Dynamics of Diaspis echinocacti (Bouché) on opuntia spp.: insights for pest management and breeding programs

Abstract

Diaspis echinocacti (Bouché), a globally distributed cochineal scale insect, poses a significant threat to Opuntia spp. in Morocco and worldwide. This study explores the ecological dynamics of D. echinocacti across different Opuntia spp. varieties, employing antixenosis and antibiosis tests in a controlled greenhouse environment (25.3 ºC). In the antixenosis test, Opuntia spp. varieties displayed varying levels of resistance at 6–24 h post-infestation. Marjana and Belara exhibited early resistance with significantly lower numbers of insects (6 h: 4.4, 9.8; 12 h: 3.2, 5.1; 24 h: 2.3, 4.4), while Aakria, Ghalia, and Karama sustained higher susceptibility (6 h: 71.3, 82.1, 85.6; 12 h: 75.2, 89.6, 105.6; 24 h: 105.6, 110.3, 118.0). In the antibiosis test, the life cycle, behavior, and reproductive parameters of D. echinocacti were assessed. Marjana and Belara exhibited longer early nymphal stages compared to Aakria, Ghalia, and Karama. Longevity in both females and males was highest in Ghalia and Karama, while Marjana and Belara showed the shortest duration. Female life cycles ranged from 63.4 to 88.2 days, with Marjana and Belara having the shortest durations and Karama the longest. Fecundity was highest in Karama (152.80 eggs) and lowest in Marjana (12.60 eggs). Population growth parameters highlighted that Karama (r = 0.09, λ = 1.10, R₀ = 61.73) and Ghalia (r = 0.09, λ = 1.09, R₀ = 56.54) exhibited the highest intrinsic rate of increase, finite rate of increase, and total reproduction per generation. This study offers essential insights into D. echinocacti dynamics, informing pest management and advancing our understanding of ecological interactions in cactus ecosystems, particularly for breeding programs targeting Opuntia spp. resistance to scale insects.