Bad weather – bad plant problems

Published 12:00 am Thursday, June 23, 2011

SALISBURY — Many home gardeners are contacting Cooperative Extension concerned about insects and diseases affecting their vegetable gardens. Unseasonable weather creates the perfect environment for plant-related problems. Below are a few situations that you may have encountered.
Q: Dr. Angela Lingle-Linders reported that the squash vines at the Millbridge Elementary School Discovery Garden are wilting. Some look very good while others are wilting and dying. What causes these to wilt and die for no apparent reason?
A: Squash plants in small gardens are often victims of squash vine borer. It is a clear-winged moth that emerges in late May and June and lays eggs on or near the base of the squash plant. Immediately pull and destroy all plants killed by borers. Using a sharp knife, split the infested stem and remove borers if feasible. Often, infested vines will recover and produce more fruit. Consider a second planting of summer squash in late July after adult borers have finished laying eggs.
Q: My potatoes have a really bad scab on the outside of the skin. What can I do to control this problem?
A: The problem is potato scab. It is a common problem caused by a soil-borne bacteria. It’s a serious problem in soils with a moderately high pH. Use resistant varieties where scab has been a problem and rotate heavily infested areas away from potatoes. Use grains as a cover crop; avoid using red clover. Maintain soil pH levels between 5.0 and 5.2 by using acid-producing fertilizers and keep them well irrigated. The surface of the potato looks terrible, but the infected skin can be peeled away and the potato itself consumed with no problems.
Q: What is causing my tomatoes to rot, especially on the end of the tomato?
A: Lack of water when the tomato plant is setting fruit causes fruit to have blossom end rot. Blossom end rot is a calcium deficiency sparked by periods of drought or in some instances, too much water. Plants must be irrigated on a regular basis to prevent blossom end rot. Tomato plants require about 1.5 inches of water per week during fruiting. This amount of water should be supplied by rain or irrigation. Extreme fluctuations in soil moisture result in a greater incidence of blossom-end rot. Fruit laden plants can use up to a gallon of water a day during peak growth. Mulching tomatoes and other vegetables with straw, pine straw, decomposed sawdust, ground decomposed corn cobs, plastic, or newspapers will conserve moisture and reduce blossom-end rot.
Darrell Blackwelder is the County Extension Director with horticulture responsibilities with the North Carolina Cooperative Extension Service in Rowan County. Learn more about Cooperative Extension events and activities by calling 704-216-8970 or online at