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March 30, 2001

Christmas Tree scouting Report

Welcome to the Christmas Tree Scouting Report for the week ending March 30, 2001. The next report will be available after 4 PM on Friday, April 6. To receive a FAX of this week’s message, please call (814) 865-1636. If you have pest activity to report, or would like to receive email reports, please leave a message at 717 772-5229.

After a brief warm-up earlier in March, temperatures returned to below seasonal norms for the end of the month. This has put pest activity on hold and gives growers an extra week or two to plan for the spring flurry of activity. If you are planning to use dormant oil to control populations of adelgids, aphids, mites or scale insects, you should be making those applications at this time. Spray dormant oil only when temperatures are above 40 °F and there is no danger of freezing before the oil dries.

White pine weevils are not active at sites scouted or at the trapping site in Perry County. To scout for this serious pest, watch terminals of eastern white pine for droplets of clear sap. These droplets are produced when the overwintering adults begin to feed. If you are planning chemical controls they should be applied at the first sign of weevil activity.

Pales weevil is another annual pest that becomes active in early spring. It breeds in stumps of Scotch pine but causes damage to shoots of healthy trees. Growers are accustomed to treating stumps from last years harvest to prevent the feeding damage from the adults. But, some plantations owners, in an effort to switch from Scotch pine to Douglas or fir, are cutting out large blocks of Scotch pine and piling them to burn. These piles make excellent breeding arenas for Pales and Northern pine weevils. Their presence puts Douglas fir, Fraser fir, and eastern white pine growing nearby in jeopardy. Weevils attracted to the piles of breeding material must still feed on live trees and adult chewing damage on lateral branches often devastates stands of healthy trees nearby. Before you remove the Scotch pine, devise a disposal plan that will not create more pest problems than you presently have.

Eriophyid rust mites are active on Colorado spruce in Adams County but eggs have not hatched in Berks County. These tiny mites are truly cool season mites. Their populations build to peak numbers in spring, before spruce spider mite is a problem. Damage from both types of mites cause chlorosis of the needles and the problem can easily be misdiagnosed. If you have had problems with bronzing of needles of spruce, check now with a 15X handlens for the wormlike eriophyid mites. Maybe you have been blaming the wrong mite for the damage to your trees.

Balsam twig aphid eggs have not hatched on true firs at any locations scouted in central Pennsylvania.The black overwintering eggs are usually found on the stems, within an inch or two of the bud. Nymphs, destined to become stem mothers for this damaging pest, will feed on the undersides of last year’s needles until buds swell. The window of control for this sucking insect is after eggs hatch but before budbreak. If you are planning on harvesting your true firs this year or next, and have had stunting and curling of new growth caused by balsam twig aphid, you should consider chemical control of this pest.

This is an excellent time of year to be doing some scouting for insect and disease problems. Many pests are easier to spot before the new growth starts. Cultural and mechanical control can also be used to eliminate pests at this time of year. Scotch pines infected with pine-pine gall or harboring initial infestations of striped pine scale can safely be cut out and destroyed now. Rhabdocline needlecast symptoms are very apparent at this time of year. Scouting your Douglas fir fields is easy before new growth starts. Look for red-brown blotches on both sides of the needles.Evaluating fields for protective fungicidal sprays will prepare you for action when budbreak occurs

Cooley adelgids are starting to produce a thin ring of white wax around their dark bodies on the undersides of Douglas fir needles.If you missed the fall window for controlling these pests, these overwintering nymphs are still susceptible to pesticides.The nymphs on Colorado spruce can also be controlled now, as can the eastern spruce gall adelgids on Norway spruce.

We would like to solicit observations of pest activity from growers statewide. This will enhance the value of this scouting report and hopefully help you and your fellow growers become better scouts. If you notice pest activity at your location, please let us know by calling 717 772-5229 . Give us as much information as possible and we will include your observations in our reports.

The next scouting report will be available Friday, April 6, after 4 pm