Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) and Streptomyces bellus E23-2 for managing Dactylopius opuntiae (Cockerell) (Hemiptera: Dactylopiidae) on Opuntia spp

Abstract

Dactylopius opuntiae (Cockerell) (Hemiptera: Dactylopiidae) is a key pest of Opuntia spp., requiring effective management strategies. This study assessed the efficacy the predatory mite Amblyseius swirskii (AS) (Acari: Phytoseiidae) and the entomopathogenic bacterium Streptomyces bellus- E23-2 (SB), both individually and in combination, against D. opuntiae under both laboratory (26 °C) and greenhouse (ranging from 23.5 to 28.8 °C) conditions. Treatments included: T1 – untreated control, T2 – 0.003% Tween 80 (TW), T3 – AS alone, T4 – SB alone, T5 – SB + AS, and T6 – d-limonene (DL) (positive control). In both settings, S. bellus and d-limonene were applied at 30 mL per plant, followed by the release of predatory mites one week later. The experiments spanned five weeks. The combined treatment SB + AS demonstrated the highest efficacy in reducing egg counts (egg counts decreased to 7.78 (lab) and 7.44 (greenhouse) by week 5). Similarly, motile stages were reduced to 6.50 (lab) and 5.22 (greenhouse) per cladode. The SB treatment alone produced the highest number of mummies (42.0 in the lab, 32.9 in the greenhouse) by week 3. Predator mite densities peaked in the AS treatment (36.6 in the lab, 25.4 in the greenhouse) by week 3, with no significant difference between AS and SB + AS treatments in the greenhouse. Overall, the SB + AS treatment effectively reduced D. opuntiae populations, preserving plant health, as indicated by high visual quality scores (>9.60) by the end of the study. This integrated approach highlights the potential of combining biological agents for sustainable management of D. opuntiae on Opuntia spp.