Monday, July 11, 2011

Pest News Update July 8, 2011


From: Steve Frank, Extension Entomologist

Dogwood Twig Borer Oviposition

The last couple of weeks I have noticed flagging branch tips on the red twig dogwoods (Cornus sericea 'Baileyi') in front of my house. The damage was characterized by a cleanly girdled branch with a 1 cm oviposition scar just below. Gradually the tip goes from yellow to brown then falls off. Investigation and help from our excellent diagnostician revealed a large egg within each scar containing a round-headed borer larva. This was the dogwood twig borer. Adults have been active lately laying eggs in twigs. The larvae will overwinter within twigs then continue boring down the twig pith in spring killing the affected branch. This is not likely to be a big nursery pest but should be on the radar. It is much better to identify the flagging branches now and prune out the eggs than wait until spring when a whole branch or small tree will be affected.

If you follow me on Twitter, you know this already! Follow @OrnaPests on Twitter for timely updates on ornamental pest activity.

Western Flower Thrips in Greenhouses

Thrips are a constant problem for growers, not just a problem this week. Western flower thrips, Frankliniella occidentalis, is the most important and damaging thrips of greenhouses and has been called the most damaging greenhouse pest in the world. This is true of greenhouse-grown food and ornamental crops. Nearly all floriculture crops are susceptible to thrips damage.

Western flower thrips reproduce rapidly and are difficult to manage because they live in the cracks and crevices of flower heads and foliage. Thus, they are difficult to contact with insecticides. Western flower thrips also develop insecticide resistance rapidly so it is important to emphasize chemical rotation and to have a resistance management plan.

Sanitation is also very important in managing thrips. Because thrips can feed and reproduce on hundreds of plant species weeds in and around a greenhouse, they have a constant supply even if the crop is sprayed. Western flower thrips pupate in soil, so cleaning up spilled potting soil and other debris can deny them a vital part of their lifecycle.

More information and chemical recommendations can be found in Ornamentals and Turf Insect Information Note at Note 72.

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

Saturday, July 2, 2011

Pest News Update July 1 2011


From: Steve Frank, Extension Entomologist

Fall Webworms Hatching

I found small nests of very young fall webworms, Hyphantria cunea, when I was hiking last weekend. Fall webworms feed on over 600 species of trees and shrubs. In North Carolina they are most often found on sourwood, persimmon and pecan. Fall webworms primarily cause cosmetic damage to shade trees because of the unsightly webs they form around the foliage on which they feed. Young caterpillars eat leaf surfaces so that only the tiny veins remain. This residue turns brown and collects in the web. Older caterpillars devour the entire leaf. Because they are most abundant in mid-late summer after the tree has had some time to store food, the weather is hot and rainfall less, a tree's life is rarely in danger. Fall webworms can be easily destroyed or disrupted by pulling down the webs and destroying he caterpillars if the webs are within reach of a stick or pole. This also exposes caterpillars to bird and wasp predation. Insecticides applications will not penetrate the tent so caterpillars can only be exposed by feeding on treated leaves near the nest. For additional information, see Ornamentals and Turf Insect Information at Note #46

Follow @OrnaPests on twitter for timely updates on ornamental pest activity.

Twospotted Spider Mites Abound!

The twospotted spider mite, Tetranychus urticae, thrives in hot, dry weather like we have had lately. I have found many spider mites in the landscape . . . even on my poor Solomon’s Seal! It is important to scout for twospotted spider mites now because they reproduce most rapidly in hot dry weather. Under these conditions they can mature from egg to reproducing adult in 5 days! Nursery crops are especially susceptible because they may be exposed to more sun than landscape plants and receive more pesticides. Twospotted spider mites feed on over 100 plant species, sucking the fluid out of leaf cells. This ‘stippling’ damage can rapidly cause entire plants to take on a bronzed appearance. Look on the underside of leaves on susceptible hosts or beat foliage on a white piece of paper to scout for spider mites. If you notice mites or their damage, a range of control options are available, the best of which are several new miticides that provide long residuals and efficacy against all mite life stages. Broad spectrum insecticides will make mite populations worse by killing natural enemies. For more information and product suggestions visit the newly revised Ornamental and Turf Insect Information at: Note # 25l.

From: Emily Meineke and Steve Frank, Department of Entomology

Scale Picnic Beetles, Cybocephalus nipponicus (Endrody-Younga)

Scale picnic beetle adults are active now in North Carolina! The scale picnic beetle provides prolonged control of armored scale, such as Euonymous and San Jose scale.

C. nipponicus is native to China and Korea and was introduced into the U.S. in the 1990s to control euonymous scale. The New Jersey Department of Agriculture started a rearing program in the mid-1990s, and since its release, C. nipponicus programs have expanded. Researchers are currently using populations to control elongate hemlock scale, a serious secondary pest of hemlock stands stressed by the hemlock wooly adelgid.

C. nipponicus eat scale as larvae and as adults. Adults live for months and can reproduce several times. Staggered generations provide year-round control, and, unlike other similar beetles, C. nipponicus can survive when prey populations are low. Larvae develop and feed under waxy covers that protect them from direct exposure to pesticides. These tiny beetles are comparatively expensive to purchase, and populations establish over multiple years. However, natural C. nipponicus populations are present throughout North Carolina and provide background control of many landscape scale species.

Assassin Bugs (Family: Reduviidae)

Assassin bugs are members of the diverse, predatory family Reduviidae. They use their long stylet to pierce and liquefy caterpillars, aphids, and other pests. Several of these beneficial species live in North Carolina, including but not limited to the lurid assassin bug (Zelus luridus), the colorful assassin (Rhiginia cruciata), the masked hunter (Reduvius personatus), and the wheelbug (Arilus cristatus). Some species of assassin bug nymphs look similar to herbivorous true bugs, such as the leaf-footed bugs, that use their stylets to suck plant juices. There is a rudimentary way to tell the difference between these groups as immature insects. Pestiferous bugs that eat plants tend to congregate, while assassin bugs hunt alone.

Assassin bugs like varied plant structure to hunt within, and also high humidity. To encourage their populations on the lawn or beside the garden, you can plant tall native grasses and flowers.

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