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Wheat Curl Mite Populations under Deficit Irrigation
A. R. SIMMONS (1), F. Worneh (2), S. O'Shaugnessy (3), S. Evett (3), C. M. Rush (4). (1) Texas A&M Agrilife, Amarillo, TX, U.S.A.; (2) Texas A&M Agrilife Research, Amarillo , TX, U.S.A.; (3) USDA-ARS, Bushland, TX, U.S.A.; (4) Texas A&M Agrilife Research, Amarillo, TX, U.S.A.

<i>Wheat streak mosaic virus</i>, transmitted by the wheat curl mite (<i>Aceria tosichella</i>), causes extensive reductions in crop water-use efficiency and wheat production across the Great Plains region of the United States.  Wheat streak severity has been observed to increase during years of severe drought, possibly due to higher mite populations. Populations of other mite species also have been reported to increase in numbers in drought stressed plants. In the Texas Panhandle, much of the wheat crop is irrigated, but due to depletion of the Ogallala Aquifer less than full irrigation often is applied and little is known about the effect of deficit irrigation on wheat curl mite populations and disease severity. Therefore, field studies were conducted with two cultivars, Karl 92 and TAM 112, at three different irrigation levels. Mite population counts, disease severity and soil moisture content were evaluated for each cultivar and water treatment. Overall, mite populations were found to increase as irrigation decreased (<i>R<sup></i>²</sup>=0.5077, <i>P</i>=0.0009). Also, there was a low but significant positive correlation between disease severity and soil moisture content (<i>R<sup></i>²</sup>=0.3307, <i>P</i>=0.0125). These results show that with deficit irrigation the wheat curl mite population increases, which in turn results in increased disease severity and reduced water use efficiency leaving unused water in the soil.

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