Population Dynamics of Helicoverpa armigera and Predator Fauna in Sunflower Crop

Abstract

The experiment was conducted during the Kharif (August) seasons of 2012 and 2013 at the Zonal Agricultural Research Station, University of Agricultural Sciences (UAS), Gandhi Krishi Vignan Kendra (GKVK), Bengaluru, to assess the seasonal incidence of Helicoverpa armigera and its natural predators on sunflower hybrid (DRSF-1) and variety (DRSH-108). Weekly observations on egg, larval and predator population were recorded from the second week of September to the last week of November during both the seasons. Peak larval infestations occurred between the 43rd and 46th standard meteorological weeks (SMW), with slightly higher infestation levels observed in 2012 compared to 2013. Predator population viz., coccinellids (Cheilomenes sexmaculata), green lacewing (Chrysoperla zastrowi), assassin bugs (Harpactor fucipes), pentatomid bugs (Eucanthecona furcellata), spiders and others also peaked during the same period, indicating a synchronized interaction with pest abundance. In the pooled analysis for DRSH-1, H. armigera incidence exhibited positive correlations with sunshine hours (r=0.373) and soil temperature (r=0.138), while maximum temperature (r=-0.595), minimum temperature (r=-0.356) and total rainfall (r=-0.289) showed negative correlations. For DRSF-108, most correlations were statistically non-significant; however, sunshine (r=0.254), afternoon relative humidity (r=0.410), and soil temperature (r=0.292) had mild positive associations. Minimum temperature (r=-0.413) and maximum temperature (r=-0.709) negatively influenced pest incidence. Multiple regression analysis revealed that the collective influence of meteorological parameters explained 88.30 to 97.10% of the variation in H. armigera incidence. The findings provide a practical basis for developing weather-based pest forecasting models and adopting timely, eco-friendly management practices that leverage natural predator activity, thereby reducing excessive reliance on chemical control in sunflower ecosystems.