Four sampling techniques were evaluated to estimate clover aphid, Nearctaphis bakeri
(Cowen), abundance in red clover fields in the Willamette Valley. The Berlese funnel method
detected one to four times more aphids than other sampling techniques. Visual assessment
often underestimated the high aphid densities during the flowering and seeding of clover.
Sweep net and Schuh shaker techniques had limitations and underrated the numbers of aphids
present in the clover fields. Strong correlations (r² = 0. 74 - 0.87) were found between the
Berlese funnel technique and visual assessment technique in a 2nd year established field.
Numerical differences in the spatial distribution of N. bakeri on clover stems were
shown during various stages of plant development over the season. During development of
buds and axils, aphid numbers on the lower half of the plant averaged 1.5 times greater than
those on the upper half. As the season progressed into the flowering and seeding stage, aphid
numbers on the upper stem halves were approximately five times greater than those on the
lower half.
Winged clover aphids were too few to show definite peaks of flight using water traps,
averaging 2.19 aphids per yellow bucket during the June-August period. No significant
differences in aphid attractiveness to the different colors were found among water pan traps.
Yellow buckets captured approximately five times more alate aphids than did yellow, red, or
green pan traps. Traps placed on the south side of the field contained higher numbers of
aphids than in other locations in the red clover fields. / Graduation date: 1991
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/38121 |
| Date | 21 November 1990 |
| Creators | Dreves, Amy J. |
| Contributors | DeAngelis, Jack |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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