May 12, 2000

Christmas Tree Scouting Report

Welcome to the Christmas Tree Scouting Report for the week ending May 12. The next report will be available after 4 PM on Friday May 19. To receive a FAX of this week’s message, please call (814) 865-1636. If you have pest activity at your location to report, or would like to receive email reports, please leave a message at 717 772-5229.

Pine needle scale crawlers are active on white and Scotch pines in Adams, Lebanon, Snyder, and York counties. Pine needle scale crawlers may not emerge from the protection of the female immediately after hatching. At all the sites visited, both unhatched eggs and crawlers were still present under the protective white covering of the female.

Cryptomeria scale, another armored pest of conifers, has started to deposit lozenge shaped, yellow eggs in York County. But in Berks, Lancaster and Lebanon counties, no eggs were present this week. We have been studying the life history of this scale for the last several years and this is the earliest we have seen eggs. In 1998, females began depositing eggs about May 22 and the yellow crawlers did not start to emerge until June 5; in 1999, eggs were present on June 4 and crawlers started to emerge one week later. Growers intending to spray for the first generation crawlers of this pest should begin monitoring their own fields and make the first of two applications when crawlers are first seen. The second application should be made 7 to 10 days after the first. The same spray schedule would apply to the pine needle scale crawlers.

In Lebanon County, rust mites are active and causing needle browning of spruce. These four-legged mites may go undetected until damage is present and many people are inclined to think the spider mites are causing the damage. However, rust mites are active long before the spider mite eggs hatch and their populations should be at their peak now. It is important to distinguish between eriophyid mites and spider mites since some pesticides will control one and not the other. Consult the label before spraying for rust mites and choose a material that specifies eriophyid or rust mites. 

Spruce spider mite populations are building at some locations and growers should be monitoring populations to prevent damage. These mites are especially common in Fraser and Canaan fir and can cause significant chlorosis or browing of needles, particularly along the base of the needles. Tapping branches over a light paper will dislodge mites and permit you to monitor the population.

Douglas fir growers attempting to control rhabdocline needlecast should be making well-timed sprays to protect new growth. The first application, when 10% of the trees in the field have broken bud, has already been completed at many locations. The second application should be made 7 days after the first and the third, two weeks after the second. In cool, moist springs, a fourth application may be necessary. Growers attempting to control this disease with a single application are wasting time and materials.

Rhizosphaera needlecast of spruce is sporulating in Carbon County. The minute black fruiting bodies can be seen on the needles, especially those that have turned brown or purple. Although this disease is usually secondary, it can be controlled by using a spray schedule with the same timing as that for rhabdocline.

In Lebanon County, European pine sawfly larvae up to 1” in length are devouring entire needles, but leaving the needle sheath, on Scotch pine. This observation can be very useful later in the season when trying to distinguish between old sawfly damage and needlecast. With needlecast, the needle sheath is also cast, with sawfly, it remains.

In Snyder and York Counties, white pine weevil eggs have not started to hatch. But, in Perry County, hatch is underway and characteristic leader damage is already visible. Look for shortened candles and sap flow from feeding punctures to detect white pine weevil damage. If you peel back the bark, you should find small legless white larvae under the bark. This pest attacks white pine as well as Douglas fir and spruces.

In southern counties, Gypsy moth larvae have hatched and spraying operations are underway. Spruce may be susceptible to larval feeding but, conifers are not suitable hosts for the larva to complete development. However, growers intending to ship trees out of the Federal Gypsy Moth Regulation area must be taking precautions to prevent egg laying later in the season.

Balsam twig aphids are feeding on new growth in many locations.  Lady beetle larvae and adults and syrphid fly larvae are significant predators for these aphids when chemical controls are no longer practical.

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