White Peach Scale Diagnostic Guide
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.
Trees at Risk
White peach scale affects peach, chinaberry, flowering peach, French mulberry, Cherry laurel, and persimmon; but other hosts include catalpa, lilac, privet, and walnut.
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.
- 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.
Management of this scale is difficult. Crawlers must be targeted because adults create an impermeable hard wax covering. For each generation that is produced, there is generally a 7 to 9 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.
* Consider using 0.5% v:v RTSA Horticultural Oil with insecticide spray applications to increase penetration, adherence and residual length of control of the insecticide.
Other Treatment Practices
- In southern states, several predators were found to prey on white peach scale: ladybird beetles, lacewings, and gall midges.
- Few parasitoids (wasps) are available for biological control.
This is a difficult scale to control and multiple applications of chemical may be needed. Dead scales may remain on the plants until new flushes of growth are produced by the plant.
A Diagnostic 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 forestryimages.org. Use of the images does not imply endorsement of treatments by forestryimages.org