Preliminary study on the effect of leaflet shape of soybeans on the efficacy of insecticide application
1998
Somsak Srisombun(Department of Agriculture, Bangkok (Thailand). Field Crops Research Institute. Chiang Mai Field Crops Research Center) | Swang Kadkao(Department of Agriculture, Bangkok (Thailand). Field Crops Research Institute. Chiang Mai Field Crops Research Center) | Boonya Anusornrachada(Department of Agriculture, Bangkok (Thailand). Field Crops Research Institute. Chiang Mai Field Crops Research Center) | Sith Dangpradub(Department of Agriculture, Bangkok (Thailand). Field Crops Research Institute. Chiang Mai Field Crops Research Center) | Jidapa Dangpradub(Department of Agriculture, Bangkok (Thailand). Field Crops Research Institute. Chiang Mai Field Crops Research Center)
There are two types of leaflet shape of soybean varieties released by Department of Agriculture, broad and narrow leaflets. The objective of this study was to investigate the effect of leaflet shape on insecticide application. Two broad leaflet cultivars, SJ 5 and Chiang Mai 60 were compared with narrow leaflet cultivars. Sukhothai 1 and Sukhothai 2. Seed were sown in the filed with single replicate at Chiang Mai Field Crops Res Center, Sansai site, in rainy season 1993. Knapsack Sprayer was used with Benzo scarlet (1 percent) spraying soybeans at seed filling growth stage. Walk speed was 0.75 m per second with 2.5 m swatch spraying. A number of droplets was counted on the paper sheets placed on soybean leaves. The results showed that in broad leaflet shape cultivars, the mean number of droplets from the upper and middle carnopies accounted for 11.5 and 4.2 per square cm which approximately twofold and threefold less than in narrow leaflet cultivars respectively. In addition, the average number of droplets from two parts of the canopy (upper and middle) of each cultivar was positively correlated with leaflet shape (length/width ratio). It was suggested that the insecticide application would be more efficient in narrow leaflet than broad leaflet cultivars presumably resulting in obtaining better productivity.
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