Climate change and its influence on scale insects and sooty mould occurrence

Discussions of potential changes in climate rarely consider how changes may affect the impact of pest insects on the yield of agricultural crops. Grain crops in temperate regions have been suggested to experience greater reductions in yield compared with more tropical-grown crops, such as rice. Grapevines are typical of temperate plants and therefore may be more susceptible to the effects of various pests as temperature and humidity change in the future. Soft scales of the genus Parthenolecanium have been reported to infest grapevines in Australia since early last century and have become more noticeable in the last 10 years as climate patterns have changed. By producing honeydew and initiating the growth of sooty mould on grapes and leaves, vineyards have suffered yield reduction and economic losses. This paper includes a series of graphical models that indicate how temperature and humidity changes associated with climate change can result in increased likelihood of sooty mould production on leaves and fruit. Increases in temperature can lead to two complete life cycles being present during the growing season. Increases in both scale population and honeydew production rate coupled with increases in humidity and temperature can result in honeydew residues that persist longer on leaves and fruit. As abiotic conditions change, differences in the cultivars with respect to scale infestation may provide ways of controlling the extent of sooty mould in the future.