Upon molting to adults, the shell hardens and becomes opaque. These scales are normally kept under control by native parasites. Because of the increase in chemical treatment in pistachio, natural enemies of scales are more frequently destroyed, and soft scales are becoming more prevalent. In spring, they produce heavy amounts of honeydew, which can affect photosynthesis. Moderate to high scale populations can also retard shoot growth and shell splitting.
Scales are most common on vigorously growing trees.
An effective parasite of soft scales is a tiny parasitic wasp, Metaphycus luteolus, which destroys the scale in its early instars before it can reproduce or cause substantial injury. This parasite produces several generations. There is a strong, indirect relationship between Phytocoris plant bugs and populations of soft scales. Where Phytocoris plant bugs are plentiful, scale populations are commonly low. When dormant oil is applied in January or February, trees bloom somewhat earlier in spring, and they become more susceptible to frost damage.