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May 18, 2005

Christmas Tree Scouting Report -
Number 7

Welcome to the Christmas Tree Scouting Report for the week ending May 11, 2005. The next report will be available after 5 PM on Wednesday, May 18. To receive a FAX of this week’s message, please call (814) 865-1636. If you have pest activity to report, or would like to receive this report by e-mail, please leave a message at 717 772-0521 or e-mail sgardosik@state.pa.us and your name will be added to the distribution list.

High populations of eriophyid mites are causing damage on Colorado blue spruce and Norway spruce in Lebanon and Snyder Counties this week. Eriophyid mites are very tiny and can only be seen with the aid of a 10X, or stronger, hand-lens. On Norway spruce look for russeting or browning of last year’s needles. When populations are high the needles look dirty and dusty. With close examination, you will see pale-orange wedge or carrot-shaped mites with only two pairs of legs. On Colorado blue spruce this mite causes needles to have a silver caste. Carbaryl, dormant oil, and horticultural spray oil are specifically labeled for eriophyid mites. New growth is too tender at this time for oil and oil will take away the blue bloom on older needles. Two sprays of an insecticide specifically labeled for rust mites will provide control at this time. These are “cool-season” mites and will almost disappear when temperatures rise later in spring.

Another “cool-season” mite is the spruce spider mite. Cool temperatures and lack of rain has been beneficial for mite populations and damage is noticeable on Fraser fir in Carbon, Dauphin and Lancaster Counties. Many growers are currently using Savey or Hexygon for mite control. They are both good products but must be used when the majority of over wintering eggs have hatched but before the second generation, when mite populations typically begin to build. It is too late for this product to yield optimum results this year. If you have high numbers of spruce spider mites now, control them with two applications of a general miticide 7 to 10 days apart.

White pine weevil adults are still being found in emergence traps or on terminals of Serbians and/or white pine in Bucks, Carbon and Lebanon Counties. Growers have been asking if they should continue with additional sprays. In an effort to provide an answer, we dissected some female weevils collected in several traps. In most, eggs were found in the abdomen, so there is still potential for damage. Growers who did not apply any controls this spring will probably experience damage even if they do attempt control at this late date.

Growers should have applied their second spray for Rhabdocline needle cast by now and be planning a third spray two weeks from the second. The question came up about waiting a little longer between sprays because of the dry weather. This sounds risky. Even without rain, with the cool nights and warm days there is enough moisture in the mornings to keep the spores viable and open the fruiting bodies for release and infection of new needles.

No midges were found in emergence traps for the Douglas fir needle midge at our experimental site in Bucks County as of Wednesday the 18th. This year the emergence period for this midge occurred over a three-week period. Two applications of Orthene TT&O spray 97 and Lorsban were made about 10 days apart at the study site. These blocks will be evaluated and results shared at a later date.

No bagworm hatch was observed in Dauphin or Lancaster counties this week. The best time to spray this pest is when the majority of larvae have hatched and are out on the needles. If you had problems with this pest last year you will want to plan on spraying for this pest in the next couple weeks. Monitoring will continue weekly till eggs hatch.

No eggs were found under adult females of cryptomeria scale in Dauphin or Lancaster counties this week. Adults usually begin to deposit eggs in the later part of May with egg hatch following a couple weeks later. Plan on spraying for this scale early to mid-June.

The cooler temperatures have also had an effect on elongate hemlock scale. In Carbon County, no crawlers were found this week. Growers who had problems with this pest last year and are in a more southern county should begin scouting for crawlers on the undersides of needles and should begin a spray program when crawlers are present.

The next report will be out on Wednesday May 25 th after 5:00pm.