Optimizing Opuntia spp. Protection: Parasitoids and Microorganisms Agents for Diaspis echinocacti Management

Diaspis echinocacti (Bouché) (Hemiptera: Diaspididae) damages Opuntia spp. by feeding on the cladodes, reducing photosynthesis and causing economic losses. This study explored an integrated pest management approach to control D. echinocacti, using a combination of parasitoids species [ectoparasitoid Aphytis debachi Azim (Hymenoptera: Aphelinidae) and endoparasitoid Plagiomerus diaspidis Crawford (Hymenoptera: Encyrtidae)] and entomopathogenic microorganisms (Alternaria murispora Ariyawansa and Hyde, Alternaria destruens (Simmons), and three different Streptomyces species: Streptomyces bellus Margalith and Beretta [strains E23-2 and E25-12], Streptomyces galilaeus (Ettlinger et al.), and Streptomyces africanus (Meyers et al.). Laboratory trials showed that A. murispora and A. destruens at 10¹⁰ conidia mL^-1 achieved the highest mortality rates (57.2% and 52.2%, respectively) after 14 days of application. Streptomyces species also proved effective, with S. bellus-E23-2 and S. galilaeus causing significant mortality (53.8% and 49.8%, respectively) at 10¹⁰ CFU mL^-1. Combining parasitoids with these entomopathogens yielded varied results, with a notable success in the pairing of P. diaspidis with A. murispora at 10¹⁰ conidia mL^-1 (89.7% mortality) and P. diaspidis with S. bellus-E23-2 at 10¹⁰ CFU mL^-1 (86.3%). These findings revealed a mix of antagonistic and additive interactions, emphasizing the complexity of combining these biological agents. Semi-field trials confirmed the laboratory results, with P. diaspidis + A. murispora at 10¹⁰ conidia mL^-1 achieving 50.4% mortality and P. diaspidis + A. destruens at 10¹⁰ conidia mL^-1 reaching 49.2% mortality after 14 days of application. Thus, the accurate mix of biological control agents can effectively contribute to D. echinocacti management, emphasizing the importance of considering their interactions.