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April 20, 2001

Christmas Tree Scouting Report

Welcome to the Christmas Tree Scouting Report for the week ending April 20. The next report will be available after 4 PM on Friday April 27. To receive a FAX of this week’s message, please call (814) 865-1636. If you would like to report pest activity at your location, please call 717 772-5229.

The overwintering eggs of spruce spider mite are starting to hatch in Chester County. But, around the Harrisburg area and in Allegheny County, there was no evidence of hatch. Larvae, the first stage to emerge from the egg, are usually salmon colored until they begin feeding on the needles. A handlens with 15X power, or higher, is needed to see the spider mite larvae that congregate at the base of the needles, rather than on the needles. Growers who are interested in applying one of the newer miticides that offer season long control, should be monitoring their own populations. Some miticides are specifically labeled to apply in spring, when the population is building, for maximum effect. But, you must be patient and allow most of the eggs to hatch before making the application.

Cooley adelgid stem mothers are starting to produce clutches of oval eggs under masses of white waxy threads produced for egg protection. In Snyder and York counties, a few egg masses were present on the trees examined. Before applying sprays at this time of year, examine the cottony masses at your location. If eggs are present, you will not achieve maximum control with a spray at this time. The next control window for Cooley and Eastern spruce adelgids is in September and October.

An amazing 107 white pine weevils were collected in four monitoring traps in use at the Perry County site we have been visiting for several years. Newly deposited eggs were found in a few terminals. Adults were feeding on terminals of Colorado spruce in Luzerne County this week. Although the period for control of these pests is ending, significant reduction in population numbers can be achieved by an application of a registered insecticide within the next week or two. A longer delay will permit additional egg laying and result in additional damage to terminals.

Rhabdocline needlecast appears to be everywhere again this year. The red-brown blotches appearing on the upper and lower surface of the Douglas fir needles are very noticeable now. But, infected needles will drop from trees by mid-summer. Next November, when trees are being purchased, no one notices the pale areas on the needles. But, when trees are indoors for some time, and exposed to heat, damaged areas become evident. Plan now to protect your Douglas fir trees from this needlecast. Excellent control can be achieved by following the program developed several years ago at Penn State. The first application of an approved fungicide should be made when 10% of the trees in the block have broken bud. The next application is made one week later, and the third two weeks after the second. Monitoring for budbreak is easy and rewarding.

Bagworms are evident on spruce and Douglas fir at this time of year. Although bagworm is considered a landscape pest, it can cause considerable damage to Christmas trees by defoliating entire branches or tops. This pest overwinters in the female’s bags and eggs do not hatch until mid-June. At this time of year, handpicking scattered bags in a field can save money by eliminating the need for spraying. Bags should be removed from the field and destroyed. Dropping bags on the ground will not offer control.

Another caterpillar that will be hatching soon is the Gypsy Moth. Although it is not considered a primary pest of conifers, it can cause significant damage, particularly to spruce. The buff-colored egg masses are sometimes difficult to find on the main trunk and underside of large branches. Holes in the egg mass indicate that parasitic wasps have been at work. These parasites offer some population reduction, but not enough to keep Gypsy moth from defoliating woodlands and occasionally, conifers.

Last week I reported on European pine sawfly larvae in Westmoreland County. We have specifically sought out populations of European pine sawfly at some of our monitoring sites and have not seen any newly hatched larvae. Some eggs did hatch when they were brought into the laboratory so emergence of the larvae cannot be far behind. In Westmoreland County, very little larval development was achieved in the last week.

The next report will be available after 4 PM on April 27.