Memorial Day weekend is the unofficial starting line for summer and, of course, planting tomatoes.
But tomato blight, which devastated home gardens and community gardeners last year on the East Coast, has been spotted again this season in a greenhouse in St. Mary's County, Maryland, and the alarm has been sounded.
It is difficult to save a tomato plant once it has been infected with the blight - even if you spot it early and remove the infected leaves. And one infected plant is all it takes to ruin your whole crop of tomatoes (and potatoes), so here is some advice, courtesy of the University of Maryland's Home and Garden Information Center and Cornell University's horticulture department.
Blight winters over on living host material, such as the potatoes that might still be in the ground in your garden. Remove them and dispose of them in plastic garbage bags.
Remove any volunteer potato plants in your garden or compost pile. They can carry the virus.
Buy healthy plants from local growers. Learn what blight loots like and examine the plants for any signs. If you see something suspicious, alert the seller and the state extension service.
If you are planting potatoes, don't use leftovers from last year's garden or anything from a grocery store.
Blight loves cool, damp conditions and cloudy days. (UV rays kill the spores carried by the wind.) So water your plants in the morning and do it at ground level, not from above.
Inspect your plants at least once a week. More often if the weather is cool and wet.
If you find late blight in your garden, let the local extension service and your neighborhood gardeners know. Act quickly.
If you are forced to remove your plants, do it on a bright sunny day to kill of the spores that may blow around.
Late blight shows up on other plants, almost unnoticed: hairy nightshade, bittersweet nightshad, tomatillos and petunias!
If you wait until late blight shows up to use a fungicide, it will be too late. It has to be done as a preventative measure and the University of Maryland isn't recommending that just yet since fungicides can actually lead to other diseases.
Once you begin spraying, the treatments must be regular thorough. Use chlorathalonil or copper-based products and follow the directions carefully.
Consider planting potato and tomato varieties that have shown some resistence to late blight, such as such as ‘Allegany', ‘Elba' or ‘Kennebec' potatoes and 'Black Plum,' 'Matt's Wild Cherry,' 'Yellow Currant' and 'Yellow Pear' tomatoes.
"Moutain Magic' and 'Plum Regal' have also shown disease resistence and their seeds should be widely available in 2011.