Roundup Ready Xtend soybeans, which can be safely sprayed with glyphosate and dicamba, offer many advantages, but there are several things to keep in mind when applying dicamba.
Dicamba provides residual weed control — 14 days or even longer under certain conditions, Allan Froese, Monsanto’s technology development representative, said during a field day June 23. But that residual effect will damage or kill non-Xtend soybeans if they happen to get reseeded after Xtend soybeans have been ripped up for some reason.
However, there are no cropping restrictions the following year — so long as dicamba, also known as Banvel, is not applied in September or later.
It’s also important to know what type of soybeans neighbours are growing in case of drift, said Bruce Murray, Dekalb’s agronomist for southeastern Manitoba (Dekalb is Monsanto’s seed company). Don’t assume all soybeans are dicamba tolerant.
Dicamba has a reputation for being a bit more volatile than some herbicides, but only improved, less volatile versions will be registered for use on Xtend soybeans, he said. Herbicide drift is potentially an issue with all herbicides and farmers and applicators need to mitigate it. Monsanto recommends applying the glyphosate-dicamba tank mix with nozzles that produce coarse to ultra-coarse droplets such as Turbo TeeJet Induction and Air Induction.
- Click here for a video demonstration of the Roundup Ready Xtend crop system for soybeans, avoiding spray drift
Those nozzles require application rates of 10 gallons of water an acre.
Applications should take place when wind speeds are three to 15 kilometres an hour and at sprayer travel speeds of no more than 24 kilometres per hour. Boom height should be no more than 50 centimetres.
“This is just common sense,” Murray said.
Monsanto also recommends triple rinsing sprayers following a glyphosate-dicamba tank mix. Even after rinsing once or twice there could be enough residual dicamba in the sprayer to injure susceptible crops, said Dekalb agronomist Danielle Berard.
The first rinse is with water. Next remove all the filters and screens and soak them overnight with an ammonia-based solution, she said. Fill the tank with a similar solution and agitate for 15 minutes, circulate and then flush everything for at least one minute. Follow that with another water flush and rinse.