By SHELLY STRAUTZ-SPRINGBORN
Michigan Correspondent

LANSING, Mich. — Although tomato planting is about two weeks from completion in Michigan and Indiana, experts are already reminding growers and home gardeners to be on the lookout for the possibility of late blight in this year’s crop.

According to the agricultural summary published by the Michigan Field Office of the U.S. Department of Agriculture National Agricultural Statistics Service for the week ending May 24, tomatoes planted under cover were growing through tunnels, and unprotected planting was under way across the state. Indiana growers reported similar progress. In Indiana, growers estimated that 9,700 acres of tomatoes would be produced this year, down one percent from 9,800 acres in 2009. Michigan production is estimated at 3,300 acres in 2010, down 6 percent from 3,500 acres in 2009.

Ron Goldy, Michigan State University (MSU) District Extension Vegetable Educator, said that about two-thirds of the Michigan’s tomatoes have been planted and the entire crop should be in by around June 15. In Michigan, he said “to some degree” tomatoes are grown throughout the state for local sales.

Larger acreage of tomatoes is raised by packers in the southwest and southeast portions of the state, near the Indiana border.
“Most commercial growers grow them on raised, plastic mulch beds with drip irrigation. They are staked and tied to get them off the ground to improve quality and reduce disease pressure,” Goldy said.

“There is always a possibility of late blight on tomatoes in Michigan,” Goldy said. “It is the same organism that causes late blight in potatoes, so it is present in the state. The threat level increases depending on weather conditions. It likes cool, wet weather like we had last year. Since last year was unusual, we hope to not see a repeat for this year, but it is possible since we have the host and the disease already present. We just need the proper conditions for the occurrence.”

Trevor Meacham of High Acres Fruit Farm near Hartford in Van Buren County, said recent weather conditions have cleared the way for significant planting progress this week.

“Planting is going full steam ahead,” Meacham said. “With good weather lately, we have been able to plant overnight to avoid the heat during the day.”

Meacham farms about 4,000 acres of fruits, vegetables, corn and soybeans, of which about 20 acres of grape and cherry tomatoes are produced for fresh sales to chain stores.

He said he is not concerned about late blight in his crop because the types of tomatoes he grows are less susceptible to the disease and disease pressure is closely monitored at his farm.

“We don’t have much of an issue with it,” he said of the disease.
However, he cautioned growers and home gardeners to be aware of what’s going on with disease pressures in their area, adding that regular scouting and spray application is a must for early detection and prevention of late blight and other diseases.

In Indiana, Purdue University Extension Plant Pathologist Daniel Egel predicts that late blight should not be as aggressive of a disease this year as it was in 2009. But, he added, it is imperative that growers watch for symptoms and take immediate action if the disease is detected.

“Late blight causes large brown lesions on tomato leaves and stems that under moist conditions are often ringed with the white fungus,” Egel said. “Symptoms caused by late blight may look like other common tomato diseases and, thus, may be easily missed if not sent for accurate diagnosis.”

MSU Plant Pathologist Mary Hausbeck agreed.

“My sense is that our biggest threat will come from potato volunteers that sprout from infected tubers that have successfully overwintered,” Hausbeck said. “Homeowners, in particular, may not realize that these potato volunteers in their gardens or compost bins may harbor the late blight pathogen. The late blight spores may spread via air currents to commercial tomato plantings.
“Last year, Michigan growers identified the disease early and successfully limited the damage using reduced-risk fungicides,” she said.

Late blight symptoms include blighting on all above ground parts of the tomato plant. Lesions on leaves often appear dark and oily with production of sporangia – seeds of the pathogen – occurring on the undersides of the leaves resulting in a whitish-purplish appearance especially when conditions are wet and humid.

“There are several highly effective fungicide sprays that can be used to protect tomato plants from late blight,” Hausbeck said.