Sustainable Management Options for Whitefly-transmitted Viruses in Cucurbit Production

View the project final report

Commodities

• Vegetables: cucurbits

Practices

• Pest Management: cultural control, disease vectors, mulches - living, mulching - plastic

More than 1/3rd of major cucurbits in the United States (squash, watermelon, pumpkin, cucumber and cantaloupe) are grown in Florida and Georgia. More than 40 percent of that production occurs in the fall season. Recently, growing fall cucurbits in these states has become a challenge; the main limiting factors being whiteflies and a complex of whitefly-transmitted viruses. At least three whitefly-transmitted viruses, Cucurbit leaf crumple virus (CuLCrV), Cucurbit yellow stunting disorder virus (CYSDV), and Squash vein yellowing virus (SqVYV) affect cucurbits. Squash, pumpkin and canteloupe are extremely susceptible to CuLCrV and CYSDV, while SqVYV causes vine decline -- a debilitating disease in watermelon. Mixed viral infections are also common. The viruses are established in Florida, and are increasingly common in southern Georgia. In Fall 2016 and 2017, whitefly-transmiited viruses in Florida and Georgia affected hundreds of fields spanning more than 10,000 acres. Due to virus-induced foliar symptoms and severe stunting, many fields of squash were plowed under causing serious monetary losses. Estimates suggest that in 2017 at least 50 percent of yellow squash and 25 percent of zucchini squash production was lost to these viruses. CuLCrV also infects snap beans, and 90 percent of fall bean production was negatively impacted in 2017. These losses amount to $50 million in farm gate receipts in Georgia alone. Coupled with the increase in pesticide applications the losses could be much higher.

If current trends continue, fall production of cucurbits will become unsustainable. The cause of alarm being that there are no effective management options. Due to lack of other effective management options, growers rely exclusively on insecticides for whiteflies and virus management. Such over reliance on insecticides has exacerbated the situation and produced undesirable outcomes such as development of insecticide resistance and whitefly control failures.

The goal of this proposal is to develop a holistic management strategy that is readily adopted by growers in the region. Growing virus-resistant cultivars is an obvious choice. However, there is no known commercial varieties with resistance to CuLCrV, CYSDV, or SqVYV. Our objective is to develop a whitefly and virus management package in which multiple management tactics will act synergistically. We intend to screen squash cultivars for tolerance to viruses, evaluate seedling protection in the greenhouse, assess the impact of mulch options, row covers, and examine the role of insecticides including biorationals in suppressing whiteflies and limited virus spread.

1. Develop a pre-planting integrated management package using cultural and chemical tactics.
2. Develop a post-planting integrated management package by examining cultivar tolerance, and using cultural and chemical tactics.
3. Formulate a Risk Reduction Index, and showcase its usefulness by performing demonstration trials.
4. Conduct econometric analyses including obtaining cost-benefit ratios.