PhD Research
Monitoring houndstongue and non-target plants (photo: W. Van Der Weide).
Does a biocontrol insect have population-level effects on a native non-target plant?
Many of the weeds in the Canadian landscape are invasive plants from foreign origins. Invasive plants establish in their new environment and cause economic and ecological damage. Biocontrol of weeds involves finding, testing, and releasing host-specific insects from a weeds’s native area to help control it in its new environment. Biocontrol can be an effective alternative or complement to spraying or pulling weeds, and is often the only cost-effective method of control when weeds grow in inaccessible places.
A perfect biocontrol insect reduces its target weed’s populations and spreads on its own, not using (feeding or laying eggs in) any other plants. This ideal insect is very rare.
In fact, many approved biocontrol insects may feed on or lay eggs in non-target plants that are closely related to their target weed, but this non-target use is rarely permanent. A few questions about this immediately come to mind: 1) what will the insects do when all the weeds are gone?, 2) when do the insects use non-targets?, and 3) when insects do use non-target plants, are the plants in danger? These and other questions are the basis for my PhD research. I am using the following study system.
Many of the weeds in the Canadian landscape are invasive plants from foreign origins. Invasive plants establish in their new environment and cause economic and ecological damage. Biocontrol of weeds involves finding, testing, and releasing host-specific insects from a weeds’s native area to help control it in its new environment. Biocontrol can be an effective alternative or complement to spraying or pulling weeds, and is often the only cost-effective method of control when weeds grow in inaccessible places.
A perfect biocontrol insect reduces its target weed’s populations and spreads on its own, not using (feeding or laying eggs in) any other plants. This ideal insect is very rare.
In fact, many approved biocontrol insects may feed on or lay eggs in non-target plants that are closely related to their target weed, but this non-target use is rarely permanent. A few questions about this immediately come to mind: 1) what will the insects do when all the weeds are gone?, 2) when do the insects use non-targets?, and 3) when insects do use non-target plants, are the plants in danger? These and other questions are the basis for my PhD research. I am using the following study system.
Invasive Plant - Houndstongue
My study weed, houndstongue (Cynoglossum officinale), is native to Eurasia and is a serious problem in western North America because it is poisonous to livestock and has barbed seeds that coat animals. Houndstongue spreads very quickly and grows on rangeland terrain that is not easy to access with sprayers.
Biocontrol Insect – Mogulones crucifer
In 1997 after years of testing in Europe, Canada approved the release of a root-feeding weevil called Mogulones crucifer for houndstongue biocontrol. Mogulones crucifer successfully controls houndstongue and spreads on its own to new infestations.
Despite its success, M. crucifer is not a perfect biocontrol insect. The weevil has been spotted occasionally utilizing native relatives of houndstongue in Canada. This non-target use was predicted in the pre-release tests, and was judged by the Canadian government to be an acceptable risk in exchange for potential houndstongue control. However, because there are endangered American relatives of houndstongue, M. crucifer was not approved for release in the USA. In 2010, the weevil was declared federal pest in the USA as weevils move naturally from Canada to houndstongue across the border. There are concerns the weevils will harm endangered Hackelia venusta, a plant reduced to a single population of 600 individuals in Washington.
Despite its success, M. crucifer is not a perfect biocontrol insect. The weevil has been spotted occasionally utilizing native relatives of houndstongue in Canada. This non-target use was predicted in the pre-release tests, and was judged by the Canadian government to be an acceptable risk in exchange for potential houndstongue control. However, because there are endangered American relatives of houndstongue, M. crucifer was not approved for release in the USA. In 2010, the weevil was declared federal pest in the USA as weevils move naturally from Canada to houndstongue across the border. There are concerns the weevils will harm endangered Hackelia venusta, a plant reduced to a single population of 600 individuals in Washington.
My Work
Under the supervision of Dr. Bob Lalonde and Dr. Rosemarie De Clerck-Floate, I have conducted field and lab experiments to determine under what conditions the weevils use non-target plants, and whether insect damage to individual plants translates to a population-level effect. Many mysteries remain about how insects affect plants at the population level. In other words, we don’t really know how biocontrol insects do their job on their target weed, nevermind their impact on non-target plants.
I am gathering information in great detail to uncover if and how the weevil reduces houndstongue populations and if the same effect is seen on the native non-target plant Hackelia micrantha. This plant is very closely related to the endangered Hackelia venusta, and therefore this research may help predict the risk to the endangered plant just across the border in Washington.
I am gathering information in great detail to uncover if and how the weevil reduces houndstongue populations and if the same effect is seen on the native non-target plant Hackelia micrantha. This plant is very closely related to the endangered Hackelia venusta, and therefore this research may help predict the risk to the endangered plant just across the border in Washington.
MSc Research
What factors explain oak decline in Winnipeg's urban forest?
I studied the decline of bur oak (Quercus macrocarpa) trees in Winnipeg’s urban forest at the University of Manitoba under the supervisor of Dr. Bill Remphrey, with collaboration from Dr. Scott St. George.
The abstract from our resulting paper:
Catton, H.A., St. George, S., and W.R. Remphrey. 2007. An evaluation of bur oak (Quercus macrocarpa) decline in the urban forest of Winnipeg, Manitoba, Canada.
Winnipeg, Manitoba, Canada, has a large, indigenous population of bur oak (Quercus macrocarpa Michx.). In the 1980s, many of these trees were showing signs of decline, a disease caused by a complex of abiotic and secondary biotic stressing agents. Potential causal factors were investigated by comparing various aspects of 120 bur oaks visually rated as healthy or declined based on crown dieback levels. The results indicated that many selected bur oak trees predated surrounding urban development and that declined trees were significantly older with more severe stem wounds and competition from surrounding trees than healthy specimens. Average annual growth ring widths of healthy and declined trees were similar in the early part of the 20th century. However, decline actually began decades before symptoms were noticed, coinciding with a period of intense city-wide urban development, as growth of declined trees was slower than that of healthy trees beginning sporadically in the 1940s and consistently from 1974 to 2001. During the early years of decline, the year-by-year separation in ring width between the two categories was significantly positively related to precipitation levels. This suggested that in wet years, declined trees may have been surrounded by unfavorable water-logged soils, possibly as a result of natural drainage patterns being impeded by urban development.