FUNGICIDE ...

Preventative fungicide application

Apply fungicide to transplanted and early direct-seeded vegetable crops

Figure 1: Brown early blight lesion with concentric rings and yellow halo on tomato leaf. (Photo: Kenny Seebold, UK)

LEXINGTON, Ky. — Transplanted and early direct-seeded vegetable crops in the field should be receiving their first fungicide application this week, if growers haven’t started their spray program yet.

A good early-season option is mancozeb tank-mixed with copper at the rates stated on the labels. This tank mix will help delay the onset of common fungal diseases like early blight and Septoria on tomato, and anthracnose on cucurbits. Including copper will additionally help protect against new bacterial infections. In some cases, tank-mixing mancozeb with copper has been shown to improve the activity of copper on the leaf surface, resulting in more effective bacterial disease management (Conover and Gerhold, 1981). However, mancozeb would not be expected to manage bacterial disease when applied on its own.

Figure 2: Lesions with white, fallen-out centers and light brown tissue on the margins, typical of anthracnose on cucumber (Photo: Kenny Seebold, UK).
Figure 2: Lesions with white, fallen-out centers and light brown tissue on the margins, typical of anthracnose on cucumber (Photo: Kenny Seebold, UK).

Other crops that may benefit from a protectant spray this week include green bean, onion, and leafy greens. In 7 to 14 days, commercial growers should follow the protectant application with a systemic fungicide labeled for the crop that addresses the major diseases of interest. Under wet conditions, use a shorter spray interval that approximates a weekly application. Once harvests start, mancozeb should not be applied since it has a 5-day preharvest interval. Instead, chlorothalonil or copper (or both) should be relied on as the protectant fungicide(s) for field production. Whenever fungicides are used, ensure good coverage of the upper and lower leaf surfaces and follow precautions on the label to protect yourself, consumers, and the environment.

For more information about products labeled for vegetable disease management and spray schedules, see Vegetable Production Guide for Commercial Growers (ID-36).

Click here to visit the University of Kentucky Pest News blog. 

— Emily Pfeufer, University of Kentucky Extension Plant Pathologist

For more news from Kentucky, click here.

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