Influence of Alfalfa Hay on Egg Predation In Adjacent Cotton Fields In New Mexico

Cotton in southern New Mexico valleys benefits from close proximity to alfalfa hay which is known for producing high populations of beneficial arthropods. Field trials were conducted on an experiment station to evaluate the impact of hay on predation in adjacent cotton using cotton bollworm eggs from an insectary colony. Eggs were placed in transects to measure the impact on distance to hay, direction, and time of year. Eggs were removed after 48 hours and examined for evidence of predation.  Lab to field assays were also conducted before, 1, 7 and 14 days after cutting to evaluate the impact of cutting on predation.

Predation was often significantly higher in alfalfa compared to cotton.  Mean predation was 79% compared to 48-59% in cotton in 2010.  Nabids and spiders were more than 7 and 3 times respectively more common in alfalfa than in adjacent cotton. Unlike California and Arkansas, there was no increase in predation after alfalfa was cut. Predation was generally similar or reduced in adjacent cotton a few days after hay was cut.