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May 4, 2005

Christmas Tree Scouting Report -
Number 5

Welcome to the Christmas Tree Scouting Report for the week ending May 4, 2005. The next report will be available after 5 PM on Wednesday, May 11. 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 this report by e-mail, please leave a message at 717 772-0521 or e-mail sgardosik@state.pa.us and your name will be added to the distribution list

The cooler spring temperatures over the last couple of weeks have helped slow bud break giving growers some extended time for digging, but running the heater into the month of May has little to be desired.

Growers in the more southern counties have begun to apply their first sprays for Rhabdocline needle cast on Douglas fir. Those further north are planning on spraying the later part of this week or early next week. Bud break can vary considerably tree-to-tree, field-to-field and farm-to-farm. The first of at least three rhabdocline fungicide sprays should be applied when 10 % of the trees in the field begin to break bud. Since most fungicides protect the new growth from coming in contact with the fungus a second and third spray are needed to insure protection as the new growth emerges. The second application should be applied one week after the first and the third application two weeks following the second. In cool wet springs when new growth is slow to harden off and the fungus is slow to dry up a fourth application may be necessary.

Another needlecast disease of Douglas fir, known as Swiss needle cast, seems to be prevalent this year. Look for pervious year’s needles that are yellow or brown from the tip of the needle half way back to the stem. With a hand-lens look for rows of tiny black fruiting structures on the bottom of needles, along the midvein. Swiss needlecast control follows the same spray schedule as Rhabdocline needlecast but since Swiss sporulates for a longer time, a fourth spray is always necessary.

Feeding damage from white pine weevil adults was found on Colorado blue spruce and white pine in Columbia and Perry Counties. Also in Perry County, feeding damage was found on Norway spruce, Douglas fir, and Scotch pine. When terminals of white pine were examined, eggs were beginning to hatch and larvae were feeding and making galleries under the bark. Feeding damage from the white pine weevil larvae interrupts flow of water and nutrients to the terminal leader. As the larvae grow the terminal leader begins to die. The only way to control this weevil once eggs hatch is to cut out the terminals and destroy them. White pine weevils and damage were also found on white pine in Lebanon County.

Cooley spruce gall adelgids were found in the new growth of Douglas fir in Dauphin County. Feeding by this adelgid on Douglas fir causes new needles to kink and turn yellow at the adelgid feeding site. This is the same adelgid that makes the galls on blue spruce.

Eggs of the eastern spruce gall adelgid are beginning to hatch on Norway spruce in Northumberland County and the new galls are beginning to form on the new growth. These galls are found at the base of the shoot while the Cooley galls are found at the growing tip. The next opportunity to control both the Cooley spruce gall adelgid and the eastern spruce gall adelgid will be in fall.

Douglas fir needle midge traps still are collecting adults in Bucks and Schuylkill counties. Emergence has been ongoing for almost two weeks with peak numbers during the last seven days. When new growth was examined from the Bucks county site, eggs were hatching and larvae were entering the needles. The window of opportunity for control of this midge is narrow and sprays should be applied as soon as emergence is detected. The grower cooperating with us on a control study has made the second application of registered insecticide to the study blocks. Numerous eggs were present on the new growth in the field today and adults are easily seen around buds and newly expanded growth.

The next report will be after 5:00 pm Wednesday the 11 th.