June 22, 2001

Christmas Tree Scouting Report

Welcome to the Christmas Tree Scouting Report for the week ending June 22.

The last report for the year will be available after 4 PM on Friday June 28. After that date, we will only be reporting on emergence of the second generation of cryptomeria scale crawlers and any other significant new pest activity.

Douglas fir shoots with symptoms of Sphaeropsis shoot blight were found in Lebanon County this week. Sphaeropsis, formerly known as diplodia, is generally thought of as a pest of Scotch pine. However, it can infect all of the conifer species grown for Christmas trees but does not reach the damage level achieved on Scotch pine. Sphaeropsis infection occurs during shoot elongation, resulting in death of the apical several inches of new growth. Needles on these shoots are usually not fully expanded and the stem turns dark red or brown at the site of infection. Shearing removes most of the damaged shoots but can help to spread the infection, especially if done when trees are wet.

In Dauphin County, larvae of the yellow, black and white spotted introduced pine sawfly are maturing on eastern white pine. Damage in not significant from these solitary feeders and removing and destroying the larvae is the most economical method of control.

Most white pine weevils checked this week are still in the larval stage but many have already created their "chip cocoons" in which they will pupate. Adults will begin to emerge in about a month. You still have some time left to prune out infected shoots to achieve mechanical control of this pest.

We are continuing to monitor several populations of cryptomeria scale on fir. In all locations scouted in Adams, Berks, Chester, Dauphin, Lancaster, Lebanon, and York counties, eggs and crawlers were present this week. In Chester County the population was largely settled crawlers. The prime opportunity for control has passed for this population, but other sites should be in the midst of their first application of insecticide directed at the crawler stage. A second and possibly third application should always be included in your control program. Allow one week between sprays.

In Columbia County, balsam twig aphids have deposited eggs on the new growth of true firs. The eggs will remain until next spring when their hatch will be one of the first significant pest events that growers should be scouting for.

Also in Columbia County, elongate hemlock scale continues to deposit eggs and crawlers continue to hatch. Most stages are present during the growing season, making elongate hemlock scale a difficult pest to control.

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