Prospects of classical biological control of papaya mealybug in Kenya: Performance of its exotic parasitoid, Acerophagus papayae, under laboratory and field conditions

Abstract

Papaya mealybug (PMB), Paracoccus marginatus, native to Mexico and Central America, invaded Kenya in 2016 causing severe yield losses of between 57% and 91% and £2224/ha household economic losses annually. A classical biological program for PMB involved the importation of Acerophagus papayae, a koinobiont endoparasitoid, from Ghana into the quarantine facility at Kenya Agricultural and Livestock Research Organization, Muguga. Laboratory bioassays were conducted to evaluate the suitability of A. papayae to parasitize PMB. Parasitism rates, sex ratio and development time of the parasitoid were evaluated under choice and no-choice experimental conditions. High parasitism rates of 72.5 ± 5.9 and 75.0 ± 3.8% were recorded in third instar and adult female PMB, respectively, and lower parasitism rates of 43.8 ± 4.6 % were recorded in second instars, under no-choice test conditions. Significant differences in host choice were noted when A. papayae was offered several host stages, with third instars being preferred over second instars. Adult females were preferred over third instars. Adult parasitoids were released and monitored for their establishment at six papaya farms in the Coastal region of Kenya from December 2021 to November 2022. Parasitoid establishment was recovered within the first month of release. Parasitism levels varied across the sites with the highest parasitism of 72.89 % recorded in Kwale. Findings from this study highlight the potential of A. papayae as a good candidate for biological control of PMB in Kenya and Africa beyond.