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May 3, 2002

Christmas Tree Scouting Report

Welcome to the Christmas Tree Scouting Report for the week ending May 3. The next report will be available after 4 PM on Friday May 10. 

This week, Eric Varodi, Dauphin County Extension Regional Specialist made the first report of pine needle scale crawler emergence. We did not see any hatch, however, at any of the site we have been monitoring in Perry and York counties. By next week, we expect the small, red crawlers will be active and the prime control period for the first generation will be started. To control this scale pest of pines, especially Scotch pine, two applications of a registered insecticide should be applied 7 - 10 days apart. The crawlers turn amber when they settle to feed and at that point, control starts to drop off noticeably.

Eriophyid rust mites are enjoying the cooler days and nights of the last two weeks and foliar discoloration is evident on spruces and firs at several locations. The needles damaged by these rust mites have a grayish cast and examination with a handlens will reveal the wormlike mites. Sevin is one of the most effective controls for these mites but growers should be cautioned that its use could lead to spider mite problems later in the season.

At the present time, spider mite populations are building and some growers in central Pennsylvania are starting to make their early season miticide application. When selecting your miticide for this year, read the label carefully to determine if a single application is recommended, or a follow-up spray will be needed. Failure to do required 2nd applications could significantly reduce the efficacy of any pesticide.

Balsam twig aphid nymphs of the 2nd generation are feeding on new growth of concolor fir in Perry and York counties but on Frasers, which have not yet broken bud, the aphids are still on last year's needles. At one site in Lebanon County, Fraser firs are producing cones and the balsam twig aphids have moved into the succulent cones to feed. Don't be deceived by the aphid's disappearance from the old growth when cones are present. As soon as budbreak occurs, they will quickly find their way to the new growth and begin to feed. Applications of insecticide are not effective in reducing damage if applied after budbreak.

Pine bark adelgid is actively feeding on elongating candles of Scotch and eastern white pine in Perry and York counties. The adelgids are producing their characteristic white waxy coating as they feed on the new growth. This is the most damaging time for this pest but controls are usually not recommended.

White pines in the Capital area are also exhibiting signs of Pales weevil feeding. Dying lateral branches, a condition referred to as flagging, is evident at some sites. When the bark of the dying branch is examined, irregular patches where bark has been removed are apparent. The Pales weevil feeds on the bark of healthy trees but breeds in stumps. Foliar applications are not nearly as effective in keeping this pest in-check as are stump treatments in very early spring. The time for effective control has passed.

Spittlebugs are noticeable on Scotch pine in Centre, Perry, and York counties. The nymphs will continue to feed in masses of their own waste material until mature in mid- to late June. If you are experiencing damage attributed to spittlebug, controls should be directed against the adults.

Cooley adelgid eggs on Douglas fir are hatching in the Harrisburg area and the nymphs are already feeding on the new growth. In State College, budbreak is just starting and no adelgid egg hatch was noted. A related adelgid, the eastern spruce gall adelgid, has already started to cause gall-like swellings at the base of new Norway spruce growth in Perry County.

European pine sawfly larvae have reached ½ inch in length in York County and are causing noticeable defoliation on Scotch pine. These gray and green striped larvae with shiny black heads are serious defoliators and can cause significant damage. Spot-spraying or hand removal of clusters of larvae is two good control methods.

Most growers in Dauphin, Perry, and York counties have already completed their first spray for rhabdocline needlecast. If your Douglas firs are starting to break bud and you have red-brown splotches on the old needles, you should consider adopting the spray schedule to control this disease. Research conducted at Penn State by Bill Merrill and Nancy Wenner demonstrated effectively a schedule based on budbreak: 1st spray when 10% of the trees have broken bud, 2nd spray one week later, 3rd spray two weeks later. The method and materials continue to be the most effective means of reducing damage from this serious needlecast of Douglas fir.

The first hatch of white pine weevil eggs was observed this week in Perry County. Heavy feeding and sap flow is obvious on terminals. Elongating candles are also being fed upon and will soon show wilting symptoms associated with this weevil pest. Chemical controls have very limited benefit at this time.

Gypsy moth egg hatch started last week and this week 1st instar larvae were found on some white pines in York County. In areas that were heavily infested with Gypsy moth last year, larvae may blow from neighboring woodlots or mountains. These small, black, hairy larvae can cause damage to fir and spruce but pines and Douglas fir are generally not damaged. Necessary controls should be delayed until the larvae reach 2nd instar and are less likely to be blown around.

We have had a few reports of browning or reddening of last year needles of Colorado spruce. This damage is reminiscent of symptoms from several years ago when misuse of herbicide not labeled for Christmas trees was to blame in some cases. Remember, always select a material properly labeled for use on your Christmas trees and read and follow label directions.

The next report will be available after 4 PM on Friday May 10.