FRUITAND
VEGETABLES
FRUIT
The information and recommendations in this newsletter are applicable to
North Carolina
and may not apply in other areas.
Downy mildew has been recently diagnosed in Johnston County. Downy mildew is one of the most important diseases of cucurbits in our area and can cause significant losses. The symptoms first appear as small yellow lesions on the topside of leaves, usually on the older leaves first and then on the expanded younger leaves. Under conditions favorable for sporulation, the underside of the leaves will have a downy appearance ranging in color from light gray to purple. A quick technique for confirmation of the disease is to dab scotch tape along the bottom side of the leaf and view it under the microscope. Spores are ovoid and lemon-shaped. The branches that bear the spores are double-branched and pointed on the ends. The lesions will continue to turn yellow or necrotic and the entire leaf can be killed. Loss of foliage can result in sun scalding of fruit.
Control recommendations. With the weather patterns predicted,
immediate action is required. Growers should ensure that they are
well protected as soon as possible. If the disease is present,
growers are best advised to use Ridomil/Bravo or Ridomil/MZ
according to label directions. If the disease is not present, the
most effective protectants include chlorothalonil (Bravo) or maneb
(Dithane M-22). These protectants are also effective for leaf spot
pathogens (target spot, anthracnose and gummy stem blight). Note
the day to harvest regulations, and some fungicides are not
recommended for use on mature plantings.
Web page last updated on 15 July 1996 by Stephen J. Toth, Jr..