Alleviating the antagonistic effect of moisture stress on smooth crabgrass (Digitaria ischaemum) control with fenoxaprop
1994
Rossi, F.S. | Neal, J.C. | Senesac, A.F.
The influence of moisture stress intensity and duration, as well as tank mixtures with pendimethalin, which mitigated the antagonistic effects of drought, on fenoxaprop efficacy were evaluated. In growth chamber tests, specific soil matric potential levels of -0.01 to -1 MPa were imposed and maintained using a polyethylene glycol semipermeable membrane system. Moisture stress was alleviated by irrigation 48 or 96 h after herbicide treatment. Fenoxaprop efficacy was influenced by moisture stress intensity, posttreatment stress duration, and application rate. Under conditions of mild stress soil matric potential greater than or equal to -0.2 MPa), both increased application rate and irrigation 48 h after treatment alleviated the effects of drought on fenoxaprop efficacy. Under moderate stress (soil matric potential = -0.4 MPa), the antagonistic effects of drought were alleviated by a combination of increased rate and irrigation 48 h after treatment. However; under more severe stress (soil matric potential less than or equal to -0.8 MPa), irrigation coupled with increased rate did not increase crabgrass control above 50%. Where irrigation within 48 h of treatments not feasible, tank mixes of fenoxaprop with pendimethalin were shown to enhance smooth crabgrass control. Field lysimeter tests indicated that under moisture stress, soil matric potential of -0.7 MPa, smooth crabgrass shoot dry weight was reduced 65 to 94% with tank-mix combinations of greater than or equal to 0.27 kg ai ha(-1) fenoxaprop plus greater than or equal to 2.2 kg ai ha(-1) pendimethalin. These rate combinations were shown to be synergistic and able to alleviate the antagonistic effect of moisture stress on fenoxaprop efficacy.
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