Eliminate standing water to minimize mosquito populations

By Lelia Kelly and David Nagel

Extension Horticulture Specialists

Distributed by Lisa Stewart, Webster County Director


To keep populations of mosquitoes to a minimum, eliminate all standing water because that is where mosquitoes breed. This includes children’s unattended swimming pools, buckets, and trashcans as well as their lids.

Fill in depressions that can hold water after a rain. If you have an ornamental pool, a few fish will be happy to keep the mosquito larvae under control. For larger bodies of water, consider the biological control, Bacillus thuringiensis Israelensis.

The bacteria are a strain of the more familiar Bt, which attacks cabbage loopers and other caterpillars. It is available as a spray or as slow-release briquettes. Check for this product at your local garden center that carries water gardening supplies.


Cut away suckers that grow from below the graft union on roses and fruit trees. When shearing hedges, remember to shape them so that when you look at the hedge from the side, the bottom is wider than the top. This will ensure that the lower branches get plenty of light and there will be thick growth all the way to the ground.

Leaf Scorch

During periods of hot weather and intense sunlight, leaves of some trees, especially newly planted ones, will scorch along the outside edge. This brown edge is also common on Japanese maples. Newly planted trees don’t have sufficient roots to meet the demands of the tree, and Japanese maples are simply stressed by high temperatures. Water frequently — more than once per week if needed — to keep the ground evenly moist, but not soaking wet.


A grower has asked what made heat-tolerant tomato varieties keep setting fruit after normal tomatoes quit. As with most seemingly simple questions, the answer is complicated.

There is evidence that pollen’s ability to survive and germinate is influenced by temperature as is the stigma’s growth pattern. Heat-setting varieties have fewer changes because of high temperatures than do normal varieties. Research is ongoing to determine the genetics and biochemistry behind these differences.

There is also evidence the heat setting plants send more sugar to the embryonic fruit. Gardeners need to realize that most large-fruited tomatoes will not set new fruit when temperatures exceed 92 degrees and should choose varieties carefully if they wish to be harvesting tomatoes in July and August. Now is the time to be starting seed of normal tomatoes for fall gardens.

Pumpkin and squash growers should be scouting their crops for signs of downy mildew. Small, pale yellow spots on leaves that will probably, but not necessarily, appear water soaked are the initial signs. The yellow areas may grow larger, but the disease symptoms will not cross veins so the spots may be angular.

Later the underside of the leaf may grow cottony looking hyphae that give the disease its name. Rainy and humid conditions are ideal for the growth of this disease that can defoliate a crop in just a few days. Apply a fungicide when you first see the symptoms for best management.

Now is the time to make your needs for fall garden transplants known. Tell your garden center folks that you want certain varieties or types of plants now and they can make arrangements to have them in September. Searching for purple cauliflower, romanesco broccoli, or kohlrabi transplants without prior request is a challenge.


Examine the cut leaf blades a couple of days after you mow. Is the cut edge ragged and discolored? These brown or tan edges give the lawn a dull appearance. The blades on the mower may need to be sharpened again. This is particularly a problem for St. Augustine grass lawns.