It may not be fall, but fall webworms are back. There is disagreement whether this is an early generation, or a subspecies which arrives first. Either way, fall webworms are beginning to appear on their favorite trees such as sourwood, pecan, and persimmon. Fall webworm damage accrues over the summer. They usually cause little long-term damage to the health of the trees they defoliate unless the trees are completely defoliated year after year. 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.
Through the summer, the webs become filled with cast skins, droppings and dead leaves. The web is 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. In July and August, another generation of moths emerges from the cocoons to continue the life cycle. There are 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 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. Thus it is best to treat as soon as the webs are first noticed. If the trees are too tall for equipment used by the amateur horticulturist, many professional landscapers and arborists offer tree spraying as a part of their services. Bacillus thuringiensis and Orthene are two of several pesticides labeled for fall webworm control. Ornamentals and Turf Insect Note No. 46 contains additional information on the biology and control of fall webworms. Copies of this note are available in the county Extension centers in North Carolina.
Japanese beetles are a real nuisance in landscapes and nurseries. The grubs feed on the roots of grasses and when they are numerous can cause damage to lawns. The adults fly readily and are pests of ornamental flowers, especially roses, hibiscus, and other flowers. Below are some suggestions for minimizing Japanese beetle damage in the landscape without using pesticides.
Host Plant Resistance
Some plants are attractive to Japanese beetles and unless protected by netting or pesticides will always be damaged where these beetles are active. Japanese beetles are especially attracted to purple leaf (and other) plums, golden sycamores, witchhazels, roses and many varieties of grapes. In areas with high Japanese beetle populations, insecticides might be the short-term remedy, but one cure is to rouge out plants that are attractive to the beetles and substitute others that are resistant to their feeding. Fortunately, the list of plants not attractive to Japanese beetles is long, and attractive landscapes featuring plants Japanese beetles avoid are conceivable. The following are plants not attractive to Japanese beetles (some even appear to be completely immune): ageratum, ailanthus, arborvitae, ash, aster, babies breath, balsam, balsam fir, bamboo, beautyberry, beebalm, begonia, black locust, bleeding heart, boxelder, browneyedsusan, butternut, caladium, candytuft, carnation, Carolina allspice, Catawba rhododendron, catnip, Chinese azalea, Chinese lantern-plant, Chinese redbud, chrysanthemum, clematis, cockscomb, columbine, coneflower, coralbells, coreopsis, cornflower, cosmos, crassula, cryptomeria, English ivy, euonymus, false dragonhead, flowering tobacco, forgetmenot, forsythia, foxgove, dogwood, dusty miller, gaillardia, gardenia, goldenglow, ginkgo, ground myrtle, hazelnut, hemlock, hickory, hollies, hydrangea, hyssop, Iceland poppy, iris, Japanese honeysuckle, Japanese pagodatree, Japanese pieris, Japanese spurge, juniper, lantana, larkspur, lilac, lilies, lily of the valley, lions heart, magnolia, maidenhair fern, maidenhair tree, maples other than Norway, matrimonyvine, mignonette, mimosa, mockorange, motherwort, mountain bluet, mountain laurel, mulberry, mullein, nasturtium, oaks other than chestnut and pin, Oriental poppy, ox-eye daisy, pampas grass, pansy, pear, persimmon, petunia, phlox, pine, pinxterbloom azalea, plaintain lily, portulaca, privet, purple loosestrife, pyracantha, pyrethrum daisy, rabbiteye blueberry, rosebay rhododendron, sedum, smoketree, snapdragon, snowberry, spearmint, spiderwort, spruce, strawflower, swamp azalea, sweetgum, sweetpea, sweetpotato, sweet scaboius, sweet William, tamarisk, tawny daylily, tiger lily, tuliptree, verbena, violet, Virginia dayflower, wandering Jew, waterlily, white top, white turtlehead, wild bergamot, wild indigo, winterberry, winter honeysuckle, yew, and yucca.
Use of Japanese Beetle Traps
I often get the question, Do Japanese beetle traps do any good? Japanese beetle traps often attract large numbers of adult beetles, but because the traps are not really efficient at catching the beetles, more harm may be done by putting a trap in the landscape than not. If a trap is to be used, it should be placed away from beetle-susceptible plants because rotting Japanese beetles release ammonia and ammonia repels the beetles. Unless the beetles are emptied from the trap regularly, the trap may become repellent to the beetles in the vicinity of the trap, while the baits are attractive to beetles over a great distance. Therefore, traps should be located some distance away from plants that are to be protected.
Trap crops
Should the landscape have an area at the edge planted with cocklebur, evening primrose, sassafras, dwarf mallow, and other plants attractive to Japanese beetles? The beetles may congregate there rather than in the landscape. In addition, the flowers of bottlebrush-buckeye are toxic as well as attractive to Japanese beetles. The beetles are also attracted to and intoxicated by the flowers and leaves of castorbean cultivars Sanguineus and Zanzibariensis, and the flowers of some red geranium cultivars.
The dry, hot weather during May and early June has certainly set the stage for serious chinch bug problems on St. Augustinegrass for July and August. Keep a close watch on St. Augustinegrass for the remainder of the summer because it appears past conditions have increased the likelihood for problems with chinch bugs later this summer.
Many areas of bermudagrass are looking poor this summer, particularly some athletic fields. One possible explanation for some of these problems can be traced back to last fall when we had serious infestations with fall armyworms. In many situations populations of fall armyworms were quite high and the bermudagrass was damaged late in the year. As a result it did not have a chance to recover before winter and the impact of all this has shown up with winter kill and bermudagrass that is slow to green. Nothing can be done about it now, but it does help explain at least a few of the problems we are seeing this year.
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 June 21, 1999 by Stephen J. Toth, Jr.
