In the heat of the battle to get crops planted on time, it is not uncommon for some herbicide misapplications to occur. The unintentional application of higher than labeled rates is a not a good thing because money is wasted, crop injury potential is increased, and rotational crop intervals are jeopardized.
Over the last few days, I have received several inquires about how peanuts might respond to Valor applied at rates higher than 3.0 oz/A due to sprayer calibration errors. Keep in mind that when an herbicide is developed, application rates are based upon a ton of data. The lowest use rate possible that will provide the most consistent weed control over a wide range of environments in carefully selected. Additionally, most herbicide use rates have a “safety” margin built into the rate just in case of application errors.
I looked back at some of my older Valor data and can tell you this regarding the response of peanuts to 6 oz/A of Valor (remember 6 oz is twice the labeled rate):
1) In 6 field trials, there was no significant difference in peanut yield between 3 oz/A and 6 oz/A.
2) In 1 field trial, 6 oz/A of Valor resulted in a 7% yield loss when compared to 3 oz/A (Figure 1).
3) In 1 field trial, 6 oz/A of Valor resulted in a 15% yield loss when compared to a non-treated check.
|Figure 1. Peanut injury caused by Valor SX 51WG @ 6 oz/A which
resulted in a 7% yield loss, Attapulgus, GA 2018.
If a grower accidentally applied the wrong rate of Valor at planting, there is a good chance that nothing disastrous will happen. With any application of Valor and regardless of rate, heavy rainfalls during the period of emergence until about 2-3 weeks after will result in significant visual injury. I strongly encourage all growers to regularly calibrate their sprayers in order to prevent herbicide application mishaps! Growers should not put all their faith in last year’s sprayer settings or sophisticated on-board computers.
For the record, both UGA and the current Valor label recommend that ONLY 3 oz/A of Valor be applied within 2 days after peanut planting (I do not want anyone reading this blog to think that its OK to apply 6 oz/A!!!!!!!!! That is not the purpose of this blog!!!!!!!).