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June 16, 2004

Christmas Tree Scouting Report -
Number 12

Welcome to the Christmas Tree Scouting Report for the week ending Wednesday June 16, 2004. The next report will be available after 5 PM on Wednesday June 23rd. To receive a FAX of this week's message, please call (814) 865-1636. If you would like to receive this report via email, please send a request to rdlehman@state.pa.us and you will be added to the distribution list. To contribute observations to this report, please email to the address above or call (717) 772-5229.

Eriophyid mites and their damage were found on Colorado blue and Norway spruce in Snyder County. These minute mites can cause significant damage on Blue and Norway spruce if populations are left unchecked. Bronzing or russeting of needles at this time is an indication of heavy numbers of mites. Eriophyid mites are cool season mites and scouting in early spring and again in fall with a hand lens can help prevent damage. Although not controlled by traditional miticides, these mites are easily killed with oil or formulations of carbaryl.

Sporulation of Rhabdocline needle cast is nearly complete. Once new growth hardens off, and nighttime temperatures stay above 55F, Rhabdocline is not infectious, and sprays are no longer necessary. Since a small percentage of infected Douglas fir in Berks, Perry, and Snyder Counties were still observed with active sporulation, growers may want to consider another spray if their last spray was more than two weeks ago, or if Swiss needle cast is also present.

Adult pine spittlebugs were found on Scotch pine in York County. These brown, oval shaped adult bugs are about 1/3 of an inch long and will jump when approached or touched. Adults, like the nymphs, extract sap from trees but they do not produce spittle masses. In addition to the unsightly spittle masses, the feeding wounds of these bugs offer excellent infection sites for Sphaeropsis shoot blight. If the spittle masses were abundant on your trees and you have dying shoot tips from Sphaeropsis shoot blight, you may wish to apply a registered insecticide against these adults to prevent problems next year. Adult control is the optimum method of control since the spittle masses protect the immatures at all times.

The overwintering eggs of Balsam twig aphid were found on the new growth of Fraser fir in York County. These black eggs, covered with silver wax threads, can be found on the stems of this year's growth with the aid of a hand lens. The next time to control this pest is in the spring before bud break.

Bagworms are still small and actively feeding on the surface of needles in York County. The more specific chemicals for Lepidoptera species ,known as mircrobials or Bacillus thuringiensis, can still be used to control this insect. As the larvae of this moth get larger, other broad-spectrum chemicals will be needed.

Some of you were fortunate this year to have experienced the sight and sound of the seventeen-year cicada. Most of the damage from the egg-laying habit of the female cicada is found on deciduous tree species. However, eggs were observed being laid in the branches of Fraser fir in Perry County. When the branch was dissected, a row of eggs was found. Some growers may experience minor damage in the form of flagging or an occasional dead branch.

A Maryland grower contacted us this week about dying shoots on his Fraser fir. He was able to find several larvae in the shoots and wanted to know what pest he had found. This is a relatively uncommon borer that is related to the Eastern pine shoot borer. It is in the genus Eucosma but we have never been able to collect the adults required for complete identification. Damage is most common on the terminals but any branch can be affected. Growth is frequently smaller and distorted when the larva feed in the elongating shoots. Because we have never been able to detect egg-laying or adult emergence, and the larvae are protected inside the shoots, chemical control is not recommended. The problem associated with this pest is generally cyclical and farms that have experienced Eucosma damage one year may not have any evidence of the borer the following year.

The next report will be issued Wednesday June 23rd, after 5:00pm.