Late blight, a plant disease affecting both potatoes and tomatoes, has been detected recently in Michigan and last weekend in northern Indiana.
Michigan State University Extension reports that the disease was found in a tomato field in LaGrange County on July 25-26. The tomato field has now been treated. The genotype is US23 - A1 mating type and is sensitive to the fungicide Ridomil.
Jeff Burbrink, Elkhart County Extension educator, says Indiana growers should follow an aggressive spraying schedule. For more information, see Purdue University Extension's bulletin at www.extension.purdue.edu/extmedia/BP/BP-80-W.pdf.
Prior to the LaGrange County detection, late blight was found in Montcalm County, Mich. The blight is the same genotype (US-23) as in LaGrange County.
Michigan State University Extension soil scientests Willie Kirk and Noah Rosenzweig recommend growers treat their fields with one of the translaminar fungicides listed on www.lateblight.org/fungrate.html.
"Growers should be aggressively treating all fields on a minimum five-day schedule in the Montcalm, Gratiot, Ionia and Mecosta counties," Kirk and Rosenzweig said last week, before the plant disease was detected in LaGrange County, near the Indiana-Michigan state line. "Applications should include a translaminar fungicide in combination with a protectant (chlorothalonil plus mancozeb) and Super Tin."
The MSU specialists say areas in fields that are particularly vulnerable are field margins, especially those close to tree lines, raised cable lines and where water can accumulate such as around pivot tracks and tractor wheel lines.
"Growers should continue to scout on a weekly basis where late blight has not been reported and treat fields aggressively in areas where late blight has been reported. Growers should sample symptomatic plants and send them for diagnosis and continue application of residual protectant fungicides."