Gary L. Hein, Entomologist
University of Nebraska
Panhandle Res. & Ext. Center
Sottsbluff, NE

During the summers of 1998-2000, wheat curl mite populations were monitored with the use of trap plants grown in pots. These trap plants were grown in the greenhouse, covered with cages and not exposed to wheat curl mites. After the plants were two weeks old, they were taken to the field and exposed in the field for 7 days after which they were again covered with cages and returned to the greenhouse. Upon return to the greenhouse, samples of the exposed plants were taken and inspected for the presence of wheat curl mites. Trap plants were put out every week from mid June into October in four fields. Areas adjacent to dryland wheat, dryland corn, irrigated wheat and irrigated corn were monitored for mite movement. From mid August to mid September, an additional four fields were monitored, including an irrigated corn field, a dryland corn field and two foxtail millet fields. The results of this sampling in 1999 are shown in Figures 1-3.

The monitoring in all fields indicated a peak of mite activity in early July which corresponds with wheat maturation. In the wheat field the mite activity began to drop after this point. In the dryland cornfield, the mite numbers continued to stay relatively high until into September. The mite numbers in the irrigated cornfield were not as high as those for the dryland corn, but they also peaked again in late August and early September. The reduced numbers in the irrigated corn compared to the dryland corn may be due to varietal differences between the different corn lines grown. It appeared that the numbers in the dryland corn began to drop off just before the numbers in the irrigated corn. This correlates with the drying down of the dryland corn. Based on work done in 1998, the lower population levels in the irrigated corn was surprisingly low as the corn field monitored in 1998 continued to >shed= mites at a high rate into October. The mite populations measured around the foxtail millet fields was surprisingly low with very few mites being trapped.

More work needs to be done to establish the relationship of mite movement in different cropping systems, but it appears that caution should be exercised by wheat growers when planting winter wheat around cornfields. Planting date should be delayed if corn is still green and actively growing. Planting wheat around dryland cornfields should not cause considerable problems unless the corn is a longer season hybrid and has favorable moisture for growth well into September.

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