Thursday, October 8, 2009

Tips to Prevent Overwintering Late Blight

Here are some tips for preventing late blight from coming back in your fields next year. The sheet can be found here as well: Tips to Prevent Overwintering Late Blight

Tips to Prevent Overwintering Late Blight

Late blight (Phytophthora infestans) occurs commonly each year in many places around the United States and the world.

There are steps we, as home gardeners, market farmers and commercial growers alike, can take in order to reduce late blight inoculum surviving the winter.

The following tips for fall will help prevent the spread of late blight (Phytophthora infestans). They are different from summer management techniques:

» If possible, start with new seed potatoes in the spring that have been certified disease free.

» Cull any potatoes that are suspect before putting them into storage - potato tubers with late blight will have a dry, reddish brown rot in the flesh.

» Turn soil in garden or fields so that crop residues can readily decompose - late blight needs live tissue to survive. This includes tomato crop residue as well. As long as tissues decompose or die (no living plant tissue), then the late blight on that plant tissue will be killed as well.

» Cull potatoes in storage throughout fall and winter months that are suspect.

» Try to dig up all possible tubers - cull volunteer plants that emerge in the spring.

» Cull piles should be thin enough to freeze solid over the winter.

» Cull piles can also be managed so that they heat up significantly - this is achieved by adding the proper mix of brown and green ingredients to your compost pile and turning. A compost thermometer might be helpful.

» In the northeast US only one type of late blight is found so all measures outlined above will help prevent late blight from overwintering. In some parts of the United States and the world two different types of late blight can be found in the same location thus allowing the pathogen to ‘mate' and produce oospores, capable of
surviving temperature extremes - in this case crop rotation is very important in reducing oospore inoculum on possible plant hosts. Crop rotation is important in all growing areas, no matter the size of your garden/field.

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