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May 26, 2000

Christmas Tree Scouting Report

Welcome to the Christmas Tree Scouting Report for the week ending May 26. The next report will be available after 4 PM on Friday June2. To receive a FAX of this week’s message, please call (814) 865-1636. If you have pest activity at your location to report, or would like to receive email reports, please leave a message at 717 772-5229.

We are still monitoring cryptomeria scale as females deposit eggs on firs in Berks, Lancaster, Lebanon, and York counties. To date, none of the eggs have hatched but we expect to find some crawlers by this time next week. Several growers to inquire when they should begin treating for this serious pest of true firs. Our best advice to anyone is to monitor their own fields for crawler emergence and begin applications as soon as possible after the first crawler is found. Crawlers must settle within a day of emergence and sprays target this active, relatively unprotected stage.

In some populations, high degrees of parasitism in are found. However, in the life history study we are conducting, parasites were not always fatal to females until after the eggs were deposited. Resulting eggs appeared to be viable.

Winged adults of balsam twig aphid were sighted on concolor fir in York County. This is the stage that migrates to new host trees and spreads the pest through the field. Mated females will produce a third generation on the new hosts but most of the damage has already been done by this time. Numerous adult and larval ladybeetles and syrphid fly larvae are usually associated with balsam twig aphid populations at this time of year.

Overwintering bagworm eggs have hatched in Lebanon County. The minute first instar larvae hatch inside the protective bag created by the female last year. In a short time, they spin a silken thread to balloon down to a feeding site on the host. Young bagworms can not consume the entire needle and damage goes largely unnoticed until late summer, when the mature larvae are defoliating branches. Applications of Bt, the biological insecticide, are very effective in controlling this pest of conifers.

In York County, the smaller grass bagworm has moved from the weeds to tops of concolor fir. These grass bagworms may be mistaken for their damaging cousin. However, they are only seeking a safe pupation site and will not cause damage to conifers.

White pine weevils continue to be active on untreated terminals of eastern white pine at our study site in Perry County. This is the first week we have not collected adults in the detection traps. The wilting of new growth on the terminals is very evident and larvae are feeding beneath the bark. Cutting out infested terminals is the best way to control white pine weevil at this time.

Pine needle scale crawlers and settled crawlers were found in Lebanon, Snyder and York counties. Some eggs are still unhatched. The presence of multiple stages of this pest is one of the reasons a second application of pesticide is required to achieve acceptable control. Twice-stabbed ladybeetles were actively feeding on the scale insects at one site. This predator is effective in reducing populations but usually does not show up until the infestation is severe.

Rhabdocline fruiting bodies continue to disperse spores at many locations in central Pennsylvania. Some growers have started to apply their third application of protective fungicide to protect this year’s growth. If you want to know if you should continue to spray at your location, examine the sporulating needles from last year. If they are dark brown to black, the sporulation period has ended and additional sprays are not needed.

Bird damage to leaders of spruce and Douglas fir is starting to appear at some locations. This may be misdiagnosed as damage from one of the pine shoot moths. If you look closely at the bird damaged leaders you will clearly see that the leader was pulled from the socket. In some cases, the new growth is bent over and may result in a malformed top.

Winged adults of pine bark adelgid were found in Snyder County this week. In York and Lebanon counties, some eggs have hatched and nymphs are feeding on the new growth.

A third instar Gypsy moth larva was feeding on spruce in Snyder County. Applications of Bt will also control this pest effectively when the larvae are still small.

On Scotch pine in York County, the pitch nodule created by a moth larva in the genus Petrova was found at the base of the new growth. When the pitch blister was removed, a small, a brown larva was found tunneling under the bark. Although pitch nodule maker is relatively common on two and three needle pines, damage rarely is significant in Christmas trees. In the landscape, this pest can cause serious damage to mugho pine.

In Lebanon County, pine-pine gall continues to sporulate on Scotch pine. Entire branches killed by the girdling effect of these branch and stem galls, are common. Trees infected with pine-pine gall should not be removed while sporulation is in progress.

The next report will be available after 4 PM on June 2.