Pest News for August 23rd

ORNAMENTALS AND TURF

From: Steve Bambara, Extension Entomologist

Orangestriped Oakworms Return

Over the last two seasons, I haven't seen much of the orangestriped oakworm. I think the ground has been too hard and dry for the insect to move into and out of the soil. That's good in a way, because the oak trees had a break from defoliation. They are somewhat back this year and devouring foliage. I see them most on willow oaks and pin oaks.

The moth is brown in color with a white spot and a dark stripe on each forewing. The moths emerge in June and July and deposit their eggs in clusters of several hundred on the underside of oak leaves. The eggs hatch in about a week. The tiny, green caterpillars eventually grow into attractive black caterpillars with yellow or orange stripes running lengthwise along their bodies. Young caterpillars feed in groups whereas older caterpillars tend to be solitary, although there may be thousands of caterpillars on a single tree. Small trees are sometimes defoliated completely by midsummer.

As the caterpillars mature, they are often seen crawling along sidewalks, driveways and yards. These caterpillars may wander for a considerable distance while searching for a place to pupate. They can drop a lot of black fecal pellets on a sidewalk. You can step on these without fear, as long as you have on shoes. They dig into the soil three or four inches and pupate there. There is usually one generation per year, and the caterpillars overwinter as pupae in the soil. Control is complicated by the size of many of the infested trees. Most people do not have sprayers that can reach very high into shade trees, and by the time the caterpillars descend and crawl about on the soil they are extremely resistant to pesticides. Fortunately, late summer defoliations are much less damaging to the health of trees than early spring defoliations. In most cases it is probably better to rely on birds, diseases and parasites to lower the population next year. A long pole can knock many out of a tree, if you can reach them. (If you're extremely tall, you could use a short pole.)

For more information, see http://www.ces.ncsu.edu/depts/ent/notes/O&T/trees/note139/note139.html. If you would like to consider boosting the paper wasp predator population with nest boxes in the spring, see http://www.ces.ncsu.edu/depts/ent/notes/Other/note121/note121.html.


European Hornets

European hornet populations have grown and so have nest sizes. This large hornet is attracted to lights and windows at night which terrifies some people. The European hornet, Vespa crabro, is an introduced species into North America. It builds large, tan, paper nests that are usually not free hanging. Nests are often located in hollow trees, but partially exposed. Sometimes they nest in structures such as a wall or outbuilding. Tom Daly of Wake County, North Carolina, was kind enough to send in a picture of his hornets that built a nest in a bird house. Like all wasps and hornets, they can be considered beneficial because they eat other insects. These hornets often eat other stinging insects. They may strip bark from soft-barked twigs. A normal foraging hornet, if left to tend to its own business, is usually not a threat. For more information about these mahogany and yellow-colored hornets and their control, if necessary, see Residential, Structural and Community Pests Insect Note No. 11 at: http://www.ces.ncsu.edu/depts/ent/notes/Urban/eurohornet.htm.

An eye catching solitary wasp is the tarantula hawk. This is just one of a group of pompilid wasps that prey upon spiders to provision a burrow. Pepsis menechma is dark metallic blue-purple with bright yellow antennae. It is easily twice the size of a paper wasp. When not hunting spiders, this wasp may be seen on flowers collecting nectar or pollen, especially milkweed and allium. Males may be territorial toward each other, but there is no aggression toward people and they won't sting unless handled roughly. As described in the August 13, 2010 issue of North Carolina Pest News, on the Schmidt pain index, the sting is at the top of the chart, akin to having a hair dryer dropped into your bathtub. Interestingly, in Bolivia, the common name of this type of wasp is "amigo del hombre," or "friend of man."

From: Steve Frank, Extension Entomologist

Beetles Attack Drought Stressed Trees

Yesterday I received a call about a cherry laurel that was riddled with very tiny holes. The tree had dead brown dead leaves on some branches and the grounds manager initially assumed the tree was drying from drought. Upon closer inspection he found the many small holes about the size of mechanical pencil lead that had little tufts of sawdust. The holes were concentrated at old twig scars though they occurred throughout the lower third of the branches. The cause of the holes was a bark beetle in the genus Hypothenemus. We recovered adults from shallow incomplete galleries which they must have just started in the past few days. These beetles made the holes, but may not have killed the tree. Although we have not determined the species, this group of beetles often target trees that are already stressed or in decline due to drought or other causes. Drought can make many plants more susceptible to pest attack. Thus, it is important to keep plants healthy and watered and investigate drought-like symptoms to determine if other problems exist.


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