April 28, 2000
Christmas Tree Scouting Report
Welcome to the Christmas Tree Scouting Report for the week ending April 28. The next report will be available after 4 PM on Friday May 5. To receive a FAX of this week’s message, please call (814) 865-1636. If you have pest activity at your location to report, or would like to receive email reports, please leave a message at 717 772-5229.
Douglas fir buds are breaking at several locations in the Capital Region. This phenological event signals the start of the infection period for rhabdocline needlecast. Early this week, bud in Berks County were showing green tips but by the end of the week, more that 50% of the trees in fields in Perry, Schuylkill, and Snyder counties had buds that were open. Budbreak is very uneven and some trees still show tight buds; but those that have opened are susceptible to rhabdocline infection. The ideal time for the first application of an approved fungicide is when 10% if the trees have one or more buds open. At sites were bud break has occurred, the rhabdocline fruiting bodies are mature and are opening to release spores.
Rhabdocline sprays, like all needlecast sprays, are not intended to kill the disease organism but are used to protect new tissue and prevent infection. With the buds breaking and spores maturing, now is the time to apply the first of three to four sprays of an approved fungicide. The second application must be made one week after the first. Thorough coverage is very important to prevent infection.
Another pest that is perfectly in tune with Douglas fir budbreak is the Cooley adelgid. Late this week, newly emerged crawlers were observed in the new growth of Douglas fir in Perry and Snyder County. At this time of year, feeding on the new growth causes the characteristic kinks in needles of infested trees. Although Cooley damage on Douglas fir is largely aesthetic, heavy populations may stunt growth of trees. Control at this time is not possible and growers should wait until fall to control this common pest.
On Colorado spruce, stem mothers of Cooley adelgid have deposited eggs but no crawlers were found in the new growth in Berks, Carbon, Schuylkill or Snyder counties. The buds are swollen and egg hatch will occur about the time of new growth. On Norway spruce, the new growth has already started to push but the eggs of eastern spruce gall adelgid have not hatched. This adelgid forms galls at the base of new growth and egg hatch is somewhat later than Cooley on Colorado spruce.
We still have not observed any white pine weevil larvae in terminals of eastern white pine in Carbon, Perry, Schuylkill and Snyder counties. In Bradford and Carbon counties, feeding wounds were present but no eggs were located. By next week, the eggs of white pine weevil should be hatched and the larvae will begin boring under the bark of the leader.
In Snyder County, the orange spores of pine-pine gall are being released to infect new growth. This gall occurs on the branches of Scotch pine and usually girdles and kills the branches. Preventative sprays are seldom effective in preventing damage. The best method of preventing spread of pine-pine gall is to remove infected trees BEFORE sporulation occurs. For the year 2000, that time has passed.
Cryptomeria scale is maturing but the optimum control period is still some time in the future. New locations for this serious scale pest of true firs were reported in Cumberland, Lebanon, and York counties. Fraser and Canaan fir growers should examine the lower branches of their trees, looking for the characteristic yellow spots on the upper needle surface.The scale insects are actually on the underside of the needles but their feeding causes the chlorotic spots to appear on the upper surface.
Pine spittlebugs are active on Scotch pine in Snyder County. At the same site, heavy pine needle scale infestation has attracted small black beetles with a red spot on each wing cover. These ladybeetles are important predators of pine needle scale but they usually do not make an appearance until the scale population has exceeded the damage threshold.
In Schuylkill and York counties, balsam twig aphids are feeding inside the green cones on Fraser fir. The aphid’s habit of entering cones between the scales and remaining there to feed may lull growers into a false sense of security regarding the need for control of this pest. If you experienced damage in 1999, be sure to monitor for this pest and remember to check the cones for aphids. Controls must be done before budbreak to be effective.
Spidermite activity continues at several sites checked this week. Populations are not out of control yet but regular scouting to track population levels will help make a decision if and when treatments should be applied.
Pine needle scale eggs are still unhatched but growers should be watching for the red, paprika-like crawlers to appear. Two applications of an approved insecticide should be applied 7-10 days apart to control this first generation of this pest.
The next report will be available after 4 PM on May 5.