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April 12, 2002

Christmas Tree Scouting Report

Welcome to the Christmas Tree Scouting Report for the week ending April 12. The next report will be available after 4 PM on Friday April 19. 

In Centre County, spruce spider mite egg hatch is underway, with about 10% of the eggs empty. No spider mite larvae were observed at any other sites. Please check you own trees by tapping branches over a white surface or using a handlens. Remember, larvae are salmon colored before they begin to feed. After feeding for a short time, they molt into the green or reddish nymphs.

Pine bark adelgids are still depositing eggs at all locations visited this week. From State College south to Huntingdon County, only eggs were observed. However, various species of lady beetles are actively feeding on the eggs. Although other species are included in the beneficial insects observed, the multicolored Asian lady beetles are the most common. Judging from the complaints received from homeowners this week, these home invading lady beetles are on the move from their overwintering site in structures to their feeding site in trees.

Balsam twig aphids are hatching and feeding on fir needles in Centre County. Jill Sidebotton, North Carolina Fraser Fir IPM Specialist, indicated that hatch of this pest was 92% complete in fir growing areas of her state. Nearer home, in Berks County, approximately 90% of the overwintering eggs have hatched. Growers wishing to control this pest should be planning applications of registered insecticides when most of the eggs have hatched at their location. Controls must be complete before budbreak.

White pine weevils continue to emerge and eggs were observed in eastern white pine terminals sampled in Perry and Huntingdon counties. In Center County, significant sap flow was resulting from feeding on terminals of susceptible host trees. Growers must remember this weevil is capable of destroying terminal growth of eastern white pine, and Douglas fir, spruce species, and occasionally true firs. Applications of registered materials should be made to host tree terminals as soon as possible.

About 10% of the Cooley adelgids stem mothers on Douglas fir in Centre and Indiana counties have started to oviposit. In Indiana County, most of these adelgids are just starting to cover themselves with wax, while in Centre County, the majority have already produced significant amounts of waxy threads over their bodies. At sites visited in Berks, Dauphin, Huntingdon, Lebanon, Perry, and York counties, similar differences were observed. The period for effective spring control ends when the majority of the stem mothers at any given site have covered themselves with the waxy threads. This applies to the Cooleys on Douglas fir as well as their counterpart on Colorado spruce. In addition, eastern spruce gall adelgids on Norway and white spruce are also subject to the same generalization. No eggs have been observed on any of the spruce this week.

Rhabdocline needlecast of Douglas fir continues to be an easily observed pest at most locations. Fruiting bodies continue to mature and as buds swell, infective spores will be maturing. Douglas fir growers cannot ignore this pest on the hopes it may go away. Rhabdocline is the most serious pest of Douglas fir in the state and any grower that has infection should plan to make preventative sprays coordinated with bud break.

Eriophyid rust mite are active on many hosts during this cooler season. These tiny mites are capable of big damage when populations peak in spring and fall. Use you hand lens to check for infestations on needles of Douglas and true firs, spruces and white pine. Although not controlled by traditional miticides, these unique mites are easily killed with oil or formulations of carbaryl.

Scouts in the field this week report seeing male cones forming on Douglas fir. These colorful structures at the tip of branches are sometimes mistaken for galls or other insect or disease conditions. Trees under stress, including drought conditions, commonly produce cones and we may see more cones than usual this year. Cone formation was also starting on Colorado spruce and eastern white pine at some locations.

A few crawlers of elongate hemlock scale were found on Fraser fir in Schuylkill County this week. This armored scale is a serious pest of hemlock and true fir at some locations in the state. Crawlers emerge through out the growing season, making repeated applications of registered insecticides necessary. We will be monitoring this pest in 2002 and reporting on crawler activity.

Another scale pest that we will also be monitoring is Aspidiotus cryptomeriae, the "cryptomeria scale". Many fir growers in southeastern and southcentral counties are having difficulty controlling this pest. Two generations each year and concentrations of scale insects near the base of the tree make it imperative to get thorough coverage in order to control this sucking insect.

The next report will be available after 4 PM on April 19.