Pest News: Ornamentals and Turf
Spiny Witch-Hazel Gall Aphids on Birch- Steve Bambara, Extension Entomologist
Spiny witch-hazel gall aphids, Hamamelistes spinosus, cause bumpy ridges on the leaves of birch (Fig. 6). The overwintering eggs are laid on witch-hazel in June and July. These eggs hatch the following spring and the new aphid nymphs crawl to the flower buds to feed; if the plant does not have flower buds, these aphids die! Feeding on the flower buds induces the plant to form a spiny gall. A second generation of winged aphids develops inside the galls, then leaves and flies to birch. These winged aphids give birth to a scale-like generation which settles and hibernates on birch until the following spring. As the buds break, the scale-like aphids feed on the leaves and induce the birch to form corrugated galls. Winged aphids that migrate back to witch-hazel or wingless aphids called accessory females develop inside these galls.
The winged aphids which migrate back to witch-hazel give birth to a generation of wingless males and females. These wingless aphids mate, and the females lay eggs for overwintering. The special accessory females produce additional generations of winged aphids which migrate to witch-hazel to give birth to males and females that lay eggs for overwintering. Thus, this aphid requires two full years to complete its cycle of life stages.
Pesticides should be applied at bud break in early spring to prevent gall formation. It is probably too late this year for effective control. This must be done every year unless the witch-hazels can be found and eliminated. The alternation of hosts is well known for other aphids (woolly apple aphid on apple and elm, woolly alder aphid on maple and alder, and green peach aphid on peach and many other hosts), but the spiny witch-hazel gall aphid seems to have the most complicated life cycle.
Lesser Canna Leafroller Derby-Steve Bambara, Extension Entomologist
If your cannas have been heavily attacked by the lesser canna leafroller in the past, it may be time to treat. As leaf whorls begin to open, attack by the leafroller becomes more likely with early larvae appearing as leaf miners. This pest is more prominently recognized in the fall as the second generation damage becomes more noticeable.
These small caterpillars are related to European corn borers, pickleworms, coneworms and sod webworms. Lesser canna leafrollers overwinter as larvae in the leaves and stems of canna and the moths emerge to mate and lay eggs after the new growth emerges in the spring. When the larvae hatch, they feed within the new, rolled leaves. Older larvae can tie the edges of older leaves together and roll the leaf like a Cuban cigar!
Sanitation is key to possibly reducing leafrollers to the point where pesticides are not needed. Canna growers should remove all the old, dead growth in the canna bed at the end of the season, after frost. Canna seems to be the only host plant for this pest, so if the plants are isolated from other cannas, sanitation may be sufficient pest management.
Early applications of Bacillus thuringiensis (B.t.) insecticides are effective for this pest. Spray the pesticide mixture directly down into the rolled leaves so that the pesticide can penetrate into the shelter around the caterpillars. A stronger product such as Orthene may control this pest by spraying several times at 10-day intervals. A surfactant may be helpful.
Cottonwood Leaf Beetles Steve Bambara, Extension Entomologist
The cottonwood leaf beetle, Chrysomela scripta, feeds on the leaves of poplar, willow, and alder throughout North Carolina. Overwintering adults emerge and lay eggs (Fig. 9). Larvae feed in groups on the new leaves and tender bark. The young larvae skeletonize the leaves. As they grow, the older larvae separate and consume entire leaves except for the midrib. When mature, the larvae pupate on the leaves, stems, trunk, or nearby objects. There are several generations per year and sometimes trees are seriously defoliated.
Sevin or a foliar pyrethroid insecticide should be effective for control. Many leaf beetles also respond to imidacloprid foliar spray or soil drench.
Boxwood Spider Mites Active on Boxwoods-Steven Frank, Extension Entomologist
Boxwood spider mites, Eurytetranychus buxi, are currently active and becoming a serious issue throughout the landscape. These brownish tetranichid mites similar in form to other spider mites such as the two-spotted spider mite are currently only a problem on boxwood hosts. Like other mites, boxwood spider mites cause stippling damage, which on an evergreen plant, will last as long as the leaves do. Light infestations can be managed with insecticidal soap or oil applied to the undersides of leaves. Otherwise, a number of miticides are available to reduce damage and populations.
Fungus Gnats by the Yard
Darkwinged fungus gnats are native insects that normally go unnoticed because they inhabit decaying organic matter outdoors and are generally not abundant in the overall landscape. This year, however they are emerging in large numbers perhaps in search of a new food source. The maggots are noticeable because they congregate around the house or on plants in the yard. They tend to stick together in ribbon-like form sometimes as much as an inch wide and a yard long moving in a snake like fashion. If you feel control is necessary, use soapy water to remove these gnats off sidewalks and driveways. Please note except for being a nuisance, fungus gnats in the yard are harmless.
Chinch Bugs Ahead- Steve Bambara, Extension Entomologist
Southern chinch bugs (Blissus insularis) are small (one-sixth inch), slender insects with black and white markings. This bug is a severe pest of St. Augustinegrass in North Carolina. It also attacks Bermudagrass, bahiagrass, zoysiagrass and centipedegrass. The damage often appears first in small circular areas which get larger over time. Damage is sometimes confused with drought stress. The best way to find the culprit is to get down near the border edge where living and dying grass meet. Look near the soil and inside of the grass blades for small red nymphs and adults which will quickly burrow underground when disturbed. Most of the damage is caused by the young, bright-red nymphs. Chinch bugs seem to be worse where there is a layer of thatch. Good thatch management helps by making the lawn less attractive to the bugs and by making it easier for pesticide to reach the chinch bugs when treated.
Astro, Sevin, and Tempo 2 insecticides are labeled for professional chinch bug manage- ment. It helps to water the lawn before treating, but not afterward for two days. However, label directions should be followed for any pesticide. Homeowner formulations of imidacloprid, cyfluthrin or Sevin insecticides are good choices for the homeowner.
2011 Landscape Color Field Day- June 29, 2011 at the JC Raulston Arboretum
Registration (by June 15th)- 25.00
Registration (after June 15th)- 40.00
This is a wonderful opportunity to see new methods of integrating beautiful blooms into different areas in the landscape. Please find attached a copy of the program for your reference.
If you are interested in attending this event, please contact N.C. Commercial Flower Growers Association 919.334.0090
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