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June 14, 2002

Christmas Tree Scouting Report

Welcome to the Christmas Tree Scouting Report for the week ending June 14. The next report will be available after 4 PM on Friday June 21.

Good news for all the growers weary from applying fungicides for rhabdocline needlecast of Douglas fir. This week's samples from Berks, Perry, and Schuylkill counties indicated the infection period for 2002 has passed - there were no viable spores present on the needles examined. Most of the trees had already shed the 2001 needles containing the fruiting bodies, and needles on those that had not, dropped at the slightest touch. Many growers were forced to apply a forth spray because of the early budbreak and extended spring. But, they will be rewarded with healthy needles next spring.Good news for all the growers weary from applying fungicides for rhabdocline needlecast of Douglas fir. This week's samples from Berks, Perry, and Schuylkill counties indicated the infection period for 2002 has passed - there were no viable spores present on the needles examined. Most of the trees had already shed the 2001 needles containing the fruiting bodies, and needles on those that had not, dropped at the slightest touch. Many growers were forced to apply a forth spray because of the early budbreak and extended spring. But, they will be rewarded with healthy needles next spring.

Cryptomeria scale crawlers are active in Berks, Chester, and Dauphin counties. An observation in Lehigh County indicated hatch had not started at that site. But, a Lehigh County grower reported at the end of the week that he was finding crawlers under the protective coverings of the dead females. No crawlers were out on the needles, which could possibly be due to the heavy rains at that location dislodging the crawlers before they are able to settle. This weekend is prime time to start applying registered insecticides to control this persistent armored scale pest of true firs. Remember, a second application will be needed in another week and thorough coverage is vital to success of any control measures against cryptomeria scale. A second generation will occur in late July or August.

In Centre, Chester, Dauphin and Northampton counties, large populations of spruce spider mites are causing damage to true firs and spruces. Spruce spider mite is a cool season mite and the populations will decrease rapidly when average daily temperatures are above about 85°F for several days. The record-breaking heat this week is not enough to collapse the populations and growers wanting to avoid damage will be forced to apply a registered miticide. New growth is already showing signs of damage at some sites. The newer miticides labeled for application as populations are building will not be successful when these mites are already out of hand.

Another cool season mite that is already starting to disappear from the foliage is the spruce rust mite. Damage is apparent but the mites themselves are difficult to find. This is normal but growers experiencing silvering or russeting from these four-legged mites will have to be on the lookout for population resurgence in late August and September. Controls for any pest should be applied when the insect or mite is active, not when the damage is noticed. The two conditions do not always coincide.

This week, Eric Vorodi, Capital Area hort agent, brought some leaders of concolor and spruce from upper Dauphin County to our attention. There was significant needle damage to the terminals. Upon closer examination, it appeared the needles were not chewed off but died back from the tips. After discussing the situation with several people at PDA, we concluded the damage was consistent with bird damage. Songbirds landing on tender new growth can cause not only breakage of the main leader and side shoots but, damage to the tender needles. To prevent this, growers can provide perches made from tall saplings or plastic pipe. The perches should be installed before new growth starts in spring and must be taller than the trees they are intended to protect.

In Dauphin and Perry counties, striped pine scale crawlers on Scotch pine are just starting to emerge from under the female. In Centre County, development is slightly behind, with nymphs maturing and producing copious amounts of honeydew. Numerous ants are active on infested trees and can be seen feeding on the sugary material.

The first pine needle midge damage of the year was found in Perry County this week. Partially elongated needle pairs on terminals are usually notably bent downward at the fascicle. In fact, some people refer to this pest as the European pine needle-bending midge. At the site in Perry County, damage was very light and will not be noticeable in the next few weeks. This pest appears to be present in low numbers for many years and suddenly reach epidemic proportions. The last major outbreak was in 1988, when many Scotch pine growers experienced terminals dying due to lack of needles.

All stages of elongate hemlock scale are present on Fraser fir in Lebanon and Schuylkill counties. The grower at the Lebanon County site is making his second application against this armored scale pest. Unlike many scale pests that have distinct generations, it appears that elongate hemlock scale reproduces continually, with crawler emergence occurring over the entire growing season. Repeated applications are required as long as new crawlers emerge.

The window for mechanical control of white pine weevil is closing with the appearance of chip cocoons in the terminals of white pine in Perry County. The chip cocoon is a characteristic pupation site for weevils in pines. The larvae create the chip cocoons by removing very thin slivers of wood and packing them inside an enlarged area in the terminal. After the chip cocoon is complete, the larva will pupate and the adult will emerge shortly thereafter. The presence of chip cocoons indicates adults will be emerging within the next several weeks and any attempt to prune out infested leaders and destroy them before adults emerge must be completed in the near future. Remember to remove infested leaders from the field and destroy them. Adults are known to emerge from leaders dutifully cut from trees and dropped on the ground.

A relatively new disease of Scotch pine, the atropellis canker, is very noticeable at the present time on one Perry County farm. Shoot death may resemble flagging from pales weevil but there is no area of bark missing at the base of the dead tissue. Instead, black fruiting bodies can be seen breaking through the bark on the dead shoot. These fruiting bodies are somewhat ribbon-like and easily seen.

Cooley spruce galls are not opening to release the winged aphids in the Capital area. But, the mature females are depositing eggs under cottony masses on 2002 needles of Douglas fir in Centre County. At this time of year, growers often ask if control is possible. The possibility of killing the nymphs always exists. But, growers must ask themselves if it is worth the time and expense to spray at this time of year. Since the generations and stages of Cooley are not synchronized at this time of year, not all the stages will be susceptible to control, regardless of the material used and quality of application. In addition, the damage has already been done for the year - no new damage will occur. In fall, from mid-September through October, the overwintering nymphs are present on both Douglas fir and Colorado spruce. They are very vulnerable to control at that time and a single spray of a registered material can prevent damage next year. Sometimes waiting is best.

Balsam twig aphid on true firs is another pest growers must wait for at this time of year. They are depositing overwintering eggs and the next opportunity to prevent the curling needles and distorted growth caused by this aphid is next spring, after the eggs hatch but before budbreak.

Larvae of the 2nd generation of white pine tube moth are active in Schuylkill County on eastern white pine. This moth is more of a curiosity than a pest. The larvae web 5-10 needles together with silk, forming a tube in which they are protected as they feed on the tips of the needles. When most of the needles are completely consumed, the larva moves on to another bunch of needles and creates a new tube. The white pine tube moth overwinters as a pupa in a tube on the host and the adult moths are one of the first insect pests to become active in spring.

The next report will be available after 4 PM on Friday, June 21.