The photo above shows leaf cupping soybean damage as a result of improper dicamba herbicide application. Photo credit: University of Illinois Extension
With a high percentage of acres planted to dicamba-tolerant soybeans, here’s how to identify symptoms of off-target movement, in case you have non-dicamba tolerant soybeans on your farm. As a reminder, post-emergence dicamba applications may be made from emergence through the R1 growth stage (beginning flowering) of soybeans, so do not apply after overserving open flowers at 1 or 2 uppermost main stem nodes.
Identifying Dicamba DamageIf you suspect your non-dicamba-tolerant soybeans may have fallen victim to off-target dicamba movement, you can check for several symptoms. However, one issue with diagnosing dicamba off-target movement is that damage doesn’t usually show until 7 to 14 days after application. During this timeframe, affected non-dicamba-tolerant soybeans may exhibit 1 or more of the following symptoms:
- Crinkling leaf tips
- Leaf cupping
- Leaf puckering with blunt tips
- Stippled upper leaves
- Twisted, swollen or split stems
Potential yield loss varies by the amount of exposure, not necessarily rate applied. Soybeans damaged during flowering stages are typically more likely suffer yield loss from dicamba than the vegetative stages. Visual damage symptoms from dicamba off-target movement is not well correlated with yield. In other words, it is extremely difficult to accurately predict the impact on yield from visual damage symptoms.
100 trials conducted at the soybean flowering stages revealed the following results:
- Vapor drift, which is the equivalent of 1,000 times less than the 1x use rate, showed a potential 1% soybean yield loss
- Physical drift, which is the equivalent of 100 times less than the 1x use rate, caused an 8.7% soybean yield decrease
- Tank contamination, which is the equivalent of 10 times less than the 1x use rate, resulted in a 48.5 to 58.6% soybean yield reduction for the soybean flowering stages
- The table below contains additional stats for yield loss from applications during the vegetative and pod stages, as well as further explanation of the research study
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Golden Harvest Seed Advisor with questions or for additional agronomic insights.
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