Preliminary evaluation of the parasitoid wasp, <i>Collyria catoptron</i>, as a potential biological control agent against the wheat stem sawfly, <i>Cephus cinctus</i>, in North America

<div><p>ABSTRACT</p><p>The wheat stem sawfly, <i>Cephus cinctus</i> (Hymenoptera: Cephidae) is the major pest of wheat in the northern plains of North America, with biological control providing a potentially useful management tool. Foreign exploration by the USDA-ARS identified <i>Collyria catoptron</i> (Hymenoptera: Ichneumonidae), a parasitoid wasp of <i>Cephus fumipennis</i> in northern China, as a potential biological control agent. Here we carry out a preliminary evaluation of the potential suitability of <i>C. catoptron</i>, as a candidate agent against <i>C. cinctus</i>. Specifically we: (1) Quantify the spatio-temporal variation in parasitism rates on the native host from collection sites in northern China over six years, and (2) Assess whether <i>C. catoptron</i> will oviposit and complete development in the novel targeted host. Maximum parasitism of the native host in the native range was 38%, exceeding the theoretical threshold for successful biological control. Site occupancy levels were high (83%) suggesting good colonisation abilities. <i>C. catoptron</i> clearly recognised and attacked <i>C. cinctus</i>, with parasitism levels exceeding those observed on the co-evolved host <i>C. fumipennis</i>. However, we found no evidence that <i>C. catoptron</i> can complete development in <i>C. cinctus</i>; no adults were reared from this host in either year of the study. In contrast 50–60% of the parasitoids survived to emerge as adults in <i>C. fumipennis</i>. Thus, <i>C. catoptron</i> is unlikely to be a suitable agent against <i>C. cinctus</i> due to basic host incompatibility. Future work will be directed towards developing conservation biological control approaches using native parasitoid species already present in the USA.</p></div

Appendix B. ANCOVA results for effects of Rhinocyllus conicus density in the focal musk thistle patch and distance to the focal patch on R. conicus egg load on wavyleaf thistles.

ANCOVA results for effects of Rhinocyllus conicus density in the focal musk thistle patch and distance to the focal patch on R. conicus egg load on wavyleaf thistles

Appendix E. ANCOVA results for effects of focal musk thistle patch area and distance to the focal patch on Rhinocyllus conicus egg load on wavyleaf thistles and a bar graph of mean R. conicus egg load on wavyleaf thistle at sites with small vs. large total area of the focal patch.

ANCOVA results for effects of focal musk thistle patch area and distance to the focal patch on Rhinocyllus conicus egg load on wavyleaf thistles and a bar graph of mean R. conicus egg load on wavyleaf thistle at sites with small vs. large total area of the focal patch

Appendix A. Characteristics of focal musk thistle patches sampled.

Characteristics of focal musk thistle patches sampled

Appendix C. ANCOVA results for effects of Rhinocyllus conicus population size in the focal musk thistle patch and distance to the focal patch on R. conicus egg load on wavyleaf thistles.

ANCOVA results for effects of Rhinocyllus conicus population size in the focal musk thistle patch and distance to the focal patch on R. conicus egg load on wavyleaf thistles

Appendix F. ANCOVA results for effects of musk thistle abundance in the focal patch and distance to the focal patch on Rhinocyllus conicus egg load on wavyleaf thistles. Bar graph of mean R. conicus egg load on wavyleaf thistle at sites with low vs. high total abundance of musk thistles in the focal patch.

ANCOVA results for effects of musk thistle abundance in the focal patch and distance to the focal patch on Rhinocyllus conicus egg load on wavyleaf thistles. Bar graph of mean R. conicus egg load on wavyleaf thistle at sites with low vs. high total abundance of musk thistles in the focal patch

Appendix G. Regression of mean number of Rhinocyllus conicus egg cases per wavyleaf thistle flower head as a function of the number of bolting native thistles within a 5-m radius of the sampled wavyleaf plant.

Regression of mean number of Rhinocyllus conicus egg cases per wavyleaf thistle flower head as a function of the number of bolting native thistles within a 5-m radius of the sampled wavyleaf plant

Appendix I. Mean number of Rhinocyllus conicus egg cases per wavyleaf thistle (Cirsium undulatum) flower head in 20×50 m sampling plots as a function of the number of bolting wavyleaf thistles within the sampling plot.

Mean number of Rhinocyllus conicus egg cases per wavyleaf thistle (Cirsium undulatum) flower head in 20×50 m sampling plots as a function of the number of bolting wavyleaf thistles within the sampling plot

Appendix D. ANCOVA results for effects of focal musk thistle patch density and distance to the focal patch on Rhinocyllus conicus egg load on wavyleaf thistles and a bar graph of mean R. conicus egg load on wavyleaf thistles at sites with low vs. high musk thistle densities in the focal patch.

ANCOVA results for effects of focal musk thistle patch density and distance to the focal patch on Rhinocyllus conicus egg load on wavyleaf thistles and a bar graph of mean R. conicus egg load on wavyleaf thistles at sites with low vs. high musk thistle densities in the focal patch

Appendix C. Taxonomic composition of specialist predators moving across the habitat edge.

Taxonomic composition of specialist predators moving across the habitat edge