April 4, 2007
Christmas Tree Scouting Report #2 - April 4, 2007
Weekly newsletter compiled by Sandy Gardosik, PA Department of Agriculture.
The white pine weevil started emerging from their hibernating sites last week after a few days of daily average temperatures above 50 degrees. Growers who were trapping for the weevil either applied their first spray or will in the next couple days, as weather permits. The white pine weevil over winters a few inches underneath host trees in tree plantations and surrounding woodlots. All Christmas tree species are susceptible but most damage seems to accrue in white pine, spruce, and Douglas fir. White pine weevils were found again in Pyramidal traps in Perry and York counties this week. Look for the adult weevils or droplets of sap from feeding damage on the main leader.
The overwintering eggs of the balsam twig aphid are beginning to hatch in York County. This is the aphid that causes stunting and distortion to the new growth on the true firs, particularly Canaan and Fraser fir. Concolor firs are also susceptible, but needles seem to grow out of the damage caused by this aphid as the season progresses. Using a hand lens, look for eggs on the bark between the needles, at the base of needles or on the buds. Eggs will be 1/16 inch long, black, and covered with fine white waxy threads. The newly hatched nymphs will be yellow to green and can be found on the undersides of needles. A little ball of honeydew on the posterior end of the body, which is waste from feeding, can help locate nymphs. Waiting to control this aphid until the new buds swell and are soon to break gives best control. By this time the overwintering "stem mothers" will all be hatched and have been feeding on previous years needles causing no damage. It is the live young produced by these matured aphids at bud break that cause damage to the new growth. Controlling this aphid after bud break will not prevent damage and will kill natural enemies that help keep aphids and other pests in check.
Lady beetles are beginning to appear in the field and are a natural control that devours aphids, adelgids and scales in large numbers. The twice-stabbed lady beetle was found on Canaan fir where balsam twig aphids were hatching. This beetle is a little less then ¼ inch long, black with an orange-red spot on each wing cover. On white pine, feeding on pine bark adelgids, was the seven-spotted lady beetle. The pine bark adelgid, which can be found on white pine, scotch and Austrian pine, does not normally become a serious pest. This adelgid can be found between buds and also on the trunk and covers themselves with white waxy threads as they mature. If this pest reaches high populations on young trees in the plantation, needles can turn yellow and drop prematurely, and small trees may be stunted or killed, warranting control.
Spruce spider mite eggs were found on Fraser and Canaan fir in Berks, and York counties but no hatch was observed. Look for red eggs on the bark of twigs now and mark trees to monitor for egg hatch in the later part of April. This is a good time to scout for a number of pests that will be out later in the spring. Look for cryptomeria and elongate hemlock scale on Canaan, Concolor, and Fraser firs and Douglas fir by looking back into the trunk of tree for necrotic or yellow spots on the surface of needles. If yellow spots are found, examine bottom of needles for the presence of scale. The best time to control these scales is when crawlers begin to emerge in late May early June. More information on these two scales will be covered in later newsletters.
Bagworms can still be removed if practical. Eggs within bag that once housed a female moth will begin to hatch late May into June. Not all bags hanging on trees now have eggs. Some housed only a male moth the previous fall that emerged from bag in search of a female. These bags are empty and may still have the remains of a pupal case hanging from the bottom of bag where the moth emerged last fall. After mating, the male moth dies and the female whose eggs were fertilized inside her body dies in bag, mummified around the egg mass that over winters. Bags that feel like something is in them are filled with eggs and should be removed.