans in India, Elassogaster sp. nr linearis, is recorded for the first time as a ginger rhizome maggot. Mimegralla sp. nr coeruleifrons was the most abundant species in all the locations surveyed and constituted 96.26 per cent of the total number of maggots collected. E. figurans accounted for 2.96 per cent of the overall population, followed by Elassogaster sp. linearis, forming 0.82 per cent of the maggots collected. Studies on the biology of Mimegralla sp. nr coeruleifrons showed the average incubation period was about 3.75 days, while the mean duration of first, second and third instars was 2.25, 3.15 and 6.70 days respectively. The mean pupal period lasted for 8.80 days. The longevity of adult male and female fly were 43.90 and 51.00 days respectively, with a sex ratio of 1:1. The morphometric observations of the different life stages of Mimegralla sp. nr coeruleifrons showed that eggs, on an average, measured 0.75 mm in length and 0.20 mm in width. The size of the first, second, and the third instar maggots averaged 0.63 × 0.16 mm, 4.2 × 0.90 mm and 8.1 × 1.68 mm in length and width respectively, while the pupae recorded a mean length of 5.36 mm and mean width of 1.65 mm. The adult male and female flies measured 11.2 × 1.30 mm and 13.56 × 2.18 mm respectively. The average fecundity of an adult female fly was 55.4 eggs during an oviposition period of 1 to 3 days. Attempts at documentation of natural enemies revealed that Trichopria malabarensis Rajmohana and Narendran sp. nov. (Hymenoptera:Diapriidae), a gregarious pupal parasitoid, was the most important natural enemy of Mimegralla sp. nr coeruleifrons in the field. An unidentified spider belonging to the family Araneidae was observed to feed on the adult flies in the field. No pathogens were isolated from maggots collected from the surveyed locations. Two entomopathogenic fungi viz. Metarhizium anisopliae (Metschnikoff) Sorokin and Beauveria bassiana (Balsamo) Vuillemin, along with two entomopathogenic nematodes Steinernema carpocapsae Weiser and Heterorhabditis indica Poinar and two insecticides, namely, fipronil and chlorpyriphos were evaluated in the laboratory for their efficacy in managing rhizome maggots. Petri plate bioassay as well as rhizome dip bioassay revealed that chlorpyriphos (20EC) @ 300 g a.i. ha-1 to be the most effective treatment, recording cent per cent mortality within 24 h after treatment. Fipronil 5SC @ 50 g a.i. ha-1 recorded an average mortality values of 90 and 66.66 per cent in Petri plate and rhizome dip assays respectively. Among the entomopathogenic organisms, the nematode H. indica recorded 16.66 per cent mortality while the fungus M. anisopliae recorded 3.33 per cent mortality in the Petri plate bioassay. Both B. bassiana and S. carpocapsae failed to induce mortality in the treated maggots. The entomopathogens failed to record any mortality in the rhizome dip study. The pot culture studies confirmed the above findings with chlorpyriphos and fipronil recording cent per cent and 78 per cent mortality respectively. Analysis of the ginger rhizomes, twenty days after exposure to fipronil, recorded a value of 0.052 mg kg-1, marginally above the detectable limit of 0.05 mg kg-1 of rhizome. Studies on the interaction between the maggots of Mimegralla sp. nr coeruleifrons with Pythium aphanidermatum, which causes rhizome rot in ginger indicated that infection by the fungus could be independent of maggot. While all the plants inoculated with P. aphanidermatum alone, as well as the plants inoculated with P. aphanidermatum along with the maggots of Mimegralla sp. nr coeruleifrons showed rhizome rot symptoms, infestation by maggots alone, failed to produce any such symptoms. The establishment of maggots, at 70 per cent was also greater in rhizomes inoculated with the fungus, as against 42 per cent in rhizomes treated with maggots alone.
Open Access
Biochemical and histopathological alterations due to root-knot nematode, Meloidogyne graminicola in rice (Oryza sativa L.) and varietal reactions
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2015) Darsana, V S Lal; KAU; Narayana, R
An experiment entitled “Biochemical and histopathological alterations due to root- knot nematode, Meloidogyne graminicola in rice (Oryza sativa L.) and varietal reactions” was undertaken at Department of Agricultural Entomology, College of Agriculture, Vellayani, during 2013-14. A progressive increase in phenol content, defense enzymes viz. Peroxidase (PO), Polyphenol Oxidase (PPO), Phenylalanine Ammonia Lyase (PAL) from both leaf and root after 45 days of nematode inoculation were observed with increase in inoculum levels. The chlorophyll a and b, NPK content and micronutrients viz. Fe, Cu, Zn and Mn were decreased with increase in nematode population. The plants inoculated with 10,000 J2 showed low pH (5.69) compared to the uninoculated plant and was significantly different from all other treatments. The starch, protein and total sugar content decreased 41.44, 41.89 and 44.95 per cent respectively in plants inoculated with 10,000 J2 compared to uninoculated plants. A progressive decrease in plant growth and yield parameters were observed with increase in population levels of nematode. The maximum reduction in plant height, fresh weight of plant, dry weight of root and dry weight of shoot and the yield parameters like thousand seed weight and number of seeds per panicle were observed in plants inoculated with 10,000 J2. Histochemical studies revealed that an accumulation of polysaccharides, proteins and nucleic acid in epidermal, cortical and stelar region of root progressively increased with increase in population density of nematode. Giant cells were formed near the xylem and phloem cells. The xylem and phloem vessels were disorganized. In studying the varietal reaction of ten popular rice varieties of Kerala against M. graminicola, all the varieties were suceptible to the nematode. Minimum number of galls (51.8) and egg mass (64.60) per plant was observed in the variety Uma and was on par with Pavizham. On the basis of egg mass index, all other varieties were highly susceptible except Uma. The PO and PPO activity of Uma, Karthika, Pavizham and Bhadra were higher than that of TN1 (Suceptible check). In Uma, the nematode population in soil and root was minimum and on par with Karthika and the reproduction rate also minimum in Uma. Based on the results of the study, M. graminicola can be considered as a potential threat to the cultivation of rice. Uma showed better performance against root knot nematode than all other varieties.
Open Access
Entomopathogenic fungi for the management of insect pests in rice ecosystem
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2015) Malini, Nilamudeen; KAU; Sudharma, K
The study entitled “Entomopathogenic fungi for the management of insect pests in rice ecosystem” was carried out during 2011 - 2014 at College of Agriculture, Vellayani. The objectives were to isolate and identify indigenous strains of entomopathogenic fungi, to evaluate the fungal pathogens viz., Beauveria bassiana (Balsamo) Vuillemin, Metarhizium anisopliae Metschnikoff (Sorokin) and indigenous fungi against insect pests of rice, to fix their effective dose, to assess the compatibility of the fungal pathogens with new generation pesticides and to develop pesticide tolerant strains of the fungi. Six new isolates of entomopathogenic fungi viz., Aspergillus flavus Link. (Af-m1), B. bassiana (Bb-m2, Bb-m3, Bb-m4 and Bb-m5) and one isolate of M. anisopliae (Ma-m1) were collected and identified on the basis of morphological and molecular characters. The accession numbers obtained for the isolates from National Center for Biotechnology Information (NCBI) were KP 739825, KP 739828, KP 739829, KP 739830, KP 739831 and KP 739826, respectively. The pathogenicity of fungal isolates viz., B. bassiana (Bb 5), M. anisopliae (Ma 4) from NBAIR, B. bassiana (Bb 21) from Department of Microbiology, College of Agriculture, Vellayani and the six new isolates A. flavus (Af-m1), B. bassiana (Bb-m2, Bb-m3, Bb-m4 and Bb-m5) and M. anisopliae (Ma-m1) were evaluated against Cnaphalocrocis medinalis Guen. and Leptocorisa acuta (Thunb). All isolates were pathogenic to larvae of C. medinalis, nymphs and adults of L. acuta. The isolates B. bassiana (Bb 5) and M. anisopliae (Ma 4) were found superior among the fungi evaluated. The bioassay of the potent fungal pathogens viz., B. bassiana (Bb 5, Bb 21), M. anisopliae (Ma 4) and A. flavus (Af-m1) was conducted against C. medinalis larvae and nymphs and adults of L. acuta and field doses were fixed on the basis of LC90 values. Spore concentration dependent mortality of the insects was seen. The LC90 values were 3.50 x 108, 3.40 x 108, 2.25 x 108 and 3.37 x 108 spores ml-1 for B. bassiana (Bb 5, Bb 21), M. anisopliae (Ma 4) and A. flavus (Af-m1) against C. medinalis larvae, 3.92 x 108, 7.55 x 108, 2.96 x 108 and 3.46 x 108 spores ml-1 against L. acuta nymphs and 4.23 x 1010, 4.11 x 1010, 2.85 x 1010 and 8.72 x 1010 spores ml-1 against L. acuta adults. Two field trials carried out at Cropping System Research Centre, Karamana during November 2012 to March 2013 (Puncha) and June 2013 to October 2013 (Virippu) to assess the efficacy of entomopathogens revealed that B. bassiana (Bb 5) @ 1010 spores ml-1 was the best treatment, on the basis of pest population and reduction in damage of pests, population of natural enemies and benefit-cost ratio. This was followed by M. anisopliae (Ma 4) @ 1010 spores ml-1, talc based formulation of Bb 5 @ 20 g l-1, talc based formulation of M. anisopliae (Ma 4) @ 20 g l-1, talc based formulation of Bb 21 @ 20 g l-1 and A. flavus @ 1010 spores ml-1. Among the insecticides evaluated, chlorantraniliprole @ 30 g a.i ha-1 was the best. Assessment of the compatibility of fungal pathogens with insecticides on the basis of the effect of insecticides on the growth, spore count, germination and bioefficacy revealed that, B. bassiana (Bb5 and Bb 21), M. anisopliae (Ma 4) and A. flavus (Af-m1) were compatible with acephate (0.075, 0.150, 0.225 per cent), chlorantraniliprole (0.004, 0.006 and 0.008 per cent) and thiamethoxam (0.003, 0.005 and 0.008 per cent). Investigations on pesticide tolerance of entomopathogens showed that, B. bassiana (Bb 5) and M. anisopliae (Ma 4) tolerated 4.0, 8.0 and 8.0 times higher the field dose of acephate, chlorantraniliprole and thiamethoxam, respectively. The growth, spore count and the bioefficacy of selected cultures (fungi gown initially in media containing highest tolerable dose of insecticide and further grown in poisoned media for 10 passages), relaxed cultures (fungi gown initially in media containing highest tolerable dose of insecticide and further grown in unpoisoned media for 10 passages) and untreated cultures (fungi grown only in unpoisoned media) of B. bassiana (Bb 5) / M. anisopliae (Ma 4) differed significantly. On culturing of the selected, relaxed and untreated cultures of the fungi after 10 passages, in still higher dose of the insecticides i.e., 4.5x, 8.5x and 8.5x times higher the field dose of acephate, chlorantraniliprole and thiamethoxam, respectively, only the selected cultures tolerated the higher doses. Molecular characterisation of the selected, relaxed and untreated cultures of B. bassiana (Bb 5) / M. anisopliae (Ma 4), which were continuously grown for 10 passages in poisoned / unpoisoned media, respectively showed no molecular variations, except a minor polymorphism of 1.61 per cent exhibited in B. bassiana (Bb 5). To conclude, the six new indigenous fungi isolated are pathogenic to C. medinalis and L. acuta. B. bassiana (Bb 5) and M. anisopliae (Ma 4) @ 1010 spores ml-1 are effective and economical for the management of C. medinalis and L. acuta besides being safe to natural enemies. As these fungi are compatible with acephate @ 750 g a.i ha-1, chlorantraniliprole @ 30 g a.i ha-1 and thiamethoxam @ 25 g a.i ha-1, and as they tolerated higher doses of insecticides, without undergoing any genetic variation they are suitable for integration with these insecticides, the best chemical suggested for integration is chlorantraniliprole @ 30 g a.i ha-1 as it is safe to natural enemies
Open Access
Pests and diseases of stingless bees trigona iridipennis smith (Meliponinae: Apidae)
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2015) Jayalekshmi, C R; KAU; Premila, K S
The study entitled “Pests and diseases of stingless bee Trigona iridipennis Smith (Meliponinae: Apidae)” was conducted with the objective to study the pests and diseases associated with the stingless bees, their documentation, assessment of their damage and yield loss during the period 2013-14 at the AICRP on Honey bees and Pollinators, Department of Agricultural Entomology, College of Agriculture, Vellayani. A survey was conducted in five Southern districts of Kerala viz., Thiruvananthapuram, Kollam, Pathanamthitta, Kottayam and Idukki. The pests of stingless bees documented were Hermitia illucens (Pathanamthitta) and Aethina sp. (Kottayam and Idukki). Predators recorded were Acanthaspis siva (Thiruvananthapuram) and Sycanus sp. (Kollam). Eight different predatory spiders, Thomisus projectus, Thomisus lobosus, Neoscona nautica, Menemerus bivittatus, Plexippus paykulli, Hersilia savignyi, Heteropoda venatoria and Crossopriza lyoni were recorded. Two pathogens viz., Paecilomyces variotii and Aspergillus niger were also observed. Out of the 100 stingless bee colonies surveyed, only five colonies were infested with H. illucens in Pathanamthitta district whereas Aethina sp. was observed in four and five stingless bee colonies each from Kottayam and Idukki districts. The reduction in honey yield due to pests and diseases ranged from 93.93 to 96.76 per cent. Nine physiochemical parameters of stingless bee honey were observed, among which wide variation was observed in hydroxy methyl furfural and diastase activity between healthy and infested samples. Regarding the nest architecture and defense mechanism of stingless bees, out of the four types of hives, majority of the beekeepers maintained stingless bee colonies in wooden hives (70.20 %) and mud pots (18.60 %). The incidence of pests/predators and diseases in stingless bee colonies showed that bamboo bits were free from pests and diseases incidence in all districts. In the case of wooden hives, short tubular hive entrance was dominant in all the districts. The length and width of entrance tube and number of guard bees in the short tubular type of entrance ranged from 3.74 to 4.63 cm, 1.49 to 1.93 cm and 6.91 to 9.00 nos. respectively. The materials used for constructing the hive entrances included natural materials viz., resins, waxes, tiny chips of wood, saw dust, sand, bee cadavers, leaves and vegetative parts, cerumen, wood and bark of trees. The hive entrance was closed after the dusk to prevent the entry of predators and pests into the hive during night time. The stingless bee hives were maintained at different heights from the ground level (3-5 ft, 6-8 ft, 9-11 ft and >12 ft) by the beekeepers. The hives maintained at 9-11ft above the ground level recorded the highest incidence of pests (5.10%) and predators (19.96%) whereas disease incidence was highest in boxes at 6-8 ft. None of the colonies maintained at 3-5 ft height from the ground level had pests/predator or disease incidence. Based on the results of the study, two pests, two pathogens, two insect predators and eight spider predators were observed to cause damage to stingless bees. Observations on the nest architecture and defense mechanism showed that the incidence of pests and diseases was meagre in bamboo hives. Even though bamboo hives were less prone to the attack of pests and diseases, majority of the beekeepers used wooden hives for domesticating stingless bees since it is easier to handle during colony division, honey harvesting and periodical observations on need basis. Considering the height from the ground level, no incidence of pests, predators and diseases were recorded in the colonies maintained at 3-5 feet.

Theses

Browse

Thesis Type

Type

Author

Date

Subject

Search Results