Jul 16, 2010Potato late blight confirmed In Wisconsin
Late blight, caused by the fungus-like pathogen Phytophthora infestans, has been confirmed in a potato field in Marquette County this morning, July 14, 2010 according to Amanda Gevens, University of Wisconsin Extension plant pathologist.
This is the first confirmed report of late blight in Wisconsin for 2010. Infection was isolated to a small section of the field and symptoms suggest that the infection occurred approximately 5-7 days ago,” Gevens said in a statement from the University of Wisconsin Extension.
The late blight pathogen is referred to as a ‘water mold’ since it thrives under wet conditions. Symptoms of tomato late blight include leaf lesions beginning as pale green or olive green areas that quickly enlarge to become brown-black, water-soaked, and oily in appearance. Lesions on leaves can also produce pathogen sporulation which looks like white-gray fuzzy growth. Stems can also exhibit dark brown to black lesions with sporulation.
Tomato fruit symptoms begin small, but quickly develop into golden to chocolate brown firm lesions or spots that can appear sunken with distinct rings within them; the pathogen can also sporulate on tomato fruit giving the appearance of white, fuzzy growth. The time from first infection to lesion development and sporulation can be as fast as 7 days, depending upon the weather.
“Last year late blight affected primarily tomatoes in Wisconsin, with the first report on July 29. This year, the first find is on potato and is 2 weeks earlier than in 2009,” Gevens said. “We do not yet know if this strain of late blight is the same as the one active last year. We will continue to investigate the potential of this year’s late blight and provide updates and appropriate recommendations to growers in the state.”
With the presence of the late blight pathogen in the state and disease-favorable weather conditions, it is critical that all growers – home gardeners and commercial producers – of tomatoes and potatoes regularly scout their plants for disease symptoms.
If late blight is suspected, contact your county extension agent, a crop consultant, the plant disease diagnostic clinic at UW-Madison, or Gevens. Additionally, protectant fungicides can manage late blight when applied in advance of infection and when re-applied as the crop grows. Please see fungicide details at the vegetable pathology website: http://www.plantpath.wisc.edu/wivegdis/.
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