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Subject: Agricultural Entomology × Author: Asha, J S × Author: KAU × End date: 2010 × Start date: 2005 × Type: Thesis ×
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    ThesisItemOpen Access
    Seasonal occurance and ecofriendly management of pests of amaranthus
    (Department of Agricultural Entomology, College of Agriculture, Vellayani, 2005) Asha, J S; KAU; Nandakumar, C
    Seasonal occurrence of pests, their natural enemies and leaf blight disease of amaranthus were studied in the Instructional Farm, College of Agriculture, Vellayani from April 2004 to April 2005. Leaf webbers Psara basalis F. and Hymenia recurvalis (F.) were the major pests of amaranthus and leaf blight disease caused by Rhizoctonia solani Kuhn. was the major disease. The leaf webber P. basalis was present in the field throughout the year. However the highest population and infestation was observed during the summer months. Maximum population of larvae was observed during the month of April 2004. The population and extent of damage by the pest exhibited significant positive correlation with maximum and minimum temperature. The leaf webber H. recurvalis was also present in the field throughout the year. The population and extent of damage by the pest was maximum during June, July and November 2004 and minimum during the summer months (April and May 2004). The population of the pest showed significant positive correlation with minimum temperature. The green grasshopper Atractomorpha crenulata F. was observed in the field throughout the year. Highest population was observed during the first fortnight of October 2004. The percentage of plants and leaves damaged by the grasshopper was maximum during the second fortnight of November 2004. The population and extent of damage of the grasshopper showed significant negative correlation with minimum temperature. The percentage of plants damaged by the tobacco caterpillar Spodoptera litura (F.) was maximum during the second fortnight of June 2004 and the leaves damaged was the highest during the first fortnight of June 2004. The leaf damage showed significant positive correlation with rainfall. A solitary braconid endoparasitoid Apanteles opacus (Ashmead) was found infesting the second instar larvae of H.recurvalis. The population of pupae of the parasitoid was maximum during the first fortnight of July 2004. Spider predators viz., Oxyopes spp., Cheiracanthium sp., Phidippus sp. and Tetragnatha sp. were found in the field throughout the year. Maximum population of spiders was observed during the second fortnight of September 2004. The population showed significant positive correlation with maximum temperature. The leaf blight disease caused by R. solani was observed throughout the year. The percentage disease index (PDI) was maximum during the second fortnight of December 2004. Studies on antifeedant effect of botanicals on major pests of amaranthus revealed that azadirachtin 0.0025 per cent was the best phagodeterrent followed by cow’s urine 10 per cent + NSKE five per cent and NSKE five per cent. Six botanical pesticides were evaluated with malathion as check in a field experiment. The treatments included neem seed kernel extract five per cent (NSKE), neem cake (NC) soil application @ 250 kg.ha-1 at planting + neem cake extract (NCE) 10 per cent spray, azadirachtin 0.0025 per cent, cow’s urine 10 per cent + NSKE five per cent, Pongamia oil soap emulsion two per cent and annona seed extract two per cent. Three sprays of the treatments were applied on the crop during the experiment. The results revealed that all the treatments were significantly superior to control in reducing the population of pests and their damage. Azadirachtin 0.0025 per cent was the most effective treatment against leaf webbers and grasshopper. This was followed by cow’s urine 10 per cent + NSKE five per cent and NSKE five per cent. The extent of damage caused by these pests in azadirachtin treated plots was statistically similar to that of malathion treated plots. . The extent of damage by the tobacco caterpillar was the lowest in NC soil application @ 250 kg ha-1 + NCE 10 per cent spray treatment. Higher population of spiders was found in botanical treated plots and control plots compared to malathion treated plots. The botanical treatments were not effective in containing the leaf blight disease. Maximum yield of marketable produce was recorded from malathion treated plots. However the B : C ratio was the highest (3.20) in botanical treatment, azadirachtin 0.0025 per cent (NeemAzal 1% TS @ 2.5 ml/litre) followed by cow’s urine 10 percent + NSKE five per cent (2.12) and NSKE five per cent (2.08). Three sprays of any of these botanicals at fortnightly intervals starting from two weeks after transplanting could manage the pests of amaranthus.