April 5, 2002
Christmas Tree Scouting Report
Welcome to the Christmas Tree Scouting Report for the week ending April 5. The next report will be available after 4 PM on Friday April 12. Please call (717) 772-5229 to report pest activity at your location or request an email report.
White pine weevils continue to feed on terminals of Douglas fir, spruce, and eastern white pine and a few eggs were found in Perry County. Weevils were observed on the terminals in Center County and a Schuylkill County grower is completing treatments following observations of adults on terminals at his site. In Westmoreland County, adults are also active. Sap flow is heavy on some terminals and pinpoint sized holes are indicative of adult feeding. Growers wishing to minimize damage from this pest should apply a registered insecticide to the terminal.
Cooley adelgids continue to develop on Colorado spruce and Douglas fir. In Center and Schuylkill counties, overwintering adelgids on the underside of Douglas fir needles are producing minimal amounts of wax around the perimeter of their dark bodies. In Schuylkill County, nymphs on Colorado spruce are present along bark crevices near the buds and have started to cover themselves with the waxy filaments. Farther south, in Lebanon County, a single stem mother was found with eggs. This event indicates the spring control period will soon end.
Eriophyid mites are active at most locations scouted this week. Spruces in Adams, Lebanon, Schuylkill, and York county sites had actively feeding spruce rust mites; fir and Douglas fir in Lebanon and York counties were supporting populations of hemlock rust mite. In North Carolina, hemlock rust mite is a serious pest on Fraser fir but in Pennsylvania, we rarely see significant damage from this pest. However, at the York County site, populations were extremely high and damage may result.
Overwintering balsam twig aphid eggs are starting to hatch in southcentral counties but near State College, hatch has not started. Where aphids are present, they are feeding on the undersides of last year needles. A small droplet of clear honeydew is often present indicting feeding is occurring. This feeding does not cause any damage and there is ample time to observe this pest since optimal control timing is after all eggs have hatched but before buds break.
Rhabdocline symptoms continue to attract attention of Douglas fir growers. The red-brown botches on needles are very noticeable at this time of year. Some swelling of these sites, which will mature into fruiting bodies, is starting to occur in York and Schuylkill counties. Douglas fir growers should make plans for preventative fungicide sprays when budbreak starts.
Sooty mold, associated with Cinara aphids, was evident on Scotch pine at a York County farm. At another farm, striped pine scale was also associated with the sooty mold. What do these two situations have in common? Both pests are actively secreting a sugary substance called honeydew. Blackened needles, indicative of sooty mold, are evidence that a sucking insect is at work. Although not especially damaging, sooty mold does reduce photosynthesis in plant tissue by blocking sunlight. It also renders plants aesthetically unsuitable. Stinging insects, attracted to the honeydew, can be a problem for workers during shearing operation later in the year.
On the bright side, multicolored Asian ladybeetles, hungry after overwintering in homes and annoying residents, are moving back to the trees. At Christmas tree farms where pine bark adelgids are present on eastern white pine, these beneficial ladybeetles are avid feeders on both eggs and crawlers; they were found feeding on the Cinara aphids mentioned earlier; and are often attracted to balsam twig aphid fir. The adult ladybeetles feed and lay eggs, establishing predator populations to control some soft-bodied pests. They would be a welcome addition to Pennsylvania agriculture, if we could just keep them out of our homes during the winter.
High numbers of spruce spider mite eggs on true firs and spruce are reported from numerous locations in the state. Hatch has not started at any sites but should begin at approximately 100 Growing Degree Days, base 50°F. The Pennsylvania Weekly Crop report includes average temperatures and growing degree day accumulations for more than 50 sites. It can be accessed at http://www.nass.usda.gov/pa/
Before budbreak is a great time to scout for several pests that will be well hidden by new growth in the next two months. Pine needle scale, cryptomeria scale, elongate hemlock scale, bagworm, and pine-pine gall are among the list of pests that will become active after new growth has started and could be missed if not located now. Taking time now for scouting can reap benefits later in the season.
The next report will be available after 4 PM on April 12.