Lecturer Nong Lam University Ho Chi Minh, Ho Chi Minh, Vietnam
Parasitoids generally attack immature stages of insect hosts, and the parasitized hosts are killed without reproduction. However, parasitized adults of some insect species such as aphids can reproduce. Such a reproduction of parasitized hosts could influence stability and/ persistence of host-parasitoid population system and thus effectiveness of parasitoids as biological control agents. The cassava mealybug Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae) invaded southeast Asia and caused serious damage to cassava in the 2000s. The introduced koinobiont parasitoid, Anagyrus lopezi (De Santis) (Hymenoptera: Encyrtidae) has been controlled the cassava mealybug population. Yet, it is unknown how A. lopezi maintains the cassava mealybug population relatively low without extinction and outbreaks. We suspected that reproduction of parasitized mealybug adults may contribute to persistency of low mealybug population. In the present study, we conducted laboratory experiments to examine development and reproduction of cassava mealybug parasitized by A lopezi. When 1-d-old 3rd instar nymphs were parasitized, they continued to develop to adults but died without reproduction However, when 3rd instar nymphs and adults were parasitized by A. lopezi, the parasitized adults laid smaller number of eggs than unparasitized adults. The parasitized adults also started laying eggs one day earlier than unparasitized mealybugs. The early commence of oviposition of hosts by parasitism by a parasitoid could partially compensate future reproduction loss by parasitism. Transgenerational fecundity compensation was not observed. The partial reproductive compensation by parasitized adults of cassava mealybug may contribute to persistence of cassava mealybug and A. lopezi populations.
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