Spring Break
Professor completes study of competing pests on hemlocks, may benefit plants
Hilary Brady
Issue date: 11/14/08 Section: News
11/In a scenario of two competing pests in an environment, one might assume that this would negatively impact their common resources. However, a new study by University of Rhode Island Biology professor, Evan Preisser, shows that this may not always be the case.
In the science journal, "Ecology," an article joint published by Presiser and Joseph Elkinton of the University of Massachusetts explain and explore the "natural phenomena" of two competing insects on the hemlock tree. It is one of the few cases in which "competing herbivores [are] good for the plant" said Pressier.
In this situation, the two species of insects, the hemlock woolly adelgid and the enlongate hemlock scale-insect, have competed for the same sap from the hemlock tree. During this process, each type of insect reduced the other species' density by approximately 30 percent.
The adelgid inject the tree with toxic chemicals during their draining of the sap. By another competing species keeping the adelgid levels lower, the tree benefits because it is injected with less toxin.
This situation can be equated to a person having a "choice between having the flu and pneumonia" said Pressier.
He added while having neither is the best option, most would choose the flu over pneumonia, because it is less detrimental.
This is similar to the relationship between the hemlock tree and the aforementioned insects. Because the adelgid's toxin is bad for the hemlock plant, it is beneficial to have another insect preying on the plant. The natural competition between the insects helps keeps the toxic pest's density lower.
While the best scenario for the tree would be to have no insects present, having both is clearly better for the hemlock's health than just the presence of the toxic insect.
Preisser said the results of the study were "suprising." He has worked with Elkington since completing his post doctorate research, and was inspired to conduct the study after noticing infestation of hemlock trees. The two wondered if the enlongate scale had any affect on the plant's life.
"No one had looked at the effect of a second pest" before, Preisser said.
The theory has only been tested on a hemlock branch. To prove that the theory is universally applicable, the test must be repeated on the entire tree to see if the conjecture works on a larger scale. The scientists are currently doing the "preliminary work" to prepare to prove their hypothesis. They are working to see what effect multiple insects have on the hemlock tree's health and chemistry, as well the source of the insects' toxins.
Their work may "lead to a recommendation to stop spraying for harmless pests" said Preisser, though there is a "real danger in taking a little bit of evidence" to create a solution. At the moment, it is a hypothesis on a natural interaction that is already occurring, which "[we are] trying to find out the implication of," Preisser said.
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In the science journal, "Ecology," an article joint published by Presiser and Joseph Elkinton of the University of Massachusetts explain and explore the "natural phenomena" of two competing insects on the hemlock tree. It is one of the few cases in which "competing herbivores [are] good for the plant" said Pressier.
In this situation, the two species of insects, the hemlock woolly adelgid and the enlongate hemlock scale-insect, have competed for the same sap from the hemlock tree. During this process, each type of insect reduced the other species' density by approximately 30 percent.
The adelgid inject the tree with toxic chemicals during their draining of the sap. By another competing species keeping the adelgid levels lower, the tree benefits because it is injected with less toxin.
This situation can be equated to a person having a "choice between having the flu and pneumonia" said Pressier.
He added while having neither is the best option, most would choose the flu over pneumonia, because it is less detrimental.
This is similar to the relationship between the hemlock tree and the aforementioned insects. Because the adelgid's toxin is bad for the hemlock plant, it is beneficial to have another insect preying on the plant. The natural competition between the insects helps keeps the toxic pest's density lower.
While the best scenario for the tree would be to have no insects present, having both is clearly better for the hemlock's health than just the presence of the toxic insect.
Preisser said the results of the study were "suprising." He has worked with Elkington since completing his post doctorate research, and was inspired to conduct the study after noticing infestation of hemlock trees. The two wondered if the enlongate scale had any affect on the plant's life.
"No one had looked at the effect of a second pest" before, Preisser said.
The theory has only been tested on a hemlock branch. To prove that the theory is universally applicable, the test must be repeated on the entire tree to see if the conjecture works on a larger scale. The scientists are currently doing the "preliminary work" to prepare to prove their hypothesis. They are working to see what effect multiple insects have on the hemlock tree's health and chemistry, as well the source of the insects' toxins.
Their work may "lead to a recommendation to stop spraying for harmless pests" said Preisser, though there is a "real danger in taking a little bit of evidence" to create a solution. At the moment, it is a hypothesis on a natural interaction that is already occurring, which "[we are] trying to find out the implication of," Preisser said.
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