A SURVEY OF THRIPS MOVEMENT INTO ONION FIELDS IN
THE TREASURE VALLEY
Malheur County Extension Service
Oregon State University
Ontario, OR, 2006
Thrips are the vector for iris yellow spot virus in onion. Two of the challenges to integrated pest management of thrips are knowing when thrips are moving into the fields and where they are coming from. This survey was a first attempt to gather that information.
Materials and Methods
Yellow sticky cards were attached to wooden stakes at a
height of 18 inches from the ground and placed on the edges of selected onion
fields throughout the
Results and Discussion
Thrips numbers moving into onion fields were evenly distributed for traps located on the north, south, and west edges of fields but were nearly double for the east edges (Fig. 2).
Surprisingly, fields with pasture as the neighboring crop had a higher influx of thrips than any other crop (Fig. 3). Onion fields adjacent to other onion fields had the fewest thrips moving into the onions. It should be noted that there was a large variation in the type of crop surrounding onion fields, so that there were very few repetitions of any particular crop. Making conclusions based on a few crops is tenuous where the crop factor is confounded with the location factor.
Oregon Slope and
Figure 2. Average number of thrips by trap direction. Malheur Experiment Station,
Figure 3. Average number of thrips by adjacent crop. Malheur Experiment Station,
Figure 4. Average number of thrips by area. Malheur Experiment Station,