Tillage Intensity Influences Insect-Pest and Predator Dynamics of Wheat Crop Grown under Different Conservation Agriculture Practices in Rice-Wheat Cropping System of Indo-Gangetic Plain

Abstract

Tillage can alter the soil habitats wherein many insect pests and their natural enemies reside during at least part of their life cycle. To enhance crop productivity and reduce climate change effects, conservation agriculture (CA) with reduced-tillage or no-tillage practices have been advocated to farmers. However, information relating to the effect of CA on insect pests and their natural enemies is very scarce, at least in the Indo-Gangetic region. In this study, the effect of tillage on the abundance of, and damage by, major insect pests (foliar aphids, root aphids, termites, and pink stem borer) and their natural enemies in wheat managed under three tillage practices, i.e., zero-till (ZT), reduced tillage (RT), and conventional tillage (CT) with (protected) and without (unprotected) insecticide protection scenarios, was investigated. Foliar aphid and termite numbers were lowest in the ZT-protected system, and highest in the CT-unprotected system. Pink stem borer damage was significantly higher in the ZT-unprotected system, whereas the root aphid number was maximum in the RT-unprotected system. The natural enemies of these four major insect pests of wheat showed variable trends under the studied tillage systems. The abundance and damage of these major insect pests showed a positive correlation with the normalized difference vegetative index (NDVI) and canopy temperature. The dynamics of the insect pests and their predators were driven by soil habitat-related changes (direct) as well as crop growth-related effects (indirect). A fine-tuning of insect-pest management tactics based on these relations would enhance the success of CA systems.