Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu
Plant pathologist, Amanda Gevens, confirmed the late blight pathogen, Phytophthora infestans, in potato seed grown in Wisconsin on April 12, 2011. Dr. Gevens says:
“Given the sampling method and size, it is not known how widespread or with what incidence this disease risk may be. Additionally, our testing methods are highly sensitive and our levels of detection were weakly positive, indicating low quantity of pathogen. This notification is to make potato seed and production growers aware of the potential risk of late blight in the 2011 crop. Infected seed may result in a poor stand or delayed emergence, and can initiate an epidemic when disease spreads from seed piece to sprout and foliage.” Long Island Fruit and Vegetable Update.4-21-2011
Given the above information, growers in Delaware and elsewhere should be watchful this season, inspecting crops on a regular basis and adhering to spray schedules when risk of disease infection and/or spread is high.
Note: The Potato Disease Advisory will be a regular feature in WCU once we get farther into the season. This does provide information on conditions that are favorable for late blight and provides growers with the information to make well-timed sprays. Wisconsin used to provide potato seed for Delaware growers and I am not sure if anyone still gets seed from Wisconsin. Delaware growers do get seed from Maine and fortunately there were no reports of late blight in Maine seed last season according to Steve Johnston, Extension Potato Specialist. Scout fields early to avoid surprises later.