Yew fletcher scales weaken plants by sucking the sap out of the leaves and twigs. This loss of plant fluid causes yellowing of the needles and early needle drop and can cause tip dieback with heavy infestations. They also create large amounts of honeydew, a sugary, sticky material that results in a crusty black sooty mold on foliage and branches.
Apply RTSA Horticultural Oil as a dormant spray to smother second instars overwintering on dormant twigs. A dormant oil spray should be applied to the trunk and branches of a tree in the spring before the leaves emerge. Spring soil applications of Xytect may provide acceptable levels of control if applied approximately 30 days prior to crawler activity. Transtect can be applied to the soil in early spring to kill current year crawlers. When an infestation reaches an undesirable level, the primary goal is to control the crawler stage of the insect’s life cycle. Crawlers are most active in the early summer, and are very susceptible to insecticide control. Once settled on leaves or twigs, they secrete a waxy covering that provides protection, so timing of sprays is important.
Arborists should use foliar sprays for immediate activity against crawlers for management of overwintering females on twigs with dormant sprays. Properly timed foliar sprays during crawler activity and as well as dormant oil sprays are generally effective against this pest. Properly timed soil applications of Xytect or Transtect will work extremely well for most soft scales.
Signs of Damage
- Yew fletcher scales are usually located deep within the plant canopy
- Yew fletcher scales produce large amounts of honeydew(a sugary, sticky material) that results in a crusty black sooty mold on foliage and branches
- Ants, bees, and wasps may be attracted to the honeydew, and could be a cue to look for yew fletcher scale
- Severe infestations can weaken plants, causing the needles to turn yellow and early leaf drop
- Crawlers are oval, flat, and yellowish
- Adult females are yellowish brown, dome-shaped, about 2-4 mm in diameter, and found on small twigs
- Heavily infested trees may display dieback of branches and twigs
Photo: Whitney Cranshaw
Colorado State University, Bugwood.org
Trees At Risk
Yew is preferred, but arborvitae and juniper and bald cypress are also susceptible
- After overwintering, the yew fletcher scales begin rapidly developing in the spring.
- Females begin laying 500-600 eggs per adult female in late spring, which hatch into crawlers when accumulated GDD reaches 730 GDD between May and early July and remain on the plant for the remainder of the season.
- Crawlers are most active from June to July(900-1388 GDD).There is one generation per year.
University of Minnesota
University of Illinois
A Treatment Guide is designed to help you identify a pest issue and management solutions. Always refer to product label for all rates and approved uses. Some images courtesy of forestryimages.org or Wikimedia Commons. Use of the images does not imply endorsement of treatments by forestryimages.org