Trophic Interactions Within a Parasitoid Guild (Hymenoptera: Chalcidoidea) From Pakistan in the Context of Asian Citrus Psyllid Classical Biological Control in California
- Author(s): Bistline East, Allison Joy
- Advisor(s): Hoddle, Mark S
- et al.
Diaphorina citri Kuwayama (ACP) (Hemiptera: Liviidae) is an important agricultural pest of citrus that was recently introduced into California in 2008. The initial response focused on controlling ACP with pesticides, however these efforts were discontinued in favor of a classical biological control program utilizing Tamarixia radiata (Waterston) and Diaphorencyrtus aligarhensis (Shafee, Alam, and Agarwal). As a part of this biological control program, D. aligarhensis underwent non-target safety testing at the University of California Riverside. This testing exposed D. aligarhensis to seven non-target psyllid species selected based on the following criteria: (1) taxonomic proximity to ACP; (2) likelihood of being encountered by D. aligarhensis near release sites; and (3) psyllid species being utilized for biological control of invasive weeds. Bactericera cockerelli (Sulc), the pestiferous potato psyllid, was the only non-target species which was successfully parasitized by D. aligarhensis, and at low levels (< 14%). Based on safety testing results, D. aligarhensis was determined to pose no significant impact to native species, and was released as a part of the ACP biological control program beginning Dec. 2014. An additional goal of the ACP biocontrol program is to identify additional species within the associated parasitoid guild from ACP’s home range which could also be utilized for the program in California. Prior records estimated this guild to contain at least nine species of primary parasitoids. Three species (Chartocerus sp., Pachyneuron crassiculme [Waterston], and Psyllaphycus diaphorinae [Hayat]) were collected from parasitized ACP mummies in Punjab, Pakistan in Apr 2013, and believed to be a part of this guild. Based on choice and no-choice exposure trials performed in quarantine at UCR, all three species were confirmed to be obligate hyperparasitoids of D. aligarhensis and T. radiata, and showed no successful parasitism on ACP nymphs. Because the original record for P. diaphorinae characterized this species specifically as a primary parasitoid, further studies were performed to describe the reproductive biology and life history of this parasitoid. Results of these studies suggest that D. aligarhensis is a superior host (compared to T. radiata), based on a higher number of offspring and higher proportion of females. These findings also support the results of previous studies which found that D. aligarhensis is subjected to higher rates of hyperparasitism than T. radiata in its home range.