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Ornamentals and Turf |
I tried to ignore this pest this year, but have already received a few telephone calls regarding fluffy stuff on maple leaves. Woolly alder aphids are noticed primarily in the spring on silver maples. They are called woolly alder aphids because of the waxy fluff the aphids secrete to cover their bodies. They do not resemble the typical aphid body, either. This aphid sucks sap from the leaves and excretes honeydew, a sweet, sticky liquid that covers lawn furniture, walks, and the ground cover under the trees. Dark sooty mold fungi grow in the honeydew and mar objects in the landscape. In late spring and early summer the aphids migrate to alders; hence, the name woolly alder aphid. Summer is spent feeding on the stems of alders. The migrating generation of woolly aphids is conspicuous because their fluffy, white wax shows up brightly as the aphids seem to float aimlessly along. In autumn, the aphids migrate back to maple trees to lay eggs on the bark for the next year's generations. The fall-migrating generation of woolly aphids is not nearly as conspicuous as the summer generation, and most people do not even notice the aphids on the bark. The woolly alder aphid is not resistant to pesticides, but it may be difficult for amateur horticulturists to spray large trees. Insecticidal soap is probably the best choice for homeowners. There is more information on the biology and control of woolly alder aphids in Ornamentals and Turf Insect Note No. 6.
Green lacewings are predators found in most environments. Several species are important predators. The common green lacewing occurs throughout North America. The light green adult has long, slender antennae, golden eyes, and large, veined, gauze-like wings that are 1/2 to 1/3 inch in length. It is a slow-flying, nocturnal insect that feeds on nectar and pollen, and it emits a foul-smelling fluid from special glands if captured. The female lacewing lays eggs usually in groups on leaves, each egg held away from the leaf surface on the end of a slender stalk. A female lacewing lays up to 300 eggs over a period of 3 to 4 weeks, but often it does not survive that long in the field.
The larva, commonly called an aphidlion, resembles a green-gray colored alligator with mouthparts like ice tongs. An aphidlion seizes and punctures its prey with long, sickle-shaped jaws, injects a paralyzing venom, and sucks out the body fluids of its prey. After feeding and growing to 1/2 inch in length during a 2 to 3 week period, the larva spins a spherical, white silken cocoon in which it pupates. The adult emerges in about 5 days through a round hole that it cuts in the top of the cocoon. It overwinters as a pupa within its cocoon or as an adult, depending on the species. An aphidlion is a voracious feeder and can consume up to 200 aphids or other prey per week. In addition to aphids, it will eat mites and a wide variety of soft-bodied insects, including insect eggs, thrips, mealybugs, immature whiteflies, and small caterpillars. Aphidlions will also consume each other if no other prey are available.
Green lacewings are available from many commercial suppliers, generally offered as eggs.
(Note: Excerpted from an article by Susan Mahr in Midwest Biological News)
This week, two telephone calls were received regarding masses of fungus gnat larvae in lawns. I suspect the wet spring has something to do with this occurrence. Darkwinged fungus gnats are native insects that are normally not noticed because they inhabit decaying organic matter outdoors and they are usually not particularly abundant in the overall landscape. Sometimes fungus gnats emerge in large numbers and are noticeable because they congregate around the house or on plants in the yard. Except for being a nuisance, fungus gnats in the yard are harmless. One exceptional thing about fungus gnat maggots is their mass migration apparently in search of a new food source. The maggots stick together and slither along in a ribbon sometimes as much as one inch wide and a yard long so that the mass of larvae resembles a silvery snake! This is a startling sight, but is perfectly harmless.
Do you need another reason not to grow, sell or plant this awful thing known as Euonymus? Another reason is called Pryeria sinica. A lepidopteran pest never before known in the U. S., Pryeria sinica was first observed in a Fairfax County, Virginia landscape in 2001 (http://everest.ento.vt.edu/~idlab/newmoth/newmoth.htm). The insect was seen there again as well as a location about 15 miles away in 2002, indicating it had been introduced prior to the 2001 observation. It was submitted to the insect identification clinic at Virginia Tech University, where it stumped the entomologist who submitted it to a specialist at the Smithsonian Institute. Its identity was finally determined about two weeks ago. This insect, which is native to Asia, has been reared from Celastrus punctatus, Euonymus sieboldianus, and Euonymus japonicus. We assume it arrived in Virginia via imported plant material. It overwinters in the egg stage and feeds in the spring. The larvae, which are white with longitudinal black stripes, are gregarious and feed in large groups. In Asia, nematodes are sold for control for this insect. So management practices to try include NemasysH or ScanMask, along with the more familiar Dipel or Conserve.
The more desirable deciduous euonymus, Euonymus alatus (winged euonymus or burning bush), has long been recommended as an alternative because of its resistance to the euonymus scale, Unaspis euonymi. However, Lepidosaphes yanagicola, a scale insect known as a pest of winged euonymus in the Midwest, has just been found in North Carolina. In Insects That Feed on Trees and Shrubs, Warren Johnson reports one generation of the insect per year in Pennsylvania. However, more recent information from Indiana is that there are three periods of crawler activity in May, July and September. Expect this to occur two to four weeks earlier in North Carolina, depending on location. This scale can be challenging because it is difficult to see. It is brown, with 1/16 inch long oystershell-shaped covers. It is restricted to the bark, where it blends well with the corky ridges. There is a photograph in Insects That Feed on Trees and Shrubs, 2nd edition, page 389, Plate 186B. Control this insect as you would Unaspis euonymi (i.e., dormant oil in winter and summer oil timed to crawler activity).
Views expressed in this article on the landscape value of certain plant material are the opinion of the author and do not reflect official policy of North Carolina State University.
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Last modified on June 9, 2003 by Stephen J. Toth, Jr.
