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Abstract: The distribution of phytophagous insects is influenced by their preference for and performance on their host plants. Biological control agents of invasive plants that prefer and perform better on their target hosts are more likely to be both effective and safe.Brachypterolus pulicarius is an herbivore used in North America to combat two invasive plants, yellow toadflax and Dalmatian toadflax (Linaria vulgaris and Linaria dalmatica). Adult beetles prefer yellow toadflax over Dalmatian toadflax, and when beetles are redistributed onto Dalmatian toadflax, populations do not consistently establish. This leads to the hypothesis that beetle larvae will perform best on yellow toadflax. A reciprocal transfer experiment was conducted to test this hypothesis. Development rate, pupal mass and percent survival were measured to assess larval performance. Development time was influenced by an interaction between the source host and the test host, a pattern suggesting that it is important to consider both the collection host and redistribution host when releasing this beetle for the control of toadflax. Pupal mass of larvae reared on yellow toadflax was, on average, 13% greater than that of larvae reared on Dalmatian toadflax, supporting the hypothesis. Survival rate was not significantly influenced by source host, test host, or their interaction, suggesting that survival rates will be similar no matter the combination of collection host and redistribution host. These results, along with the preference that adult beetles show for yellow toadflax, do not support the redistribution of B. pulicarius onto Dalmatian toadflax in North America. [Copyright &y& Elsevier]

• Manipulating plant defense hormones increases the impact of fungal pathogens. • Jasmonic acid application increased the impact of CT-Rust on Cirsium arvense. • This effect was seen for belowground but not aboveground biomass. Cirsium arvense, or Canada thistle, is one of the most detrimental weeds for agricultural production. Native to south-eastern Europe, the species is now found in Many parts of Asia, North America and Australasia. In North America and New Zealand the species is considered invasive, displacing native vegetation and reducing the quality of forage in rangelands and pastures. The autoecious fungus, Puccinia punctiformis , or CT-rust, shows potential as a control agent but rarely reaches epidemic proportions in natural populations. Manipulating plant defense hormones could alter host susceptibility and allow CT-rust to have more widespread impact. To determine if applying hormones increases the infection by the fungal pathogen, Canada thistle plants were inoculated and sprayed with jasmonic acid (JA) and salicylic acid (SA). Results show that jasmonic acid application interacted with inoculation, increasing infection rates, both incidence and severity, and impact of CT-rust. We found that JA increased infection rates by nearly 20%. Infection consistently reduced root biomass and this reduction was 45% greater with the addition of JA compared to untreated control. Addition of JA at the time of inoculation could make it a more effective control agent for Canada thistle. [ABSTRACT FROM AUTHOR]

Abstract: Many researchers have hypothesized that reduced genetic diversity in introduced populations of biological control agents can compromise the agent’s ability to establish and then adapt to novel environments. Strategies such as collecting from a wide geographic area or maintaining large colony sizes through the quarantine process have been used to minimize the loss of genetic diversity. Few studies have examined how the process of collection, quarantine, and establishment could affect patterns of genetic diversity in biological control agents. In this paper, we examine patterns in neutral genetic diversity in Spurgia capitigena, a gall midge introduced as a biological control agent of leafy spurge (Euphorbia esula) from its original collection site in Italy, a newly discovered population of the midge from southern France, and in two established populations in North America. By comparing the existing populations with historical samples collected shortly after the original introductions in 1991, we found that there is evidence of a mild bottleneck in both of the introduced populations. Further, we also examined the population structure in European populations of the fly collected from leafy spurge and a closely related species, cypress spurge (Euphorbia cyparissias) and found evidence for local restrictions in gene flow between populations on the two plants, but no evidence to support the current taxonomy of the genus with two distinct fly species. [Copyright &y& Elsevier]