April 16, 2008
Christmas Tree Scouting Report #4 - April 16, 2008
This report is compiled by Sarah Pickel of the PA Department of Agriculture from the scouting recordings of Tim Abbey of Penn State’s York County Cooperative Extension, Steve Derstine of J.C. Hill Tree Farm in Schuylkill County, Ann Echard of Penn State University, Jim Fogarty and Kyle Halabura of Halabura Tree Farm in Schuylkill County, Susan Newhart of Indiana County and Mel Nye of American Green Corporation in Schuylkill County.
Balsam twig aphids have been hatching this week in Adams and York Counties. The light yellow-green nymphs can be difficult to distinguish against the green of the needles, so when scouting for this pests, keep an eye out for clear bubbles of “honeydew” as the aphids excrete them. These aphids will mature quickly and will begin to give birth to live young as the tree buds begin to swell. These young will enter the developing buds to feed on the tender, young needle tissue. This feeding is what causes the typical twisted and kinked needle appearance. Insecticide sprays should be applied before bud break, but if growers wait until the majority of the over-wintering eggs are hatched, one spray may be sufficient for control.
White Pine Weevils have been emerging this week in Adams, Schuylkill and York Counties. In Schuylkill County, this emergence began at 12 growing degree days. Also, feeding damage from the weevils has been observed in Adams and Schuylkill Counties on white pine, Colorado blue spruce and Serbian spruce. This damaged can be spotted by scouting for sap bubbles visible on the terminals. No eggs were found in the terminals where feeding damage was observed. If growers have had a problem with white pine weevil in previous seasons and they have begun to see weevils in traps or tree terminals, they may want to consider spraying the upper third of susceptible trees with an appropriate insecticide within a week to 10 days of weevil emergence. It is possible that only one to two sprays will be necessary to achieve control.
In Adams and Schuylkill counties, spruce spider mites have just begun to hatch on arborvitae, Douglas fir, spruce and true firs. To scout for these pests, look on branches that show damage from last season. The damage appears as yellow stippling which is concentrated at the base of the needles. On the underside of these twigs, you will see small, red, spherical eggs which will give rise to round, red mites. In Adams, Schuylkill and York Counties, eriophyid mites are continuing to hatch. They have been observed on arborvitae, Douglas fir, spruce and true firs. These mites can cause a washed out or rusty appearance to trees.
In Schuylkill and York Counties, cooley spruce gall adelgids on Douglas have just begun to form the wax on the margins of their bodies. However, in Adams County, cooleys on Douglas fir have begun to completely wax over. Cooley spruce gall adelgids have been completely waxed over on Colorado blue spruce for a week and a half now in Adams County. Eastern spruce gall adelgids on Norway spruce are also completely waxed over in Adams County. Growers should scout to see how advanced the coating is on these pests on their farms. Once the wax is completely formed, it is too late for chemical treatment. Growers who have damage can look to spray in the fall for this pest.
In addition to pest insects, there are beneficial insects to be on the look out for in your fields. This week in Adams County, lady beetles and syrphid flies were observed in conifer fields. These insects feed on aphids, scales and other pest insects. As growers use fewer broad-spectrum pesticides and more specific and safer pesticides, chances of seeing these natural pest fighters will increase.