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Subject: Agricultural Entomology × End date: 1994 × Start date: 1994 ×
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    ThesisItemOpen Access
    Bioecology of orthogalumna terebrants wallwork on waterhyacinth
    (Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1994) Babykala, P; KAU; Joy, P J
    The mite biology, morphology, nature of extent of damage and interaction with N. eichhorniae were studied. The might laid solitary eggs sideways to the oviposition holes, deeply embedded in the aerenchyma cells. The incubation period was 5.8 days. The larvae and nymphs fed by making galleries. The larvae, proto and deuto nymphal stages were completed in 3 days each, while that of tritonymph took 4 days. The duration of inactive stages from larva to proto, proto to deuto and deuto to tritonymphal stage were 1.6 days each, whereas from tritonymph to adult, it was 3 days. Adult longevity was 57.3 days. pre-ovipositional period was 4 days and the total number of eggs produced during the whole life period was 41.5 eggs. The larvae have three pairs of legs but no genital opening. The nymphal stages have four pairs of legs, ending in single claws. The proto, deuto and tritonymphal stages, have one, two and three pairs of genital papillae respectively. This character helps in identification of larval and nymphal stages. The adults are pteromorphs and sexual dimorphism is absent. Sensillus is relatively short with curved stem and globular roughened head. Terminally the tarsus of the leg has three claws on a short peduncle the lateral claws more slender than the median and sharply angled. The larval and nymphal feeding produces galleries on leaves of waterrhyacinth resulting in brown streaks on the leaf lamina. Such brown streaks later coalesce to form large brown areas, leading to drying up of the entire leaf. As the mite load increased from ten to eighty the number of plants and number of leaves showed significant reduction 90 days after release. The extent of damage caused by O. terebrantis with or without weevil under open and partially shaded conditions of waterhyacinth plants was experimented upon, and it showed that, the root length, petiole length ( in open condition), laminar width and length, number of leaves and number of plants under both light intensities (partially shaded and open condition), in general showed a decreasing trend. The plants in tanks having ten weevils alone per tank and 10 weevils plus 100 mites per tank under partially shaded conditions collapsed within 60 days, whereas in open condition of that having 10 weevils plus 100 mites per tank, all the plants collapsed by the 75th day. In the treatment with ten weevils alone per tank in open condition the collapse occurred only at 105 days. In the treatment with 100 mites alone per tank, there was no collapse of plants upto 105 days (in both conditions). The number of mite galleries and mite population per leaf with Neochetina feeding marks was comparatively more in the presence of weevils than in their absence. Fungi like Fusarium, Aspergillus and Rhizopus were isolated and also the spider mite and insects like aphids and grasshoppers were noticed.
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    ThesisItemOpen Access
    Relative susceptibility of populations of Amrasca biguttula biguttula (ISHIDA) infesting Bittergourd (memordica charantia L.) collected from different locations to insecticides part II
    (Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1994) Jyothi, Bindu P; KAU; Sosamma, Jacob
    A study was undertaken at the college of Horticulture, Vellanikkara during 1993-94 to evaluate the relative susceptibility of eight different populations of Amrasca biguttula biguttula (Ishida) on bittergourd collected from four districts of Kerala state to six insecticides belonging to different chemical groups. Two different localities were selected for the collection of the leaf hopper, from each district. The selected localities were, Pattikadu and Nedupuzha (Thrissur district), Pothappara and Odanallur (Palakkad district), Wandoor and Chattipparambu (Malappuram district) and Vempalli and Kurichi (Kottayam district). All the populations were collected from farmers fields which were subjected to regular insecticidal spraying. The insecticides selected for the study belong to different chemical groups viz. organophosphorus compounds (quinalphos, monocrotophos and phosphamidon), organochlorine compounds (endosulfan), synthetic pyrethroid (deltamethrin) and CHO compound (ethofenporx). Among these insecticides, the organophosphorus compounds were widely used by the farmers for controlling this pest in the field. Relative toxicity of different insecticides to different populations were found by leaf dipping technique of bioassay and the results were subjected to probit analysis (Finney, 1971). Based on the relative toxicity studies it was clear that endosulfan was the most toxic insecticide against A.biguttula biguttula collected from all the eight localities. Monocrotophos ranked second in toxicity against populations from Thrissur district while deltamethrin was proved to be the second highly toxic insecticide to Palakkad and Kottayam hopper populations. Against Malappuram populations of A.biguttula biguttula highest toxicity of endosulfan was followed by ethofenprox. Phosphamidon was found to be relatively less toxic to this pest. Quinalphos, the commonly used organophosphorus insecticide was found to have least toxicity and thereby it was observed to be ineffective in controlling this pest in bitttergourd in all the four districts. Great variation was observed in the relative toxicity values of different insecticides indicating their difference in toxicity level to A. biguttula biguttula. The order of toxicity of different insecticides was found to be the same between the two populations from each district but varied with populations from different districts. Organophosphorus compounds were found to be relatively less toxic than endosulfan, deltamethrin and ethofenprox belonging to other groups. Therefore, the use of quinalphos against A.biguttula biguttula among the farmers has to be discouraged and endosulfan can be advocated against A. biguttula biguttula in bitterfourd as an alternative. Carbaryl was proved to be ineffective against leaf hopper populations in bittergourd earlier (Sabitha, 1992). The relative susceptibility studies with populations of A. biguttula biguttula from the four districts revealed that all the eight populations were highly susceptible to endosulfan. The LC50 value of endosulfan was found to be very low, ranging from 0.00022 to 0.00041 per cent. At the same time all the populations were least susceptible to the most commonly used organophosphorus insecticide quinalphos. All the populations showed higher susceptibility to endosulfan, deltamethrin and ethofenprox than the organophosphorus insecticides. Thrissur population was more susceptible to monocrotophos next to endosulfan. Palakkad and Kottayam populations were more susceptible to deltamethrin while Malappuram populations indicated more susceptibility to ethofenprox, next to endosulfan. The LC50 value of phosphamidon ranged from 0.02 to 0.06 and all the eight populations of A.biguttula biguttula manifested lower susceptibility to this insecticide in comparison with the other chemicals
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    ThesisItemOpen Access
    Distribution of coconut lacewing bug Stephanitis typicus distant and its natural enemy complex and assessment of biocontrol potential of the major natural enemies
    (Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1994) Unnimon, N K; KAU; Ranjith, A M
    A study on the distribution of the coconut lacewing bug Stephanitis typicus and its natural enemy complex was carried out during the period 1991-92 at four selected root (wilt) prone districts of kerala . The bio-control potential of the major identified natural enemies were also carried out during the same period . The results revealed that population of S.typicus showed a fluctuation throughout the year . The population was higher in the field during the dry seasons and it was at lower levels in rainy periods. The numbers of the pests increased from January onwards and recorded its maximum in March-April. The population started decreasing from May onwards and recorded the lowest level in June-July . From August the number of pest again started increasing and reached the second maximum in September - October. The level of population recorded was lowest in November- December. Congregation of S. typicus was observed in higher numbers on the inner whorls of coconut crown. Compared to leaves of inner whorls, the number of pest were fewer in middle and outer whorls. Natural enemy population was observed to remain stagnant throughout the year. Only a slight fluctuation was recorded in population of natural enemies , in accordance with the increased level of pest population . Generally a low level of natural enemy population was observed in the field throughout the study period . Rearing of S. typicus in glasshouse condition on different host plants like coconut , turmeric and arrowroot showed the preference by the pest to the coconut plants. Compared to other host plants the multiplication and survival of the pest was more on coconut plants. Among the natural enemies observed in the field , the mired predator S. praefectus was recorded as the important one . other natural enemies observed in the field included spiders and one pentatomid bug. It was noticed that the mired predator consumed both adults and nymphs of the pest . But in case of spiders they preferred adults of the pest to nymphs.