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June 13, 2007

Christmas Tree Scouting Report #12 - June 13, 2007

Weekly newsletter compiled by Sandy Gardosik, PA Department of Agriculture, Harrisburg, PA.

Last week, only a few crawlers of cryptomeria scale were present on Fraser fir. This week, many more crawlers were found on the undersides of the needles of Fraser fir in Berks, Dauphin, Juniata, Lebanon and Schuylkill counties. Now would be the time to consider spraying to control the first generation of this scale. Two to three applications of a registered insecticide, 7-10 days apart, will help control this scale.  To scout for this scale, begin by looking for necrotic spots on the surface of needles on the lower branches, back near the trunk of the tree. If symptoms are found, yellowing may be from scale feeding on the undersides of the needles. When needles are examined from underneath, they will look crusty from the presence of adult scales, which are round, flat, and whitish-tan with a golden center. The appearance of this scale reminds me of a sunny side up egg. With a hand-lens, tiny yellow eggs can be found under the scale cover and yellow crawlers can be found out on the needles.

While scouting for cryptomeria scale, I'm still seeing spruce spider mites on Fraser fir in Centre, Lebanon, Juniata, Perry and Schuylkill counties. Mites and eggs can now be found on the new growth, but damage is not yet noticeable.  With a hand-lens, inspect new growth for tiny red eggs and red mites with lighter colored legs. Or you can tap a branch over a white paper plate to see if mites are present by examining the plate for mite activity. Two applications of a registered insecticide, unless label says otherwise, 7-10 days apart should control mite populations.

Bagworms are about ¼ inch long in Dauphin County this week. The caterpillars are still too small to eat whole needles but their surface feeding is causing the needles to turn brown. The softer insecticides, such as the bacterial insecticide BT (Bacillus thuringiensis), will still be effective at controlling this pest.

Elongate hemlock scale crawlers were present out on the needles of Fraser fir in Monroe County. This scale should be scouted for in the same manner as cryptomeria scale. Begin looking for the yellow spots on the top surface of the needles, then examine lower surface for scale. The female covering is elongate and amber in color and the male covering is white and fuzzy looking because of long waxy fibers that make up his covering. Three to four applications applied 3-4 weeks apart will give good control.

Rhabdocline needle cast is coming to an end in Schuylkill County. Areas on needles with Rhabdocline are drying up and turning black. Needles that were infected will all be cast from the trees in the next few weeks.

Light frost damage is apparent on Douglas fir in Centre and Schuylkill counties. Some concolor firs were damaged in Centre County as well.  Since damage was light, shearing will remove any damage caused by frost.

Growers are beginning to shear pine trees. Now is the time to cut out any damage caused by the white pine weevil. Remember to cut down far enough so that all wood infested with larvae or pupae of the white pine weevil are removed. Do not let infested terminals lay in the field. If larvae are mature, or if they have already made their pupal case, chances are good they will complete development and emerge as adult weevils later in the summer to reinfest trees next year.