08-14-2009
Tomatoes with Late Blight Confirmed in Potato Growing Area; Infected Plants Must Be Properly Destroyed
Contact: Jane Larson
608-224-5005
MADISON--Tomato plants infected with late blight have been found in Portage County--a major potato growing area of Wisconsin. Late blight can also infect potatoes so gardeners and growers of any size who have infected tomato plants need to destroy those plants appropriately to prevent the spread of the disease to other areas and to protect Wisconsin's commercial potato and tomato crops.
So far, late blight has not been found on any potato plants in Wisconsin and state agriculture officials want growers and gardeners in potato growing areas to remain on the lookout for late blight symptoms.
"This particular strain of late blight can be very aggressive on potatoes so the risk for spread from tomato to potato is still very great and gardeners and large commercial producers should not get complacent at this time," explained Amanda Gevens, University of Wisconsin plant pathologist.
As of August 14, there were confirmed cases of late blight in tomatoes in five counties, Dane, Green, Rock, Portage and Lafayette. Previous reports of late blight in Langlade County were incorrect.
"Late blight spores can travel great distances on wind, rain and machinery. If your garden is infected, there is a potential risk to potato fields in your county," said Brian Kuhn, Department of Agriculture, Trade and Consumer Protection plant industry bureau director. "Know the signs and symptoms of late blight. Check your gardens and your fields. If you're unsure, contact your county extension office for guidance. If you have late blight, you need to destroy the infected plants to limit the spread of the disease."
Pictures of late blight and similar looking plant diseases are available at www.datcp.state.wi.us/arm/environment/insects/late-blight/LateBlight.pdf.
For infected tomato plants, pull up the plants and the fruit, seal them in garbage bags and dispose of the plants. Do not compost the plants because the fungus can survive on green plant tissue. If you have many tomato plants, another option is to thoroughly till the plants into the soil.
DATCP is also tracking the disease in Wisconsin. If your plants are diagnosed with late blight, or you are confident that your plants have the disease, growers and gardeners of all sizes are asked to contact Adrian Barta, plant disease specialist, (608) 224-4592 or email adrian.barta@wisconsin.gov.
Late blight is harmful to plants not humans. "If your tomatoes are ripe, you can eat them but long term storage won't be possible if they are infected with late blight," Kuhn said.
The Pennsylvania State University Cooperative Extension has published some guidelines for canning tomatoes with late blight found at foodsafety.psu.edu/LateBlight.htm.
While potato fields appear to be blight-free at this time, growers are reminded of state laws established to prevent and control the spread of late blight should the disease be identified in potato fields.
"It's been a number of years but we've had late blight outbreaks in potatoes in the past," Kuhn said. "Wisconsin growers have been very diligent about managing volunteer potatoes, those plants that show up in the field the following year, and managing cull piles to prevent the spread of late blight and other potato diseases."
State agriculture officials remind growers to handle their cull piles, those potatoes that aren't market quality, one of three ways:
- Landspread the culls onto fields then incorporate the culls into the soil.
- Feed the culls to livestock, making sure the culls are completely eaten.
- Landfill the culls after gaining permission from the landfill operator.
If a grower does not take the appropriate steps to manage late blight in their fields or to manage their cull piles, the state agriculture department can direct that grower to take corrective action in order to protect Wisconsin's commercial potato crop.
"If late blight shows up on potato plants in your home garden, remove the vines, bag the vines and dispose of the bags. The potatoes can be dug but must be used quickly. Tubers that are infected with late blight can't be stored long-term, they'll rot. If you have cull potatoes in your garden, either bag and dispose of the culls or bury them in the ground," Kuhn said.
Fungicide recommendations for tomatoes, potatoes and organic growers are available from the University of Wisconsin-Extension at www.plantpath.wisc.edu/wivegdis/.
Wisconsin ranks third nationally in potato production with 2008 production valued at $238 million. The 2007 Census of Agriculture indicated there were 776 Wisconsin farms that harvested 406 acres of tomatoes for fresh market use.
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