March 28, 2002
Christmas Tree Preseason Scouting Report
Welcome to the Christmas Tree Scouting Report for the week ending March 28. The next report will be available after 4 PM on Friday April 5. To receive a FAX of this week's message, please call (814) 865-1636. To report pest activity at your location or request email report, please call 717 772-5229. For local Growing Degree Day information, please go to www.nass.usda.gov/pa; click on Crop Weather along the top margin.
2002 is off to an interesting start. Warm winter weather and cold spring temperatures have many growers scratching their heads about pest activity. In mid-March, we issued a "pre-season" report due to early insect activity. Updates on those pests, and others that are now active, are included here.
White pine weevils have been active since mid-March at our study site in Perry County and in Centre County, feeding punctures were evident on white pine terminals. Growers should be looking for clear droplets of sap originating at the feeding site and applying a persistent, registered insecticide to the leader when feeding or adults are found. Applications are most effective before eggs are deposited. White pine weevils are usually active when more than 25 Growing Degree Days (base 50°F) have accumulated.
Pales weevil is also active and causing damage at several locations. This dark brown to black weevil is larger that white pine weevil and is also attracted to our white pine weevil detection traps due to the turpentine and alcohol bait. Pales weevil can seriously damage standing trees, including eastern white pine, Douglas fir, and true firs, when hungry adults feed on the bark. As large patches of bark are removed from branches of the healthy tree, the nutrient supply is cut and the terminal portion of the branch dies, or flags. Severe flagging has been noted at several sites this spring. Practical control includes treatment of stumps between 25 and 100 GDD (base 50°F) or stump removal. Foliar applications are only advisable in extreme cases.
With forsythia blooming at many locations, growers should be completing controls for Cooley and eastern spruce gall adelgids. Spring pesticide applications are only effective in preventing damage when directed against the overwintering nymphs before they mature into stem mothers and begin to deposit eggs. In Centre, Columbia, Dauphin, and York counties, Cooley nymphs are evident on the undersides of Douglas fir needles and have only produced a minimal amount of white waxy threads over their bodies. Cooley females on Colorado spruce in Perry County and eastern females on white spruce in Columbia County are almost covered with waxy threads and will be depositing eggs in the near future. The presence of tufts of white waxy material on the needles of Douglas fir and the bark of Colorado and Norway spruce are indications that females are already mature and starting to deposit eggs. Pesticide efficacy will be reduced at this stage and control may not be possible.
Overwintering balsam twig aphid eggs are beginning to hatch in Columbia and York counties but no nymphs were found in the State College area. The small, gray-green nymphs can be seen on the undersides of last year's needles. Often a droplet of honeydew, produced by the feeding aphid, is also present. If you experienced curling and distortion to new growth on your true firs, you probably have this pest. Control is relatively easy for these soft-bodied insects, but timing is critical. The aphid's feeding on new growth will result in needle curl and stunting of growth. Applications of registered insecticides should be made after hatch is complete but before bud break. We will continue to monitor for this pest at various locations. First generation balsam twig aphid nymphs are usually active between 58 and 120 GDD(base 50°F).
Mike Masiuk, Allegheny County extension, reports overwintering eggs of European pine sawfly are swelling inside needles and will be hatching soon. These grayish-green larvae with shiny black heads are particularly troublesome on Scotch pine. They will defoliate entire branches as they feed gregariously on last years growth. Early detection and removal of clusters of larva can prevent damage.
Spruce rust mites are active in Columbia, Perry, and Westmoreland counties. A related species is also hatching on Fraser fir in York County. Rust mites are in a group referred to as eriophyids. They are much smaller than spider mites but their sheer numbers can cause significant chlorosis of the needles and result in early needle drop. They are usually the first pests to become active in spring. A handlens is required to see these wormlike mites, and their eggs, on host needles. At this time, both are very susceptible to oil, but this material will cause a temporary loss of bloom on the bluer trees.
Pine bark adelgids in Centre and York county sites have deposited eggs on the bark of host eastern white pines. These sucking insects feed only on the bark - not the needles. Heavy populations may weaken and degrade trees but light populations do not usually require control. The introduced multicolored Asian ladybeetle is an effective predator on these adelgids.
Spruce spider mite eggs are heavy on some host trees but no hatch has been observed. Look for this important pest of conifers, especially true firs, to become active when Growing Degree Days are closer to 100, base 50°F. Scouting now for the red overwintering eggs can yield results later when monitoring the hatch is important.
Statewide, rhabdocline needlecast symptoms are very strong on Douglas fir. If you see reddish-brown needles, making the trees appear scorched from a distance, you probably have this serious needlecast. It is limited to Douglas fir, but very common in Pennsylvania. Examination of individual needles shows a distinct border between the green portion and brown portion and both sides of the needle are effected. Symptoms of rhabdocline are usually heaviest at the bottom of the tree. Control is possible with several applications of a registered fungicide and we will provide information on timing of controls at a more appropriate time.
Another disease notable at this time is atropellis canker of pine. The fungal disease was observed at sites in Columbia and Perry County on Austrian and Scotch pines respectively. Black, tongue-like, fruiting bodies on small twigs protrude through the bark and can easily be seen with an unaided eye. Flagging of branches caused by atropellis cankers girdling the branch can be confused with pales weevil damage. Close examination of the bark is required to separate the two pests. Atropellis infections are accompanied by dark stained wood.
In Columbia County, Zimmerman pine moth infestation is evident on some Austrian pine. This pest is often associated with stressed trees but has been appearing at an increasing number of sites in the last 5 years. Globs of white and yellow pitch on the main trunk are usually mixed with frass from larvae feeding under the bark. This pest overwinters as a young larva and will be creating new galleries in the main trunk in the near future. Rouging of infested trees is somewhat helpful since repeated attacks on the same tree are common.
Another moth pest was found at the same Columbia county site. The pitch nodule maker is not uncommon on Scotch pine but is usually not damaging. On the main trunk and large branches of infested trees, a large, solid, blister of pitch covers the larval feeding site. When the blister is broken open, the overwintering larva can be seen tunneling in the wood.
Elongate hemlock scale is becoming a serious pest of Fraser and Canaan fir in some counties. We will be following crawler activity at sites in Columbia and Schuylkill counties this year and will report on the progress of this pest regularly. This week, no crawlers were noted but some females had started to produce eggs inside their bodies at the Columbia County study site.
Last week, some Scotch pines in Perry County were showing signs of black sooty mold. Closer examination showed active Cinara aphid nymphs already feeding on the bark. On nearby white pine, the overwintering eggs of white pine aphid, also a Cinara had not hatched. Cinara aphids are the pests frequently misdiagnosed by consumers as spiders or ticks coming from their cut trees.
The next report will be available after 4 PM on April 5.