The present study was motivated by a lack of information on how to control Helicoverpa armigera in soybean fields in Brazil. Nine chemical and four biological treatments were tested. Control efficiency was evaluated at 3, 7, 10, and 14 days after spraying. Moreover, the cost benefit ratio by the yield and cost of insecticide application and the economic injury level (EIL) were used to calculate the chemical and biological treatments. Chemical insecticides chlorantraniliprole, flubendiamide, chlorfenapyr, spinosad and acephate with 90.9, 90.9, 90.9, 72.7 and 90.9% of control efficiency, respectively, were efficient to control H. armigera along the evaluations. Bt Control® was efficient controlling small and large larvae, with 100 and 66.7% of control efficiency, respectively. Gemstar® and HzNPV CCAB® were efficient against small larvae. The treatments acephate (1:10), chlorantraniliprole (1:6.6), flubendiamide (1:5.3), Bt Control® (1:6.6), Gemstar® (1:5) and HzNPV CCAB® (1:5.7) had higher cost benefit ratio (ratios are indicated in parentheses after the treatments names). The EIL is flexible and vary according to the control efficiency, cost of treatment application and market value of soybean. The lowest value of EIL was Dipel® (0.2) and the highest value was chlorfenapyr (2.3). These findings support a decision of when, which treatment, and dose to spray to control H. armigera on soybean with a high cost benefit ratio.
Key words: Old world bollworm, control pest, chemical insecticide, biological insecticide.
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