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May 17, 2002

Christmas Tree Scouting Report

Welcome to the Christmas Tree Scouting Report for the week ending May 17. The next report will be available after 4 PM on Friday May 24. 

Pest activity during the past week was much the same as the previous period, with no additional pest "events" of note. On-going efforts to control some pests and prevent damage from others are occupying growers across the state.

Overwintering pine needle scale eggs continue to hatch from Northumberland County southward, were some settled crawlers were already present. At another nearby site, eggs, crawlers, and settled crawlers were present in equal numbers. In Centre and Columbia counties, pine needle scale eggs have not started to hatch. An interesting observation was made at one of the Northumberland County sites. On eastern white pine, hatch of pine needle scale eggs was well underway while on Austrian pine no hatch was detected.

Douglas fir growers are continuing the application of protective fungicides for control of rhabdocline needlecast. In Centre County, budbreak is estimated to be 100%. A Lehigh County grower reports he is do his third application, but spraying has been delayed due to rain and wind during the past week. At this site, fruiting bodies are split open on the underside of the browned needles. The rain and wind, while hampering sprays, enhances the ability of this fungus to infect new growth. To determine if fruiting bodies are mature at your site, examine the undersides of the symptomatic needles during damp periods, such as early morning. The pincushion-like tan areas are masses of spores ready to be released. If you can't see this in the field, dropping a sample into warm tap water will open the fruiting bodies. This method is also effective when growers wish to determine if it is safe to stop spraying. When the fruiting period is over, the opened fruiting body will appear blackened, rather than tan.

Another pest on Douglas fir, the Cooley spruce gall adelgid, is causing damage to new growth at several sites visited. The dark nymphs can be seed on the tender needles and the chlorotic spots and bending and kinking of needles is very apparent. Some needles will outgrow some of the damage but in heavy infestations, damage will remain as the needles mature

Balsam twig aphids are also damaging new growth of firs at many locations, where distortion of needles is evident. On later breaking trees, the aphids are still feeding inside the tender cones, where they will not cause damage. Although balsam and Canaan fir have had buds open for several weeks at some sites, Fraser firs budbreak is just starting. Generally, balsam twig aphid does not cause significant damage to concolor fir. In Berks and Northumberland counties, the aphids are occupying the new growth but a number of syrphid fly larvae and lady beetles are also present. These naturally occurring predators will feed readily on the aphids.

European pine sawfly larvae are up to 1 inch long in Centre County. The larvae are causing extensive damage on some Scotch pine trees examined. In more southern locations, larvae are not present and may have already dropped to the ground to pupate.

Although we are not conducting life history studies of cryptomeria scale on firs in 2002, we will continue to monitor the pest for crawler emergence. At sites in Berks and Lehigh counties, female scales are maturing but no oviposition has been noted.

Another scale that we are observing this season is the elongate hemlock scale. This armored scale has been around for many years but has become a serious pest of true firs in north central counties of the state. In Columbia and Northumberland counties, crawler activity is increasing and growers should be making regular applications of a registered insecticide to reduce the population. This scale does not have distinct generations but reproduces throughout the growing season, making control very difficult. Repeated sprays are necessary if any success in controlling elongate hemlock scale is desired.

Spittlebugs are abundant this year and being reported from virtually every species of Christmas tree grown. Although considered primarily a pest of Scotch pine, these sucking insects are easily adapted to other hosts. Damage is generally not sufficient to warrant control.

Eastern spruce galls and Cooley spruce galls are apparent on new growth of trees infested with their respective species of adelgid. As these insects feed on tender new growth, the tree produces the succulent galls. When the galls are broken open, the immature adelgids can be seen inside, where they will remain until mature.

In Berks County, reddish-brown Cinara aphids are feeding on old growth of Norway spruce. These aphids generally do not cause significant damage but the honeydew they secrete may be attractive to hornets and ants.

White pine weevil larvae are at least 1/16 inch long in terminals examined in Perry County this week. The ration of larvae to eggs is approximately 1:1. In addition, adults are still feeding on the terminals at this site and in Columbia County. Mechanical control can be effective in preventing significant loss of leaders if damaged leaders are pruned out of the trees early, when wilting is first noticed.

Pine shoot beetle flight period is almost over. Any growers who deployed trap logs to control this introduced pest can begin removing them from their fields and destroying them logs by grinding or burning.

The next report will be available after 4 PM on May 24.