9477 Impact of Alfalfa on Biological Control of Cotton Insect Pests in New Mexico

Tuesday, January 6, 2009
Salon H (Marriott Rivercenter Hotel)
Wednesday, January 7, 2009
Salon H (Marriott Rivercenter Hotel)
Thursday, January 8, 2009
Salon H (Marriott Rivercenter Hotel)
Jane Breen Pierce and Patricia Monk, New Mexico State University, Artesia, NM
Alfalfa can be a source of beneficial arthropods for other crops.  Field trials were conducted on an experiment station and a commercial farm to evaluate the impact of hay on predation in adjacent cotton using cotton bollworm eggs from a laboratory colony.  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 trial, mean predation in alfalfa was 78% compared to 48-58% in cotton.  The primary predators were ladybug adults, nabids and various spiders.  At very high predation rates, there was little difference in predation rates between adjacent alfalfa and cotton fields with 85-97% predation in alfalfa and up to 300 feet into cotton.  However, there was significantly less predation 1000 feet into the cotton field with 67% predation on one date suggesting that close proximity may have the highest impact.   After cutting and cooler weather, predation rates declined in the commercial field with a mean 65% predation in alfalfa but only 28% predation in the commercial cotton field.  September also produced lower predation rates in the experiment station trial with 35% predation compared to 53-77% predation in July and August.

On the experiment farm, four transects from hay into cotton were placed on each border of a small cotton field.  Each transect was replicated four times for each of the four borders of the field.  Eggs were placed 10 feet into hay and  10, 30 and 80 feet into the cotton field.  Predation of eggs was evaluated in the laboratory. Sweep net samples were collected to identify and quantify predators in each location.  Results from that trial will be discussed.