Study on dosage, application time and application rate of nuclear polyhedrosis virus (NPV) to control the cotton bollworm, helicoverpa armigera hubner on grape
1998
Uthai Ketunuti (Department of Agriculture, Bangkok (Thailand). Entomology and Zoology Div. Biological Control Research Group)
Efficacy tests of Helicoverpa armigera nuclear polyhedrosis virus (HaNPV) on grape were conducted at Ban Paew district, Samutsakorn province during 1994-1997. Five rates of HaNPV at 3.0, 3.8, 4.5, 6.0 and 7.5*10*[12) occlusion bodies (OB) per rai (6.25 rai = 1 ha) were applied two times with 4-day intervals in order to control the larvae and fruit damage at the stages of blooming and fruit setting. Application of HaNPV starting at 20 and 50 percent of blooming stage were also tested. It was found that there were not significantly different in efficacy among 4.5, 6.0 and 7.5*10*[12) OBs per rai at 20 percent of blooming but at the rate of 7.5*10*[12) OBs per rai gave the best control for fruit damage. The results also showed that starting application at 20 percent of blooming stage better controlled both larvae and number of fruit damage less than application at 50 percent. Three different spray volumes at 150, 250 and 400 litres per rai with high pressure sprayer installed on boat were applied in order to select the optimum control on grape. The results showed that the rate of 250 litres per rai gave good larvae control and optimum consumption of HaNPV. Four dosages of HaNPV 3.0, 3.8, 4.5, 6.0*10*[12) OBs per rai were compared with 2 insecticides, chlorfluazuron (Atabron 5 percent EC) 150 ml per rai and alpha cypemethrin per PBO (Supercord 30 percent EC) 187.5 ml per rai at 20 percent of blooming stage. The results showed that HaNPV at the rate of 6.0*10*[12) OBs per rai gave superior control to both insecticides.
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