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May 30, 2003

Christmas Tree Scouting Report -
Number 10

Welcome to the Christmas Tree Scouting Report for the week ending May 30. The next report will be available after 4 PM on Friday, June 6, 2003. To receive a FAX of this week's message, please call (814) 865-1636. To report pest activity at your location or request email report, please call 717 772-5229. 

We have been monitoring for the emergence of the Pine needle scale crawlers for the last two weeks in Dauphin and York counties, and had not seen any crawlers. This week, a few eggs are beginning to hatch underneath the female scale cover but no crawlers were found out on the needles. Normally egg hatch for this scale is mid-May and the tiny red crawlers can be seen out on the needles. For the last two years, crawlers had already settled by June 1 but the cool spring temperatures of 2003 have set the pest back a couple weeks. This is an excellent example of why you can't effectively time your sprays by a calendar date. As with most scales, this pest is most susceptible to control as exposed newly hatched crawlers or newly settled nymphs. Take the time to scout and apply your sprays when they will be the most effective.

Another scale insect we are monitoring is Cryptomeria scale. This is an armored scale that can reach populations high enough to affect the health and aesthetic value of Christmas trees. This scale is most often seen on true firs in Christmas tree plantations, but is also known to attack Spruce and Douglas fir. The female scales begin producing lemon yellow eggs under their protective armor cover at the end of May, early June. This week in Berks and York counties no eggs were found. Once egg lying begins crawler emergence follows about two or three weeks after. Again, the best time to control this pest is when crawlers begin to emerge from underneath the scale cover. We will continue to monitor for eggs and crawlers in the coming weeks.

Another scale of concern for those who grow Scotch pine is the striped pine scale. This soft scale was frequently misidentified as pine tortoise scale until about 10 year ago, when the taxonomic differences between the two species were identified. In the field, these two scale insects are very close in appearance and crawler emergence periods are similar. Most of the scale populations found in Pennsylvania have been found to be stripped pine scale. What does this all mean when it comes to control? Nothing. Control tactics are similar to those traditionally used against pine tortoise scale. Dormant oil sprays will be effective in the early spring against the over-wintering nymphs. Summer sprays directed at the crawlers will depend on when they emerge, and this is determined by scouting for crawlers on infested stock at your farm, no matter which scale species is involved. Both species have one generation per year and crawler emergence can be as early as late-May to mid-June.

The overwintering eggs of the bagworm will be hatching soon. At our monitoring site in Dauphin County this week no larvae were present out on the needles. Bagworms attack most Christmas tree species. The best control is hand picking the bags and destroying them if the infestation is not severe or widespread. This must be done before the eggs hatch and larvae begin to emerge. For widespread infestations, spray trees with a Bt (Bacillus thuringiensis) solution when caterpillars are young.

Winged females of the Balsam twig aphid were found on firs in York County this week. It is these winged aphids that fly to other trees to spread the infestation. At the end of the next generation, the overwintering eggs will be deposited. This also means the life cycle for this pest is coming to an end and the next time to control this insect is before bud break and cone formation next year.

White pine weevil adults were found out on heavily damaged terminals of white pine in Carbon County this week. When terminals were examined most of the eggs were hatched and larvae were feeding and making galleries under the bark. Once eggs are laid in the terminals the only control is cutting out the infested leaders and removing them from the field.

The next report will be available after 4 PM on June 6, 2003.