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April 28, 2004

Christmas Tree Scouting Report -
Number 5

Welcome to the Christmas Tree Scouting Report for the week ending Wednesday April 28, 2004. The next report will be available after 5 PM on Wednesday May 5th. To receive a FAX of this week's message, please call (814) 865-1636. If you would like to receive this report via email, please send a request to rdlehman@state.pa.us and you will be added to the distribution list. Frequently, the email/fax report contains more information than we are able to fit into the 3-minute recording. To contribute observations to this report, please email to the address above or call (717) 772-5229.

This week growers in Adams, Berks, Lancaster, Lebanon and York counties are applying their first spray for Rhabdocline. Your 1st spray should be applied when your field of Douglas is at 10% bud break. To determine 10% bud break walk your field and if only one bud on a tree is bushing out green tips of new needles that tree is at bud break. If ten trees in a hundred are showing any green tips you're at 10% bud break.

Your second spray will follow one week after your 1st spray, followed by a third spray two weeks after the second. An additional fourth spray three weeks after the third will be needed if cool, wet weather persists or if you also have Swiss needle cast in your Douglas fir. Swiss needle cast sporulates a little later and longer then Rhabdocline needle cast so the fourth spray is necessary to gain control.

This week we are beginning to receive reports from growers in Bucks and Montgomery counties of adult Douglas fir needle midge emergence. What looks like clouds of minute insects or gnats flying around Douglas fir trees could be a congregation of emerging adult midges. Adults can also be found resting on the new growth. Adults only live for a few days, just long enough to mate and lay eggs. We have not detected any adults in our traps in Bucks, Lehigh, Northampton, Schuylkill, or York counties, as of yet, but expect to see adults within the next week. Timing of insecticide applications is critical for control. Adult midges must encounter treated foliage and be killed before females oviposit. Once the eggs hatch and larvae enter the needle, control is not possible. Trapping to detect emergence can help with timely sprays.

Crawlers of Elongate hemlock scale are beginning to hatch on grand fir in Adams County this week. This armored scale is hard to control because of the multiple overlapping generations. Since this scale and all armored scales feed on parenchyma cells in leaves and not in the vascular systems, a vascular translocated systemic will not give good control. Select a contact spray that will kill crawlers for best results. Unfortunately, multiple sprays will be needed until more research is done on control measures.

European pine sawfly larvae were observed hatching on Scotch pine in York County. Look for straw-like needles just below the new growth and you will probably find a group of young larvae 1/8 of an inch long. When young, the larvae feed only on the outer edges of old needles causing the remaining part of the needle to twist and turn brown. As they grow, these larvae continue to feed in groups consuming whole needles and can strip an entire branch of its needles. Since this insect only feeds on older growth, the tree does not die but damage can take away from the appearance of the tree. The best control is spot spraying or removing the colonies by hand.

Pine spittlebug was found on blue spruce and white and scotch pine in Adams and York Counties. The nymphs overwinter as eggs under the bark of shoots and once hatched feed on the sap. They immediately begin producing the characteristic frothy mass of spittle, which is made up of tiny air bubbles coated with the partially digested sap. Unless abundant, this insect does little damage. However, if heavy spittlebug populations occur, Sphaeropsis shoot blight fungus may enter through feeding sites and cause heavy flagging of shoot tips.

Spruce spider mites continue to hatch in Adams, Lebanon, and Perry Counties. An easy way to scout for this mite is to place a white paper plate under a branch and tap it gently to dislodge the mites. Look closely for any small moving objects. Newly hatched spruce spider mites are pale but, on true firs, most mature forms are red and when squashed they leave a red mark. On some hosts, spruce spider mites are green when actively feeding.

The next report will be Wednesday May 5th after 5:00pm