White Peach Scale

White peach scale, Pseudaulacaspis pentagona, is believed to have originated in Japan or China, although one report places the point of origin in Italy where it was first described in 1886. This insect is an important economic pest of peach trees as well as woody ornamentals in the southeastern United States. In the early part of this century, white peach scale destroyed numerous peach orchards in Florida and completely decimated a grove of 10,000 peach trees in southern Georgia

Treatment Strategy

Management of this scale is difficult. Crawlers must be targeted because adults create an impermeable wax covering. There is generally a 7 to nine day period when crawlers are susceptible to insecticides. To determine when this stage occurs one must observe when egg hatch occurs, and when crawlers are actively moving. Check scale development twice a week to find crawlers. The timing of these insects varies among regions.

Other Treatment Practices

  • In southern states, several predators were found to prey on white peach scale: ladybird beetles, lacewings, gall midges.
  • Few parasitoids (wasps) are available for biological control.

Limb/Foliar Spray, Soil Application, or Basal Bark Spray Using Transtect

Tree Injection Using Transtect Infusible

Foliar Spray Using Proxite + RTSA Horticultural Oil

Foliar Spray Using RTSA Horticultural Oil

Expected Results

This is a difficult scale to control and multiple applications of chemical may be needed. Dead scales may remain on the plants. Contact sprays such as bifenthrin and distance should be reapplied to each new flush of growth when active crawlers are present (every 14-21 days). Crawlers must be targeted because adults create an impermeable wax covering. Transtect Infusible as a tree injection treatment for trees that cannot be treated with foliar sprays or other systemic options. In one trial bark application rates of Transtect seemed to work when applied directly to the insects.

Signs of Damage

  • Foliage of infested trees may become sparse and yellow
  • Fruit size may be reduced and premature drop is likely to occur
  • Heavy infestations can result in the death of twigs, branches, and even trees if left unattended for 2 to 3 years
  • In severe cases, insects appear as white, cottony masses encrusting the bark of the tree
  • Female scale is 1 to 2.25 mm in diameter, circular, convex, and thickened
  • It is white, yellowish white, or grayish white with a yellow or reddish spot
  • The male adult scale is a small, two-winged insect that looks like a gnat but has two tail filaments
  • Crawlers are active:
    • May to mid-June, 145-260 GDD
    • mid July to mid-August, 707-1151 GDD
    • the month of September, 2000-2400 GDD

Photo: Patrick Anderson, Rainbow Ecoscience

Photo: John A. Weidhass
Virginia Polytechnic Institute and State University, Bugwood.org

Trees At Risk

Peach, cherry laurel, chinaberry, flowering peach, mulberry, French mulberry, and persimmon; but other hosts include catalpa, lilac, privet, and walnut.

Biology

  • There are two generations per year in northern states. In the southern states, there are as many as four generations per year.
  • Overwinter as adult females.
  • Eggs are laid underneath their scales in the spring. Nymphs hatch from eggs in about 4 days.
  • Adult females develop from the second nymphal stage in about 12 days, and winged males develop for about 5 days.
  • Development from egg to adult can occur within 35 to 40 days. •Mated females begin laying eggs after about 16 days.
  • In general crawler activity in which treatment will be effective occurs within 145-260 GDD, 707-1151 GDD, and 2000-2400 GDD.

References

University of Florida Institute of Food and Agricultural Sciences
http://entnemdept.ufl.edu/creatures/orn/scales/white_peach_scale.htm

Texas A&M University
http://insects.tamu.edu/fieldguide/bimg113.html

VirginiaTech University
http://www.virginiafruit.ento.vt.edu/WPS.html

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

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