Effects of deficit irrigation on wheat curl mite, Aceria tosichella, abundance and disease severity in the Texas panhandle

Wheat curl mite (Aceria tosichella) transmits Wheat streak mosaic virus, which can cause severe reductions in crop water-use efficiency and wheat production across the Great Plains region of the United States.   A rise in population of  various other mites have been observed in years of severe drought, but only anecdotal observation have been made on the effects drought has on the wheat curl mite.  As the Ogallala Aquifer is being depleted croplands in the Texas Panhandle are using less than full irrigation.  Little is known how deficit irrigation impacts wheat curl mite populations and disease severity.   Therefore, a two year field study was conducted using two cultivars, Karl 92 and TAM 112, at three different water replacement 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 the lower water replacement level (P>0.0001).  Also, there was a low but significant positive correlation between disease severity and soil moisture content (R=0.3307, P=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.  With this knowledge irrigation of a field already infested by viraliferous mites can lead to water wasted in an area limited by this resource.