Coleotechnites spp.

Hemlock needle miner damage. (Photo: Connecticut Agricultural Experiment Station, Bugwood.org)
Scientific Name: 
Coleotechnites spp.
Common Name: 
Hemlock Needleminer
Growing Degree Days (GDD's): 
None available at this time.
Host Plant(s) Common Name (Scientific Name): 
Hemlock (Tsuga spp.)
Insect Description: 

Johnson and Lyon (1991) notes that there are at least 45 species of small, narrow-winged, and generally gray colored moths in this genus, all of whom are leaf miners in their caterpillar stage. Two species are referred to as the green hemlock needleminer (Coleotechnites apicitripunctella) and the brown hemlock needleminer (Coleotechnites macleodi) and have very similar life cycles on hemlock. The green hemlock needleminer is a leaf mining and webbing insect found both in Canada and the United States. In mid-to-late July, the young larva enters the needle at the base and begins to mine the needle. It will continue this feeding behavior until the end of the season. Immature larvae overwinter in their mines and begin feeding again in the spring. Once fully mature, the larva will leave its mines and tie multiple needles together with silk. At that time, the insect will feed externally from the needles, feeding between the midvein and the leaf margin. This feeding injury is considered diagnostic of either species. By the time this feeding injury is produced, the larva is 6-8 mm in length. Coleotechnites apicitripunctella are pale green caterpillars with light brown heads with occasional hairs seen on the body under magnification. Caterpillars will pupate by the early summer inside a silken tube formed within the webbed together needles. C. macleodi larvae are reddish brown in color and undergo a very similar life cycle and timing of activity in the season. Both species are found in eastern Canada and the northeastern United States. 

Damage to Host: 

These small caterpillars web several needles together and skeletonize them, causing needles to brown. Typically, injury is aesthetic only and management is not necessary. On occasion, localized outbreaks may occur in urban and forested areas.

Monitoring: 

Starting in mid-to-late July, monitor for mining in hemlock needles. By the fall, look for browned or pale colored needles that are webbed together.

Cultural Management: 

Prune out and destroy mined needles before the spring, or whenever found.

Natural Enemies & Biological Control: 

None noted.

Chemical Management: 

Not necessary.

Notes: 

Chemical management of this insect is not necessary.

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