Good garden sanitation practices now can prevent plant diseases next season

As frigid winter temperatures begin to grip the state, most gardeners are heading inside to stay warm and read the latest seed catalogs and garden magazines, looking forward to the next growing season.

But if good garden sanitation isn’t done before next year’s planting season, what they may have left in their gardens could come back to haunt them. Plant diseases, such as potato late blight (Phytophthora infestans), can threaten their crops next year, as well as their neighbors’. Gardeners can take proactive steps to keep their gardens free of potato late blight by cleaning up potato plant materials and disposing of them properly. Found in Michigan potato and tomato plantings in 2010, potato late blight has the potential to be a very destructive disease of potatoes and tomatoes under favorable weather conditions.

“Potato late blight overwinters in potato tubers,” William “Willie” Kirk, Michigan State University (MSU) potato specialist and plant pathologist, says. “The disease needs live plant tissue to thrive and survive, and potatoes left in the soil and covered with snow are protected from temperatures that would be low enough to kill the disease.”

Kirk recommends that gardeners make a point of digging up any potatoes left over in their gardens and disposing of those old potatoes properly. He also says any stored potatoes from growers’ gardens should be checked over carefully for signs of disease and disposed of – but not in a compost pile.

“Unfortunately, compost piles act as insulators in cold weather, so diseased potatoes left in the garden in winter or stored in homes could harbor the disease, and if thrown in a compost pile, will contaminate it,” he says. “Those potatoes should be thrown in the trash or sanitary landfill, whichever is most accessible.”

If gardeners are considering planting potatoes next spring, Kirk says the best option is to buy clean, certified seed potatoes, rather than planting potatoes saved for seed.

“Gardeners should check their saved potato seed very carefully for signs of disease before planting,” he says. “It is best to plant new, certified seed.”

Spread through the air and from plant to plant, late blight can also affect tomato plants. By learning about the disease and sharing this information with their fellow gardeners, neighbors and gardening groups, home gardeners can help prevent the spread of this disease.

“This is a community-managed plant disease,” Christopher Long, MSU potato specialist, says. “Whatever method it takes to spread the word about potato late blight helps growers keep it out of their gardens, as well as any other potato or tomato grower’s garden nearby.”

Long stresses that doing nothing is not an option with late blight – growers should plan now to prevent outbreaks in both tomatoes and potatoes.

“Start early next spring by looking for volunteer potato plants and destroying them,” he says. “Again, don’t put them in a compost pile. Plan a spray program, as it will be very important to keep that up. Be diligent.”

Kirk’s website, has m,any resources that can assist gardeners, such as photos, publications and links to information. To follow the late blight site on Twitter, click on the “Follow us on Twitter” button on the home page or go to Count.y MSU Extension offices are also a good source of information. Find yours at Click. on “Offices/Staff” on the left side of the page.

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