1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)

The rice caseworm, Parapoynx stagnalis (Zeller) (Lepidoptera: Crambidae), has emerged as a serious pest of rice, particularly in South India in recent years. It is reported to cause a reduction in yield by about 30 per cent in rice. Sporadic incidence of the caseworm has been reported recently from many rice growing tracts of Kerala as well. Yet, hardly any study has been conducted either on the biology or management of this pest. The study was conducted at the Department of Agricultural Entomology, Regional Agricultural Research Station, Pattambi during 2023-24. The objectives of the study were to investigate the biology of rice caseworm, the population dynamics of rice caseworm and its natural enemies and to evaluate the bio-efficacy of plant products and insecticides against the pest. The life cycle of P. stagnalis consisted of egg, larva, pre-pupa, pupa, and adult. The caseworm recorded an incubation period of 3.25 days in male and 3.48 days in female. The total larval period was 16.93 and 18.63 days in male and female, respectively. The pre-pupal and pupal duration was 1.30 and 5.4 days in male and 1.58 and 6.18 days in female, respectively. The total duration from egg to adult was shorter for male (30.83 days) as compared to female (34.52 days). The maximum adult emergence was recorded during 6.00 pm to 12.00 am. Pre-oviposition, oviposition and post-oviposition periods of female moth lasted for 1.3, 2.4, and 1.7 days, respectively. The sex ratio was found to be 1:1.43. The female moth laid 45 to 104 eggs, varying in different seasons with 43 to 81 per cent hatchability. The morphometrics study on different stages of caseworm showed that the mean length and width of the egg were 0.65 ± 0.12 and 0.50 ± 0.05 mm. The length and width of 1st, 2nd, 3rd, 4th, and 5th larval instars were 1.95 ± 0.23 and 0.21 ± 0.0 mm, 5.21 ± 0.18 and 0.39 ± 0.09 mm, 6.92 ± 0.13 and 0.65 ± 0.06 mm, 8.95 ± 0.21 and 0.88 ± 0.14 mm, 11.45 ± 0.20 and 1.28 ± 0.14 mm. The pupa measured 7.95 ± 0.34 mm in length and 1.54 ± 0.13 mm in width. In the Rabi season, the highest moth population was recorded in the field after four weeks of transplanting in sweep net catch, viz., 8.5 moths/10 sweeps during 3rd week of January, while in Kharif, the highest catch (7.5 moths/10 sweeps) was recorded during 1st week of September. In light trap, the highest catch was obtained during 3rd week of August in Kharif (7.86) and 2nd week of November (12.14) in Rabi season. The correlation study concluded a significant positive correlation with maximum temperature (0.756) and a significant negative correlation with minimum temperature (-0.88) and relative humidity (-0.778) in the Kharif season. In contrast, no significant correlation was obtained in the Rabi season. The joint effect of weather variables showed a significant negative correlation with minimum temperature and relative humidity (Tmin*RH) in the Kharif season. The highest leaf damage was caused by 4th instar larva with a mean per cent damage of 26.74. The rice field weed, Isachne miliaceae (Naringa) was identified as an alternate host to rice caseworm. In the field, the spider, Plexippus paykulli (Araneae: Salticidae) was recorded as a predator of rice caseworm larvae. A hymenopteran wasp, Apsilops scotinus (Ichneumonidae) was recorded as a larval pupal parasitoid of rice caseworm. The evaluation of oil cakes and bio-pesticides under net house conditions against rice caseworm larva showed that mahua cake at 3 % was the most effective treatment followed by B.t and mahua cake at 2 %. Mahua cake at 3% recorded the lowest leaf damage (7.73 %) followed by mahua cake at 2%, neem cake at 3 %, and B.t. In the field evaluation, Cartap hydrochloride + Emamectin benzoate was found to be the superior treatment recording 100 per cent mortality in Rabi and 95.95 per cent mortality in Kharif. This was followed by Carbosulfan and Fipronil. During Rabi season, significant mortality was observed in the treatment with Bacillus thuringiensis (71.99 %). A higher yield was recorded in the plot treated with Cartap hydrochloride Emamectin benzoate (3344.13 kg/ha in Rabi and 3117.30 kg/ha in Kharif), followed by fipronil and carbosulfan. This study provides valuable insights into the biology, ecology, population dynamics, and management of Parapoynx stagnalis, contributing to the development of effective and sustainable management strategies for rice caseworm, for the enhancement of rice production and food security.

Literature on the insect pests of the important pilse crops, with special reference to the work done in India has been reviewed. The biology and bionomics of the pea leaf roller Nacoleia vulgalis Gn. (Pyralidae) have been worked out in detail. The moths mate a day after emergence. The female moth lays creamy yellow, oval, scale like eggs during night in rows, generally on tender leaves . On an average , about 542 eggs are laid by one female. Incubation period is 4 days. Larval period lasts 13 to 15 days, the larva undergoing five instars. Durations of the different instars are 3 to 4 , 2 to 3, 2 to 3, 2 to 3 and 4 to 6 days respectively. The first instar caterpillars nibble and feed on the green matter on the undersurface at the base of the leaves and the later stage caterpillars web the leaves together and feed from inside skeletonising the leaves.

1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)

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