Influence of alfalfa on biological control of insect pests in New Mexico

New Mexico crops may benefit from close proximity to alfalfa hay since hay may act as a source of predators that  may enhance biological control on nearby crops.  Field trials were conducted on NMSU experiment station and commercial farms from 2008-2012 to evaluate the impact of alfalfa on predation in cotton and pecan.

Predation was often significantly higher in alfalfa compared to cotton.  In experiment station trials mean predation in alfalfa was 79% compared to 53% in adjacent cotton. Nabids and spiders were collected more than seven and three times more often in alfalfa than in adjacent cotton.  Other predators were more likely to move. Ladybugs and green lacewings were found at similar levels in alfalfa and adjacent cotton.  Unlike other areas there was no increase in predation in cotton after alfalfa was cut, instead predation was either not significantly different or reduced. 

Unlike cotton, predation in pecan was not affected by proximity to hay.  Direct observations of predation in pecan indicated Hibana incursa a spider specific to trees was the key predator in pecan with up to 72% of observations being H. incursa.