Extended-duration row covers to suppress bacterial wilt on muskmelon: optimizing a new management strategy for organic growers

View the project final report

• 2010 annual report

Commodities

• Fruits: melons

Practices

• Crop Production: application rate management
• Education and Training: demonstration, extension, networking, on-farm/ranch research, participatory research
• Pest Management: cultural control, disease vectors, integrated pest management, mulching - plastic, row covers (for pests)
• Production Systems: organic agriculture

Many organic vegetable farmers in the Midwest avoid growing muskmelons due to the difficulty of controlling bacterial wilt, a fatal disease caused by Erwinia tracheiphila that is vectored by two species of cucumber beetles (Acalymma vittatum and Diabrotica undecimpunctata). Bacterial wilt can cause up to 80% crop loss, and no genetic resistance is available in muskmelon. Organic practices to suppress cucumber beetles and manage the disease often fail or are too costly for farmers to implement. The proposed project will validate a method to control bacterial wilt by delaying the removal of row covers until 10 days after the start of flowering. In preliminary field trials in Iowa, extended-duration row covers provided season-long protection from bacterial wilt, and efficient pollination was achieved either by opening the row ends at the start of bloom or inserting a bumblebee box under the cover. In two field experiments and three on-farm trials on cv. Athena in 2010, these strategies will be compared to controls (row cover removal at the start of flowering, and no row covers); incidence of bacterial wilt will be evaluated as well as marketable yield. A 5-member Advisory Panel of Iowa organic vegetable growers will help to shape the project’s research and outreach efforts throughout the state. Outreach will include on-farm trials at three cooperator farms, a field day, a project website, presentations at two vegetable grower meetings, and an article in the regional trade journal Vegetable Grower News. These activities will insure that the project’s findings reach cucurbit growers throughout the Midwest, increase their willingness to use row covers, and advance the implementation of extended-duration row covers to control bacterial wilt under organic production.

Objective 1. Compare the use of row covers with different times of removal to prevent the incidence of bacterial wilt on muskmelon.

Thirty-foot-long rows of 15 ‘Athena’ muskmelon seedlings will be planted into black plastic mulch with drip irrigation. Single-row treatments will have polymer row covers (Agribon AG-30®) on wire hoops, in a randomized complete block design with four treatments:

1. Row covers removed at anthesis (start of flowering).
2. Extended-duration row covers removed 10 days after anthesis. At anthesis, both ends of row covers will be opened to allow pollination.
3. Extended-duration row covers removed 10 days after anthesis. At anthesis, a bumblebee hive (Koppert Inc.) will be inserted under one end of the row cover, and then re-sealed.
4. No row covers (control).

Incidence of bacterial wilt will be monitored weekly and cucumber beetle populations will be monitored on yellow sticky traps. At harvest, melons will be counted, weighed, and classified into marketable and cull. The trials will be carried out at ISU research farms at Gilbert and Muscatine, along with three on-farm demonstration trials with commercial organic growers.

Outputs. We expect that delaying the removal of row covers will effectively suppress bacterial wilt incidence to less than 20% incidence, resulting in higher yields than the non-covered control and removal of row covers at anthesis. By inserting bee hives, we anticipate that pollination will be more efficient and enhance earliness of harvest. In the open-end treatment (Treatment 2) we expect similar yields to Treatment 3, but this option is likely to be cheaper for growers since no bee hives will be needed. Preliminary trials with this strategy in 2007 and 2008 suggest that opening the row-covers ends will effectively exclude cucumber beetle vectoring of wilt, but allow natural pollinators to enter.

Objective 2. Involve organic growers in on-farm trials of extended-duration row covers. Communicate results to growers through a project website, presentations at regional meetings, field days, and trade journal publications.

Cooperators and the 5-member Advisory Panel will meet in February and October of 2010 and February of 2011 to provide comments and advice on the methods and approaches to be used for the field experiments. Growers outside the panel will also be invited to participate in a field day at the site of an on-farm trial in order to learn how to use row covers. Results of the trials will be presented in 2011 at the annual winter meeting of Practical Farmers of Iowa (PFI) and Iowa Fruit & Vegetable Growers Association (IFVGA) meetings, published in the regional trade journal Vegetable Grower News, and posted on the project’s website.

Outputs. Meetings with the 5-member Advisory Panel and cooperators before and after the 2010 field season will provide feedback on implementation of row covers for organic growers in Iowa, and discuss how to spread the information to growers throughout the North Central Region. On-farm trials and the field days will train growers on the uses of row covers. The presentations at PFI and IFVGA meetings and the website will provide practical tips and answer questions for growers who have not used row covers but are interested in organic muskmelon production. The website and meetings will inform growers about the time and place of the field days and other presentations, as well as post the project results.