Pests, Pathogens, and Organic Onions
Organic onions are a valuable commodity in the Great Lakes region, but their economic viability has been critically threatened by pests and pathogens that are difficult to manage. Stakeholders have identified onion thrips, Thrips tabaci, as the most serious insect pest and Stemphylium leaf blight (SLB), caused by Stemphylium vesicarium, as the most important foliar pathogen in this region. Furthermore, damage by onion thrips can make plants more susceptible to SLB, which can lead to the loss of entire crops.
Brian A. Nault, Entomology, is leading a team of Cornell researchers to develop and implement an effective integrated pest management (IPM) program for onion thrips and SLB that will ensure the sustainability and profitability of organic onion production in the Great Lakes. Their approach includes a combination of plant resistance and crop protectants listed by the Organic Materials Review Institute (OMRI).
The team, which includes entomologists, plant pathologists, and a plant breeder, has already identified some promising OMRI-listed crop protectants that may significantly reduce damage by onion thrips and SLB. They have also demonstrated that onions characterized as having semi-glossy wax foliage have less thrips damage, and these selections may be less vulnerable to SLB. Next steps include evaluating OMRI-listed crop protectants in combination with thrips-resistant onions to manage the pests and blight and demonstrating an IPM strategy in participating organic growers’ fields. The team plans to develop web-based resources to help other producers implement the IPM program. They also hope to develop and release new early-maturing, multiple-pest-resistant onion cultivars for organic growers.