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April 15, 2005

Christmas Tree Scouting Report -
Number 3

Welcome to the Christmas Tree Scouting Report for the week ending April 15, 2005. The next report will be available after 5 PM on Wednesday, April 20. To receive a FAX of this week’s message, please call (814) 865-1636. If you have pest activity to report, or would like to receive this report by e-mail, please leave a message at 717 772-0521 or e-mail sgardosik@state.pa.us and your name will be added to the distribution list.

With the warm spring weather and the absence of rain the last couple of weeks, fields have dried out enough to allow growers to begin planting this year’s new seedling crop. This nice weather has put spruce spider mite hatch ahead about a week from last year. Spider mite eggs are beginning to hatch on Fraser and Canaan fir in York County. In Adams County, no hatched eggs were found on Canaan fir. Once eggs begin to hatch an easy way to scout for this mite is by placing a white paper plate under a branch and tapping it a few times to dislodge the mites. Wait a couple of seconds and look for pepper-sized, salmon - to red moving objects. As these mites mature they become dark red and will leave a red mark when squashed. Miticides that interfere with chitin production are best applied when most of the overwintering eggs have hatched but before the adult stage has been reached. Some pesticides require two sprays applied 7-10 days apart to achieve effective control. Some of the newer miticides may only be applied once a year and may require skipping a year before being used again.

White pine weevils and/or their feeding damage was found on the terminals of scotch and white pine in Adams, Dauphin, and York counties. Sap from the feeding holes was visible on sunny afternoons. Weevil counts were as high as 30 in some of the traps set at our monitoring site in Perry County. Adult females will soon begin laying eggs under the bark of the terminals. Once eggs are laid, chemicals can no longer control the larvae. Growers should have applied their 1st spray already. With all the weevil activity this week and weevil counts in traps, a second spray may be warranted.

With forsythia in full bloom, your opportunity to control the adelgids on spruce and Douglas fir is coming to an end. The forsythia bloom is commonly used as an indicator as to when insecticide sprays are no longer effective for the control of the adelgids on Blue spruce, Douglas fir and Norway spruce. In Dauphin County, overwintering eastern spruce gall adelgids on Norway spruce were mature and covered with long waxing white fibers but no eggs were found. Mature adults can be found at the base of the new buds or on the twigs. In York County, Cooley spruce gall adelgids on the undersides of the needles of Douglas fir were also covered with the protective waxy fibers, and eggs were found underneath the waxy material. Mature females begin to lay eggs before bud break.

This is the time to scout for Rhabdocline needle cast on Douglas fir. Look for reddish-brown bands on both the top and bottom of last year’s needles only. In York County, the buds of Douglas fir were beginning to swell and the bud scales were starting to peel back. Keep an eye on the south side of trees, as this is where buds will break first. Fungicide sprays for Rhabdocline needle cast will only protect the needles if applied before the infectious spores disperse to the current year’s emerging needles. Your first spray should be applied when the field is at 10% bud break.

Overwintering stem mothers of the balsam twig aphid are hatching on Fraser and Canaan fir in York County. You can find them feeding on the undersides of the needles by looking for the sap known as “honey dew” on the posterior end of the aphid. These aphids cause stunting and distortion of new needles. If populations get heavy, a black fungus called ‘’sooty mold’’ begins to grow on the needles where the honeydew was expelled by the aphids. Control these aphids before bud break with a registered insecticide.

No crawlers of the elongate hemlock scale were found on Grand or Fraser fir in Adams County. This scale can infest all true fir species, Douglas fir and spruce. However, this scale tends to do the most damage on the true firs. Once crawlers begin to emerge from the protective cover of the adult female a spray program should begin. According to Dr. Paul Heller, PSU research entomologist, spray trials using three applications of dimethoate applied at four-week intervals showed promise. Dr. Heller is completing a three- year study of this scale at the end of the 2005 growing year.

Several emergence traps for Douglas fir needle midge have been placed in Bucks and York Counties. This small fly is expected to emerge from its over wintering site (underneath infested Douglas fir trees) at the time of budbreak. Since the control period for this midge is very short, control applications need to be applied at first signs of emergence.

The next report will be after 5:00pm Wednesday April 20th.