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Ornamentals and Turf |
The cicada killer wasp uses cicadas to provision its nest. Cicadas are caught and stung by the wasp, then dragged back to the nest. Once in the nest, the female wasp lays her eggs on the cicada. Soon wasp larvae hatch from the eggs and feed upon the cicada. When mature, the wasp larvae pupate and another generation of wasps emerges to carry on the life cycle. The cicada killer wasp is one of the most attractive-looking wasps, and the sight and sound of many wasps swarming in a yard is impressive. Although these wasps appear to be ferocious, I know of no one who has been stung by them even though the females have an impressive stinger (males do not sting). Control is usually not nearly as necessary as the homeowner thinks since the wasps represent little danger to humans. The active period only lasts a few weeks, anyway. Because they control cicadas, these wasps can be regarded as beneficial. Ornamentals and Turf Insect Information Note No. 63 provides additional information on the biology and control of cicada killer wasps. Populations may be low this year due to the dry, hard ground which affects cicada and wasp emergence.
Damage caused by the lesser canna leafroller, Geshna cannalis, is now being seen at the Plant Insect and Disease Clinic at North Carolina State University. It is active from late June until frost. It is a small caterpillar related to the European corn borer and the sod webworm. The lesser canna leafroller overwinters as larvae in the leaves and stems of canna, and the moths emerge to mate and lay eggs after the new growth emerges in spring. One mistake that canna growers make is to leave the old dead growth on the canna bed as a mulch. As canna seems to be the only host plant for this pest, it may be possible to drastically reduce the lesser canna leafroller population just by removing dead leaves and stems in the fall after the frost has killed the plants.
When the larvae hatch, they feed within the new, rolled leaves. If not managed, lesser canna leafrollers may completely destroy the aesthetic value of cannas. Dipel, Conserve, or Orthene are recommended. Addition of a spreader-sticker will help the pesticide adhere to the waxy canna leaves. Spray the pesticide directly into the rolled leaves so that the pesticide can soak into the shelter around the caterpillars. Also pick up and destroy all of the dead tops from the cannas this winter after frost.
Evidence of fall webworm activity is starting to be observed. Because fall webworm damage accrues over the summer, they usually cause little long term health damage to the trees they defoliate. At any one location, the populations of fall webworms wax and wane so that they are conspicuous and damaging for a year or two and then the populations seem to disappear. Fall webworms feed on over 600 kinds of trees, shrubs and other plants. In North Carolina they seem to prefer pecans, persimmons, sourwoods and willows. The webs they create as they feed and grow become filled with cast skins, droppings and dead leaves. The web starts at the branch tips and becomes enlarged to encompass fresh, green leaves until the web may become two to three feet long. Small trees infested with several broods of caterpillars may be entirely enclosed in webs. After feeding for four or five weeks, the caterpillars crawl down, spin cocoons and pupate in mulch or soil. There are at least two or three generations each year in North Carolina depending upon how early or late in the spring the first moths emerge. They overwinter as pupae in cocoons in the litter. White fall webworm moths (some moths have small black spots) emerge to mate and lay 350 to 900 eggs on the lower leaf surface. The hairy caterpillars spin the webs as they feed. Fall webworms can be destroyed by pulling down the webs and destroying the caterpillars if the webs are in reach of a pole. If the webs are within reach of a hose-end sprayer, several insecticides can be sprayed for control. Insecticides work best when the caterpillars are young, so it is best to treat as soon as the webs are first noticed. A product containing Bacillus thuringiensis is appropriate for homeowner use, while commercial applicators should use B.t. (e.g., Dipel) or Conserve. Orthene or Talstar are other options.
Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age or disability. North Carolina State University, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
Last modified on July 21, 2003 by Stephen J. Toth, Jr.
