Browsing by Author "Karthikeyan, K"

Now showing 1 - 3 of 3

Bio -ecology and management of rice caseworm, Paraponyx stagnalis (Zeller) (Lepidoptera : Crambidae)
(Department of Agricultural Entomology, College of Agriculture, Vellanikkara, 2025-02-13) Muhammed Arshad, V; Karthikeyan, K
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.
Bio efficacy of newer isecticides against leaf hopper, empoasca motti pruthi in bitter gourd
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2003) Karthikeyan, K; Mani Chellappan
Bio efficacy of newer insecticides was evaluated by two field experiments at the College of Horticulture, Vellanikkara during rabi, 2001 and summer, 2002.against major pests of bitter gourd. Imidacloprid (2 g a.i.kg") and acetamiprid (1.5 g a.i.kg") were used as a seed dressers .The newer molecules namely acetamiprid, ethofenprox and imidacloprid were sprayed at different crop stages viz., early vegetative (30 DAS), pre flowering (50 DAS) and fruiting stage (64 DAS) as separate treatments. Acephate was used as a standard check. The present investigation revealed that acetamiprid (1.5 g a. i. kg") was the most effective insecticide as seed dressers against sap feeders viz., leaf hoppers and aphids. Foliar spray application revealed that both imidacloprid (20 g a.i.ha") and acetamiprid (10 g a.i. ha") consistently effective in reducing the sucking pests viz., leaf hopper and aphids followed by ethofenprox (50 g a.i.ha") in both the season. Fruiting stage spray by acetamiprid and imidacloprid had registered the lowest fruitfly infestation .The fruit borer infestation was less in the plots, which received the preflowering and fruiting stage insecticide sprays. The highest yield of bitter gourd was recorded in the imidacloprid (pre flowering stage spray) treated plots in both rabi (1 o 1. 66'fruits/Sm2) and summer (1 02. 66fruits/Sm2) seasons. Seed treatment of newer insecticides had no harmful effect 'on soil micro flora (fungi, bacteria and actinomycetes). Population of natural enemies was unaffected by the insecticide applied along with the seed compared to the foliar applications. Studies on the residues of imidacloprid by high performance liquid chromatography indicated that imidacloprid applied at different stage of the crop viz., sowing, early vegetative, preflowering and fruiting stage to bitter gourd resulted no detectable residue in the harvested fruits.
Bioecology, population dynamics and integrated management of rice blue beetle, Leptispa pygmaea Baly (Chrysomelidae:Coleoptera)
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2007) Karthikeyan, K; Sosamma Jacob