Application of Thai Entomopathogenic Nematode for Insect Pests of Chinese Kale Control

Abstract

A random count of the number and type of important insect pests infested Chinese kale grown in Nong Sua district, Pathum Thani province in the first growing season (January – March 2003) and 5 species of insects were found. Listed from the most dominant of the least were common cutworm (Spodoptera litula Fabricius), flea beetle (Phyllotreta sinuata Stephen), cabbage webworm (Hellula undalis Fabricius), cabbage looper (Trichoplusia ni Hubner) and beet armyworm (Spodoptera exigua Hubner). The highest number of insects was 1.12 larvae/plant at 48 days resulting in 76% unmarketable Chinese kale damage the crop. During the second and third seasons, tests were made on the use of Thai entomopathogenic nematodes (steinernema sp., Thai isolate) on the same land to control insects. Five time of sprayings were made on the crop growing at rates of 1x105, 1x106 and 1.5x 106 nematodes / 5 m2 , compared with farmer’s practices (7 insecticide sprays), hygienic’s practices (5 insecticide sprays) and no chemical spray. Results were indicated that in the May – July 2003 season, common cutworm namely, flea beetle and cabbage looper were infested at the rates of 1.8, 1.2 and 0.7 insects / plant, respectively. Spray rate of 1x106 nematodes/ 5 m2 (60 plants) was effective at reducing insect pests by 57.63 % and yielded 80.42% (48.25 plants) marketable Chinese kale, and was not statistically different from farmer’s and hygienic’s practices. The five applications of nematodes on 5 m2 plot cost 17.50 baht, producing a harvest of 7.68 kg of Chinese kale worth 192 baht. (Non-chemically treated Chinese kale fetched 25 baht/kg). This is in comparison with 7 sprays of insecticides costing 22.75 baht, yielding 9.11 kg of Chinese kale worth 109.32 baht (chemically treated Chinese kale fetched 12 baht/kg). When kale was planted again during August- October 2003, common cutworm and cabbage looper were increased to 3.58 and 0.81 / plant. This required an increased rate of nematode at 1.5x106 per 5 m2 (60 plants), resulting in a 46.94% reduction of insect number. Yield was at 78.46% (47.08 plants), that was not significantly different from farmer’s and hygienic’s practice. The cost of nematodes for 5 applications was 26.25 baht and 22.75 baht for 7 insecticide applications. Marketable yields were 8.46 and 8.94 kg/ 5 m2, worth 211.50 and 107.28 baht respectively. After deducting costs of nematodes and insecticides it was found that the use of nematodes gave higher returns for both plantings. Therefore, the use of Thai entomopathogenic nematode to control insect pests in Chinese kale production at the rate of 1- 1.5 x 106 nematodes / 5 m2 gave higher marketable yield of higher priced organic Chinese kale than when using chemicals.