Monday, June 27, 2011

Pest News for June 27th


From: Christine Nalepa and Whitney Swink, Research Specialists, North Carolina Department of Agriculture & Consumer Services

Hemlock Borers Collected by the Native Wasp Cerceris fumipennis in the North Carolina Mountains

The Beneficial Insects Laboratory of the North Carolina Department of Agriculture & Consumer Services has been using the solitary wasp Cerceris fumipennis as a biosurveillance tool to monitor for the Emerald Ash Borer and other pest Buprestidae throughout the state Solitary Wasp. The wasps nest on the hard-packed sandy soil typical of baseball and softball diamonds. They forage for buprestid beetles in the canopy, bringing them back to the nest to feed their offspring. The pest survey consists of intercepting Cerceris females at the nest when they return from foraging trips, and collecting and identifying the beetles they carry.

In recent weeks Cerceris surveys in the mountains of the state indicate that the wasps are bringing in large numbers of hemlock borers (Melanophila fulvoguttata), a pest of eastern hemlock (Tsuga canadensis), throughout its natural range. Hemlock borers are secondary pests that can reach significant levels in hosts weakened by hemlock woolly adelgids and other pests (see the June 11, 2010 issue of the North Carolina Pest News at Hemlock Borer).

The Cerceris surveys suggest that hemlock borers may be at or near outbreak levels in some locations of the North Carolina mountains. Melanophila fulvoguttata to date has been collected in seven sites, in the cities of Andrews, Asheville, Franklin, Murphy, and Bryson City. In the latter, 97% (57 of 59) of the beetles collected from the wasps were hemlock borers. Specimens have been deposited in the North Carolina State University Insect Museum.

From: Steve Bambara, Extension Entomologist

Where are the Green June Beetles?

We know that Mary had a little lamb, a little pork, a little jam. And she probably also had green June beetles. Expect to see them soon. They rarely do harm to landscape plants and do not harm people. They can be handled without fear. There are possible control measures available for larvae in turf and pasture (later in the season). I have rarely ever seen this justified in residential turf (unless your backyard used to be a pasture). Grubs are sometimes a problem in pastures and heavy manure-applied fields because they like the decaying organic matter. Adults are sometimes a problem in fruit trees and grapes. Adult populations should start to decline after two weeks and they should be gone after three to four weeks. Patience 25W* (a.i. time) is the best recommendation and can be applied without environmental concern. No, that's not a new pesticide, it's called waiting. For more information on green June beetles, see the following insect notes available on the web:

Green June Beetles
Green June Beetle Note

* Wait 25 days

Yellowjackets Building

Yellowjacket nests start from scratch each spring, as they do not reuse old nests. I've seen more yellowjackets out foraging recently. I've had one contact who reported disturbing a nest and being stung twice. If this episode had been a few weeks from now, I'm sure the number of stings would have been much greater. The nests are probably at their largest around the end of July. Wasps and yellow jackets are great predators of other flying insects and caterpillars.

Be aware of the potential for yellowjacket nests around shrubs and when mowing the lawn. Undisturbed "natural" areas in the landscape are good spots for them. They generally nest in the ground in loose-rooted areas at the base of shrubs and trees or below-ground rotted wood. Once-containerized plants that are now in the landscape often have voids where the media has degraded away. If the nest poses a stinging threat to humans or pets, control may be appropriate. Spray an aerosol hornet and wasp insecticide directly into the entrance hole at night. Don't use gasoline for a bunch of reasons! (Besides, it is too expensive.) Yellowjacket traps that are sold in stores (or homemade) have not been shown to be effective in North Carolina, though they make great conversation pieces in the yard.

Return of Oak Blotch Leafminers?

This week we received a report of an infestation of oak blotch leafminers in a Wake County neighborhood. The last outbreak I recall was about five years ago. Caterpillars of a small moth in the genus Cameraria mine in the leaves primarily of white oak (oak leaves with rounded lobes) leaving brown blotches. These blotches start small and may increase to the size of a dime or larger. There can be many blotches per leaf. There are several species of these moths that may attack oak leaves. Some of the caterpillars are gregarious and there may be several caterpillars in each blotch mine.

Now that the caterpillars are a bit larger, the mines are quite noticeable and the silvery blotches will begin to turn brown. A severe infestation can cause most of the leaf area to turn brown by mid-summer. Leaves may drop prematurely. Two or three generations could be possible per season.

Control by insecticides is not effective and not practical. Trees are not likely to be killed. These caterpillars are present every year, but it may be worse this year in some places. This insect overwinters as a larva in the leaf. Collecting and destroying fallen leaves may be a good idea this year. Oak trees often shed their leaves over a long period of time and may not drop them all until spring. If you are in an area surrounded by woods or neighbors with oak trees, there may be a plentiful supply of new caterpillars next year. Hopefully, the normally plentiful supply of parasitoid wasps will keep numbers lower.

Cicada Killer Wasps

The cicada killer wasps are beginning to emerge. Adult cicadas are caught and stung by this wasp, then dragged back to the nest. The most noticeable feature is often the large amount of soil excavated and mounded outside the burrow. Once in the nest, the female wasp lays her eggs on the cicada. Soon the egg hatches and the larva feeds on the cicada. When mature, the wasp larva pupates and another generation of wasps emerges to carry on the life cycle. This is one of our most "showy" wasps and the sight and sound of these coming and going is impressive. These wasps can be regarded as beneficial or neutral. They are also downright interesting. Ornamentals and Turf Insect Information Note No. 63 (see Cicada Killer Wasp) has additional information on the biology and control of cicada killer wasps, but I prefer the entertainment aspect of them.

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