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May 11, 2005

Christmas Tree Scouting Report -
Number 6

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.

By now fields planted with Douglas fir are beyond the 10% bud break mark and growers should have applied their first spray for Rhabdocline needle cast. The control for this needle cast consists of three to four sprays. The second spray follows one week after the first, the third spray two weeks after the second and if weather is cool and damp a forth spray is usually needed. This is also the spray schedule to follow for Swiss needle cast on Douglas fir with the fourth spray needed because Swiss needle cast sporulates longer then Rhabdocline needle cast.

Spruce needle rust is beginning to sporulate on Colorado blue spruce in Cumberland County. This needle rust has been a problem for growers in the Northeastern counties since first detected in 1991. In 2004 this needle rust was found further south in Bucks, Lancaster and Schuylkill counties. As of spring of 2005 spruce needle rust was found in Cumberland County. During late winter and early spring, infected needles have yellow banding on both top and bottom of needles. Around the time of bud break, these areas will swell and break open exposing orange spores when rust is infectious. To control this rust, fungicides need to be applied as the new growth elongates, similar to Rhabdocline and Swiss needlecasts on Douglas fir.

Pine needle scale eggs are beginning to hatch on white pine in Adams and Cumberland counties. The majority of hatched crawlers are still under the females white cover but a few are out on the needles in Cumberland County. In Dauphin and Perry counties only eggs were found on Scotch pine. Look for tiny red crawlers resembling paprika on last year’s needles. Control is best achieved when two or three spray applications are applied 7 to 10 days apart during the crawler stage. This scale has a second generation in mid-July but good control of the first generation will eliminate the need for spray later in the year.

European pine sawflies have hatched in Cumberland County on Scotch pine. Sawflies are not flies at all but a primitive wasp in the order Hymenoptera. They get their name from the female’s saw-like ovipositor. She uses the ovipositor to saw a slit in the needle, where she deposits an egg. Young larvae of this species feed in groups on the surface of old needles but are unable to digests the entire needle when young. Older larvae eat entire needles and can completely defoliate a branch or, if colonies are numerous, an entire tree can be defoliated. Since European pine sawfly only has one generation a year and feed on older needles they do not kill a tree but can make it unmarketable. At this time of year look for 1 cm long, green larvae with shiny black heads feeding in groups near tufts of dry, straw-like needles. Usually colonies are few and removing larvae by hand and destroying them can be the best control.

Two weeks ago only two elongate hemlock scale crawlers were observed on grand fir in Adams County. With the warmer temperatures, a few more crawlers were found this week. Growers who have had problems with this scale may want to begin their spray program in the next week or so.

Pine-pine gall rust is beginning to sporulate on Scotch pine in Dauphin County. This rust creates a round swelling on the trunk or branches of affected trees. During the infectious period, orange spores are exposed on the surface of galls. The best control is to prune galls out before they sporulate. Do not remove trees or branches during sporulation as this will effectively spread the fungus to other nearby trees.

Balsam twig aphids were found in cones and new growth on Canaan fir in York County. If you had problems with this aphid on true firs, and buds at your location have not yet broken, you may want to consider spraying if trees are near market size.

Last week a chemical company representative pointed out some previous research conducted by Dr. Dave Shetlar on white pine weevil control with MSR Spray concentrate. In his work, Dr. Shetlar found that MSR had positive effects on controlling young larvae within the terminals. This may be an option if you missed your applications earlier and larvae are already present in the terminals at your location.

The next report will be Wednesday the 18 th after 5:00pm.