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April 7, 2004

Christmas Tree Scouting Report -
Number 2

Welcome to the Christmas Tree Scouting Report for the week ending Wednesday April 7, 2004. The next report will be available after 5 PM on Wednesday April 14th. 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. Frequently, the email/fax report contains more information than we are able to fit into the 3-minute recording. To contribute observations to this report, please email to the address above or call 717 772-5229.

The weather during the second week of scouting has been quite cool. No white pine weevils were found in traps in Perry County this week, whereas last week more than 20 weevils were in the traps. At a site in Perry County where the white pine weevil had caused damage to Douglas fir the previous year there were no signs of feeding damage yet this year. Each farm has its own microclimate making it important to scout your own field for pest problems rather than rely on our observations to determine your spray schedule. The white pine weevils will be emerging from their overwintering sites during the next couple weeks and feeding for a short time. These next few weeks are the most important time to be scouting and preparing for chemical sprays if needed. Remember, white pine weevil attacks the terminals of pines, spruces and Douglas fir, and occasionally true firs. If you have had dead terminals on these hosts in the past, white pine weevil may be the culprit.

The overwintering Eastern spruce gall adelgids on Norway spruce were found covered with white wax on the new buds in Northumberland County. This says the time for chemical control is ending. Once the adelgids are covered with this protective wax material, chemical sprays have little or no effect. The Cooley spruce gall adelgid on Douglas fir in Dauphin, Northumberland, and Perry counties were beginning to form wax on the top of their bodies. Last week the waxy filaments were only on the sides of the nymphs. With the appearance of wax on the top of the body, it is going to be more difficult to control these pests with chemical sprays. Chemical applications after the overwintering nymphs have molted into the stem mothers are a waste of time and money. Effective control is not possible after the overwintering nymph stage because of the large number of individuals who are protected by the waxy coating secreted by the nymphs and stem mothers. If you want to prevent galls and distorted needles, now is the time to act.

Several emergence traps for Douglas fir needle midge have been deployed at sites in Bucks County. We will be monitoring for adult emergence, which is expected to occur about the time of budbreak. Growers with severe infestations and apparent damage may wish to control the adults at emergence with a registered insecticide.

Balsam twig aphids are continuing to emerge but the rate of hatch has decreased due to the cooler weather. In Perry County, overwintering eggs have not started to hatch but in Bucks County the first instar nymphs of the stem mother generation are actively feeding on the undersides of last year's needles.

In Perry County, nests of pine webworm were found on Scotch pine. The nests are from last year's population and appear very unsightly on the terminals of branches that have been partially defoliated by the larvae. The larvae are currently in the soil beneath these trees and adults will emerge in late June. The females deposit a single row of black, jelly-bean-like eggs along the needles. When larvae emerge from the eggs, they begin to construct a communal nest by clipping off needles. Most of the nest is composed of silk and frass, with a few dead needles incorporated. Nests look unsightly and the best control is removal and destruction of the active nest.

Spruce spider mite eggs will not hatch for several weeks but now is a great time to scout for the overwintering eggs and determine the level of population you can anticipate.

In Dauphin and Northumberland counties Swiss needlecast was found at several additional locations. Diagnosis of this disease of Douglas fir depends on sighting the rows of black fruiting bodies on the underside of the needles.

The next report will be available after 5 pm on Wednesday, April 14.