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May 19, 2004

Christmas Tree Scouting Report -
Number 8

Welcome to the Christmas Tree Scouting Report for the week ending Wednesday May 19, 2004. The next report will be available after 5 PM on Wednesday May 26th. To receive a FAX of this week's message, please call (814) 865-1636. If you would like to receive this report via email, please send a request to rdlehman@state.pa.us and you will be added to the distribution list. To contribute observations to this report, please email to the address above or call (717) 772-5229.

Bagworms are beginning to hatch on Fraser fir in Cumberland County this week. Look for very small caterpillars about 1/16 of an inch long with black heads dropping from a fine silk thread at the base of bags. Soon after exiting bag, these small moth larvae begin forming tan-colored protective bags about their body. The bags are composed of bits of needles or leaves held together with silk spun by the caterpillar. The bags are small at first but if you look closely, they can be seen on branches and needles. When small, these caterpillars cause feeding damage on the surface of needles however, as they grow and add host material and silk to their protective bag whole needles are consumed. This pest can defoliate whole trees so controls are needed. Sprays are most effective when applied to the host when the larvae are small and actively feeding. Allowing one to two weeks for eggs to hatch and larvae to exit bags and begin feeding before applying sprays will expose more larvae to pesticide and be more effective. Because of their size the little damage that will accrue during the waiting period will be slight.

Eggs are beginning to be laid underneath the female covering of cryptomeria scale on Fraser fir in Cumberland, Dauphin and Lebanon counties. Within the next two weeks crawlers will begin to hatch and emerge from underneath the protective armor of the adult female scale. The recommended time to spray armored scale is when the crawlers are out and exposed on the needles and before they begin to produce an armor coat. We will continue to monitor for crawler emergence in the coming weeks.

Another scale that will be laying eggs in the next couple weeks is the stripped pine scale. This week, maturing adults were observed on Scotch pine in Adams and Lebanon counties. This is a soft scale, which means it does not produce a hard, protective covering over its body. Dormant oil in early spring is effective against the overwintering females but by late spring the surface of the body becomes leathery and control is not effective or recommended at this time. Crawlers emerge shortly after eggs are laid underneath the adult females, and can be found out on the branches. Control measures against the crawlers are the most effective.

Rhabdocline needle cast is still actively sporulating on Douglas fir in Carbon, Cumberland, Dauphin, Lebanon, and York counties. Growers should be monitoring their own plantations and continuing with the recommended spray schedule to get control of this devastating disease.

Introduced pine sawfly larvae are actively consuming whole needles of Scotch pine in Cumberland and Lebanon counties. This larva is dark brown to black with yellow and white spots down the side of the body. When larvae first hatch they feeds in clusters and then disperse and feed alone. This insect is not usually abundant enough to cause injury. Most frequently it is seen on white pine.

Spruce spider mites were found in the new growth of grand fir in Adams County but damage was not evident. In Lebanon County the new growth of Fraser fir was showing damage from spruce spider feeding. Spruce spider mites can cause browning of needles and premature needle drop if left untreated.

The white pine weevil larvae are creating feeding galleries underneath the bark in Cumberland, Dauphin and Perry Counties. These feeding galleries stop the translocation of nutrients up and down the tree and soon cause the terminal to die.
Cut out and destroy any wilting tops for non-chemical control.

Galls from the eastern spruce gall adelgids are forming at the base of new growth on Norway spruce in Adams County. The feeding of the overwintering stem mother and the new nymphs causes this swelling of the needles. The next time to control this pest is in the fall.

Pine needle scale crawlers were observed on pine needles in Lebanon and York counties. Look for little red crawlers out on the needles and apply a recommended insecticide to active crawlers if this pest is in need of control.

Damage from the Pales weevil is evident on white pine in Cumberland, Lebanon and York counties. Feeding of the stem bark by the adult weevil girdles and kills shoots which, when heavy can degrade trees. Control this weevil in the early spring by applying a stump spray to recently cut Scotch pine.

The next report will be issued Wednesday May 26th, after 5:00 pm.