June 6, 2007

Christmas Tree Scouting Report #11 - June 6, 2007

Weekly newsletter compiled by Sandy Gardosik, PA Department of Agriculture, Harrisburg, PA.

Last week only a few eggs of Cryptomeria scale could be found under the protective coverings of the female scales.  Many more eggs were found this week in Dauphin, Lancaster, Lebanon and York counties when the scale covers were removed.  In Dauphin and York counties the first few crawlers of the year were found. If you were planning on controlling this scale on your farm, now is the time to begin planning to include it in your spray program within the next week or so. Crawlers will be out on the underside of both the old and new needles, but if you look on the new growth it will be easier to observe crawler emergence:  look for oval, bright yellow crawlers on the underside of the new growth. Crawlers settle and begin feeding within just 24-36 hours after hatching if they are to survive, so you may see settled crawlers on the new growth. Settled crawlers will have a thin wax covering over their body. Controls will usually take care of early settled crawlers. Begin your spray program when crawlers are observed, and follow with two to four sprays 7-10 days apart.

Rhabdocline needle cast is still viable in Adams, Dauphin, and Lebanon counties. Growers in the south and south-central counties have either already applied their third spray, or are scheduled to do so. Growers are asking if I feel a fourth spray for Rhabdocline will be necessary.  I'm beginning to see some senescing of the lesions, which appear black, and dry, in both Dauphin and Lebanon counties but there are still lesions that are swollen and orange, which is an indication that they are still viable. The fourth spray application for Rhabdocline should follow 2-3 weeks after the third, so if temperatures are hot and dry then a fourth application may not be necessary.  However, if you are trying to control Swiss needle cast in the same field, you will need to apply the fourth spray.

Damage from the white pine weevil was evident in York County this week. The leaders of white pines were discolored and "shepherd crooks" were evident. Prune out the infested leaders, making sure the cuts are below all infested tissue.   Remove the prunings from field to assure that no larvae will complete development there and reinfest that field the following year. The sooner infested tops are removed, the less growth from previous years will be lost; also, a new leader will be easier to train.

Pine pine gall, also known as gall rust on Scotch pine, is producing spores at this time in Dauphin County. Look for globe-like swellings with cream-colored blisters filled with orange spores on the surface of galls, located on trunk or branches. Now is not the time to control this rust; instead, wait until the infestation period is over, then remove the galls from infested trees before they produce spores the following year.

Overwintering eggs of Balsam twig aphids were found in Adams County.  The presence of these eggs and winged forms of the aphid indicate the life cycle is coming to an end. Look for the overwintering eggs on the undersides of branches, between the needle bases. The eggs are light green with wax fibers covering the surface. As the eggs age they will turn black and the wax fibers will appear silver. All aphids will die by early July, and this insect will not appear again until early next spring. Chemical sprays are not recommended against the overwintering eggs; the next time to control this aphid is at bud swell the following year.

Striped pine scales on Scotch pine are beginning to produce crawlers. In Adams County the tiny orange crawlers had not yet emerged from under the adult females. In Dauphin County no crawlers were found. You will attain the best control if you wait until crawlers are out and exposed on the needles.

Bagworms are still about 1/8 of an inch long and chewing just the surface of needles. When these caterpillars become larger they are capable of consuming whole needles, and that is when damage becomes noticeable.  At that point, control is more difficult, and harsher chemicals are needed. Bagworms have been active for about a week now, and I expect the majority of them to be hatched and out feeding on the needles within a week. With this in mind, plan on spraying for this insect in the next week or so. If controlled early, the bacterial insecticide BT (Bacillus thuringiensis) can be used.  Some trade names to look for are Biobit HP, Crymax, Dipel ES, Javelin WG and Foray 76B.

Elongate hemlock scale crawlers can be found out on needles in Adams County. If you plan to spray for this scale, remember that 3 or 4 sprays are needed 3 to 4 weeks apart. Dimethoate has shown to give the best control in spray trials.