Optimizing Row Covers and Perimeter Trap Crops for Cucurbit Pest Management

View the project final report

• 2011 annual report
• 2012 annual report

Commodities

• Fruits: melons

Practices

• Crop Production: catch crops, organic fertilizers
• Pest Management: chemical control, cultural control, row covers (for pests), trap crops
• Production Systems: transitioning to organic
• Soil Management: organic matter

Field experiments in Iowa and Ohio during 2011 and 2012 showed that two new pest management tactics – perimeter trap cropping and delayed removal of row covers – have encouraging potential for control of bacterial wilt on muskmelon with less reliance on insecticides in organic and conventional production. In conventional production, perimeter trap cropping (PTC) reduced the use of insecticides on a muskmelon main crop by an average of about 50% while incidence of bacterial wilt was lowered and yield was equivalent to non-PTC plots. The presence of a double row of ‘Buttercup’ winter squash as a perimeter trap crop successfully intercepted most cucumber beetles (the insects that spread bacterial wilt) before they entered the muskmelon crop. Although these squash perimeter rows required several insecticide sprays to protect against squash bug and squash vine borer, total insecticide use on treatment plots was still lower than on control plots. Under organic production, delaying row cover removal until 10 days after anthesis resulted in lower incidence of bacterial wilt than in control treatments (no row covers, and removal of row covers at anthesis) in all three site-years in which the disease appeared. Row covers also significantly suppressed a fungal disease, Alternaria leaf spot, in both years in OH. In general, use of row covers resulted in higher marketable yield than no row covers. However, the yield impact of the two delayed row cover removal treatments – opening the ends at anthesis, or leaving them closed – was variable compared to the row cover control (removal at anthesis). The project’s findings have been shared with cucurbit growers throughout the Midwest by presentations at state and regional grower meetings (Great Plains Fruit and Vegetable Growers Conference, PA Association for Sustainable Agriculture (PASA), Iowa Fruit and Vegetable Growers Conference, and Great Lakes Fruit and Vegetable Expo), two articles in the trade magazine American Vegetable Grower, and a webinar.

Introduction:

Bacterial wilt, caused by the bacterium Erwinia tracheiphila, is a severe threat to cucurbit crop production in the North Central Region. Bacterial wilt costs cucurbit growers more than $13 million annually (Adams and Riley, 1997; NASS, 2008). Two insects spread the wilt bacterium: striped cucumber beetle (Acalymma vittatum) and spotted cucumber beetle (Diabrotica undecimpunctata). The beetles carry the bacterium in their mouthparts and gut. When they feed and defecate on cucurbit plants, they transfer the bacterium, which then invades the plants and causes wilting. The highest risk of infection is in the springtime, when overwintering adult beetles emerge from the ground and seek out young cucurbit plants to feed on. Both organic and conventional muskmelon growers rank the cucumber beetle/bacterial wilt complex as their #1 pest problem (Hoffman, 1999; Bessin et al., 2003; Cavanagh et al., 2009). Stopping cucumber beetles is the key to stopping the disease. Conventional growers rely primarily on neonicotinoid insecticides such as imidacloprid and thiomethoxam to suppress cucumber beetles, but this practice is not sustainable. Several insecticides can weaken or even kill pollinating insects when these chemicals are carried back to hives in pollen (Milkovich, 2009; Cavanagh et al., 2009). As a result, growers urgently need safer strategies to manage cucumber beetles and bacterial wilt. Organic insecticides are considerably less effective than conventional ones, and frequently fail to prevent heavy losses from bacterial wilt epidemics. As a result, organic growers greatly over-plant in hopes of salvaging some marketable yield. Although some organic growers delay planting in order to avoid the highest-risk bacterial wilt period in the spring, planting late can result in lower market prices and greater losses from late-season diseases, particularly downy mildew. As a result, the threat of bacterial wilt limits crop diversification and marketing opportunities for organic cucurbit growers. Our project was designed to explore the usefulness of two strategies – perimeter trap cropping and delaying removal of row covers – for suppressing damage to muskmelon from bacterial wilt, reducing the need for insecticides, and improving profitability.

1. Assess ability of a) perimeter trap cropping, and b) extended-duration row covers, to suppress bacterial wilt and deliver acceptable yield in muskmelon. 2. Calculate costs and profits of applying perimeter trap cropping in conventional muskmelon production, and extended-duration row covers in organic production. 3. Communicate the findings to cucurbit growers throughout the North Central Region by means of on-farm demonstration trials, field days, webinars, a project website, trade journal articles, and regional meeting presentations. Performance targets for research, stated in the project proposal: • In 2 years of replicated field trials on muskmelon in Iowa and Ohio (2011 and 2012), determine the ability of perimeter trap cropping (PTC) to suppress bacterial wilt and reduce insecticide use under conventional production. • In 2 years of replicated field trials in Iowa and Ohio, determine the ability of delayed row cover removal (DRCR) to suppress bacterial wilt and reduce insecticide use under organic production practices. • Estimate costs and returns to each practice (PTC and DRCR) for North Central Region growers, using a partial budget analysis, based on results from the 2011-2012 field trials. Outreach targets: • Four on-farm demonstration trials per year, focusing on the DRCR tactic. • A field day in each state in both years, highlighting the project at an experimental trial site or at the farm of a cooperating grower. • Two 20-minute webinars, each highlighting one of the new practices (PTC and DRCR) used in the project. • Two articles on the project’s findings in regional or national trade journals (for example, American Vegetable Grower). • Presentations on project findings at regional grower meetings: the Great Plains Vegetable Growers Conference in St. Joseph, MO, the Great Lakes Fruit and Vegetable Expo, Grand Rapids, MI, and the Pennsylvania Society for Sustainable Agriculture (PASA).