Interference of ants (Hymenoptera: Formicidae) with biological control of the vine mealybug Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae)

Anagyrus sp. and Coccidoxenoides perminutus are well known parasitoids used for the biological control of the vine mealybug Planococcus ficus, a key pest in vineyards. In South Africa, three ant species, Anoplolepis steingroeveri, Crematogaster peringueyi and Linepithema humile form a trophobiotic relationship with the vine mealybug in vineyards and promote the latter’s infestations to unacceptable levels. In a manipulative laboratory experiment, ants and parasitoids were allowed to forage on vine mealybug-infested butternuts and numbers were recorded for a 1 min period at 10 min intervals for 2 h. Parasitoid mortality and the number of parasitized vine mealybug females were then recorded in the presence and absence of the three ant species. Data were analyzed using a repeated measures generalized linear model (GEEs). The mean number of ants and parasitoids on the mealybug-infested butternuts differed significantly between ant species and time intervals (p < 0.0001 in all cases). Crematogaster peringueyi and L. humile caused significantly higher mortality of both parasitoids than A. steingroeveri during the 24-h exposure period (p < 0.0001). Coccidoxenoides perminutus parasitized significantly more vine mealybugs than Anagyrus sp. for all treatments (p < 0.0001). Ants should therefore be controlled prior to release of parasitoids to suppress populations of ant-tended Hemiptera in vineyards.