Charles, J.G., Cole, L., Mundy, D., & Walker, J. 2005 Soft scales in New Zealand vineyards . Research report commissioned by Winegrowers New Zealand Ltd. No. 15419: 4 pp.

Notes: ‘Soft scales’ (Hemiptera: Coccidae) are sap-sucking insects in the superfamily Coccoidea. They are closely related to armoured scale insects (Diaspididae) and mealybugs (Pseudococcidae). Coccidae have an ‘open’ digestive system, and they produce copious quantities of honeydew (like mealybugs, but unlike armoured scale insects). Their biology is often not well known. This is especially so in New Zealand. There are many species of native Coccidae in New Zealand, but all of the pest species are exotic (Table 1). They are all rather similar, and some species are very polymorphic (i.e. the same species may come in different shapes, sizes and colour). Identification can often only reliably be made by an expert taxonomist. Most of the pest species are parthenogenetic – reproducing from females only – and may produce many hundreds of offspring / female. Yet, unlike mealybugs, they are usually univoltine (have only one generation a year), which tends to reduce their ability to spread rapidly. The result is that populations of these scale insects tend to be very patchy – often occurring on only a few vines in a block. Because they also usually live on the wood (rather than on leaves), and are generally a rather dark, mottled brown colour, they are very inconspicuous and their presence may go undetected for many years. Even though they may produce copious quantities of honeydew, this can often be mistakenly associated with other insects such as mealybugs. The exotic soft scales present in New Zealand are well known as important or minor pests from many countries around the world. On fruit crops, they are generally considered minor pests because of the honeydew they produce. If, as suspected, they are proved to be vectors of grapevine leafroll disease, then they may well have to be considered major pests in New Zealand vineyards.