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Aim: To study the seasonal incidence pattern of gram pod borer, Helicoverpa armigera (Hübner) and tur pod fly, Melanagromyza obtusa (Malloch) in pigeonpea ecosystem.
Study Design: Complete Randomized Block Design.
Place and Duration of Study: Field experiments were conducted at Agriculture Research Farm, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi during Kharif seasons of 2015-16 and 2016-17.
Methodology: The pigeonpea crop (cv. Bahar) was grown in plots of 10 m X 5 m (50 m2) replicated thrice and the crop fields were kept free from pesticide sprays. Five plants were selected randomly from each plot and weekly observations of the respective pests were taken through Plant Inspection Method (PIM) starting from 50 per cent flowering stage to till maturity of the crop and then correlated with the meteorological data.
Results: The results revealed that the infestation and severity of these insect pests were highly influenced by weather parameters. H. armigera population reached its peak (4.50 and 4.20 larvae per plant, respectively) in the 9th standard week of both the years. Similarly maximum incidence of M. obtusa in terms of maggot population was also recorded in 9th standard week with population of 8.00 and 7.75 maggots per plant. Correlation studies indicated that the population of these insect pests exhibited a significant positive correlation with maximum temperature whereas a significant negative correlation was established with relative humidity. The multiple regression analysis revealed that variations of different weather variables caused approximately 89.6 and 86.4 per cent variations in H. armigera population and 90.7 and 94.6 per cent variations in M. obtusa population during both years, respectively.
Conclusion: Different weather parameters determine seasonal activity and population dynamics of H. armigera and M. obtusa on pigeonpea and this information would help in developing weather based forecasting models for successful development and implementation of the pest management strategies against these major insect-pests of pigeonpea.