Despite various environmentally-sensitive control techniques for the tortricid complex, many macadamia growers still prefer to use contact insecticides. For maximum efficacy, these chemicals have to be applied against eggs and neonate larval instars. Timing and spray target selection are therefore two very important factors to consider when a contact insecticide is used against this pest complex. Current results indicate higher incidence of the total number of tortricid eggs in the basal section of the tree but no statistically significant differences in the abundances of larval stages as well as number of infested nuts at the various heights were evident. More eggs were recorded in the denser inner parts of the trees than in the parts of the trees facing towards the working rows. While this phenomenon could possibly be related to the shielding of pesticides by dense lower side branches, a similar trend was also visible in sparsely-foliaged orchards where negligible shielding could have occurred. Findings from the density survey indicated that this pest complex has a propensity for denser orchards and it is postulated that tree density rather than tree height is the overriding factor affecting tortricid dispersal in South African macadamia orchards. It was speculated that higher oviposition rates in denser parts of macadamia orchards could be related to predator/parasitoid avoidance.
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Vol. 24 • No. 2