April 26, 2002
Christmas Tree Scouting Report
Welcome to the Christmas Tree Scouting Report for the week ending April 26. The next report will be available after 4 PM on Friday May 3.
Douglas fir budbreak is the hot topic this week, as Douglas fir growers prepare to make applications of fungicide to prevent rhabdocline needlecast infection on 2002 growth. This serious disease usually appears when trees reach saleable size. The disease cycle is completed in one year, starting with the infection period at, or shortly after, budbreak. Symptoms generally are not apparent until the fall or winter following infection. This time lag makes rhabdocline control difficult to evaluate. But, experience has proven that control can be achieved with good timing and coverage.
To control rhabdocline, the first application of a registered fungicide should be made when 10% of the trees at the location have broken bud. This budbreak-based timing can vary tremendously from place to place and even within any grower's fields, with southern exposures more likely to break bud early. Seed source can also contribute to variations in budbreak. Later breaking buds are, in general, less susceptible to rhabdocline than those that break early, when most of the spores are released.
In order to get good control, a second and third fungicide spray must be applied to assure continued protection for new growth as it emerges. The second application should occur one week after the first, and the third application, two weeks after the second. In cool springs, when new growth hardens slowly, a forth spray may be required.
How are we doing with Douglas fir budbreak statewide? In Dauphin County, the 10% mark was reached on Tuesday, when the fruiting bodies were also splitting open following the rain on Monday. In Northampton County, fruiting bodies were also splitting open earlier in the week, and by today, budbreak was just starting. However, in Centre County no Douglas fir budbreak was noted. In 2001, budbreak started 1 week later, but in 2000 it was also reported at this time of year. Maybe spring isn't as early as it seems.
The other important pest that has people asking questions is Cooley adelgid, both on Douglas fir and on Colorado spruce. Since all reports from as far north as Centre County indicate the stem mothers have already covered themselves with waxy material and started to deposit clusters of eggs, control is not practical to prevent damage to new growth. Although some nymphs could be killed between hatching and reaching the new growth, the level of control achieved will not be high enough to justify the cost of the spray. The next opportunity for chemical control will be in fall of 2002. In Dauphin County, syrphid fly larvae were seen feeding on Cooley eggs masses on Douglas fir. This naturally occurring predator will not keep the pest under control but will contribute to a reduction of adelgid numbers.
Balsam twig aphids are hatched at all locations visited. In Dauphin and Berks counties, 2nd generation nymphs are present and ready to feed on new growth. Canaan fir budbreak has started in Berks County where the nymphs are feeding on the new growth. The Fraser buds at the same site are still closed. The level of damage to Canaan and Fraser will mirror their budbreak sequence. Concolor is another host for balsam twig aphid but damage is usually not significant on this species of fir. Controls for balsam twig aphid should be completed before budbreak.
The majority of spruce spider mite eggs have hatched on Fraser fir in Centre County. At this time, application of a miticide will have maximum impact. If one of the newer miticides designed to give season-long control is used, it is important to wait until 90% or more of the overwintering eggs have hatched. If a more traditional miticide is used, don't forget a second application in 7-10 days.
White pine weevil eggs are increasing in numbers at our Perry County trap site but no larvae have been found. In Dauphin County, evidence of weevil feeding on terminals of Norway spruce lead to the discovery of numerous eggs in the terminals. The period for effective chemical control of white pine weevil is ending.
In Dauphin and Lancaster counties, pine bark adelgid eggs have hatched and the nymphs are feeding and producing white wax on elongating candles of eastern white pine. At that same site, eriophyid rust mites are still active on Colorado spruce. Another report of eriophyids on white spruce in Northampton County was received earlier in the week. Cooler temperatures this week will benefit these mites.
In Luzerne and Sullivan counties, spruce needle rust is starting to sporulate on Colorado spruce. New growth has not started so no infection is occurring at this time. However, as soon as the new growth pushes, spores of this serious rust disease will be released to cause infection. The disease cycle for spruce needle rust is somewhat like that of rhabdocline on Douglas. Spores released from fruiting structures on last years needles infect new growth but symptoms are not apparent until late fall or winter. Control strategy is also similar - protect the new growth to stop the disease cycle.
Pine needle scale eggs will be hatching in the next week or two. This elongate white scale insect is particularly troublesome on Scotch pine but can infest all pines as well as a number of other conifers. We will be monitoring for the red, paprika-like crawlers and inform you of their emergence.
European pine sawfly larvae are about 1/3 inch long and consuming entire needles of Scotch pine at a Dauphin County location. In Westmoreland County, the larvae are slightly larger.
Male Cryptomeria scales are starting to emerge in Berks County. This will result in eggs in the next several weeks and crawlers a few weeks after that. No control is effective at this time of year. Crawlers of elongate hemlock scale, however, are emerging in low numbers in Columbia and Lancaster counties. A few settled crawlers were found at the Columbia County site. Growers battling this scale pest should be starting their sprays at this time.
Spittlebugs are active in Berks and Centre counties on Scotch and eastern white pine, and Douglas fir. Although disgusting to look at, the spittle masses produced by these sucking insects are not damaging to the host tree and will disappear after adults emerge later this year.
The next report will be available after 4 PM on May 3.