Project Number: 8010-22000-033-14-I
Project Type: Interagency Reimbursable Agreement
Start Date: Jun 1, 2020
End Date: May 30, 2021
The ultimate outcome of the proposed research is to limit or reduce population growth of BMSB populations through wider regional establishment and distribution of a safe and effective, adapted natural enemy of BMSB (Trissolcus japonicus). Objective 1) Determine the numbers of parasitoids to be field released and the corresponding BMSB host density for optimal parasitoid establishment at a location. Objective 2) Evaluate the influence and impact of kairomone traces deposited on host plant foliage by BMSB and select non-target species on parasitism by T. japonicus under field conditions. Objective 3) Conduct surveys for the presence of endosymbiotic Wolbachia in adventive T. japonicus populations, and if found, determine their impact on parasitoid efficacy.
Objective 1) Field redistribution of T. japonicus and associated field experiments, egg mass surveys and sentinel egg mass placements will be conducted during the summer months (June-August) when BMSB egg masses occur naturally in the field. By experimentally manipulating the number of T. japonicus released at different sites across Delaware, we will evaluate the impact of propagule pressure (size of release) on successful establishment of the parasitoid. In large-scale releases, we will replicate releases of hundreds to thousands of female wasps and conduct follow-up sampling of BMSB and non-target egg masses using sentinel egg masses and yellow sticky cards (known to effectively attract and capture scelionid wasps including Trissolcus). In smaller-scale tests conducted on site at BIIRU, we will investigate local-scale retention, host finding and dispersal by using arrays of potted maple trees upon which we will attach sentinel egg masses of BMSB and spined soldier bug (according to the experiment goal). Parasitoids will be released onto a tree at the center of the array and their movement outwards to adjacent trees will be monitored. Objective 2) Laboratory behavioral assays will be conducted throughout the late spring, summer and early fall; this is possible because BMSB and T. japonicus cultures are maintained year-round at ARS/BIIR. Kairomone field experiments will be conducted during the summer months (June-August), during the time when field populations of T. japonicus are naturally foraging for BMSB egg masses. Using lab bioassays with Noldus Observer software, we will test varying concentrations and ratios of the known kairomone components as well as the effect of smaller secondary components present at low amounts in the kairomone blend. This will be tested by measuring the behavioral response of female wasps to surfaces treated with the experimental materials. In small-scale outdoor tests on site at BIIRU, we will investigate local-scale retention, host finding and dispersal as influenced by the presence of kairomone or its individual components by using arrays of potted maple trees upon which we will attach sentinel egg masses of BMSB and spined soldier bug (according to the experiment goal) in replicated experiments. Objective 3) Three T. japonicus subpopulations are recognized by where they were detected: 1) New York, 2) the mid-Atlantic, and 3) West Coast haplotypes. We will evaluate samples of T. japonicus which we have already collected or obtain anew from cooperators from multiple locations representing all three haplotype clusters to detect and characterize Wolbachia. We will screen for Wolbachia using the established Universal and Supergroup A primers. Initial presence/absence of Wolbachia will be performed using PCR-based assays and gel electrophoresis. If Wolbachia is detected, sequences will be generated at the University of Delaware DNA Sequencing and Genotyping Center and compared to known sequence reads using BLAST. If Wolbachia is detected in adventive populations, subsequent experiments will be conducted to characterize the effects of the bacterial infections on wasp longevity, searching behavior and fecundity.