Progress against Onion Pests

  An onion variety trial.

IPM Adoption Helps Onion Growers Manage Thrips and Other Pests

For Las Cruces onion and pepper farmer Steve Lyles, following integrated pest management principles is a necessity. Much of his acreage is right on the outskirts of town, so he’s been proactive in managing dust, noise and pesticides.

“I farm around one school, so we have to be careful of what and when we spray,” he told Growing Produce in a profile published in 2012. “We monitor the insect populations closely and use the softest chemistries available.”

Lyles has won awards for his progressive approach to farming, including the New Mexico State University Leyendecker Agriculturalist of Distinction award for 2013, but more and more onion growers are also adopting IPM practices and benefitting from IPM strategies, according to Howard Schwartz, a professor of plant pathology at Colorado State University. Schwartz is the lead author of a recently published national Pest Management Strategic Plan for dry bulb storage onions, which was created with Western Integrated Pest Management Center funding.

“We’re seeing good adoption of IPM by growers, either as individuals, or coming from crop consultants,” he said. “We’ve been pleased with that.”

Managing Thrips

The recently published PMSP updates a 2004 document that was less national in scope, and highlights some of the advances made over those nine years. One area that’s improved is managing thrips and the Iris yellow spot virus that they carry.

“Cultivar selection is making a difference when it comes to thrips,” explained Mark Uchanski, an assistant professor of horticulture at New Mexico State University who contributed to the new onion Pest Management Strategic Plan and is involved in related research. “More glossy and green foliage is less attractive to thrips. More waxy and blue foliage is more attractive.”

Plant breeders are also developing more vigorous onion cultivars as well.

“They’re better able to stand up to the feeding of thrips,” Schwartz explained. “That’s one thing we’re able to share through field trials.”

Both Schwartz and Uchanski see widespread adoption of other IPM practices by onion growers trying to manage thrips, including crop rotation, better management of debris and weeds where thrips populations can grow, and pest scouting to time pesticide applications appropriately.

“They’re heavy on the scouting to make sure they stay ahead of the curve,” Uchanski said. “I’m seeing growers who will time or at least be aware of alfalfa cutting in nearby fields because that will cause thrips to move.”

Despite the gains, thrips remain the leading onion pest in the U.S., especially when combined with the damage done by Iris yellow spot virus.

Other Pests and Pathogens

Other major disease challenges for onion producers are soil-borne and bulb infecting fungal and bacterial pathogens.

“White rot is still an issue,” Schwartz said, “and so are Fusarium, pink root and Botrytis neck rot.”

Fungicides and proper storage practices can help combat losses to those diseases, and Schwartz sees a need for a quick bacterial and fungal diagnostic tool for the onion industry.

“There are 10 or 15 different bacterial pathogens that can attack onions,” he said. “A DNA-based test is being developed by Brenda Schroeder at Washington State University so you can blot a sample on a card and within a few hours be able to say what’s attacking your onions and be able to treat it correctly.”

And that’s one of the biggest benefits of a new Pest Management Strategic Plan: it identifies needs and helps direct research going forward. The new PMSP also integrates closely with other national projects like the W2008 Research and Extension Committee “Biology and Management of Iris yellow spot virus, Other Diseases and Thrips in Onions.”

“Because of the PMSP, we’re on the same page and organized,” Uchanski said. “This was written by representatives of the onion industry, USDA, academics and growers and packers, so now when we apply for a research grant, there’s weight behind that request.”

The dry bulb storage onion PMSP can be downloaded here.