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May 30. 2007

Christmas Tree Scouting Report #10 - May 30, 2007

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

Eggs of Cryptomeria scale are beginning to appear beneath the female's armor covering on Fraser fir in Berks, Lebanon and Juniata counties. Eggs are tiny, yellow, and oval shaped and can be seen with a 16x hand-lens when the scale cover is removed.  Eggs can also be dislodged when an infested branch is tapped over a white surface.  Hatch usually follows about two weeks after eggs are laid. Plan to begin a spray program by mid-June. Best control is achieved when chemical sprays are directed at the crawlers and before scales settle, begin to feed, and produce a protective armor covering. Crawlers emerge over an extended period, making repeat sprays of 2-4 applications necessary.

Young bagworm caterpillars are beginning to emerge from the overwintering bags made by females the previous year in Berks, Dauphin and Lancaster counties. Look for fine silk strains and tiny bags about 4mm long on the needles. Once the newly hatched caterpillars emerge from the overwintering bag they build a protective bag out of silk and host material. When still small, the young larvae cannot eat the whole needle, but begin by chewing holes on the surface of the needle turning this area brown. Once larvae begin to emerge, wait about a week or two till most eggs have hatched and the larvae are out on the needles and feeding before applying a registered insecticide. This way only one spray application is needed.

Rhabdocline needle cast is still viable in Dauphin County. The best time to check for viability is early morning when temperatures are still cool and dew may be present. Look at the bottom of needles where the brick red lesions are present. If the fungus is still infectious, the needle surface will be split and swollen with orange spores visible. Most growers have applied their third spray and if controlling for Swiss needle cast in the same field a fourth spray 2-3 weeks after the third spray will be necessary. If Rhabdocline is still viable, two to three weeks after your third spray you may want to consider a fourth spray. 

Galls formed by the Cooley spruce gall adelgids can be found on Colorado blue spruce. Look for light green galls about 2 to 4 inches long on the new growth. By mid-summer, the galls turn brown and open releasing the mature winged adelgids, some of which fly to the Douglas fir. If practical, remove galls before mid summer; otherwise, the next time to control this insect is late October to early November.

Terminals of white pine in Juniata County were beginning to show signs of white pine weevil damage. The leader was turning a light brown and the new growth was stunted. Begin looking for discolored, stunted leaders, and when examined up close, small round pinholes can be seen where adult weevils were feeding or laying eggs. Removing infested leaders as soon as possible can save a few years of terminal growth.

Cinara aphids were found on the new growth of Colorado blue spruce in Juniata County and Scotch pine in Lancaster County. Usually these aphids are found scattered in colonies on the new growth in association with bees and ants that are attracted to the sweet honeydew produced by the aphids. Affected trees may lose their needles if populations reach high numbers but beneficial insects usually help keep numbers in check. If control measures are needed, insecticidal soap may be a good alternative to a conventional insecticide to preserve beneficial insects.

The pine spittlebug has been making an appearance on all Christmas tree species in the last couple of weeks. This insect is more of an aesthetic problem because of the frothy spittle masses they produce than it is a serious pest. Newly hatched nymphs feed near twig terminals, covering themselves with frothy spittle composed of tiny, sap-coated air bubbles. These xylem-feeding nymphs excrete clear liquid through the anus, and by a  series of movements involving the abdomen and legs they force air into the excreted fluid to produce bubbles. This spittle provides a moist environment and protection from natural enemies. Damage from spittlebug feeding can open wounds for the fungus known as sphaeropsis tip blight on pines. Healthy trees are less susceptible to this disease than those under stress.