• J S Bentur

      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

      More Details Abstract Fulltext PDF

      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.

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

      J S Bentur M B Kalode

      More Details Abstract Fulltext PDF

      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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