Potential of parasitoids to control Diaspis echinocacti (Bouché) (Hemiptera: Diaspididae) on Opuntia spp. cactus pear

Abstract

Abstract Background Diaspis echinocacti (Bouché) is a major pest of cactus pear species worldwide. Over the past three years, this scale insect has seen increasing interest regarding its spread and importance, as well as the efficacy of its primary parasitoids Aphytis debachi Azim, and Plagiomerus diaspidis Crawford, as biocontrol agents. Infestation of cactus pear plants by D. echinocacti and parasitism rates of its two parasitoids were evaluated in fields in Zemamra-Morocco, for three years (2020–2022). Infested cladodes were collected and incubated in the laboratory (27 ± 1 °C) for parasitism study. Results Infestation of cactus pear plants by the cochineal increased continuously during the study period to reach 66% in 2022. Parasitism rates were lowest in 2020 and increased thereafter to 74.10 and 38.38% in 2022 for P. diaspidis, and A. debachi, respectively. The most abundant parasitoid was P. diaspidis. The functional response and mutual interference of P. diaspidis and A. debachi attacking D. echinocacti second instar nymphs were studied in the laboratory. Logistic regression for both parasitoids tested had a negative linear parameter indicating a type II functional response. Attack rates were 0.73 and 0.60 and handling times were 0.09 and 0.06 h for P. diaspidis and A. debachi, respectively, were estimated using Holling's disk equation. Search efficiency decreased significantly from 0.060 to 0.002 for P. diaspidis and from 0.067 to 0.003 for A. debachi when the parasitoids density increased from 1 to 8. Conclusions Parasitism potential, functional response and mutual interference of P. diaspidis and A. debachi attacking D. echinocacti were reported. The results of this investigation suggest that both P. diaspidis and A. debachi had the potential to effectively control infestations of D. echinocacti on cactus pear plantations.

Keywords

• Diaspis echinocacti
• Plagiomerus diaspidis
• Aphytis debachi
• Cactus pear
• Parasitism rate