Hot weather brings disease, pest woes

The first day of summer is still a week away, but the last two weeks made you think we were in July or August. The heat, combined with the lack of rain, has caused some problems with lawns and vegetable gardens.

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Also, one of the worst pests that we have in our landscape emerged in the past two weeks: the Japanese beetle. I found them in my vegetable garden this week.

The first problem that I have received many calls on is disease problems in grass. Right now, there are few problems with our turfgrass. The hot, dry weather is not the right conditions for most disease problems.

The one disease that can be active during these conditions is called Dollar Spot. Dollar Spot is a fungus that causes a lesion on the leaf blade of the turfgrass. It usually has a dark border around the lesion. It is most common in Bermuda and zoysia grass. This disease attacks grass that is low in nitrogen or is drought stressed. The best way to control it is to fertilize the grass and to water it deeply. If you remove the stress, the disease will go away.

I have also received many calls about suspected grass diseases. There are areas in yards that can be circular or varied in size or shape. The ones I have looked at are not diseases; the ones I have seen have been dry areas in lawns. When a turf plant is under drought stress, the plant will roll its leaves and have a bluish/gray color. The rolling of the leaves is a measure that the plant has to conserve moisture.

There are a number of reasons for dry areas in lawns. The first is compacted soils, which don't allow water to penetrate the soil so you have less water for the plants to use. The second cause is irrigation systems that are not working properly. The system could have heads that are not working or they don't have proper overlap. Most of the time, the dry areas are receiving half the water of other areas.

The second problem that I am hearing about is with tomatoes. Tomatoes are gardeners' favorite vegetable, so when there are problems with them, I receive many calls. The most common calls are about blossom end rot, which occurs on the bottom of the tomato. Blossom end rot is caused by a calcium deficiency.

In order for calcium to move into a plant, there must be water movement into the plant. If there is reduced water flow into the plant when it is setting fruit, blossom end rot can start. This is most common during a drought.

You can supply calcium to help your tomatoes by adding lime to the planting hole or using gypsum or a product called Stop Rot. Stop Rot has calcium chloride in it. You also need to keep a good moisture level in the soil. One of the easiest ways to do this is by mulching the tomato plants.

The last problem that I am getting calls on is Japanese beetles. These are very striking insects. They are bright metallic green with coppery-brown forewings that reach almost to the tip of the abdomen. There is a row of five white spots along the side of the abdomen and a pair of white spots on the top of the last abdominal segment. These spots help distinguish this beetle from similar beetles, such as the green June beetle.

To control Japanese beetles, you need to control the adults and the white grub stage.

There are a number of ways to control the adults. First, hand pick them when you first see them in your garden. I use a small bucket of soapy water and knock the beetles into it.

Another organic control option is to use Bacillus thuringiensis var. kurstaki. This is a fungus the beetles eat and later die from. You can find this in products such as Bt or Dipel.

If you want to use an insecticide, you can use Sevin. It should be used late in the afternoon to reduce the chance of exposure to bees. Imidacloprid is another good option.

There is one control option that I would like to caution you about: We do not recommend the use of Japanese beetle traps. These traps have sex pheromones in them. They will trap the beetles, but they also will draw them to your yard. The beetles can fly in from as far as a quarter of a mile away.

Columbia County Extension Agent Charles Phillips can be reached at (706) 868-3413 or by e-mail at charlesp@uga.edu. The Extension Web address is www.ugaextension.com/columbia.