Suitability of the eggs of two species of eucalyptus longhorned borers (Phoracantha recurva and P-semipunctata) as hosts for the encyrtid parasitoid Avetianella longoi

Eggs of the eucalyptus longhorned borer (Phoracantha semipunctata F.) are t he typical host of the encyrtid egg parasitoid Avetianella longoi Siscaro. Both P. semipunctata and Phoracantha recurva Newman have become established in California, but A. longoi appears to differentially parasitize these co ngeners. Eggs of the two beetle species were tested for ovipositional and d evelopmental suitability for A. longoi at 0.5, 1.5, 2.5, 3.5, and 4.5 days after deposition in both no-choice and choice bioassays. In no-choice exper iments, the parasitoid oviposition rate was similar in the two host species when the host eggs were 0.5 days old, but higher in P. semipunctata eggs w hen the host eggs were greater than or equal to 1.5 days old. Females alloc ated significantly more eggs per host egg to P. semipunctata eggs than to P . recurva eggs when the eggs were 0.5-3.5 days old. Survival of the parasit oids was significantly lower in P. recurva eggs of all age classes than in P. semipunctata eggs. In choice experiments, female parasitoid oviposition rate was significantly higher in P. semipunctata eggs regardless of host eg g age. Parasitoid survival was also significantly higher in P. semipunctata eggs. In both choice and no-choice experiments, some P. recurva embryos su rvived the parasitoid attack and emerged as neonate larvae from parasitized eggs, whereas P. semipunctata embryos never successfully developed in para sitized eggs. These results have important implications for biological cont rol of the two beetle species by A. longoi. (C) 2000 Academic Press.