April 21, 2000

Christmas Tree Scouting Report

Welcome to the Christmas Tree Scouting Report for the week ending April 21. The next report will be available after 4 PM on Friday April 28. To receive a FAX of this week’s message, please call (814) 865-1636. 

In Perry County, white pine weevilscontinue to feed on terminals of white pine and deposit eggs in their feeding niches. To date, no larvae have been found. If you have not already applied white pine weevil controls and wish to do so, control of most of the population is still possible. Growers who make these later applications should remember to watch for symptoms of infestationin late June and hand prune the terminals to control the few eggs that were deposited before sprays were applied.

The first pine spittlebugs of the season were found this week on Scotch pine in York County. This sucking insect creates unsightly frothy masses of excrement as it feeds through the bark of host trees. Although Scotch pine is a favored host, all conifers are susceptible to pine spittlebug feeding. Damage may not be apparent for some time and the feeding punctures in the bark make excellent sites for disease organisms to enter. Sphaeopsis tip blight frequently follows spittlebug feeding.

Pine bark adelgid eggs have been slow to hatch in the Capital area. A few crawlers were active on eastern white pine in Perry County but eggs were the only stage at most other sites.

Balsam twig aphid, an important pest of true firs, is active at most sites visited. In Chester County, unhatched eggs were present and honeydew was found on some trees but no active aphids were present. It is unknown if predators or rain may have been responsible for the lack of active aphids. In Dauphin and York counties, small cones are forming on Frasers. Balsam twig aphids will feed in the tender green cones before budbreak. If your trees have cones starting and you have trouble finding the aphids, break open some of the cones and look for feeding aphids. Controls for balsam twig aphid should be applied anytime between now and budbreak. In Adams County, small Frasers on a southern slope had a few buds already opening, but, in most locations, bud break is several weeks away.

Pales weevil adults continue to feed on eastern white pine branches in York County. At this location, the Scotch pine stumps were ground out but weevil activity remains high. It is important to remember that these weevils can also reproduce in large roots, which may be the source of this infestation.

The cooler weather has slowed down the development of some pests. Cooley adelgids on Douglas fir are still in the egg stage in Columbia, Dauphin, Lebanon, and York counties. Buds are beginning to swell and show light green at the tips at several sites around Harrisburg and south. This indicates Douglas fir budbreak is not too far away and the Cooley eggs can be expected to hatch at just the right time to permit the crawlers to feed on the new needles.

Of course, budbreak of Douglas fir is also a significant event for timing of rhabdocline needlecast sprays. Growers should be monitoring the progress of both the buds and disease in their plantations. This week, when we placed fruiting bodies in water, they still did not open, indicating they are not mature.

Pine needle scale will be one of the next pests to become active. Eggs are present under the white coverings of females and crawlers will begin to emerge within the next several weeks. Common lilac is starting to bloom in Lebanon County. Full bloom of this plant has been used as an indicator for crawler emergence for many years. However, in our experience, crawlers do not emerge until the blooms of lilac are well past prime. You should, however, start to monitor your scale populations now if you wish to control the first generation of this important pest.

Cryptomeria scale is maturing on true firs but no eggs have been deposited to date. Fir growers should check for damage from this pest and be prepared to control the crawlers when emergence starts.

Spruce spider mites are active at many sites. This week the eight-legged nymphs and the first adults of the season were observed in Adams and Dauphin counties. High mite populations have been reported from Indiana County and growers should be monitoring populations and applying a registered miticide before damaging levels are reached.

Eastern spruce gall adelgids have begun to deposit eggs at a few sites in York County. At some locations, buds of this species have already started to open. Gall formation starts immediately after budbreak and the period of control has already passed for this spring.

European pine sawfly larvae are about ¼ inch long in Lebanon County. Several weeks ago we reported European pine sawfly larvae from Douglas fir. Contrary to expectations, some of the larvae have survived and are continuing to feed on the Douglas fir needles in the laboratory.

Scotch pine growers should be scouting for striped pine scale and deciding a course of action to combat this soft scale pest. If only a few trees are infested, it may effective to remove those trees and spray the few around the infestation before the pest spreads and the entire block must be treated. However, all infested trees should be removed well before crawler emergence to prevent spread through the row as the trees are pulled from the field. To scout for striped pine scale, look for trees with black sooty mold on the bark of branches. The scale, previously confused with pine tortoise scale, can be found on the bark.

The next report will be available after 4 PM on April 28.