San Jose scale and other scale insects - chemical control

Insect growth regulators (IGRs)
Insect growth regulators are chemicals which interfere with the development of insects. Many are of low human toxicity and are selective because they are specifically targeted at processes occurring in particular stages of insects e.g. moulting of scale insects. There is one IGR currently registered (below) for scale control on apples, and its selectivity makes it the preferred chemical for use in IFP. Another IGR called fenoxycarb (Insegar®) is not registered in New Zealand but is used for scale control overseas. The registered chemical is:

Buprofezin (Applaud®). This IGR belongs to the chemical group thiadiazines, which interfere with the development of the insect's exoskeleton (chitin synthesis inhibitor). It is toxic to eggs and disrupts moulting of the young stages of scale insects, with similar effects on mealybugs, whiteflies, and Froggatt's apple leafhopper. It does not control adults but reduces the development of females and lowers their egg production (fecundity). It is selective, being non-toxic or of low toxicity to many beneficial species.

When spraying of an IGR for scale control is justified at green tip, it is normally combined with oil to improve coverage and efficacy. However, oil should not be used at green-tip on oil sensitive cultivars such as Cox's Orange. An application of insecticide alone should be applied instead.

Spraying of scale-infested shelter can contribute significantly to improving scale control. Because shelter species often provide a refuge for beneficial insects, the preferred IFP insecticide treatments are 2% oil or 2% oil + Applaud® in spring. 2% Oil is also effective in summer if applied at the start of crawler release.