ORNAMENTALSAND
TURF
ORNAMENTALS
The information and recommendations in this newsletter are applicable to North Carolina and may not apply in other areas.
Green June beetles, Japanese beetles, cranberry rootworms and spider mites continue to be problems in the landscape. Perhaps the spider mites will die, thanks to the rain and humidity from the remnants of Hurricane Danny. The bagworms are getting older, tougher and harder to manage; remember to treat with insecticide soon!
The cottonwood leaf beetle feeds on the leaves of poplars, willows, and alders throughout North Carolina. Adults are the overwintering stage. They emerge in early spring and feed on the new leaves and tender bark. Eggs are laid in masses and the tiny, new larvae feed in groups. 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. Available in the county Extension Centers in North Carolina is Ornamentals and Turf Insect Note No. 24 that explains which pesticides are useful for beetle control.
The rhododendron gall midge is a pest that seems to attack the new growth of rhododendrons out of nowhere. The adult is a small midge that lays eggs in the emerging buds. When many larvae infest a bud, the bud may die completely. When the buds are infested later, the new leaves roll in on the margins and the tiny white maggots develop inside the cavity formed by the tightly-rolled plant tissue. Infested leaves may die after the maggots drop to the soil to pupate. The larvae develop rapidly and are fully grown in a few days. There are at least two generations per year. Often the first flush of growth may be heavily damaged and then the second summer flush is likewise heavily damaged. Both Rhododendron catawbiensis and R. maximum are susceptible to the rhododendron tip midge. Available in the county Extension Centers is Ornamentals and Turf Insect Note No. 58 (Rhododendron Pest Control Calendar) that provides information on when pests occur and what can be used for control. Unfortunately, the rhododendron tip midge does not seem to be included on any pesticide product labels. I recommend the use of Cygon or Orthene as a thorough spray as the new growth emerges to try to control the maggots before extensive damage is done. Because insect and mite populations vary from year to year and place to place, it may not be necessary to use pesticides for rhododendron tip midges year after year.
Twobanded Japanese weevils remarkably feed during the day (most
other weevil pests of ornamental plants feed at night), although
they usually drop to the soil and remain motionless for a while
when disturbed. This small, dark gray beetle usually has two
irregular dark bands across the wing covers. Twobanded Japanese
weevils cannot fly. Hence, their damage tends to be severe in
small areas such as plant beds in a landscape where they probably
arrived in an infested plant. Twobanded Japanese weevils attack
almost any ornamental plant. Damaged plants appear tattered and
unhealthy. Females lay their eggs in the folds of leaves that they
tie together. The grubs feed on roots. Twobanded Japanese weevils
are also unusual because they are resistant to several insecticides
commonly used in the home garden, including Sevin, malathion and
diazinon. Fortunately they are susceptible to Orthene insecticide
which is labeled for home use and has the advantage of being
systemic and not very toxic to humans. Commercial growers and
landscapers can use a pyrethroid (Astro, Mavrik, Talstar or Tempo
2) for control. Because twobanded Japanese weevils drop from
infested plants when disturbed, many can be trapped by carefully
placing a cloth or large sheet of paper under the shrubs and then
tapping or shaking the plant vigorously. The weevils can then be
transferred to a container and destroyed. Ornamentals and Turf
Insect Note No. 34 provides more information on the biology and
control of twobanded Japanese weevils. Copies of this note should
be available in each county Extension center in North Carolina.
Web page last updated on July 28, 1997 by Stephen J. Toth, Jr..
