July 26, 1996
At least 3 different species of wasps construct nests in the ground in Iowa. These "digger wasps" include the cicada killer wasp, the largest wasp found in Iowa. Cicada killer wasps may be up to 2 inches long. They are black with yellow markings on the thorax and abdomen and they have rusty colored wings. The great golden digger wasp is slightly smaller. The abdomen is reddish-orange except at the tip which is black. A third species is 1 inch long and completely black with iridescent blue wings.
Drying or preserving flowers is a popular gardening activity. Dried materials are long lasting and can be used to add warmth and color to the home during the cold, gray winter months.
Grasshoppers are a more or less serious pest in the home garden depending on the weather and other factors. This could be one of those years when we see more grasshoppers than usual.
The grasshoppers commonly found in Iowa gardens spend the winter as eggs in the soil. Eggs are deposited in turfgrass or other sod areas by the female during late summer.
The Plant Disease Clinic has been receiving several samples, especially coniferous trees, with the new growth shriveling and turning brown. Several factors can cause this type of injury but the most likely cause is heat stress. The cool spring this year delayed new growth on many plants. The young, emerging tissue on plants is vulnerable to many stresses. Young tissue is usually not actively involved in transpiration. Transpiration is the fancy name for how plants cool themselves.
Honeysuckle leaf blight is caused by the fungus Insolibasidium deformans. The disease appears in the spring on newly emerging leaves. The first symptom is a yellowing of leaf tissue. This tissue becomes tan brown and finally necrotic and dry with brown areas involving an entire leaf or a large portion of it. The lower surface of infected leaves show a silvery-white coloration, caused by the presence of the fungus. The leaves are often rolled and twisted and drop prematurely. The fungus overwinters in dead leaves.
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Two reports of Japanese beetles have been received as a result of the article in this newsletter two weeks ago (HHPN, July 12, 1996, page 116). First, we received confirmation that Japanese beetle adults had emerged from the soil and were active in Rock Island County Illinois, just across the river from Davenport, as of July 15.
After a severe winter and the third cool, wet spring in a row, many home gardeners know firsthand the problems associated with growing many species of evergreens.
In an earlier newsletter this spring, junipers were on the list of evergreens experiencing problems with diseases. One of the main ways to avoid disease problems is to plant disease resistent varieties when available.