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April 11, 2007

Christmas Tree Scouting Report #3 - April 11, 2007

Weekly newsletter compiled by Sandy Gardosik, PA Department of Agriculture.

Even with the drop in temperature since last week's scouting report, white pine weevils were still showing up in traps in Perry, Schuylkill and Lycoming counties. The trap being monitored outside of Duncannon, Perry County, is in an over grown white pine plantation and had a total of 45 weevils. These traps not only catch the white pine weevil, but three other species closely related: Eastern pine weevil, Pales weevil and Pine root collar weevil.  Of these four species, the white pine weevil causes the most damage for Christmas tree growers and nurserymen.  Although white pine is the favored host, other pines, spruce, and Douglas fir are also hosts of this pest. Of the other three weevils, Pales weevil is probably the next most evident in the Christmas tree plantation. Look for "flagging" or yellowing to browning of the side shoots beginning at this time of year. Feeding from this weevil girdles the twig causing the shoots to die. The eastern pine weevil usually takes advantage of a tree that has been weakened due to some other reason. Larvae of this weevil feed under the bark on the lower half of the tree.

Treat fresh cut stumps of Scotch pine and surrounding soil with a registered insecticide, and removing dead and dying Scotch pines helps eliminate breeding sites for both Pales and eastern white pine weevils. Pine root collar weevil is the most elusive weevil of the four because this weevil damages the collar and roots of trees. We rarely have problem with this weevil in Christmas tree plantations because their preferred hosts are Scotch, red, jack and Austrian pine.  

Eggs of the spruce spider mite have not begun to hatch on Fraser fir in Adams, Dauphin or Northumberland counties. Temperatures are predicted to warm up, so we may start to see eggs hatch in the next week. Look for the red over-wintering eggs on the bark of twigs. Damage from spruce spider mites begins at the base of needles and gives needles a bleached look. When the damage is heavy, the base of needles turn brown and can fall prematurely.

Swiss Needlecast is heavy this year and is showing up in fields of small trees that were not treated for Rhabdocline Needlecast from the time when they were planted out in the field. Needles will look brown starting from the tip of the needle, progressing towards the base, sometimes going as far as the base of the needle. When needles are examined from underneath with a hand lens, two bands of tiny black structures arising from the stomata can be seen.  Swiss Needle cast is usually kept in check with a forth spray when controlling for Rhabdocline needlecast.

With these cool temperatures there is still time to control Cooley spruce gall adelgids on Colorado blue spruce and Douglas fir. In Adams County this week the protective wax produced by the over wintering females is beginning to cover their entire bodies. Once the female is covered she will begin to produce eggs and both her and her eggs will be protected from chemical sprays.

Balsam twig aphid nymphs that have hatched can be found feeding on the undersides of needles of Fraser and Canaan fir in Adams, Northumberland and Schuylkill counties. This stage does not damage the older growth. Since chemical controls do not kill the aphid in the egg stage, waiting closer to bud break insures that all eggs will be hatched, and best control can be achieved previous to bud break.