On Guard in the Garden

Continuous maintenance helps to avert plant diseases

By Mary Ann Ebner

Local home gardens, from spacious backyards to modest balcony container plantings, generate peak rewards when given proper attention. To keep gardens growing well to produce healthy tomatoes, leafy greens, bright berries or vibrant herbs, continuous maintenance and observation help boost a garden’s output. Community Educator Jen Stengle with the Cornell University Cooperative Extension of Putnam County encourages home gardeners to stay alert in the garden throughout the gardening season. “Each plant can get its own little nasty disease,” Stengle said, “and what you should be doing as a home gardener is staying alert. Infection is possible in many situations, and over-watering can do damage to a root system, but the home garden can be easily managed.”

Septoria leaf spot

Stengle promotes garden sanitation, good spacing and plant variation as positive approaches to successful gardening. “Good spacing between tomatoes is very important,” Stengle said. “If you don’t use good spacing, all of a sudden you’re growing 12 tomato plants in a space for four. Plants need good air circulation and pruning up, and if you’re watching them, you’ll notice changes. We are seeing some ​​​Septoria leaf spot on tomatoes which can be successfully treated with good sanitation, removal of lower leaves, and treated with safe fungicides.”

“Late blight was responsible for the Irish potato famine,” Stengle said. “These diseases don’t distinguish between container gardens or commercial farms. Late blight is raising its head in New Jersey and we’ve had reports in Pennsylvania, but so far we don’t have any reports locally, though it is just the right kind of season for it with wet and cool weather.”

Jay Armour of Four Winds Farms

Cold Spring Farmers’ Market vendor Jay Armour of Four Winds Farms in Gardiner agreed that everyone should be watching for changing conditions. Armour described signs of late blight on tomato plant foliage presenting as grey spots with a white border around the spots. The veteran organic farmer noted that when cloudy and cool weather prevail, late blight can be a concern. “Late blight has been identified on potatoes on Long Island in Suffolk County,” Armour said. “As long as it stays sunny, it won’t travel very far. ​​​Hopefully, we won’t see it.”

Downy mildew

Recognizing problems and irregularities in home garden plants can save crops and prevent further infection. According to the Cornell Cooperative Extension, another problem that has surfaced in local gardens this season is downy mildew Downy mildew has been reported locally, and Stengle said that downey mildew has been moving through basil crops and presents itself with yellowing and spores on leaf surfaces. Downy mildew has also attacked ornamental coleus and impatiens. Before removing plants that may be infected, home gardeners can seek help to positively identify problems, whether caused by poor sanitation, pests or diseases.

“Home gardeners can always call us at the lab and speak to us if they’re not sure about a concern,” Stengle said. “If we can’t answer the question over the phone, we’ll put it under a microscope, though there is a $10 fee for lab testing. There’s also a wonderful website, for home gardening questions.”

For more information in assessing questionable symptoms, call the Cornell Cooperative Extension Horticulture Hotline at 845-278-6738 from 9 a.m. to noon Monday through Friday. Check out Frequently Asked Questions related to gardening and plant diseases at the following websites:

Cornell Cooperative Extension of Putnam County

​​Cornell Garden Based Learning 

Long Island Horticultural Research & Extension Center

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