May 11, 2001

Christmas Tree Scouting Report

Welcome to the Christmas Tree Scouting Report for the week ending May 11.The next report will be available after 4 PM on Friday May 18. To receive a FAX of this week’s message, please call (814) 865-1636. If you would like to report pest activity at your location, please call 717 772-5229.

Pine needle scale crawlers have started to emerge in Lebanon and Snyder counties. Earlier this week, a few crawlers were found under the dead female’s covering in Snyder County. By the end of the week, the red crawlers were active on needles of Scotch pine in Lebanon County. This is the first of two annual generations of this armored scale. The primary hosts of pine needle scale pines; Scotch pine is especially susceptible. In extreme populations, lady beetles will be attracted to the trees and will exert tremendous predatory pressure, bring a large population down quickly. However, until the high population is reached, the scales cause the trees to be unsightly and unthrifty. As with all scale insect controls, two applications must be made to control the crawlers. The applications should be 7 to 10 days apart. A second generation of pine needle scale will emerge in late summer.

Growers in warmer counties are making their second application to Douglas fir to prevent rhabdocline infection on the new growth. Most fruiting bodies in the Harrisburg area are mature and opening during periods of rain or high humidity. The spores they release are capable of infecting new growth. In Luzerne County, budbreak of Douglas fir occurred last week while Bradford County Douglas firs are breaking bud this week.

Balsam fir is starting to break bud in Adams County.This marks the end of the control period for Balsam twig aphid. For the remainder of the season, growers should rely on naturally occurring predators, such as ladybeetles and syrphid flies, to control the aphids. The larvae of these predators are very adept at crawling between honeydew-coated needles to reach the nymphs and adults of balsam twig aphid. Within the next month, overwintering eggs will be deposited and the aphid will be dormant until next spring.

We continue to capture white pine weevils in our detection traps. Eggs and young larvae are present under the bark of infested terminals at many locations. Growers should start watching for the characteristic terminal wilt, referred to as shepherds crook. On white pine and Douglas fir this is quite pronounced and can be used to identify the terminals that must be removed to mechanically control the weevil infestation.

Pine-pine gall is sporulating on Scotch pine in Perry County. This rust disease of pine easily spreads through a plantation and is capable of killing lateral branches. Trees already infected should not be removed until the sporulation period has passed. To determine if pine-pine gall is the cause of dead lateral branches in your Scotch pine, look behind the dead tissue for a branch enlargement. The galls can be the size of a walnut, up to the size of a softball. There is no cure for the rust once it is established in a branch.

According to a report from Luzerne County, another rust that is sporulating this week is spruce needle rust. This is a relatively new disease and is specific to spruce in northeastern counties. Needles infected last year will have yellow bands with orange pustules. The orange spore mass is usually on the undersides of the needles and is quite noticeable during sporulation. As with rhabdocline on Douglas fir, the new growth of Colorado spruce must be protected from infection by application of a protective fungicide.

Pine bark adelgids nymphs have emerged from egg masses under the female and are active feeding on the candles of eastern white pine. Their feeding on the tender growth may cause yellowing and stunting. Natural enemies appear to have been keeping these adelgids in check during the last several years.

Spruce spider mites continue to feed and spin silk at many locations. The cool days and even cooler nights favor buildup of large populations of this pest. If your trees sustained damage last year and mites are present again this year, you may wish to consider application of a miticide. In addition to the obvious chlorosis associated with spider mite feeding, premature needle loss of cut trees is a common complaint. Most miticides require two applications, 7 to 10 days apart, to control the population. If you used one of the newer chitin inhibiting miticides, you may observe active mites for several days following application. These miticides prevent molting into the next stage but do not offer quick knockdown associated with some other materials.

Cooley nymphs are feeding on new growth of Douglas fir and causing pale spots on needles as well as the typical needle kinking. It is too late to be effective with any control. The next opportunity will be in fall, from mid-September through most of October.

Gypsy moth larvae are active and feeding on spruce trees in Snyder County. This introduced pest prefers to feed on many hardwoods but, when they find themselves in the middle of a conifer block, they will do their best to survive. Defoliation of conifers, resulting in tree death is rare. However, partial defoliation is not uncommon. In addition, egg masses deposited on trunks of host trees will be of concern for growers wishing to ship trees out of the Gypsy Moth quarantine area.

European pine sawfly larvae are continuing to feed on Scotch pine in Lebanon and Snyder counties. The larvae are ½” long and causing considerable defoliation. At this time, general sprays are not as effective as directed sprays or hand removal of the larvae.

For those growers in southeastern locations, a note about cryptomeria scale. At sites we are monitoring, females have not started to deposit eggs. We will keep you informed of the status and when the first generation crawlers are emerging.

The next report will be available after 4 PM on Friday, May 18.