Entomologist David Crowder. (Photos courtesy of David Crowder)
A previous study by Crowder, Snyder and others – published in the journal Nature in July 2010 – presented an impressive step in describing biological pest control in potatoes. The authors suggested that organic potato fields have significantly more natural insect enemies – and thus a better balance among pest and predator communities – than conventionally grown potato fields.
In more recent work, the researchers found that planting crops such as alfalfa and peas close to potato fields can aid natural potato pest management by increasing the populations of natural enemies and decreasing the densities of pests.
PULLMAN, Wash. Researchers at Washington State University are conducting a study with potato farmers to determine if promoting biodiversity in insect communities helps insects, especially beneficial ones, withstand the effects of a warming climate.
“There really isn’t much research being done on biodiversity and how it can help make communities continue to function in climate change,” said WSU entomologist David Crowder. “This field is still fairly new.”
Transition to biocontrol
For farmers, results could point to better ways of implementing biological control to help their systems adapt to climate change, he said. Biological control is a pest-management strategy that uses pests’ natural insect enemies to control problematic bugs.
“Biological control by naturally occurring predatory insects and spiders is an ecologically friendly and sustainable approach to pest management,” Crowder said.
“Greater diversity of species results in ‘niche overlap,’” he said. “If one species is knocked out of a particular nichefor instance, the Colorado potato beetle predatoranother can step in to fill that niche.
“However,” he said, “biological control in potatoes is underutilized, in part because we know very little about how to successfully encourage predators and maximize their impacts on pests.”
Planting adjacent crops that encourage insect movement, matching insects to specific microclimates and controlling fertilization to promote biodiversity are among the areas to be explored.
“There is a transition to biocontrol,” Crowder said, “and this research could help farmers make that transition more easily.
Study area offers wide variety
Lady beetles prey upon insects
that damage crops.
With support from a $130,000 grant from the U.S. Department of Agriculture’s National Institute of Food and Agriculture Fellowships Grant Program, Crowder and colleagues are investigating how regional changes in temperature and precipitation affect Columbia Basin insect communities and whether organic farming practices maintain balance among those communities.
“The Columbia Basin is a perfect living laboratory to investigate the potential effects of climate change on insect biodiversity,” said Crowder.
The region is unusual for its wide range of climatic conditions yet similar insect communities – both pests and their predators or “natural enemies.” From north to south, average temperatures can vary from 3 to 5 degrees Fahrenheit, while precipitation ranges from 3 to 15 inches a year.
Since Columbia Basin potato growers raise a mix of conventional and organic crops, Crowder and his colleagues can observe how different cropping systems affect insect communities amid the region’s various climates.
“In areas with higher temperatures and somewhat higher precipitation, the natural enemy communities tend to be not as balanced,” Crowder said. The imbalance results in higher pest populations.
“Our study will look at the effects of this broad climatic variation on these insect populations,” he said.
Insecticide use decreasing
Potatoes are one of many high-value crops grown in the Columbia Basin, but they require insecticides to control several devastating pests, Crowder said. With McDonald’s, Sysco and other major corporate potato buyers requiring that growers pass audits to justify each insecticide application, use of broad-spectrum insecticides is falling out of favor and organic potato production is increasing.
Crowder said he hopes more research into biological control will help farmers practice more insect-friendly growing methods and still produce a robust potato crop.
Since 2009, Crowder and the research team – including entomology professor William Snyder, graduate student Christine Lynch and soil science professor John Reganold – have worked with Columbia Basin potato farmers to sample crops and collect native insect specimens.