Cultural Management of Onion Thrips and Iris yellow Spot Virus

View the project final report

• 2008 annual report
• 2009 annual report

Commodities

• Agronomic: corn, wheat
• Vegetables: carrots, onions

Practices

• Crop Production: intercropping, application rate management
• Education and Training: extension, on-farm/ranch research
• Farm Business Management: budgets/cost and returns
• Pest Management: cultural control, disease vectors, trap crops
• Production Systems: agroecosystems
• Soil Management: nutrient mineralization

Iris yellow spot virus (IYSV) and onion thrips threaten sustainable, profitable onion production in Utah and the Western US. Onion growers in Utah rely on high-risk insecticides for thrips management, which has increased insecticide resistance and may increase the severity of IYSV outbreaks. Very little is known about how to effectively manage IYSV. We do not know if cultural practices affect its spread and whether more intensive thrips insecticide programs really reduce IYSV incidence or severity. In collaboration with growers we propose to survey the Utah onion industry to ascertain the effectiveness of IYSV and thrips management strategies used on commercial onion farms. Field surveys in 2008 and 2009 will determine the incidence of thrips, IYSV pressure, and key timing of pest outbreaks, and if these are correlated to commonly used farm practices such as fertility, herbicides, insecticides, fungicides, irrigation, and crop rotation. Two additional two-year replicated field studies will evaluate the impact of reduced plant nitrogen (N) status, trap crops, and crop rotation on incidence of thrips and IYSV. The first experiment is designed to evaluate cultural practices employed by a local grower (Morgan Reeder, Corinne, Utah) who reportedly has not sprayed for thrips in 3 years as a result of adopting new management strategies. The second experiment is to evaluate the efficacy of trap crops, under western onion growing conditions, that are known to be highly attractive to thrips. Through research, grower surveys, grower meetings, field days, and publications, we anticipate the development and dissemination of more sustainable and effective thrips and IYSV management strategies. In addition to enhanced economic stability, we anticipate increased worker safety through pesticide reductions, increased cropping system diversity through evaluation of trap crops and novel rotations, and reduced N leaching potential through improved N management. The project will be evaluated through meetings with all cooperators and grower surveys.

In order to meet the multiple goals of increased environmental and economic sustainability, enhanced quality of life and worker safety, and increased farmland diversification in onion cropping systems, we propose the following six objectives:

1) work with local growers to determine onion thrips and IYSV pressure in primary Utah onion growing areas and correlate IYSV pressure to common farm practices;

2) determine the effects of crop and pest management strategies on thrips survival and population size;

3) evaluate nitrogen (N) inputs, N leaching potential, alternative fertilizers, trap crops, and rotation on thrips, IYSV, onion yields, and storage quality;

4) conduct grower workshops and field days on control options of onion thrips and IYSV;

5) conduct economic cost-benefit analysis of proposed changes to management of onion thrips and IYSV; and

6) disseminate results through extension bulletins, the internet, trade journals, and scientific literature.