An ecological study of the damage done to avocado fruits by citrus leafhopper Penthimiola bella (Cicadellidae) and coconut bug Pseudotheraptus wayi (Coreidae) in South Africa

Feeding on young avocado fruit by citrus leafhopper Penthimiola bella (Still (Homoptera: Cicadellidae) causes protrusions on the surfaces of the maturing fruits, rendering them unacceptable for export. In the present study it was found that the incidence of protrusions on Hass avocados (10%) was five times greater than on Fuerte (2%) avocados. The damage was inflicted during early fruit development and did not increase above 11% (average 9%) during the study period. Protrusions were distributed throughout the study site with no edge effect. Feeding was strongly linearly density-dependent, and fruits with protrusions were not aborted (i.e. the trees utilize resources to mature fruit that are lost to the grower). A technique for monitoring the incidence of fruit bearing protrusions is described. In contrast, feeding by coconut bug Pseudotheraptus wayi (Brown) (Heteroptera: Coreidae) was exponentially density-dependent, but did enhance fruit drop. The mass of indented fruit was 28% lower than that of healthy fruit and those bearing protrusions, indicating that these fruits are less energy-expensive than those bearing protrusions whose mass did not differ from that of healthy fruits.