In a Michigan State University Extension bulletin, Mary Hausbeck, a specialist with Michigan State University Extension, says cucumber growers in the state have seen the earliest outbreak of downy mildew in many years.
Hausbeck says the overcast, humid and wet weather as of late has favored pathogen growth and with more moderate temperatures expected, there’s even greater risk of pathogen spread and crop infection.
As of now, the outbreak has been reported in Cass, Lenawee, Monroe and VanBuren counties in pickling cucumbers.
“The first cucumbers of the season and subsequent plantings are going to be challenged by disease given the amount of downy mildew that has been reported in the state in the last few days,” she writes.
Hausbeck warns that cotyledons of an emerging cucumber crop can become infected, much like what happened a few years ago.
“The cucumber yield is most likely to be impacted when the plants become infected early, and the pathogen is not controlled,” she says.
In her bulletin, Hausbeck offers several fungicides that growers should deploy that have proven downy mildew control, and she cautions growers not to stretch spray intervals beyond seven days.
“This interval should not be an issue if the recommended fungicides are used in alternation,” she says. “Look at the fungicide labels carefully to ensure you’re within the guidelines; the label is the law.”
