Conservation agriculture contributes to higher predator abundance in central Mexico

Globally, conservation agriculture (CA) is recommended as an alternative to conventional agricultural production for its contributions to increased yields and mitigation of the effects of climate change. As a series of practices involving crop rotations, reduced soil disturbance, and the retention of organic matter at the soil surface, CA increases soil quality and reduces erosion, and provides a more favorable habitat for beneficial soil-dwelling organisms. In spite of the many benefits of CA, aspects of CA may contribute to increased insect pests. This may only be a problem, however, if generalist arthropod predators are not present to contribute to pest control.  To determine the effect of CA on generalist arthropod predator and pest dynamics, we assessed the arthropod community in a long-term CA trial at the International Maize and Wheat Improvement Center (CIMMYT) in central Mexico. On three dates in summer of 2013, we evaluated a corn-wheat rotation, planted under conservation agriculture (zero tillage, retention of residues) and conventional agriculture (tillage and no residue), by sampling arthropods by pitfall, and assessing in-field predation with the use of sentinel waxworms. Activity densities of certain predatory arthropods, e.g., spiders, were greater in CA treatments, while activity densities of certain herbivores (e.g., leafhoppers) were greater in conventional treatments. Predation rates of sentinel insects were consistently high in all treatments, except under conventional agriculture on one date in wheat. This first report of the effects of CA on arthropods in this long-term trial indicates that CA may contribute to generalist predator conservation.