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April 6, 2001

Christmas Tree Scouting Report

Welcome to the Christmas Tree Scouting Report for the week ending April 6. The next report will be available after 4 PM on Friday, April 13. To receive a FAX of this week’s message, please call (814) 865-1636. If you would like to report pest activity at your location, or would like to receive this report via email, please leave a message at 717 772-5229.

Pine bark adelgids stem mothers are producing white wax to protect the eggs they will deposit within the next two weeks. Dormant oil can be used at this time to control these adelgids on pines. Only very heavily infested trees should be treated since this pest seldom causes significant damage. Lady beetles will feed on these adelgids and we have noticed them feeding on the adelgids in spring during the last several years. The primary lady beetle species involved is the multicolored Asian ladybeetle that was introduced to control aphids in pecan orchards. This ladybeetle has itself become a problem due to its habit of overwintering in homes. Large aggregates of the beetles, sometimes numbering tens of thousands, are common and at times the ladybeetles themselves are pests. However, with warm weather, they will be moving out of their overwintering areas and one of their first meals may be the pine bark adelgids.

Another favorite spring food for the multicolored Asian ladybeetle is the balsam twig aphid on true firs. Overwintering eggs of the balsam twig aphid are still not hatching, according to scouting activities in the central Pennsylvania area. Dr. Jill Sidebottom, Fraser fir IPM specialist in North Carolina, reported about 20% hatch at a monitoring site in Avery County, North Carolina on April 4. In Pennsylvania last year, egg hatch was underway on March 31 but, in 1999, it only started about April 9. This year, growing degree-days are slow to accumulate and pest and host development will be delayed accordingly. We should see the first balsam twig aphids within the next week or two. If you are planning to control this pest of true firs, it is best to wait until all the eggs are hatched before you spray.

The first northern pine weevil was collected in a white pine weevil trap this week in Perry County. Northern pine weevils are usually active earlier than white pine weevils. They look exactly like white pine weevils but are much larger. These weevils can be pests of seedlings and breed in dead and dying trees, the same site one would expect to find Pales weevil. Sanitation, or removal of dead trees and stumps, is very helpful in eliminating these two weevils.

On the other hand, white pine weevil breeds in healthy terminals. There has not been any evidence of feeding at any sites visited in the Harrisburg area. Mike Masiuk,

Allegheny County Extension, reports lack of weevil activity in his area, as well. This is another pest that should become active within the next several weeks.

Cooley adelgids on Douglas fir and Colorado spruce are starting to produce white waxy threads to cover their bodies. This usually coincides with bloom of forsythia ­ the time tested phenological indicator for timing applications of pesticide to control Cooley and Eastern adelgids in spring. Remember that good coverage is essential for control.

Symptoms of Rhabdocline needlecast are evident at many sites visited. If you did not complete the series of 3-4 sprays last year, you can expect to see the disease rebound. Always remember, insects are controlled, or killed, but diseases must be prevented. To do a good job of preventing Rhabdocline infection to current years growth, protective fungicides must be applied at set intervals, starting at budbreak. If you do not get all the applications on, your control will be less than desired.

Another pest that has not hatched from overwintering eggs is the Cinara aphids on Scotch and white pine. These are the aphids that have long legs and move quickly when disturbed. They are also the insects that homeowners often mistake for ticks coming from their real Christmas tree. The overwintering eggs are shiny black and lined up end to end, along the needle, just like miniature black jellybeans.

Reports of Zimmerman pine moth damage to Scotch and Austrian pines are increasing statewide. Larvae of this moth feed under the bark of the host tree and can usually be diagnosed by large amounts of sap collecting around the feeding area. The caterpillar’s droppings are usually mixed into the sap, which turns white with age. Favorite feeding sites for Zimmerman pine moth are at the first whorl of branches and in the terminal. As a result of larval feeding, large branches may easily break from the trunk, disfiguring the tree. Controls must be directed at the adults, in late spring. There is some evidence that Zimmerman pine moth is related to poor growing conditions.

The next report will be available after 4 PM on April 13.