Several scale insects attack peach trees. The most common scale are white peach scale and San Jose scale, both serious pests, and both usually present to some extent in every orchard. The white peach scale, also called West Indian peach scale or Oleander scale, destroyed numerous peach orchards in Florida and Georgia in the early 1900s. Both scale insects attack many plants. Scales will cause branch die back and eventually tree death if not treated.
White peach scale have as many as four generations per year in Florida. Adult females begin laying eggs two weeks after mating and continue to lay eggs for nine days before dying. The first eggs are orange and will hatch female offspring, while later eggs are white and hatch male offspring. The young crawlers emerge 3-4 days after being deposited and move about the host plant for up to 12 hours before settling to feed. Adult females are dull white to yellowish, immobile and covered with a protective waxy shell sometimes camouflaged with bits of bark. Adult males have a long white to yellowish colored shell and emerge as an orange winged adult to fly to females located by pheromones. More details and photos.
Crawlers emerge during the growing season and may be monitored with black tape coated with petroleum jelly. The yellow mite-like crawlers are easier to see on this dark background. Place tape on a branch where scales are located, monitor twice weekly, and replace every two weeks. Crawlers are the most vulnerable life stage to chemical control. Spray recommendations for dormant and growing season may be found in the Southeastern Peach, Nectarine and Plum IPM and Culture Guide.
The San Jose Scale looks different from the white peach scale, but is monitored and controlled in a similar fashion. More details.
Several predators feed on white peach scale in Florida, including ladybird beetles, lacewings, and parasitoid wasps. However, these are not sufficient to control large infestations.
Scale insects overwinter on trees and this is the easiest time to target control. Every year two dormant oil applications should be made to every acre. Dormant oils are more effective than summer horticultural oils and more phytotoxic. Dormant oil sprays are applied dilute at 150-200 gallons/acre timed for early winter, just after 95% of the leaves have fallen, and again in spring as buds swell and begin to break. Apply when temperatures are within 280 to 650 range and there is no forecasted harsh cold snap within the next 2-3 days to avoid phytotoxicity. Thorough coverage is critical.