Monday, May 2, 2011

Pest News Update- May 2,2011


From: Steve Bambara, Extension Entomologist

Oak Apple Galls Appealing

Oak-apple gall wasps form large spherical galls on the leaves or leaf petioles of various red, black and scarlet oaks. These galls are up to two inches in diameter, green tinged with red when fresh, and gradually turn brown.

Another common golf ball-sized gall on oak is the wool sower gall. Distinct and unusual fuzzy plant growth is induced by the secretions of the grubs of a tiny gall wasp, Callirhytis seminator. If a fresh wool sower gall is held in a plastic bag out of the sun (so it will not get too hot), within one to three weeks the tiny, harmless gall wasps will emerge. The wool sower gall is specific to white oak and only occurs in the spring. Pulling the gall apart exposes small seed-like structures. The gall wasp grubs develop inside these structures. (This gall is also called the oak seed gall.) Wool sower galls are not abundant and don't cause harm to white oaks. For more information on these galls, see Ornamentals and Turf Insect Note No. 5 at Oak-apple gall.

Predatory Stink Bug Euthyrhychus floridanus

Euthyrhynchus floridanus is not a pest stink bug, but one that feeds on other insects. It is very colorful, yet different in both adult and nymphal stages.

Normally we don't see this until later in the season, but we have had a report already this spring. This is one of the more attractive stink bug adults with three orange spots on a dark, metallic blue-black background. These insects overwinter as adults probably in some dry, sheltered location. Eggs are laid the following spring. The eggs hatch 19 to 33 days later. Nymphs of Euthyrhynchus floridanus take a long time to develop through five stages (40 to 67 days). New adult females wait 5 or 6 days before mating and the eggs are laid 23 to 67 days later. Total developmental time for this species is much longer than for plant-feeding stink bugs.

Nymphs are metallic blue-green with red and are highly aggregated. They even attack larger prey in concert. Apparently, aggregation behavior allows them to successfully attack prey too large to be subdued by a single nymph. Sometimes the adults aggregate with nymphs, although when times get hard these bugs sometimes feed on smaller individuals. When the bugs jab their prey with their proboscis, they inject a toxin that slowly immobilizes the prey. Euthyrhynchus floridanus bugs have an unusual wagging behavior in which the bug rocks its body from side to side while it grips the substrate firmly with its feet. This is thought to be a defensive behavior. Some other predaceous stink bugs feed on plant tissue when insect prey is not available. Plant feeding is not reported for Euthyrhynchus floridanus.

Predatory Ground Beetle Calosoma

Beetles in the genus Calosoma are called caterpillar hunters. They are among the largest in the Carabidae ground beetle family. Adults and larvae are active predators. Calosoma sycophanta is a large, metallic green beetle that was imported from Europe to New England for the biological control of the gypsy moth in 1905. The larva feeds day and night, consuming 50 caterpillars during its two-week developmental period. The adult will eat several hundred caterpillars during a life span of two to four years. There are also several native species of Calosoma. (from the Midwest Biocontrol News). We have had several reports of these insects already this spring.

Crane Flies

Periodically, the public will inquire about "those large mosquitoes." They are usually referring to crane flies. Crane fly larvae live in wet areas and can grow to be quite large. They are rarely a pest to anything. The adults are very fragile creatures and may be seen resting on the sides of a house or under an overhang. Occasionally, they make it into a house. They cannot bite and will usually die with 24 hours once inside. They can be gently relocated outdoors or ignored and swept up later. They are frequently missing appendages. For additional information, see the following web site:

Crane Fly

Eastern Juniper Bark Beetles

A sample of eastern red cedar (Juniperus) containing bark beetles was recently sent from Dare County. The eastern juniper bark beetle, Phloeosinus dentatus, usually attacks eastern red cedar, but it also infests arborvitae and even infests Leyland cypress. These small, blackish-colored beetles bore into the tree and then bore upward with the grain. Eggs are laid in short galleries that extend upward from the entrance hole. Infestations are usually found in cut, broken or fire damaged trees. The eastern juniper bark beetle also attacks red cedars infested with Heterobasion annosum fungus. Together, infested trees of all sizes succumb. The beetle/disease correlation is not clearly defined. Keeping trees in a healthy, unstressed condition should help. Protective bark sprays are less than highly effective against the beetles. For more information, see the following web sites:

Juniper Bark Beetle
Eastern Red Cedar

Springtime Fall Cankerworms in Cabarrus County

I'm a little late with this notice, but thought I'd still mention it. Fall cankerworms are small "inchworms" that hatch in the spring and are fond of young oak and maple foliage. Fall cankerworms have three prologs while spring cankerworms have only two at the end of the abdomen. Caterpillars emerge and consume foliage at some time in March and feed through April. The city of Charlotte has been the major center of this population since 1987, for unknown reasons. Cabarrus County also reported a small outbreak again this year. Durham County had a suspected report, too. Natural controls, which regulate outbreaks in uninhabited forests, have not been effective in reducing fall cankerworm populations in this urban environment. Charlotte has a large number of mature willow oaks that provide an almost unbroken canopy over much of the city.

Control strategies for fall cankerworms involve mostly trunk banding for flightless female moth trapping in November through December as flightless female moths crawl up the tree. Pesticide sprays in the spring with B.t. or other foliage protectors can be used, but are expensive on large trees. See Cankerworms on the web for additional information.

Azalea Bark Scales

An infestation of azalea bark scales was recently reported from Wilson County. Heavily infested plants may appear chlorotic and unthrifty. The bushes are often covered with sooty mold, a black fungus that grows in the honeydew excreted by the azalea bark scales as they feed. Eventually twigs may die back. Adult females and eggs are protected inside the egg sac from most pesticides. The key to control is treatment in late spring and late fall when the nymphs are present. Horticultural oil sprays should work while crawlers are present, which is about now. Retreatment may be necessary. Orthene is another choice. Imidacloprid as a soil drench at the base of the plant should be effective. This may also occur on rhododendron. For more information, see the following web sites:

Note 134
Azalea Bark Scale

Seedcorn Maggot Flies – Dead, But Still Alive

This week we have received several reports about dead flies on branches. It is an unusual sight and may cause undue concern to gardeners. These flies are adults of seedcorn maggot (Delia platura), which is sometimes a pest of agriculture. Seedcorn maggot flies are grayish-brown in color and about one-fifth of an inch in length. The legs are black and there are bristles scattered on the body. Some seedcorn maggot flies become infected with a live fungus of the genus Entomophthora. Infected flies are swollen and have pinkish bands on the abdomen. Sometimes, gray Entomophthora spores are visible on the fly and on the substrate nearby. This fungus apparently causes the flies to land on protruding objects such as any twigs, clotheslines, and fence posts. The flies cling there and usually die in the afternoon as their abdomens swell with fungal strands inside.

Early the next morning, the fungal spores are released into the air while the humidity is high. The spores infest other seedcorn maggots. Although the fungus-infected flies appear to be damaging the plant, these adult flies are harmless. The seedcorn maggot is found throughout North Carolina. Seedcorn maggots feed primarily on decaying organic matter, but sometimes infest the seeds and seedlings of berries or vegetables. The dead, fungus-infected flies are sometime abundant on the dead twigs of dogwood and crape myrtle in the spring. For more information, see Ornamentals and Turf Insect Note No. 20 on the Internet at Seedcorn Maggots.

From: Steven Frank, Extension Entomologist

Lecanium Scales on Oaks

Oak lecanium scale is one of the largest soft scales in our area. Scales are brown and rounded reaching 6 mm in diameter. As soft scales, lecanium scales produce honeydew that can cause sooty mold on oaks or plants below. It primarily infests oaks trees. Large populations can reduce growth and vitality especially in newly planted trees.

Eggs are present now under adult scale covers indicating crawlers will emerge in the next week or so or may be emerging now in your area. The crawler stage should be targeted for best efficacy. On trees small enough to treat the foliage, horticultural oil can be used. On larger trees, a systemic insecticide such as dinotefuran can be applied as a drench or trunk spray. This scale is not easily eradicated and optimal control measures are still unclear. It is attacked by many parasitoids and predators that can reduce scale abundance if protected from insecticides. For more information, see the following web site: Lecanium Scale

Juniper Scale Crawlers are Active

The juniper scale, Carulaspis juniper, attacks some of the most commonly used plants in ornamental landscapes, including all juniper species but also cypress species and false cypress. There is one generation per year in which females fill up their armored cover with eggs in spring from which crawlers hatch and look for new feeding sites. Infestations can lead to foliage that becomes yellow or brown and generally less lustrous than normal. Large infestations can cause the tips of branches to die and the plant to become sparsely foliated. Isolated infestations can be pruned off of plants. Natural enemies will often keep scale below damaging thresholds. However, in environments where natural enemies are not abundant control may be necessary. Horticultural oil will smother crawlers. Other chemicals such as dinotefuran (Safari), acetamiprid (TriStar), pyroproxifen (Distance) and others can be used to manage infestations. More information on armored scale management can be found at: Armored Scale

For more information contact your local Cooperative Extension Center and ask for the Commercial Horticulture Agent.