June 28, 2006

Christmas Tree Scouting Report Number 16 - June 28, 2006


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

This will be the last weekly report for the 2006 season. I will be sending out short reports on the second generation of Cryptomeria scale (CS) beginning about the last week in July -- early August when eggs are expected, followed by egg hatch/crawler emergence a couple weeks later.

This week there are still eggs of Cryptomeria scale that have not yet hatched on Fraser fir in Dauphin, Lancaster, Lebanon, and York counties. To check for remaining eggs, tap an infested branch over a white surface and look for tiny, bright yellow, jellybean-shaped eggs. Or, pull back the female covering with a fingernail or pin and look for any eggs with a hand lens. When I removed female covers I found: thin white remains of egg shells; crawlers that had not made their way out from beneath the adult female covers; and a few bright yellow eggs yet to hatch. If eggs still remain and your last spray was a week or two ago, I suggest applying an additional spray for best control. Eggs of the second generation of Cryptomeria scale appear anytime from the last week in July to the first week in August.  Scout for eggs at that time in those fields that were infested by first generation CS. 

Bagworm larvae are now about one cm (3/8") long and big enough that feeding damage is becoming evident. Needles that have been chewed are now brown, and young shoots that have been girdled by larvae chewing on tender young bark are beginning to wilt. If you have not yet applied a spray for bagworm, now is the time, (that is, whenever it stops raining!), before the larvae get bigger and are able to totally strip off the foliage.

Eriophyid mites, also known as rust mites, have been heavy on conifers this year.  Damage by rust mites is common on Norway- and Colorado blue spruce, on white pine (known on this host as the sheath mite on white pine), and occasionally on Concolor fir. In York County, eriophyid mites were heavy on 2005 needles of Canaan fir, and were causing russeting on needles. Damage from eriophyid mites on Canaan or Fraser fir is actually uncommon in Pennsylvania. In North Carolina eriophyids are known to do damage on Fraser fir. Eriophyids feed in much the same manner as spider mites, by inserting their mouthparts into the host tissue, which causes a russeting and premature needle drop. The typical eriophyid is wedge-shaped, soft and wormlike, with only two pairs of legs just behind the mouthparts. These mites are less then 1 mm long and impossible to see without a 10-20X hand lens. Eriophyids are not generally controlled with standard miticides. 

Admes mites were found on Colorado blue spruce in Northumberland County. This mite has been found occasionally causing damage on spruce in Pennsylvania. Damage from Admes mite resembles spruce spider mite damage but Admes mite is larger and has a red body and long orange legs. We have been sampling for this mite over the last few years to learn more about the life history.

Thank you for your support of the Christmas Tree Scouting Report during the 2006 spring season. Please send any comments or suggestions for improvement to or call (717)-772-0521. Thank you and have a good year.