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Title: Host instar susceptibility and selection and interspecific competition of three introduced parasitoids of the mealybug Paracoccus marginatus (Hemiptera: Pseudococccidae)

Author
item AMARASEKARE, KAUSHALYA - University Of Florida
item MANNION, CATHARINE - University Of Florida
item Epsky, Nancy

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/2/2010
Publication Date: 10/1/2010
Citation: Amarasekare, K.G., Mannion, C.M., Epsky, N.D. 2010. Host instar susceptibility and selection and interspecific competition of three introduced parasitoids of the mealybug Paracoccus marginatus (Hemiptera: Pseudococccidae).. Environmental Entomology. 39(5):1506-1512.

Interpretive Summary: Three species of parasitoid wasps were introduced into south Florida in 2003 as biological control agents for the papaya mealybug, a threat to numerous agricultural products in the US. However, there is little information on their effectiveness in controlling mealybug populations. Knowledge of host selection and interspecific competition of parasitoids is needed to better understanding of the population dynamics of the host and the parasitoids. Therefore, research was conducted by scientists SHRS in collaboration with scientists at the University of Florida to determine the effect of host stage on host susceptibility and parasitoid sex ratio, and effect of interspecific competition on parasitoid effectiveness. Although all three species were able to complete development in all host stages that were tested, one parasitoid was able to utilize all host stages more effectively than other two species when tested singly or in competition with them. This species is the most promising of the three tested for control of the papaya mealybug. These results will be used by scientists, pest control operators and regulatory agencies to understand further the biological control potential for these parasitoid wasps, and to optimize their use for population suppression of this pest.

Technical Abstract: Acerophagus papayae, Anagyrus loecki, and Pseudleptomastix mexicana, three introduced parasitoids of Paracoccus marginatus were investigated for host stage susceptibility and sex ratio, host stage suitability, and interspecific competition. All three parasitoid species were able to develop and emerge successfully in the second instars, third-instar females, and adult females of P. marginatus. None of the parasitoids was able to emerge from the first-instar nymphs. The proportion of female emergence was increased with increasing host size. Although, in the second-instar hosts, the progeny of A. papayae had a similar number of males and females, A. loecki and P. mexicana had a lower number of females compared to the males. In the third instar and the adult-female hosts, all three parasitoid species had a higher number of females than males. Acerophagus papayae and P. mexicana preferred the second instars to third instars and adult females, while A. loecki preferred the third instars and adult females to second instars. Between the third instar and adult female, A. papayae and A. loecki preferred the third instar mealybugs while P. mexicana had no preference. When either A. loecki or P. mexicana or both were present and compete for the second-instar hosts, A. papayae had higher percent parasitism. On the other hand, A. loecki had higher percent parasitism in the third-instar P. marginatus, when present with either A. papayae or P. mexicana or both. Overall, A. papayae provided better control of the host, when present singly or with the other two parasitoids. Pseudleptomastix mexicana was less competitive when mixed with A. papayae and A. loecki. This information is important for evaluating the efficiency of A. papayae, A. loecki, and P. mexicana in the classical biological control program of P. marginatus.