Eucalypt susceptibility towards the invasive Glycaspis brimblecombei Moore (Hemiptera: Aphalaridae) in South Africa

Abstract

Glycaspis brimblecombei (Hemiptera: Aphalaridae) is a eucalypt feeder native to Australia. Infestations of G. brimblecombei can cause leaf wilt,  dieback and death in weak or severely infested plants. In many countries where G. brimblecombei has been introduced, patterns of susceptibility of different Eucalyptus hosts have been observed or tested. However, these host susceptibilities are not always comparable between countries due to the different composition of species planted, and the possible influence of the different environments on host susceptibility. We investigated the patterns of host susceptibility of 28 commercial eucalypt varieties in South Africa by comparing the number of early and late instar nymphs, using both choice and no choice tests. We also examined the possible influence of leaf colour on susceptibility, following a previous report that G. brimblecombei preferred red to other colours. Our study confirmed the susceptibility of specific varieties towards G. brimblecombei, in particular Eucalyptus grandis W.Hill × Eucalyptus camaldulensis Dehnh. One of the least and one of the most susceptible eucalypts had almost identical  wavelengths, indicating that leaf colour, with particular reference to red, is unlikely to play a role in host plant selection.

Keywords: Eucalyptus, host location, host susceptibility, leaf colour, spectrophotometer, vision