June 4, 2008

Christmas Tree Scouting Report #11 - June 4, 2008

This report is compiled by Sarah Pickel of the PA Department of Agriculture from the scouting recordings of Jim Fogarty and Kyle Halabura of Halabura Tree Farms, Gerald Nesvold of Tannenbaum Enterprises in Schuylkill County, Susan Newhart of Arcadia Trees in Indiana County, and Sandy Gardosik, Karen Najda, and Cathy Thomas of the PA Department of Agriculture.

In Lehigh and Schuylkill Counties, Cryptomeria scales on Frasier and Canaan firs are just beginning to lay eggs.  Growers can expect to see heavier egg laying next week.  Within two weeks of the appearance of eggs, crawlers will begin to emerge.  The crawler stage is the life stage that is most susceptible to insecticide sprays because the young scales have not yet developed the protective, waxy scale covering.  The recommended spray program for this scale is to spray once when the crawlers emerge and then to spray a second time 7 to 10 days later.  If the population is very heavy, a third spray may be necessary 7 – 10 days after the second spray.

In Adams County, females of Elongate Hemlock scale are laying eggs.  Because this scale may over winter in several life stages, crawlers may be present now.  Growers can start their spray program now because of this.  There are two options:  spraying 3 times, once every 4 weeks, or spray 4 times, once every 3 weeks.  For product options, check the 2008 Insecticides and Miticides list for PA Christmas Tree Pests available.

In Lehigh and Schuylkill Counties, Rabdocline and Swiss Needlecasts continue to sporulate on Douglas Fir and Spruce Needle Rust continues to sporulate on Colorado Blue spruce.  Growers may want to consider applying a fourth fungicide spray.  This should be applied 2 – 3 weeks after they applied their third spray.

White Pine Weevil larvae have been found feeding in tree leaders in Lehigh County.  Wilting damage is beginning to be visible.  Growers will want to be on the look out for the typical shepherd’s crook symptom in fields with susceptible trees (White and Scotch pine, Serbian, Norway and Colorado Blue spruces, and Douglas fir).  By cutting out the infected leaders below the point of larvae feeding, growers will prevent the emergence of those adults in their fields.

While no one has yet reported the emergence of bagworm larvae from their cases, hatched larvae, or caterpillars have been found inside of cases in Lehigh County.  Growers may expect to see larvae emerging from cases soon.  One means of control is to hand pick the bags and remove them from the fields before the larvae emerge.  For more serious infestations, a Bt (Bacillus thuringiensis var. kurstaki) solution may be applied to control the young larvae.  Several trade names, such as DiPel and Foray are commercially available.

Some growers have expressed concern about seeing gypsy moth larvae in their conifers.  When populations of the moth are high, as they are this year, these larvae can move away from the tree line and into conifer plots.  While oak and other hard woods are their preferred hosts, they can feed on conifers.  If clusters of the larvae are found on trees, they can do damage to the tree.  If control is necessary, growers can use any of the insecticides listed on the Insecticides and Miticides list.  The PA Bureau of Forestry uses Bt in its spray program, so this is an option for growers as well.  For more information on the gypsy moth, visit the PA Bureau of Forestry website at:

On a positive note, lady beetles have been very visible in several of the fields I visit.  The larval and adult stages of these insects are important predators in Christmas tree farms.  This larva was feasting on Balsam twig aphids.  Growers can be pleased when they see these beneficials in their fields.