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Ornamentals and Turf |
The azalea lace bug is among the most frequently reported insect pest in the landscape. Lace bugs feed by inserting their needle-like mouthparts into leaves and injecting saliva. When the lace bug sucks out the predigested fluid, the empty cells left behind are conspicuously pale. After what appears to be a short time, lace bugs cause the leaves to become completely bleached and have a bronzed appearance on the upper leaf surface. Lace bugs also leave shiny, black excrement (fly specks) on the lower leaf surface. Azalea lace bugs are relatively difficult to completely eliminate. Fortunately, they rarely kill plants.
Insecticidal soap can control small populations, or Orthene may be used for control is pressure is high. Be sure to treat the undersides of the leaves. Imidacloprid can be used as a soil drench in specimen or small, valuable plantings. The azalea plant bug, Rhinocapsis vanduzeii, is a predatory bug that can provide some azalea lace bug control when used in conjunction with insecticidal soap. There has been some success with the release of green lacewings for azalea lace bug control as well. Azaleas planted in full sun are said to suffer more than those planted in partial sun. Ornamentals and Turf Insect Note Number 39 contains additional information on the azalea and other lace bugs.
That woolly-looking material on plant stems may jump when touched. If it does, it is probably a flatid planthopper. I recently received a report of planthopper nymph activity on azaleas. Sometimes it is only the residue which is left behind by the insect that is noticed. Planthopper nymphs closely resemble woolly aphids in appearance and by the honeydew they secrete. The biggest difference is that planthoppers move quickly when disturbed and often jump or hop for several inches whereas woolly aphids are more sedentary. Normally they are not found in numbers that require attention, but most of the pesticides labeled for home use will give adequate control of flatid planthoppers (Orthene, malathion, soap, etc.).
Female flower thrips are yellow-brown to amber in color with an orange-colored thorax and are barely visible to the eye (1/16 inch). Males are slightly smaller and more pale in color than females. The most notable character is the fringe or feather-like wings. Because of their small size, flower thrips are carried over large areas by wind systems. Flower thrips are found throughout North Carolina with the peak migration occurring during the first week of June. They reproduce throughout the year in North Carolina, with the majority of their 12 to 15 generations occurring in the warmer months. Flower thrips have been collected from plants in 29 orders, including various berries, cotton, day lilies, field crops, forage crops, grass flowers, legumes, peonies, privet, roses, trees, truck crops, and vines. They seem to prefer grasses and yellow or pale blossoms. Roses seem most susceptible in June. Flower thrips feed by piercing the leaf or petal surface and drawing sap from injured cells. On ornamental plants, this damage is usually restricted to the flowers. For example, rose blossoms turn brown and buds open only partially. The petals, distorted with brown edges, seem to stick together. The large numbers of thrips account for their considerable and rapid damage to flowers, especially those with pale petals. During warm periods, swarms of these tiny, orange-colored insects often fly in late afternoon. Thrips bite people, causing an attention-getting sensation. More information on thrips is contained in Ornamentals and Turf Insect Information Note No. 21.
I am beginning to receive reports of western flower thrips. These are mostly a concern in greenhouses because of the potential to vector viruses. The western flower thrips can transmit impatiens necrotic spot virus and tomato spotted wilt virus to ornamental plants. Western flower thrips overwinter in North Carolina as well as areas further south. One threat to greenhouse plants is that larvae of western flower thrips outside the greenhouse may pick up tomato spotted wilt virus from infected weeds, and then new adults can fly through the evaporative cooling pads into greenhouses where they can then spread the virus among susceptible crops. Another threat is that western flower thrips may blow into greenhouses and become established (because of its great pesticide resistance). Later a plant with impatiens necrotic spot virus may be brought in and the virus acquired by immature western flower thrips and spread through the rest of the range by the new, infected adults. Conserve is an effective pesticide for western flower thrips management that is labeled for ornamental plants. To slow down the acquisition of pesticide resistance, pesticide rotation is recommended. Other pesticides labeled for western flower thrips control are listed in the North Carolina Agricultural Chemicals Manual. Ornamentals and Turf Insect Information Note No. 72 provides additional information on the biology and suppression of western flower thrips. General information about impatiens necrotic spot virus and thrips management (including screening and monitoring) are available in Ornamental and Turf Insect Information Note No. 120.
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 May 20, 2002 by Stephen J. Toth, Jr.
