Evaluation of Cricotopus myriophylli Oliver (diptera : chironomidae) as a potential biocontrol agent for Eurasian Water Milfoil, Myriophyllum spicatum

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dc.contributor.authorMacRae, Ian Vanceen_US
dc.date.accessioned2024-08-14T22:33:48Z
dc.date.available2024-08-14T22:33:48Z
dc.date.copyright1988en_US
dc.date.issued1988
dc.degree.departmentDepartment of Biology
dc.degree.levelMaster of Science M.Sc.en
dc.description.abstractMyriophyllum spicatum (Eurasian Water Milfoil, or E.W.M.) is a rooted aquatic macrophyte which grows and spreads rapidly forming dense, mats of surfacing vegetation. These mats clog irrigation and navigation ditches, shallow lakes and beaches and bas led to the plant being considered a nuisance weed in B.C. The phytophagous larvae of the chironomid, Cricotopus myriophylli Oliver, feed on the meristematic tissue located at the plant's apical tips, thereby suppressing growth. This insect has demonstrated the ability to locally control this aquatic weed through its feeding habits. Ecological studies and laboratory trials were preformed to assess this species as a potential biocontrol agent for E.W.M., and to determine any possible hazards associated with its introduction. Life history investigations show that the insect has 4 larval instars, is univoltine, and the 2nd to 4th larval stadia are present throughout the entire year. Adult emergence of C. myriophylli is apparently affected by temperature, occurring only when water temperature is between 16 - 25 C. Trials indicate that: larval feeding significantly suppresses the growth of M. spicatum; the optimum number of larvae necessary to suppress growth of the plant is one per meristem ; and the larvae are specific to Myriophyllum spp., preferring the introduced M. spicatum over all native plants tested. In addition, the larvae will relocate to fresh sources of M. spicatum growing tissue when original source bas been depleted. Mechanical harvesting of M. spicatum was shown to decrease populations of C. myriophylli, although these populations subsequently recover, likely through immigration. The insect has been reported only from B.C. and S.E. Ontario, and has not been found in any other E.W.M. infestations in North America. This limited distribution, coupled with its feeding preferences, strongly suggests that the species is introduced. Adults mate in swarms, and the conditions necessary to induce this behaviour are difficult to replicate. It is concluded that this species is safe to introduce anywhere in British Columbia and is considered a good candidate for a biocontrol agent of Myriophyllum spicatum in certain circumstances.
dc.format.extent134 pages
dc.identifier.urihttps://hdl.handle.net/1828/18823
dc.rightsAvailable to the World Wide Weben_US
dc.titleEvaluation of Cricotopus myriophylli Oliver (diptera : chironomidae) as a potential biocontrol agent for Eurasian Water Milfoil, Myriophyllum spicatumen_US
dc.typeThesisen_US

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