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June 29, 2001

Christmas Tree Scouting Report

Welcome to the final weekly Christmas Tree Scouting Report for 2001. Again, we have enjoyed bringing you these reports and hope you found the information useful. We will continue to monitor cryptomeria scale for the second generation and a report will be prepared when that event occurs. Otherwise, unless significant pest activity is noted, we will not have any reports until March 29, 2002.

During the week ending June 29, several unusual insect pests were found, including two different sawflies. The first sawfly resembles a pale version of the European pine sawfly. The body is longitudinally stripped gray and green but the head is brown, rather than the shiny black head of the common European pine sawfly. In addition, this sawfly is a solitary feeder on spruce and caused very little damage.

The second sawfly is the white pine sawfly. It was causing minor damage to eastern white pine in York County. These larvae feed gregariously and occasionally can cause minor defoliation. They resemble larvae of the redheaded pine sawfly, but have a black head and white body with black spots, rather than the red head and yellow body with black spots.

The third insect, pine tube moth, is also a minor pest of eastern white pine. Damage is aesthetic and generally not significant enough to warrant control. Pine tube moth has two generations a year and is one of the first insects to be active in spring. It overwinters as a pupa and adult moths emerge in early to mid-April. Second generation adults are active in July. Larvae feed on needles from within narrow tubes they create by webbing together 5-20 needles. These hollow tubes allow the larvae to move out to feed on the tips of needles but afford excellent protection. When larvae have consumed the needles down to about 1 inch, they construct a new tube from another group of needles.

White pine weevils are still not pupating at our trapping site in Perry County. What appears to be bird activity has been reducing the number of larvae, as the outer bark is being stripped from infested terminals. There is still an opportunity to prune out infected terminals to provide mechanical control of this conifer pest. Recently, a nematode was found associated with the weevil larvae in the Perry County terminals. The nematode was identified as Neodiplogaster pinacola. This nematode is recorded as parasite of white pine weevil eggs.

Cooley spruce galls are beginning to open in Perry County. However, eastern spruce galls on Norway spruce are still not mature. In very low populations, some control can be expected by hand removing the galls before they mature and open to release the winged adults. However, in plantations, that is not always practical and fall applications of registered insecticides are recommended.

We are continuing to observe spider mite populations on spruce and fir at several locations. Growers are reminded that the best time to control spider mites is when you know you have an active population. Spruce spider mite is known as a "cool season mite" with peak populations in spring and fall. However, that does not mean scouting and control should be reserved for only those times of year. Only with regular monitoring can you avoid damaging populations of spider mites.

Cinara aphids are still active on Scotch pine. These are the insects often misidentified as ticks when they are found by homeowners in association with their live Christmas tree. They rarely cause significant damage to the trees but may have an impact on your real tree sales.

Bagworms are finally starting to attach entire needles to their bags as they feed on spruce in Lebanon County. Damage from these defoliators can leave trees bare, especially on the top, if left uncontrolled.

Crawlers of cryptomeria scale are still emerging from eggs at several locations in southeastern counties. The program for control of these armored scale insects requires multiple applications of insecticide during crawler emergence. Since crawlers may emerge for several weeks, sprays must continue for several weeks. One grower reports 50% of the eggs are still not hatched at his Lehigh County farm. He expects to have to make a total of four applications this year to control this damaging pest of true firs.

Thank you for you encouragement and support for this scouting report over the last 6 years. We look forward to serving you again in 2002 and welcome suggestions for improvement.