|Mint Flea Beetle|
|An ABSTRACT OF THE THESIS
Mark Alan Morris
for the degree of Masters of Science in Entomology
presented on March 7 1989,
Oregon State University
Title: Sampling methods, Biology. and Management of the Mint Flea Beetle in Central Oregon Peppermint
Sampling techniques were evaluated to quantify immature mint flea beetle (MFB), Longitarsus waterhousei Kutschera (Coleoptera: Chrysomelidae), on peppermint (Mentha piperita L.), in central Oregon. During the study period, 1985-1988, soil samples of 350 cm³ were effective for collecting immature MFB. Sifting soil samples through screens was effective for estimating post-feeding third instar, prepupae, pupae, and teneral adult MFB in the soil. Berlese funnel extraction was the most effective method for estimating MFB larvae from peppermint rhizomes.
Results of Iwao's (1968) patchiness regression indicated that MFB have an aggregated spatial distribution in the field. Aggregation could be influenced by the original deposition of MFB eggs and by agronomic practices on peppermint in central Oregon.
Yearly accumulation of degree-days was more effective to predict immature MFB
development than either calendar dates or twenty-year degree-day averages. Degree days
were calculated using; the Baskerville Emin single sine method and a lower development
threshold of 5oC. In the rhizomes initial detection of first instar MFB were observed at
226 degree-days, initial detection of second instar MFB were observed at 319 degree-days
and initial detection of third instar MFB were observed at 433 degree-days. In the soil
initial detection of prepurae MFB were observed at 582 degree-days, initial detection of
pupae were observed at 757 degree-days and initial detection Of teneral adults were
observed at 864 degree-days. Initial detection of first instar MFB was considered to be an
approximation of egg hatch. Results also suggested that the climatic station closest to
where developmental predictions are to be made should be used.
Two species of entomogenous nematodes, Heterorhabditis heliothidis and Neoaplectana carpocapsae effectively controlled third instar, prepupae and pupae MFB in the soil during early June. However, early spring applications may not be effective because of the cold temperatures, small size of the larvae, and their concealment in the rhizomes.