June 22, 2002
Christmas Tree Scouting Report
After an earlier than usual beginning, 2002 pest activity is finally slowing down. Rhabdocline infection period is over at most sites, white pine weevils are finished laying eggs, Cooley adelgids have done their damage for the year, spittlebug adults will be emerging, pine needle scale crawlers are settled, cool season mites are starting to slow down, and balsam twig aphids have deposited their overwintering eggs and are finished for the year. But, that does not mean your pest concerns are over.
Larvae of white pine weevils at all sites are preparing to pupate in their characteristic "chip cocoons". The pest can still be controlled mechanically for the next week or two. Infested terminals are obvious, making selection of terminals to cut out much easier. Two things to remember: cut down to good wood and remove the infested terminal from the field. Frequently, well-intentioned growers cut terminals down to the first whorl, only to find out in another week or two that the larvae were below that point. When cutting out the damaged tops, make sure the inner bark on the stub left is green, not reddish brown. If necessary, peel back the bark to check. Also, there is plenty of moisture left in the terminals and if they are thrown on the ground, the adult weevils will simply have farther to fly when then emerge. Be sure all infested wood is removed and destroyed by burning or chipping as soon as possible. At several locations, Serbian spruces were very hard hit with this pest in 2002. Although we call the bug white pine weevil, it has a real fondness for Douglas fir and certain spruces.
Striped pine scale crawlers are still emerging on Scotch pine in Northumberland and Perry counties. The crawlers settling on the needles are the males; females settle on the bark. In Centre County, the crawlers have not emerged but sooty mold and stinging insects are associating with the honeydew. Although this soft scale prefers Scotch pine, some eastern white pine at the Perry County location was also infested with this scale.
The attractive yellow, white, and black introduced pine sawfly larvae are reaching ¾ to 1 inch in length in Columbia, Northumberland and Snyder counties. This sawfly does prefer white pine but, because it feeds singly, usually does not cause extensive damage.
In Schuylkill County, high spruce spider mite populations are causing extensive damage to new growth of Fraser fir. The damaged needles have small dark spots - the mites- and small light spots - their feeding sites - and webbing. Unless there is immediate attention to these trees, they will be severely damaged by the end of summer. Spruce spider mite damage looks even worse with stress, including hot, dry weather. So, the appearance of trees may continue to deteriorate, even if the population is under control or collapses naturally. In Centre County, a few eggs were observed but active mites were not evident.
The Admes spider mite mentioned in previous reports is still active on spruce in Northumberland County. But, the mites appear to be retreating to the inner portions of the trees. Other mites that are starting to be more difficult to find include the eriophyids on spruce. These rust mites usually disappear with hot weather, only to reappear in late summer or fall. But, their damage also remains.
Bagworm sacs are about ¼ inch long in Northumberland County. They are consuming needles of Douglas fir and control is still relatively easy at this stage. In another month, the larvae will be almost mature and the bags and damage much more noticeable. Control will, however, be much more difficult when the larvae are larger.
We continue to see populations of Cinara aphids, accompanied by black ants feeding on the aphids feeding by-product, honeydew. There has not been any noticeable damage to date.
This week, shoots damaged by eastern pine shoot borer are starting to brown and droop. When the shoot is opened, a tan to dark brown larvae is present. The shoot is hollow, except for some packed frass. This pest of pines is common but spotty. Pheromone traps deployed for detection of the adult moths did not indicate any pest pressure at two sites. However, one of the sites has damage this year.
An introduced shoot borer in pine, the pine shoot beetle, was detected in four counties for the first time in 2002. Centre, Fulton, Susquehanna and Wyoming are now positive and will fall under the federal quarantine for this pest.
Cryptomeria scale crawlers continue to emerge in northern Lehigh, Northampton, and York counties. The York County site had both active and settled crawlers and some unhatched eggs of the first generation. At the Northampton County site, most of the eggs had hatched.The last report for 2002 will be available after 5 PM on June 28.