April 2, 2008

Christmas Tree Scouting Report #2 - April 2, 2008
Weekly newsletter compiled by Sandy Gardosik and Sarah Pickel of the PA Department of Agriculture.

In Schuylkill County, growers have accumulated 4.5 Growing Degree Days since March 1st.  The accepted Growing Degree Day range for white pine weevil emergence is 7-58.  As of yet, no weevils have been seen in traps or on tree leaders in Adams, Franklin, Lancaster, Schuylkill and York Counties.  The weather forecast for the rest of the week calls for warmer temperatures in the 60’s, so those who are monitoring for white pine weevil should be finding them in the traps within the next week.   Once the weevils emerge in your fields, plan to start your spray program within 7-10 days.   

Scouts are reporting that Eriophyid mite eggs are hatching on blue spruce in Adams County, on arborvitaes in Schuylkill County, and on concolor firs in York County.  Growers might want to wait until more eggs hatch before applying a spray treatment.  Not all chemicals labeled for mites are effective on Eriophyid mites.  Check the 2008 Insecticide and Miticide sheet for PA Christmas tree pests for miticides that work specifically for these mites.   

In Adams County, cooley spruce gall adelgids on blue spruce are beginning to develop a light waxy coating.  On Norway spruce in Adams and Indiana Counties, eastern spruce gall adelgids have also begun developing a light wax covering.   However, in Schuylkill and York Counties, cooleys on Douglas have not started to form this wax covering yet.  Once the adelgid coverings are well developed, which will happen quickly, pesticides will be less effective for control. Try to apply spray treatment before the wax coverings form.

Balsam Twig Aphids should be hatching soon. Look for the overwintering eggs, which are covered with long silvery wax threads, on the bark between the needles.    When the stem mothers emerge, they will feed on previous years needles, causing no damage.   When buds are close to swell, these stem mothers will begin laying eggs.  Treatment should be applied by late bud swell, or feeding from live young will damage the new growth.