Influence of harvesting practices on predation in alfalfa and adjacent cotton in New Mexico

Cotton in New Mexico may benefit from close proximity to alfalfa hay if alfalfa serves as a source of beneficial arthropods.  Field trials were conducted in 2009-2011 on an experiment station and a commercial farm to evaluate the impact of hay on predation in adjacent cotton using cotton bollworm eggs from an insectary.  Eggs were placed in transects to measure the impact on distance to hay and time of year in both trials.  Eggs were removed after 48 hours and examined for evidence of predation.     Predation was often significantly higher in alfalfa compared to cotton.  In an experiment station trials, mean predation in alfalfa was 79% compared to 48-59% in cotton.  Nabids and spiders were more than seven and three times respectively more common in alfalfa than in adjacent cotton. Unlike other states there was no increase in predation in cotton after alfalfa was cut. In experiment station and commercial field trials predation generally was similar or reduced in adjacent cotton a few days after hay was cut.