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April 19, 2006

Christmas Tree Scouting Report Number 6 - April 19, 2006
Weekly newsletter compiled by Sandy Gardosik, PA Department of Agriculture.

There was a lot of white pine weevil activity in the field this week. Traps being monitored in Juniata, Perry and Schuylkill counties still contained weevils. Adults were found feeding and mating on the terminals of Colorado blue spruce, Douglas fir, and Serbian spruce in Lancaster County, and on white pine in Schuylkill County. Larvae were found in the terminals of Colorado blue spruce and Douglas fir in Lancaster County this week. The larvae are legless grubs about 1mm long and are creamy white with a light brown head capsule.  As they hatch and begin feeding in the cambium, they create galleries as they work their way downward. These feeding galleries eventually meet, creating a “feeding ring” that completely girdles the terminal.

A few early buds on Douglas fir were beginning to break in Bucks and Lancaster counties. Colorado blue spruce and Norway spruce were also breaking bud this week in Lancaster County. It will soon be time to begin spraying for Rhabdocline needlecast and Swiss needlecast on Douglas fir. At this time of year Rhabdocline produces brick red areas on both the top and bottom of the previous year's needles (2005) where lesions will appear. These lesions begin to swell on the undersides of needles at the same time the Douglas fir buds are beginning to swell. As soon as the buds begin to break, so will the lesions exposing the infectious fungal spores to the new growth. Control is achieved by protecting the new growth as it expands. Apply the first spray for Rhabdocline needlecast when 10 % of the trees in the field have at least one bud breaking; follow with a second spray one week after the first; finally, a third spray follows two weeks after the second. If it is a wet spring, or if you also have Swiss needlecast, a fourth spray three weeks after the third is recommended. Swiss needlecast can affect current-, second-, and third-year needles. With this disease, needles can turn a yellow to brown color, and the undersides will display rows of black fungal spores.

Pales weevil damage was found on white and Scotch pine in Lancaster County. This weevil feeds on branch bark on all species of Christmas trees. Feeding girdles and kills side shoots, producing a damage called “flagging”. To control damage from this weevil treat fresh cut pine stumps, particularly those of Scotch pine from the previous season’s harvest, in early spring with a registered insecticide.

Traps to detect first emergence of the Douglas fir needle midge were placed under trees exhibiting midge damage at a spray trial site near Yardley, Bucks County. This midge overwinters in the soil beneath infested host trees. In 2005 adult midges emerged at this test site on April 22nd with a Growing Degree Day (GDD) reading of 208 (base 50). On Tuesday, April 18th, 2006, the GDD reading was 202 (base 50F), and a few buds were beginning to show green tips. There were no adults in the traps, and none observed flying around the new buds. In 2005, Lorsban and Orthene were sprayed two days after adults were first detected; a second application was made 7 days later and a third 14 days following the second. The results were disappointing. This year, Lorsban and Orthene will again be tested, but will be applied before midge emergence. An additional chemical, TriStar, will be tested and applied before midge emergence also. The Douglas fir needle midge has one generation per year, and so the opportunity for control is short. Adults begin to emerge at the beginning of bud break, mate immediately, and females begin laying eggs between the bud scales and on the new needles within a couple of days. Egg hatch begins within about 5 days, and the larvae immediately enter the needles and are protected from chemical control. Results from spray trials will be shared in future newsletters and training meetings.

New, strange-looking cones are beginning to form on Douglas fir and Fraser fir.

If you have any pest information to report, please email Sandy Gardosik at sgardosik@state.pa.us  or call (717) 772-0521 and give pest, host plant and county where observation was made and I will include this information in the next report.