Host Plant Suitability Of The Papaya Mealybug, Paracoccus Marginatus Williams And Granara De Willink (Hemiptera: Pseudococcidae), And The Host Specificity Of Its Natural Enemy, Acerophagus Pa

ABSTRACT

The papaya mealybug Paracoccus marginatus Williams and Granara De Willink (Hemiptera: Pseudococcidae) is an invasive pest insect that can damage a wide range of agricultural crops. Successful biological control of this pest strongly relies on its mass rearing in order to produce its introduced natural enemy, Acerophagus papayae. Host susceptibility studies of P. marginatus were done on four different host plants: Manihot esculenta (cassava), Solanum macrocarpon (African egg-plant), Vernonia amygdalina (bitter leaf) and the primary host, Carica papaya (papaya) at 28° C, 75% RH and a photoperiod of 12:12 (D/N) h. P. marginatus failed to complete its development on V. amygdalina. The development and survival of host instars, the cumulative development time (first instar to adult), adult fecundity and longevity were significantly affected by host plants species. C. papaya has permitted the complete development of both male and female of P. marginatus. Females had the shortest developmental time on C. papaya (15 days) with low mortality registered during the late instars and the highest fecundity (277.40 eggs). The longest developmental time (19 days) and the longest longevity period (31.50 days) of the adult female were on M. esculenta. On this host plant, females laid 227.75 eggs within 10 days. P. marginatus developmental time on S. macrocarpon was about 18 days. Adult females live longer on S. macrocarpon but had laid the lowest number of eggs (141.23 eggs). The pre-oviposition periods were not affected by the host plants while the oviposition and the post-oviposition were significantly different. On the other hand, the potential non-target effects of its natural enemy, Acerophagus papayae were assessed. Host specificity tests were conducted on three associated mealybugs (Phenacoccus manihoti, P. solenopsis and Ferrisia virgata) sharing at least one host plant with the target insect pest, P. marginatus. The suitability of the four selected mealybug species was evaluated under choice, P. marginatus paired with one of the non-target mealybug

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and no-choice test conditions. Foraging behavior of the parasitoid recorded in one-minute time segments over a full hour shows that in both choice and no-choice condition, A. papayae parasitized all stages of P. marginatus except for the ovisacs. First instars and female plus ovisacs being the least parasitized, however, A. papayae preferred the third instars and the young females (pre-reproductive females). The presence of non-target organisms does not affect the behavior of A. papayae in host selection for oviposition.