June 21, 2006

Christmas Tree Scouting Report No. 15 - June 21, 2006

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

Cryptomeria scale activity has increased since last week's report. Crawlers and early settled nymphs can be found on both old and new needles of Fraser fir in Dauphin, Lancaster, Schuylkill and York Counties. Crawlers were also found on Canaan and concolor fir in York County. At the site observed in Lebanon County, eggs were just beginning to hatch and had not crawled out from underneath the adult female. Each adult female lays about 40 eggs. Eggs and crawlers can be present for six to seven weeks, with peak numbers of crawlers emerging during the first two to three weeks. Once crawlers are detected out on the needles, a spray program should begin if control is to be achieved. Since eggs hatch over several weeks, three sprays are suggested. This scale attacks virtually all genera of conifers. In Pennsylvania it is most often seen on fir (Abies) and hemlock (Tsuga). To scout for Cryptomeria scale, begin by looking for chlorosis or yellow spots on the tops of needles on those branches lower down and in toward the trunk of the tree. If chlorotic spots are found, examine the bottom of needles for scale. Look for round, flat, tan color scale with a yellow center about 1 to 1.5 mm wide. Males and female coverings of this armored scale look similar in appearance.

Another scale that favors fir and hemlock is elongate hemlock scale. Other hosts of this scale include Douglas fir and spruces. This armored scale is also found on the undersides of the needles and is usually first found on the lower branches and in toward the trunk of the tree.  This scale also causes chlorosis on the surface of needles and when examined from underneath takes on a different appearance than Cryptomeria scale. Females are about 1-3 mm long and somewhat narrow, transparent light-to medium-brown. Males are smaller, narrower, and powdery white. The undersides of branches take on a dirty, whitewashed appearance due to the buildup of male scale coverings. Research carried out by Paul Heller, Professor of Entomology, Penn State University suggests four applications of Dimethoate three weeks apart when crawlers are first observed for best control.

There is still time to remove and destroy those Cooley spruce gall adelgids from Colorado blue spruce and those eastern spruce gall adelgids on Norway spruce by hand if galls are not too numerous. On Douglas fir, those white cottony balls that seem to be so prolific this year are the same Cooley spruce gall adelgids found on Colorado blue spruce. This adelgid, however, does not make the gall on Douglas fir but does yellow and kink the needles where the adelgids are feeding. Spraying now for the Cooley spruce gall adelgid on Douglas fir may give considerable control but the damage is there and shearing will remove a portion of this. Growers will have to evaluate their own trees and consider if this is a salable year and what percentage of aesthetic value may be compensated. The best time to spray for Cooley spruce gall adelgid and Eastern spruce gall adelgid is in September or October or early spring when there is no white, cottony wax protecting them. 

If you have any pest information to report please email Sandy Gardosik at or call (717) 772-0521 and give pest, host plant and county where observation was made and I will include this information in the next report.