Biological control against Opuntia aurantiaca Lindley (Cactaceae) and the perceptions of land-users in the Eastern Cape Province of South Africa

Abstract

ABSTRACT Invasive alien cacti threaten indigenous biodiversity and negatively impact agricultural productivity in the Eastern Cape Province. One of the most problematic species is jointed cactus, Opuntia aurantiaca Lindley (Cactaceae). A biological control agent, the cochineal insect Dactylopius austrinus De Lotto (Dactylopiidae), is mass-reared and released against O. aurantiaca in the province. The aim of this study was to evaluate the efficacy and safety of D. austrinus against O. aurantiaca through post-release monitoring as perceived by land-users. Post-release monitoring indicated that the number of cladodes of O. aurantiaca declined from 30 (SE ± 1.1)/m2 to 5 (SE ± 1.7)/m2 during a 30-month study period. Forty-seven land-users who had received D. austrinus for O. aurantiaca were interviewed with standardised questionnaires. Most land-users perceived biocontrol as effective, with 71% of land-users reporting a decrease of O. aurantiaca after the release of D. austrinus, and 62% of land-users indicating that the reduction in O. aurantiaca had resulted in environmental and agricultural benefits. Ninety-four per cent of the land-users perceived biocontrol as a safe method without non-target impacts. This study confirms that biological control has been accepted by land-users and they believe it is effective and that mass-rearing of the agent should be increased so that more releases can be made.