BACTERIAL FRUIT BLOTCH OF WATERMELON

Last fall, I wrote about the dreaded watermelon disease called "Bacterial Fruit Blotch". This disease devastated many of the watermelon crops in the southeastern U.S. last year. It also resulted in several lawsuits against some of the seed companies. Several of the larger seed companies didn't sell watermelon seed this year while others asked buyers to sign an agreement not to hold the seed company responsible if their crop contracts the blotch. Many of you probably paid more for your watermelon seed as well.

As I stated in the last article, I didn't receive any reports of the blotch in the Cumberland County crop during the last season. If you think that your crop may have the blotch, call me so that we can confirm what you have. Here is a reminder of what to look for:

Bacterial fruit blotch starts out as water-soaked, brown lesions on the leaves that may be bordered by leaf veins or yellow tissue. Look for these lesions on the underside of the leaves and near the midrib (vein). The leaf lesions serve as a source of infection for the fruit lesions.

The fruit lesions cause the real damage. They start as small, greasy-looking, water-soaked spots that enlarge rapidly until the entire melon is covered. As the lesion ages, it will crack in the center. A white ooze can be seen on the fruit and decay soon follows.

This disease is caused by a bacterium called Acidovorax avenae subsp. citrulli. The bacterium can be introduced to a field by infested seed, infected transplants, volunteer watermelon or by spread from alternate hosts. Once introduced, the bacterium can be spread by wind-driven rain, by handling and touching and other mechanical means.

The best control measure for fruit blotch is to avoid getting the bacterium into the field in the first place. Purchase seed from a reliable company. Avoid planting transplants that show symptoms. Eliminate volunteer watermelon seedlings and other cucurbits. Avoid moving equipment from an infested field into a non-infested field. Avoid working in the field when the plants are wet. Maintain a good crop rotation schedule.

If symptoms do appear, you can use a copper fungicide. However, copper can cause stunting in watermelons, so use it no more than three times per season.

If you suspect that your watermelons are infected with bacterial fruit blotch or for more information, call me.

Squash bugs literally suck the life out of their host plants. They only attack plants in the cucurbit family (squash, pumpkins, watermelon, cucumbers etc.) and they are most damaging to squash and pumpkins. Adults and nymphs (younger stages) feed in colonies, sucking plant juices and injecting a toxic substance that causes the vines to turn black and die. With heavy infestations, fruit may not form. When fruit does form, they will feed on it as well.

Adult squash bugs are about 5/8 inch long, brownish black or gray and flat across the back. They are usually found on the underside of the leaves. Look, also on the underside of the leaves, for reddish brown to bronze eggs in clusters of fifteen and in the angles of the leaf veins. Nymphs that hatch from these eggs are green with red to dark appendages. Older nymphs are grayish white with dark heads, legs and antennae. During the course of the summer, you may see several nymphal stages and adults at the same time.

Control strategies include the use of resistant varieties, maintaining a vigorous crop and completely destroying the crop after harvest and tilling it in. Chemical controls include the use of carbaryl (Sevin), endosulfin (Thiodan), esfenvalerate (Asana), naled (Dibrom) and malathion. As with pesticides, follow the label's directions from applications. Sprays work best on the nymphs, adult squash bugs are difficult to kill.

MORE WATER PROBLEMS

The heavy rains that have occurred in June have been devastating to many of our produce crops. Crops that have not drowned are either suffering from disease or lack of fertilizer (especially nitrogen). With the weather pattern of daily afternoon thunderstorms, getting back into the fieldl to do anything may be delayed for a white.

If your crop has not drowned and the weather cooperates, I suggest that you do the following: sidedress with fertilizer and make an application of fungicide. Of course you will also have to evaluate the costs of doing this versus the current price of your particular crop to determine if it is worth the extra expense.

DO YOU HAVE A FAX MACHINE?

If you have a fax machine, please call us and give us your number. The reason for this is that we want to be able to get important information out to you as quickly as possible. Faxing is the quickest way to get urgent information to you. So please take the time to give us your fax number if you have one.

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Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention of listing of commercial products or services in this publication does not imply endorsement by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage and examine a current product label before applying any chemical. For assistance, contact an agent of the North Carolina Cooperative Extension Service in your county.

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