Effect of Actigard on Wheat Resistance to Orange Wheat Blossom Midge

Objective:       

To evaluate the efficacy of Actigard for the control of OWBM in susceptible and resistant spring wheat cultivars.          

Materials and Methods:

Spring wheat varieties containing the Sm1 gene for resistance to the wheat midge are available to aid in their control.  However, some damage is incurred prior to the synthesis of the active compound.  This study was designed to determine if treatment with Actigard prior to larval feeding could upregulate the Sm1 gene and shorten the lag phase.  This study was established as a split plot design with three replications. Egan, a cultivar with resistance to the OWBM, and McNeal, a non-resistant cultivar were the whole plot treatments.  Actigard was applied to both varieties at three rates and at three wheat growth stages.  Actigard was applied at 0.0, 0.25, and 0.50 oz/A when wheat was at the late boot stage, 50% headed, and 50% flowering growth stages. Lorsban was applied at 50% heading to serve as a control.

Results:           

The study site experienced severe drought and low midge pressure.  As a result, any treatment affects that might have been present were largely masked by these environmental conditions. However, a few treatment effects were detected, and were largely associated with differences between the two spring wheat varieties. Spring wheat yields averaged 20.4 bu/A, with McNeal producing slightly higher yields that Egan (21.0 and 19.9 bu/A, respectively).  Egan had greater protein and higher falling number values, but McNeal had higher test weight and greater thousand kernel weight.  Most importantly, midge larvae were not detect in the heads of Egan, while McNeal averaged 0.037 larvae per head.  There was a trend in the data (Pr=0.0536) which indicated a slight yield increase for the Actigard and Lorsban treatments, compared to the non-treated check. However, the timing of Actigard treatments had no impact on any of the variables measured.

Summary:       

Record breaking drought and low midge populations prevented an accurate assessment of Actigard for improving crop resistance against the orange wheat blossom midge.