• M B Kalode

      Articles written in Proceedings – Animal Sciences

    • Studies on egg and nymphal parasites of rice planthoppers,Nilaparvata lugetts (stål) andSogatella furcifera (Horvath)

      J S Bentur Mangal Sain M B Kalode

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      Three species of egg parasites, viz.,Anagrus sp.,A. optabilis (Mymaridae) andOligosita sp. (Trichogrammatidae), and a nymphal/adult parasiteGonatopus sp. of rice planthoppers were studied for their biology and control potential. Larger number of adult mymarids emerged from host eggs between 8·30 a.m. and 12·30 p.m. of the day whereas trichogrammatid adults emerged between 12·30 p.m. to 4·30 p.m. All the three species parasitised both brown planthopper (BPH) and white backed planthopper (WBPH) but, in general, failed to parasitise rice leaf-hoppers.

      Developmental duration from oviposit ion to adult emergence noted for these parasites indicated that males of mymarids, in general, developed faster (10–11 days) than females (12–13 days) at 20–32° C prevailing during October, whereasOligosita females developed more slowly (14–15 days). However, bothA. optabilis andOligosita developed three days faster at 30–38° C prevailing during April, Fecundity in terms of number of eggs parasitised per female varied from 12·3 to 20·3. Under greenhouse conditions, release of 1 and 5 pairs of mymarid parasites for 10 days reduced the nymphal hatch of BPH by 60 and 85%, respectively. Nymphal/adult parasiteGonatopus sp. completed its life cycle in 19·5 to 31 days on both BPH and WBPH. While the 4th and 5th instar nymphs of BPH were parasitised more frequently, green leafhopper nymphs were not parasitised. Besides being endoparasitic, the adult females also predated on and killed as many as 5·2 nymphs a day.

    • Comparative study on varietal resistance to rice green leafhoppersNephoteitix virescens (Distant) andN. nigropictus (St⇘l)

      Kasi Viswanathan M B Kalode

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      Employing three different methods, 108 rice varieties were screened for resistance againstN. virescens andN. nigropictus. In mass screening test, 76 varieties suffered significantly less damage byN. virescens, whileN. nigropictus caused less damage to 72 varieties. Ten varietiesviz. Ptb 2, Ptb 18, Ptb 7, Khama 49/8, Ptb 21, DS 1, ARC 6049, Khama 49/2, ARC 10243 and Jhingasail were greatly detrimental to insect bionomics in the studies using first instar nymphs and newly emerged adults. Adult longevity test could be a good criterion to identify the high degree of resistance in the varieties. From an overall assessment, Ptb 18, Ptb 2 and Ptb 7 were identified as highly resistant to both the species.

    • Mechanism of resistance in rice varieties showing differential reaction to brown planthopper

      K Venugopala Reddy M B Kalode

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      A total of 1070 rice varieties, mainly from Assam Rice Collection, were evaluated to identify better sources of resistance to brown planthopper,Nilaparvata lugens (Stål). In mass screening replicated tests 17 varieties were identified as resistant. Moderate resistance was observed in 73 varieties.

      All the resistant and moderately resistant varieties were relatively less preferred by nymphs and there was a positive correlation between the number of nymphs settled and the damage score. Test varieties non-preferred by adult insects for feeding and shelter were also less suitable for oviposition with the exception of ARC 13854, and ARC 14766A. On resistant varieties the nymphal survival was much lower (18·5–28·4%) and nymphal duration was prolonged by 5–7 days as against those on the susceptible check. Results of probing behaviour tests indicated that resistant varieties received more number of probing punctures (80–121) than the susceptible check (31). Further, insects caged on resistant varieties quickly lost their body weight while those on the susceptible check registered gain in weight. Honey dew excretion by brown planthopper adults on resistant varieties was 6·6 to 11·9 times less than that on susceptible T(N)1. Selected varieties showing moderate damage reaction (ARC 5918, ARC 10443, ARC 13984, ARC 14529 and ARC 14864) exhibited more feeding marks, greater amounts of excretion, and higher gain in body weight of the insects, thus confirming a moderate degree of resistance. Based on various parameters, ARC 5780, ARC 5988 and ARC 14394 were comparable to resistant check, Ptb 33 in level of resistance. No association of Lemma and Palea colour with brown planthopper resistance was observed in the rice varieties tested.

    • Host specificity of rice green leafhoppers,Nephotettix virescens (Distant) andN. nigropictus (Stål)

      Kasi Viswanathan M B Kalode

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      Intensive host range studies comprising of 55 common weeds and eight cultivated plant species indicated thatNephotettix virescens could survive and breed only on susceptible rice variety, whileN. nigropictus had a wider host range consisting of rice, sugarcane and five graminaceous weeds.N. virescens preferred rice plant both for settling and egg laying whileN. nigropictus showed greater preference toLeersia hexandra than others. Both species selected the host plants by gustation rather than by vision or olfaction.

    • Nature of resistance in selected rice varieties and population fluctuation of green leafhoppers,Nephotettix virescens (Distant) andNephotettix nigropictus (Stål)

      Kasi Viswanathan M B Kalode

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      In multiple-choice tests with 30-day-old plants of resistant and susceptible varieties, both the species of green leafhoppers,Nephotettix virescens (Distant) andNephotettix nigropictus (Stål) exhibited relative non-preference to highly resistant varieties (Ptb 2, Ptb 7 and Ptb 18) both for settling and oviposition. Even when 100 first instar nymphs were caged on individual 25-day-old plants of highly resistant varieties, the plants suffered very low damage and also induced high mortality of nymphs. Different ages of the plants had no influence on the antibiosis mechanism of resistant varieties. Feeding behaviour studies revealed that both the species made more punctures and excreted less honeydew while feeding on resistant varieties than on susceptible ones. Histological studies indicated no mechanical barrier for feeding in resistant varieties.

      Field investigations indicated that resistant varieties viz Ptb 18, Ptb 2 and Ptb 7 harboured less population of green leafhoppers and had relatively nil or very low incidence of tungro virus disease. An year round survey in the rice ecosystem and marshy habitat whereLeersia hexandra grows in abundance revealed that although both the species coexisted in rice fields,Nephotettix nigropictus alone was present in the marshy habitat.

    • Biochemical aspect of varietal resistance to rice green leafhoppers,Nephotettix virescens (Distant) andNephotettix nigropictus (Stål)

      Kasi Viswanathan M B Kalode

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      Biochemical analysis of 4 rice varieties and a weed showed that the total free amino acid content was greater in the susceptible variety TN 1 than in Ptb 2, Ptb 7 and Ptb 18 which are resistant to both the species of green leafhoppers. However, the weed Leersia hexandra the most suitable host ofNephotettix nigropictus, had the lowest amount of free amino acids. No apparent differences were observed in relation to sucrose, glucose and fructose content in the test varieties. Total phenol content was the highest inLeersia hexandra followed by resistant varieties, while it was the lowest in the susceptible rice variety.

      Bioassay of plant extracts in various organic solvents showed that the chloroform and acetone extracts of the resistant variety Ptb 18 were phagodeterrents to either species of green leafhoppers, while the extract of the susceptible variety with the same solvent was phagostimulant. Of the various chemicals bioassayed, sucrose (5%) among the sugars tested, was found to be highly stimulatory for feeding. Among amino acids, serine, alanine and glutamine were feeding stimulatory in nature. On the other hand, most of the amino acid derivatives, all organic acids and phenolic compounds tested exhibited phagodeterrency.

    • A feeding test to identify rice varieties resistant to the leaf folder,Cnaphalocrocis medinalis (Guenee)

      J S Bentur M B Kalode

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      Dynamics of leaf feeding by the larvae of rice leaf folderCnaphalocrocis medinalis (Guenee) was studied under greenhouse conditions to develop a feeding test to identify varietal resistance. Area of leaf damaged by larvae during their development indicated that first 3 instars accounted for only 8-06% and V instar alone for 66-3% of the total feeding. In view of the highest feeding rate and the longest feeding duration, V instar was chosen for feeding test. No significant differences in area of leaf damaged were recorded when V instar larvae fed for 48 h on 30, 45 and 60 days old plants or when leaf nitrogen content varied from 2–3·4%. Inherent variability among individual larvae in feeding rate could be maintained within acceptable limits with 5 replications.

      The proposed feeding test involved caging of individual V instar larvae for 48 h on 30–45 days old plants of test varieties and recording area of leaf damage. The test revealed varietal differences in area of leaf damaged by the leaf folder and displayed consistency over time. Based on feeding test, 19 rice varieties have been identified as resistant against leaf folder.

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