Below is a summary of control methods. For more detailed explanations, consult the UC IPM Guidelines for Citrus: Citricola scale.
Biological Control: Metaphycus wasps attack soft scales including citricola scale, black scale and brown soft scale. These parasites are very effective in southern California where the weather is a fairly uniform temperature. In the San Joaquin Valley they are not effective in reducing citricola scale below damaging levels because there are periods of time during summer and winter when weather conditions are too extreme for the parasites and during the summer there are no suitable stages of scale available for parasitism (2nd instar scales).
Cultural Control: Reduce dust and ants that may hinder natural enemies, prune trees to achieve better spray coverage and conduct activities that produce a vigorously growing tree.
There are four groups of insecticides that are effective in reducing citricola scales, but each has characteristics tht may make it more more appropriate for a a particular orchard.
Organophosphate and carbamate insecticides
These pesticides act as broad spectrum nerve poisons. They are toxic to the scales and their natural enemies. They were very effective for many years. In fact, treatments for thrips and red scale reduced citricola scale below detectable levels. They are best applied during July-September when the scales are small and on the leaves on the outside of the tree. There is evidence of resistance developing in some San Joaquin Valley populations.
These insecticide can be applied to the foliage or the root system. They are broad spectrum and will eliminate most natural enemies. They are moderately effective against adult females in the spring, but are best applied when the scales are nymphs on the leaves on the outside of the tree.
Foliar: Provado (imidacloprid), Assail (acetamiprid)
Systemic: Admire (imidacloprid), Platinum (thiamethoxam)
Insect Growth Regulators:
These pesticides prevent scales from molting to the next stage. Because citricola scale doesn't molt very often insect growth regulators are slow acting.
Narrow Range Petroleum Oils:
Oils kill by smothering the insect on contact. They are only temporarily toxic to natural enemies. They are only partially effective against citricola scale and sometimes require more than one treatment per year. This is the only option available for organic growers.
415, 440, and 450 distillation point oils