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June 7, 2002

Christmas Tree Scouting Report

 

 

Welcome to the Christmas Tree Scouting Report for the week ending May 31. The next report will be available after 4 PM on Friday June 7. 

Last week's report contained an error in the information regarding pine tortoise scale in Dauphin, Northumberland and Perry counties. The scale in question is actually striped pine scale, not pine tortoise scale as reported. These two soft scales have been often confused and can only be accurately identified by examining one or more stages under a microscope. Field identification is not accurate.

For many years both of these soft scales on Scotch pine were called tortoise scale but a scale expert finally made separation of the two species possible in the mid-1990's. Following his publication, it was apparent that most of the scales we were seeing in Christmas tree farms are actually striped pine scale. However, the life histories of the two species are quite similar, with a single generation each year. There did not appear to be much difference in timing of crawler emergence so, for the most part, accurate identification was not critical.

In 2002, crawlers of pine tortoise scale were identified by Jim Stimmel, PDA entomologist, from Adams County during the week of May 20. Curiously, female soft scales on Scotch pine at a nearby site had not deposited eggs on the same day these crawlers were observed. At several sites in Dauphin, Northumberland, and Perry counties, females were still not depositing eggs the following week. This week, however, crawlers were active at the sites in Adams and Northumberland counties and they were positively identified as striped pine scale. Could the crawler emergence periods for the two species of scale actually be separated time wise? Regardless of whether or not you grow Scotch pine, these observations point out that regardless of what the "spray schedule" indicates, the time to spray is when the susceptible stage is present at YOUR site.

In Lebanon County, the attractive yellow, white and black larvae of the introduced pine sawfly are feeding on white pine. They are approximately 3/8" long and can be difficult to find at this size. This sawfly does not feed in a group, as does the European pine sawfly, so detection can be more difficult. Damage is rarely severe but with two generations each year, the introduced pine sawfly has the potential to cause serious damage to both last year's and the current year's needles.

In Columbia County, web-spinning sawflies were also found on eastern white pine. These larvae build nests of loose silk and frass and consume entire needles around the nest. They are rarely common enough to require chemical control. Hand removal of the nest is a more economical, direct approach. To distinguish these green larvae with black heads from other sawflies, look for a pair of "feelers" on the back end of the larvae.

Cinara aphids are extremely active on spruces and pines at this time. This is the aphid species that the consumer can confused with ticks emerging from their Christmas trees. Although Cinara aphids don't usually cause serious damage, high populations may result in tip burn on needles of spruce. The aphids are easy to locate on branches, particularly near the top of the trees. Look for the presence of large black ants, drawn to the site by the honeydew excreted by the aphids. Colonies of aphids are another one of Nature's curiosities. Like the sawfly larvae that respond to threats by rearing up, these insects quickly move, en mass, to the other side of the branch when approached.

In Northumberland County, bagworm larvae are approximately 1/8th inch in length and causing damage as they feed on new growth of Douglas fir. This is the ideal time to control the young larvae - when they are actively feeding but still young. Bacillus thuringiensis, or Bt, is very effective on these caterpillars if used at this stage.

In Columbia County, white pine weevil damage is evident on white pine and spruce. The bark is "soggy" to the touch where larvae have consumed all the inner bark, leaving only red-brown frass. At this time, the only available control is removal of infested tissues. The tops should be cut back to good wood and removed from the field, to be destroyed.

Cryptomeria scale crawlers are hatching from eggs but are remaining under the protective covering of the females on true first in Berks, Dauphin and York counties. In Lehigh County, a grower making observations reported no eggs had hatched by the end of this week. This troublesome armored scale is a serious pest of true firs, particularly in the southeastern counties. It is similar to elongate hemlock scale in its preference for Fraser, balsam, and Canaan fir. However the two species are distinctly different, with different life histories.

Cryptomeria scale, Aspidiotus cryptomeriae, appears to have two generations each year in Pennsylvania - elongate hemlock scale only has one long, drawn-out generation. To separate the two species in the field, the coverings of the adults should be examined closely. In simple, non-taxonomic terms, cryptomeria scales are oval, tan to light gray, with a central yellow area. Elongate hemlock scale females are chestnut brown and, as the name implies, elongate. Male elongate hemlock scales secrete some white waxy threads over their bodies, similar to, but much less than those produced by some of the adelgids. Both scales result in distinct yellow spots on the upper surface of the needles while feeding on the underside and both are difficult to control, requiring repeated applications of registered pesticides. Occasionally, trees with both species can be found in plantations.

Winged adult balsam twig aphids are present in Columbia and York counties and newly deposited eggs were found on new growth of Fraser fir in Adams County. The freshest eggs are light tan with white waxy rods but they quickly turn dark brown to black as they harden. This stage will be present until next spring, when nymphs will emerge prior to budbreak.

The next report will be available after 4 PM on June 14.Welcome to the Christmas Tree Scouting Report for the week ending May 31. The next report will be available after 4 PM on Friday June 7. To receive a FAX of this week's message, please call (814) 865-1636. To report pest activity at your location or request email report, please call 717 772-5229. For local Growing Degree Day information, please go to http://www.nass.usda.gov/pa/ and click on Crop Weather along the top margin.

Last week's report contained an error in the information regarding pine tortoise scale in Dauphin, Northumberland and Perry counties. The scale in question is actually striped pine scale, not pine tortoise scale as reported. These two soft scales have been often confused and can only be accurately identified by examining one or more stages under a microscope. Field identification is not accurate.

For many years both of these soft scales on Scotch pine were called tortoise scale but a scale expert finally made separation of the two species possible in the mid-1990's. Following his publication, it was apparent that most of the scales we were seeing in Christmas tree farms are actually striped pine scale. However, the life histories of the two species are quite similar, with a single generation each year. There did not appear to be much difference in timing of crawler emergence so, for the most part, accurate identification was not critical.

In 2002, crawlers of pine tortoise scale were identified by Jim Stimmel, PDA entomologist, from Adams County during the week of May 20. Curiously, female soft scales on Scotch pine at a nearby site had not deposited eggs on the same day these crawlers were observed. At several sites in Dauphin, Northumberland, and Perry counties, females were still not depositing eggs the following week. This week, however, crawlers were active at the sites in Adams and Northumberland counties and they were positively identified as striped pine scale. Could the crawler emergence periods for the two species of scale actually be separated time wise? Regardless of whether or not you grow Scotch pine, these observations point out that regardless of what the "spray schedule" indicates, the time to spray is when the susceptible stage is present at YOUR site.

In Lebanon County, the attractive yellow, white and black larvae of the introduced pine sawfly are feeding on white pine. They are approximately 3/8" long and can be difficult to find at this size. This sawfly does not feed in a group, as does the European pine sawfly, so detection can be more difficult. Damage is rarely severe but with two generations each year, the introduced pine sawfly has the potential to cause serious damage to both last year's and the current year's needles.

In Columbia County, web-spinning sawflies were also found on eastern white pine. These larvae build nests of loose silk and frass and consume entire needles around the nest. They are rarely common enough to require chemical control. Hand removal of the nest is a more economical, direct approach. To distinguish these green larvae with black heads from other sawflies, look for a pair of "feelers" on the back end of the larvae.

Cinara aphids are extremely active on spruces and pines at this time. This is the aphid species that the consumer can confused with ticks emerging from their Christmas trees. Although Cinara aphids don't usually cause serious damage, high populations may result in tip burn on needles of spruce. The aphids are easy to locate on branches, particularly near the top of the trees. Look for the presence of large black ants, drawn to the site by the honeydew excreted by the aphids. Colonies of aphids are another one of Nature's curiosities. Like the sawfly larvae that respond to threats by rearing up, these insects quickly move, en mass, to the other side of the branch when approached.

In Northumberland County, bagworm larvae are approximately 1/8th inch in length and causing damage as they feed on new growth of Douglas fir. This is the ideal time to control the young larvae - when they are actively feeding but still young. Bacillus thuringiensis, or Bt, is very effective on these caterpillars if used at this stage.

In Columbia County, white pine weevil damage is evident on white pine and spruce. The bark is "soggy" to the touch where larvae have consumed all the inner bark, leaving only red-brown frass. At this time, the only available control is removal of infested tissues. The tops should be cut back to good wood and removed from the field, to be destroyed.

Cryptomeria scale crawlers are hatching from eggs but are remaining under the protective covering of the females on true first in Berks, Dauphin and York counties. In Lehigh County, a grower making observations reported no eggs had hatched by the end of this week. This troublesome armored scale is a serious pest of true firs, particularly in the southeastern counties. It is similar to elongate hemlock scale in its preference for Fraser, balsam, and Canaan fir. However the two species are distinctly different, with different life histories.

Cryptomeria scale, Aspidiotus cryptomeriae, appears to have two generations each year in Pennsylvania - elongate hemlock scale only has one long, drawn-out generation. To separate the two species in the field, the coverings of the adults should be examined closely. In simple, non-taxonomic terms, cryptomeria scales are oval, tan to light gray, with a central yellow area. Elongate hemlock scale females are chestnut brown and, as the name implies, elongate. Male elongate hemlock scales secrete some white waxy threads over their bodies, similar to, but much less than those produced by some of the adelgids. Both scales result in distinct yellow spots on the upper surface of the needles while feeding on the underside and both are difficult to control, requiring repeated applications of registered pesticides. Occasionally, trees with both species can be found in plantations.

Winged adult balsam twig aphids are present in Columbia and York counties and newly deposited eggs were found on new growth of Fraser fir in Adams County. The freshest eggs are light tan with white waxy rods but they quickly turn dark brown to black as they harden. This stage will be present until next spring, when nymphs will emerge prior to budbreak.

The next report will be available after 4 PM on June 14.