*** Fact Sheets on Late Blight ***

*** PLEASE NOTE ***
Any phone numbers or hotlines appearing in these fact sheets are for those respective state's residents. If you have questions about submitting a sample for identification in Pennsylvania, please call your local Cooperative Extension office.
Click Here for a directory by county.

Frequently Asked Questions (Cornell University)

Corrections of Misinformation (Cornell University)

Late Blight Alert (University of Massachusetts)

*** Photos of Late Blight ***

Click Here for excellent photos of stems, leaves, and fruits in various stages of infection from Cornell University.

Excerpt from UMass Fact Sheet:

Home gardeners need to act quickly to protect garden-grown tomato and potato plants and to make sure that your plants don’t become a source of spores that could infect commercial farms, as late blight spores are easily dispersed by wind.

Many families have taken up vegetable gardening given the tough economic times, and tomato is the most important crop in many gardens. This organism is not seedborne (however, it is tuberborne in potato), so that tomato plants started from seed locally would be free of the disease, at least for now. So far, in the region, small local garden centers have not been found to have infected plants. Some regional farm and garden centers did distribute infected plants from the same supplier. It is likely that many infected tomato plants have been planted across the entire region if they originated from larger wholesale stores. And, all tomatoes and potatoes could become infected within the upcoming days and weeks.

Here are the steps you should take:
1. Please inspect your tomato plants frequently! If symptoms are already appearing on plants in your garden, these plants should be removed. Plants should be placed in a plastic bag, secured and discarded in the trash or completely buried 2 feet or so underground so plants decompose and will not re-sprout. Plants should not be composted, put on a cull pile, or left outside. Your neighbors, not to mention commercial growers, will appreciate your taking this action immediately.

2. If you want to try to control late blight with fungicides, you need to begin spraying fungicide now – before you see symptoms – and you need to continue spraying regularly. Use a product that contains chlorothalonil. Even here, these products are only effective if used before the disease appears and should be reapplied every 5-7 days if wet weather persists. Chlorothalonil is a protectant fungicide, with no systemic movement in the plant, so thorough coverage is necessary. For organic farmers and gardeners, the options are very limited, since only copper fungicides can be used, and copper is not very effective on late blight. It is easily washed off by rainfall.

3. Consider growing more of the other vegetables instead of tomatoes and potatoes this year. Enjoy your lettuce, eggplant, peppers, squash, carrots, green beans, and broccoli.

Always follow label directions and wear protective clothing when applying pesticides.