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20004
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Subject: Agricultural Entomology × End date: 2000 × Start date: 2000 × Type: Thesis × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Survey and quantification of natural enemy fauna in the rice ecosystems in Thrissur district
    (Department of Agricultural Entomology, College of Horticulture,Vellanikkara, 2000) Parvathy Meera, KAU; Pathummal Beevi, S
    A pilot study was carried out with the objective of identification, quantification and comparison of the pest and natural enemy complex present in two different rice ecosystems in Thrissur district of Kerala, viz. non-kole and kole area. The species composition, abundance and relative occurrence of pests, parasitoids and predators collected in sweep net samples from six locations each of non-kole and kole area were studied. Six samples were drawn at weekly intervals from each location starting from 15 days after transplanting till the emergence of panicles and the mean data used for analysis. The species richness, diversity and evenness of all the pests and important natural enemies were also assessed. In situ count of leaf and planthoppers and associated generalist predators were recorded. The extent of natural parasitism on the field collected immature stages of stem borer, leaf folder and gall fly was recorded and identified the important species. In the sweep net samples taken from 12 rice fields, altogether 29 species of phytophages representing 19 families of six insect orders could be identified. Among the 96 species of natural enemies (entomophages) identified, 19 species were predators and 77 were the hymenopteran parasitoids. Except in the case of one or two locations, the occurrence of most common and regular pests and the associated natural enemy fauna were found to be the same in the non-kole and kole area. The entomophages comprising of parasitoids and predators were found to be higher than the phytophages in most of the locations. Homoptera comprising of leaf and planthoppers and Thysanoptera (thrips) were the predominant phytophages. Nephotettix spp. were dominant among the leaf and planthopper while it was Sogatella furcifera (Horvath) among the planthoppers. A significant difference was observed in the mean count of pests as well as natural enemies within the six locations of each situation. Spiders (8 species) cocinellid beetles (3 species), mirid bug (Cyrtorhinus Iividepennis Reuter), damselflies (2 species) and veliid bug [Microvelia douglasi atrolineata (Bergoth)] were the important predators. The predominant predator species were Tetragnatha maxillosa Thorell (Aranae), Cyrtorhinus lividipennis Reuter (Miridae), Micraspis spp. (Coccinallidae) and Agriocnemis pygmea Rambur (Odonata). Highest diversity was noticed in the case of hymenopteran parasitoids and was the single largest group of entomophages. In the non-kole area, spiders were most abundant followed by Odonata, whereas in kole area C. lividipennis was abundant followed by spiders. In the case of phytophages, between the two situations studied, significant difference was noticed only in the case of planthoppers, which was significantly high in kole lands. Spiders, C. Iividipennis and the total predators population were significantly high in kole area, whereas Odonata (damselflies) were significantly high in non-kole area. A highly significant positive correlation existed between the leaf and planthoppers with predators like C. lividipennis and spiders. In situ population count of leaf and planthoppers and their associated natural enemies viz. C. lividipennis and Lycosa indicated a density dependent relationship. From the field collected samples, three species of parasitoids VlZ. Telenomus spp. Tetrastichus spp. and Trichogramma spp. were obtained from the stem borer eggs. The parasitoids emerged from the leaf folder larvae and pupae were Cotesia (=Apanteles) spp. Brachymeria excarinata Gahal, Cardiochilus philippinensis Ashmead, Goniozus spp., Macrocentrus philippinensis Ashmead and Xanthopimpla spp. Only a single species (Platygaster sp.) was obtained from gallfly pupae.
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    ThesisItemOpen Access
    Impact of botanicals on pests and defenders in rice ecosystem
    (Department of Entomology, College of Agriculture, Vellayani, 2000) Ajaya Kumar, C; KAU; Nalina Kumari, T
    The magnitude and intensity of insect pest and their defenders at different growth stages of rice were assessed in a survey during the virippu season of 1998, adopting random sampling technique, in three taluks of Thiruvananthapuram district. The survey revealed that the occurrence and distribution of the population of pests and defenders were same in the various locations, where the tolerant variety Jyothi was cultivated. The total population of pests and defenders observed at different growth stages of the crop followed a definite pattern in the three locations. Different concentrations of the leaf extracts of A. indica, and C. infortunatum and nimbecidine were evaluated in the laboratory for their antifeedant and deterrent activity and contact toxicity against important pests of rice and their defenders. Based on the percentage of leaf protection, the plant products tested were superior to control against C. medinalis. The same effect was noticed with N. depunctalis, only with the highest dose of leaf extracts of A. indica and nimbecidine. Seventy five per cent deterrent effect was observed to N. lugens at the highest dose of the plant products. None of the plant products showed any deterrent action against L. acuta or exhibited contact toxicity to L. acuta, C. medinalis. N. depunctalis andN. lugens. Both the defenders tested CL. pseudoannulata and O. nigrofasciatay; were safe with the plant products. 2 Replicated experiment was conducted on rice to evaluate the efficacy of plant products in suppressing the pests as well as in augmenting the defenders under field conditions. The leaf extract of C. infortunatum was found to be efficient in suppressing the population of C. medinalis. The effect was same as that with insecticides. The population of N. depunctalis was reduced by the leaf extracts of A. indica and C. infortunatum as observed in treatment with carbaryl. The suppressing effect observed on N. lugens was same with both the leaf extracts and insecticides, whereas, none of the treatments showed reduction in the population of L. acuta. The total population of the pests in general, showed a varying effect of plant products at different growth stages of the crop. Leaf extracts of C. infortunatum resulted in an immediate suppression of the total population of the pest at 20 DAT, whereas, A. indica gave significant reduction at 40 DAT. The treatments didnot show any effect on the total pest population at 60 DAT. The effect of plant products on spider population revealed that they were found to be safe. The leaf extract of A. indica increased the spider population at 20 DAT and C. infortunatum at 60 DAT, whereas, insecticides showed harmful effect up to three days after application. Adverse effect with plant products on the population of 0. nigrofasciata was not observed in any of the treatments. An increase in the population of the predator was observed with leaf extracts of A. indica at 20 DAT and with C. infortunatum at 40 and 60 DAT. Significant reduction in the population of Agriocnemis spp. was recorded in treatment with leaf extract of C. infortunatum, whereas, significantly higher population was observed in treatment with leaf extract of A. indica. The population of M crocea was reduced due to the application of plant products and the effect was retained up to three days after application. 3 The influence of plant products on the total population of defenders has clearly indicated that the leaf extracts of A. indica and C. infortunatum were safe to the defenders. Based on the P:D ratio, these products were found to have the best effect in augmenting the population of defenders and suppressing the population of pests. Significant differences in the grain and straw yield was not recorded either in treatments with plant products or with insecticides when compared with control. Overall assessment of the results obtained revealed that A. indica and C. infortunatum can be effectively and safely used for the management of important pests of rice with out much adverse effect on non target organisms in the rice ecosystem. Just like A. indica, C. infortunatum could also be utilised for developing effective plant protection chemicals for replacing undesirable synthetic insecticides in integrated pest management.
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    ThesisItemOpen Access
    Biopesticides for integrated pest management in bitter gourd (Momordica charantia L.)
    (Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2000) Sunil Dutt, M; KAU; Maicykutty, P Mathew
    A field study was undertaken at the College of Horticulture, Vellanikkara during 1998-99 to compare the efficacy of two chemical insecticides viz., acephate, carbofuran, two biopesticides based on B. thuringiensis and B. bassiana and their combinations against the major pests of bitter gourd. Carbofuran was applied as granules at seeding, while the other treatments were applied as spray at fortnightly intervals from 35 DAS. It was observed from the study that application of acephate at 0.1 per cent was the most effective insecticide against sap feeders viz., leaf hopper and aphids. The combined application of B. thuringiensis or B. bassiana with acephate 0.05 per cent was also found effective. In controlling hadda beetle also, acephate at 0.1 per cent gave consistently good results. Gallfly infestation was minimum in acephate 0.1 per cent treated plots followed by B. thuringiensis + acephate 0.05 per cent sprayed plots. In the case offruitfly, B. bassiana + acephate 0.05 per cent registered the lowest infestation. The borer infestation was less in B. thuringiensis + acephate 0.05 per cent sprayed plots. This treatment also recorded the highest marketable yield (7573 kg ha") with the highest net profit of Rs. 25,344 ha-I and benefit cost ratio of 3.71 : 1. Studies on the residues of carbofuran by high performance liquid chromatography revealed that application of carbofuran either at 0.6 or 1.2 kg a.i.ha' at seeding resulted in no detectable terminal residue in bitter gourd fruits.
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    ThesisItemOpen Access
    Bio- ecology and management of stingless bees
    (Department of Agricultural Entomology, College of Agriculture, Vellayani, 2000) Raakhee Mohan; KAU; Devanesan, S
    With the objective of studying the bio-ecology and management of stingless bees, a study was conducted at the College of Agriculture, Vellayani during 1997-99. The bee samples collected from all districts of Kerala were identified to be of the same species viz., Trigona iridipennis Smith. The colony consisted of a queen, workers and few drones during the colony breeding season. The building material used by T. iridipennis was cerumen. The species arranged their brood in clusters. Queen cells were larger than worker brood cells. Food chamber of the species lay outside the brood nest. The food chamber consisted of honey and pollen pots which were larger than brood cells. Feral colonies which were transferred to different types of hives ('~II ablished and this showed that the bees could be hived in artificial domiciles which was a satisfactory step towards domestication. Different management practices were tried. Division of the bee colony could be successfully carried out by transferring half the amount of brood cells, pollen and honey pots along a queen cell to the daughter colony. Wooden hives were found to be more suitable for hiving T. iridipennis since the brood development and honey yield were superior in this type of hive. The studies on the method of extraction of honey indicated the feasibility of collecting honey by keeping the storage pots in trays under sunlight. Observations on the behaviour of T. iridipennis showed that each brood cell was constructed by the summation of activities of several workers. Mass provisioning of the brood cells was noticed. The brood cells were seen used only once. Queen laid egg in the provisioned cell and after the oviposition a worker closed the cell. The bees used their mandibles as a means of defence. The average egg, larval and pupal period of T. iridipennis was found to be 4.7, 18.6 and 21.8 days respectively with a total developmental period of 45.1 days. The species had reduced wing venation. The mandibles were modified. The hind leg of the worker bees had the 'pencillium'. The stingless bee queens were larger than workers Investigations on the foraging behaviour showed two peak periods of activity one at 1200 h and the other at 1500 h. Twenty seven plants were recorded as bee flora. Of the 27 plants recorded, twelve plants (rubber, cashew, coconut, chilly, cannon ball tree, coral creeper, drumstick, guava, rose, birds cherry and tamarind) provided both nectar and pollen. Eight plants (anthurium, bajra, sponge gourd, cinnamon, ixora, mango, touch-me-not and sunflower) noted, were sources of pollen while seven plants (balsam, banana, duranta, euphorbia, hamelia, marigold and phyllanthus) provided nectar only. Two species of spiders (unidentified) and ants (Solenopsis geminata) were found as enemies of T. iridipennis. Stingless bee honey was slightly acidic to taste and had a dark brown colour with the acidity and pH values being 0.294 and 3.98 respectively. The specific gravity was l.394 g/cc. It had a moisture content of 20.7 per cent. Glucose and fructose were 37.1 per cent and 4l.6 per cent respectively. The honey had a higher protein content of 1.49 per cent and ash content of 1.1 per cent.