Estimation of economic injury level (EIL) of cotton bollworm Helicoverpa armigera Hb. (Lep., Noctuidae) on cotton
Subject Areas : entomology and othea arthropods
1 - Agricultural and Natural Resources Research Center of Khorasan-e-Shomali province, Bojnourd, Iran.
2 - University of Tehran, Faculty of Agriculture, Karaj, Iran
Keywords:
Abstract :
Economic Injury Level (EIL) of cotton bollworm Helicoverpa armigera Hb. was evaluated on Sahel variety in Gorgan, Iran during 1999-2000. Infestation levels of 0, 2, 3, 4, 6 and 8 neonate larvae per 100 reproductive organs were studied in three generations of the pest by releasing them on cotton plants in the field. Statistically significant differences between treatments were observed in all generations. In the first generation, infestation level of 8%, in the second and third gernerations, infestation levels of 4, 6 and 8% caused significant reduction in yield (p≤0.05). Reduction yields for infestation level of 8% in the first-generation was 13.94%, in the second generation the infestation levels of 4, 6 and 8% were 9.8, 16.77 and 22% respectively, and in the same infestation levels in the third generation were 8.25, 14.85 and 19.17%. Linear regression between the cotton yield and pest density was obtained in different generations. Considering the total cost of chemical control operations and cost of yield, the economic injury level of the pest for the first, second and third generations were 1.19, 0.66 and 0.79 neonate larvae per 100 reproductive organs respectively, which is equal to 22.25, 15.77 and 21.33 neonate larvae per 100 cotton plants, respectively.
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