May 16, 2007
Christmas Tree Scouting Report #8 - May 16, 2007
Weekly newsletter compiled by Sandy Gardosik, PA Department of Agriculture.
Most growers in the southeast and south central counties are in the process of applying their second spray for Rhabdocline needle cast this week. With the revolving spring temperatures from cool to warm to cool we have been experiencing this season, the new growth pushed quickly when the temperatures warmed and in some areas the new growth is out about two inches. If we continue with cool temperatures, new growth could harden off slowly and a fourth spray may be necessary. Remember, if spraying for both Rhabdocline and Swiss needle cast in the same field, a fourth spray is recommended for the control of Swiss needle cast.
The control period for balsam twig aphid on true firs has passed in Adams, Dauphin, Lancaster, Northumberland and York counties. Once the new buds break, damage cannot be prevented and effective control of this pest is not possible. In Schuylkill County, growers still have time to control this pest since buds have not yet broken.
White pine weevils were still found on the terminals of white pine in Adams County this week. When examined for egg hatch, only eggs were found. In Lancaster County, larvae were found in Norway spruce. Normally, larvae and feeding galleries would be more prevalent by this time of the season.
Eggs of the pine needle scale are beginning to hatch on Scotch pine in Adams, Lancaster and York counties. In Lancaster County, the crawlers were beginning to settle out on the needles. In Adams and York counties, crawlers were still under the female cover. All Christmas tree species can be hosts of this scale but Scotch is the favored host. Look for dark red crawlers out on the needles. Once crawlers settle and begin to feed, their bodies will lighten to a yellow color. As they develop, their covering turns the familiar white alerting the grower of this pest. Once crawlers are found out on the needles, 2-3 sprays with a registered insecticide seven days apart is recommended. Look for the second generation of crawlers of this scale in mid-July.
A few crawlers of the elongate hemlock scale were found out on the needles on Fraser and Grand fir in Adams County and on Fraser fir in Northumberland County. Look for small oval shaped yellow crawlers on the underside of needles. The female scale covering is amber and the male covering is white with long waxy fibers. Once crawlers are present, begin a spray program but be consistent. Research by Dr. Paul Heller found 3 applications of dimethoate applied 4 weeks apart or 4 applications of dimethoate applied 3 weeks apart resulted in over 95% control.
No eggs of the cryptomeria scale were found when female scale coverings were removed and examined for eggs on Fraser fir in Dauphin, Lancaster and York Counties. Adult males were found under their oval yellow covering when removed or found out on the needles. The males actually look like a small winged insect whereas the adult female appears as a yellow tear drop. Once males are present, mating follows with the presence of eggs within 2-3 weeks. I expect to begin seeing eggs near the later part of the month.
Spruce spider mites were found on Fraser fir in Adams, Dauphin and Lancaster counties this week. Eggs from this year's generation are beginning to appear. This means populations are building and soon the mites will be in the new growth. If you have spider mites and want to protect the new growth, begin a spray program soon by applying a registered insecticide or miticide following with a second spray 7 to 10 days apart unless the label says otherwise.