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Subject: Agricultural Entomology × Author: KAU × End date: 1991 × Start date: 1991 ×
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    ThesisItemOpen Access
    Effect of chitin synthesis inhibitors on rice swarming caterpillar spodoptera mauritia and rice moth corcyra cephalonica and a larval parasitoid bracon brevicornis
    (Department of Agricultural Entomology, College of Agriculture, Vellayani, 1991) Prathapan, K D; KAU; Dale, D
    Effects of four chitin synthesis inhibitors viz. diflubenzuron, chlorfluazuron, PH 70-23 and BASF LAB 153 959 I were assessed on two insect pests, the rice swarming caterpillar Spodoptera mauritia ( Boisduval) and rice moth Corcyra cephalonica (Stainton) and on its larval parasitoid Bracon brevicornis (Wesmael). Ovicidal action was assessed by treating one and two-day old eggs of S. mauritia in aqueous and mathanilic media. It was low in aqueous medium. But in methanolic medium diflubenzuron and the highest doses of the other three compounds showed enhanced action. In general, high ovicidal action was observed in methanolic medium. There was no significant difference between one and two-day old eggs in their susceptibility to chitin synthesis inhibitors. Chlorfluazuron was the most toxic causing cent per cent mortality at doses as low as 2 x 10 -5% when treated on second and fifth instar larvae of S. mauritia. Diflubenzuron, PH 70-23 and BASF LAB 153 959 I were also highly effective. Second instar larvae were more susceptible than fifth instar ones. Besides stomach action, a high degree of contact action was also observed. Final instar larvae of S. mauritia when treated with the test chemicals, produced larval-pupal intermediates and caused pupal mortality and emergence of deformed adults. All the four moult inhibitors were highly active during larval – pupal transformations. Pupae were less susceptible to chitin synthesis inhibitors. Yet, some treatments caused mortality and emergence of deformed adults. Chlorfluazuron was the most toxic to pupae. Fecundity, hatchability of eggs and longevity were reduced when the male moths of S. mauritia were fed on sugar solution containing the moult inhibitors. Antifeedant action of the chitin synthesis inhibitors was found to be less pronounced. Residual effect of all the four compounds persisted on the treated rice foliage throughout a study period of 36 days. But the efficacy of residues exposed to sunlight and rain was very low. Ovicidal action of the moult inhibitors was low to moderate on one and four-day old eggs of C. cephalonica in aqueous medium. In methanolic medium diflubenzuron at 2 x 10 -1 %, 2 x 10 -2 % and 2 x 10 -3 % and PH 70-23 and BASF LAB 153 959 I at 2 x 10 -1 % caused enhanced ovicidal action. In general there was no significant difference between the susceptibility of one and four-day old eggs. Chlorfluazuron was found to be the most toxic compound against larvae of C. cephalonica followed by BASF LAB 153 959 I. Diflubenzuron and PH 70-23 were less effective. Early larval instars were more susceptible. Contact action of compounds other than chlorfluazuron was low. Larval – pupal intermediates, pupal mortality and emergence of deformed adults were resulted when the last instar larvae of C. cephalonica were treated with the chemicals. Chlorfluazuron was found to be the most toxic compound. Prepupal treatment also caused the above juvenomimetic effects. But treatments other than chlorfluazuron 2 x 10 – 2% were less effective. Treatment of pupae of C. cephalonica resulted in pupal mortality and emergence of deformed adults. But pupae were less susceptible to the moult inhibitors as compared to the larval stages. External application of Chitin synthesis inhibitors to moths of C. cephalonica had no adverse had no adverse effect on fecundity, hatchability of eggs and longevity of the treated moths. Chlorfluazuron was found to inhibit the emergence of adult parasites from treated hosts and adversely affect the progeny production of B. brevicornis. Diflubenzuron, PH 70-23 and BASF LAB 153 959 I were non-toxic or only slightly toxic to the parasite.
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    ThesisItemOpen Access
    Resurgence potential of the rice leaf folder. Cnaphalocrocis.medinalis Guen. as influenced by the soil application of carbofuran granules
    (Department of Agricultural Entomology , College of Horticulture, Vellanikkara, 1991) Baby, P Skaria; KAU; Abraham, C C
    In investigations on the changes taking place in the extent of feeding, growth and development of the rice leaf folder, Cnaphalocrocis medinalis Guen. on rice plants receiving soil application of carbofuran granules at 0.50, 0.75 and 1.00 kg ai/ha/application at 20, 50 and 20 and 50 days after transplanting, the extent of larval feeding on leaves did not show any variations as a result of carbofuran treatments. In the third, fourth and fifth larval instars and pupae, carbofuran treatments led to their weight gain due to possible enhancement of the digestibility and more effective conversion of ingested food into body matter, under .influence of factors mediated by the metabolites of carbofuran in leaf tissues. In respect of mean larval and pupal mortality, the insecticidal treatments did not show any impact, but the metabolites showed a negative correlation with the mortality levels thereby indicating the favourable influence of the metabolites on the development of C. medinalis. There was improvement in female emergence as a result of treatment with 1.00 kg ai/ha of carbofuran applied at 20 as well as 50 DAT as compared to untreated control, but the sex-ratio variations as a result of treatments were not pronounced. The first instar larval emergence (F1 generation) showed a positive influence by different metabolites of carbofuran. Carbofuran treated plants showed distinctly positive orientational stimulus to C. medinalis adults due to positive olfactory stimuli probably due to emission of vapour-phase admixture of carbofuran metabolites, but there was no improvement in fecundity under such treatments. There was distinct improvement in progeny production from females developing from carbofuran treated rice plants. This is mainly due to the ingress of more female moths and the resultant increase in overall ovipositional output rather than increase in fecundity'. Carbofuran treatments caused increase in the density of leaf hairs in a dose-dependent manner, but such variations were not significant as compared to untreated control. The positive relationship between ovipositional preference on the one hand and leaf hair density of treated plants .on the other brings to focus the role of tactile stimuli provided by leaf hairs in the acceptance of host plants for oviposition. The residues and metabolites of carbofuran in leaves favourably influenced most of the growth and developmental attributes of the rice leaf folder. None of the plant biochemicals showed any changes under influence of carbofuran treatments.