Question: Besides Buctril M (bromoxynil/MCPA), are there other winter wheat herbicides that we can use to control weeds when we have underseeded red clover?
The short answer is, “Not really.” There are other broadleaf herbicides including MCPA sodium and MCPA/MCPB that can also be used on winter wheat that is underseeded with red clover, but the former is considered too limited in the spectrum of weeds it controls while the latter is considered too expensive.
Experiments were conducted in 2009 and 2010 at four different Ontario locations to assess the crop tolerance of underseeded red clover to 10 winter wheat herbicides. Each herbicide was applied at three different timings.
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The first timing was referred to as “early” and occurred later than April 15 but when an air temperature of 0 C was forecast. The second timing was referred to as “normal” and occurred during winter wheat tillering (Zadoks 21-29, typically during the first two weeks of May). The final application timing was referred to as “late” and occurred at the flag leaf stage (Zadoks 37-39, typically late May to early June).
A couple of key learnings came from this study:
The risk of red clover injury that reduced its biomass increased the later a herbicide application was made to the winter wheat crop. Table 1 illustrates the impact that the application timing of Buctril M had on red clover density.
The 10 herbicides tested fall into three categories for their impact on red clover: “safe to use,” “roll the dice” and “forget about it.” Table 2 provides more detail as to the risks involved with each herbicide.
To learn more about these experiments, read “Response of underseeeded red clover to winter wheat herbicides as affected by application timing” recently published in Agricultural Sciences.
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