Luring natural predators to protect orchards

 

 

Researchers and orchardists know quite a bit about the major pests in tree fruit systems, but what about the natural enemies of those pests? Scientists at WSU’s Tree Fruit Research and Extension Center in Wenatchee are working to learn more about these beneficial bugs in an effort to better leverage them in pest control.

 

Shawn Steffan

“Understanding how many, where and when natural predators are in the orchard is extremely important to building an effective biocontrol system,” said Shawn Steffan, a post-doctoral research associate working with WSU researcher Vince Jones. Steffan was a presenter at the first-ever field day at the WSU’s Sunrise Research Orchard southeast of Wenatchee last month.

 

One aspect of Steffan’s work is using new ways to lure natural predators into the orchard, including a chemical “cocktail” that lures a variety of good insects, including green lacewings, parasitic wasps and hoverflies. Lacewings spend much of their lives in the orchard tree canopy and attack codling moth eggs and larvae before they make it into the fruit.

 

Another facet of the research entails measuring when beneficial insects are most prevalent in the orchard. “There are windows of time in the cycle of your orchard when you’d like to spray for key pests, but knowing when their natural enemies are present in high numbers can help refine that spray cycle to make it more precise and more powerful,” Steffan said.

 

Green lacewing

The work presented at the field day is part of a large specialty crops research initiative grant led by WSU that involves scientists from USDA–ARS in Wapato, Oregon State University and the University of California, Berkeley. This research team is exploring a range of different ways to enhance biological control in Western orchards, including evaluating the sublethal effects of some orchard chemicals on natural predators. “What we’re looking at is whether exposure to those chemicals changes their longevity and fecundity,” Steffan said.

 

He noted that research by team member Tom Unruh (USDA-ARS Wapato) also includes analyzing the gut contents of ground beetles to see how often codling moth larvae get eaten when they leave the apples to pupate on the lower tree trunk or in ground litter. “Ground beetles really are the lions and tigers of the orchard floor,” Steffan said.