June 1, 2001
Christmas Tree Scouting Report
Welcome to the Christmas Tree Scouting Report for the week ending June 1. The next report will be available after 4 PM on Friday June 8.
Aspidiotus cryptomeriae, referred to as cryptomeria scale, has started to deposit eggs on firs in Berks and Chester counties. But, in Lancaster County, there were no eggs found. This is the start of the ovoposition period for the first of two generations of this pest of true firs. For the next several weeks, the females will continue to deposit yellow, oval eggs under their waxy coverings. Eggs have hatched about 3 weeks after the first eggs were deposited at our study sites during the last several years. We will be monitoring intensely for crawlers emergence again this year.
Chemicals for controlling this armored scale should be applied when the first crawlers hatch. Several applications, each a week apart, will be needed to effectively control cryptomeria scale on firs. You can check for the yellow eggs under the scale covering by using a straight pine to gently lift the covering.If you work over a dark surface, the eggs will be easier to see. Frequently eggs blow away in the breeze, so you may want to do this in a protected area. To monitor crawlers at your location, and precisely time the sprays, closely examine the undersides of the branches, looking for minute, flat, yellow objects that move when beaten over a dark surface. A 15X handlens is needed to see the eggs and will be extremely helpful when looking for crawlers.
Spruce spider mite has continued to have large populations on spruce and fir in many locations. Our cool Spring temperatures, and lack of rain, have both contributed to the continued growth of mite populations. Although it is too late in the year to apply one of the newer materials that will provide season long control, miticides should be used if you can find active mites and damage is occurring. Conventional miticides usually require two applications, 7 to 10 days apart, to gain control of a damaging mite population.
Elongate hemlock scale is another armored scale pest we are seeing on firs in some areas. These scale insects resemble cryptomeria scale but can be separated by the appearance of the male. Elongate hemlock scale males have white waxy threads covering their testes. Cryptomeria scale males strongly resemble the larger females. Elongate hemlock scale has a very long ovoposition period, starting in April and continuing through the season. Regular applications of a material registered for scale control must be made to reduce the damage from elongate hemlock scale.
We are continuing to receive questions about sprays for balsam twig aphid on true firs. Now that growers are noticing the curled and stunted needles resulting from the aphid’s feeding on new growth, everyone wants to take immediate action to get the aphids under control. At this time of year, controlling balsam twig aphid is possible but may not be advisable. Many different predators are attracted to balsam twig aphid infested trees and these natural enemies will provide free pest control if you avoid sprays. Eggs, larvae and adults of the multicolored Asian lady beetle were observed on infested trees this week. Flower fly, or syrphid larvae were also active in Chester County. These larvae are strange looking, appearing to have two tails and no head. They are properly called maggots and can be observed moving and feeding among the aphids, where they are effective predators. Sprays applied now may reduce next year’s pest population, but the aphids have already done the damage. Why not let the predators take care of the aphids?
White pine weevil larvae are starting to pupate in leaders of Serbian Spruce in Chester County, and in eastern white pine in Perry County. The larvae are starting to prepare their characteristic “chip cocoons” under the bark. These cocoons consist of numerous wood fibers and resemble the packaging material excelsior, but on a much smaller scale. When the “chip cocoon” is opened, the plump white larvae of the white pine weevil can be found. In a week or two, the larvae will complete development and pupate. Adults will emerge from the leaders in early July. To complete mechanical control of white pine weevil, cut the infested leader out before the adults emerge. Be sure you trim the leader back far enough to reach good solid wood all around. Too often, growers trim leaders only back to the apparent damage. Thinking they have control, they stop there. New adults emerge from below the apparent damage area and the pest cycle goes on. At this time of year, the pruned leader must be carried out of the field and destroyed before adults emerge.
Bagworm eggs are hatching in Lebanon County. Although the first instar larvae have not ballooned out of the bag created by the female last season, they will soon be starting to feed on the needles below the bags. At this time, the biological insecticide, Bacillus thuringiensis, is very effective. Bt, as this product is known in the industry, must be ingested by the caterpillar and will cause death in several days from bacterial infection. Bagworms are spotty pests and controls usually do not have to be directed to the entire field. Spruce and Douglas fir appear to be their favorite Christmas tree hosts with spruce frequently sustaining considerable damage.
In Lebanon County, rhabdocline needlecast fruiting bodies are mostly blackened indicating they have reached the end of their spore releasing stage. Sprays at your locations should only be discontinued when the fruiting bodies opening on the underside of the needles are dark brown to black, rather than reddish-brown.
Also in Lebanon County, pine needle scale crawlers have settled on Scotch pine and some are starting to turn white. The opportunity for controlling this spring generation has passed and growers must now wait until mid-July to control the second-generation crawlers.
In Perry County, we are again seeing crawlers of striped pine scale. A few crawlers of this soft scale were found several weeks ago in several locations. Early June is more typically the time frame associated with crawler emergence. These crawlers are very active and can infest trees down a row by hitching a ride on a passing mower, or even animal. Bees are attracted to the honeydew produced by the feeding scales and infested trees often appear black because of the sooty mold that develops on the honeydew.
The next report will be available after 4 PM on June 8.