By Thom Weir, Senior Precision Agronomist
Last year, Xtend Soybeans were introduced into the market. This product offered promise to growers who were battling glyphosate resistant horseweed (marestail), waterhemp and Palmer’s Amaranth. Normally, soybeans are very susceptible to injury from dicamba but Xtend soybeans can withstand the application of the herbicide to control these resistant weeds.
The darker side of Xtend Soybeans and Xtend Cotton is that there were several situations where the dicamba that was applied to one of these two crops drifted onto “non-Xtend” soybeans, causing damage that varied from visual damage to significant yield damage. The situation was exacerbated by the fact that the dicamba formulations being developed for Xtend crops were yet to be registered. This led to many growers using traditional dicamba formulations that were cheap and effective but highly volatile. They were not and are not registered today for use on Xtend crops. What resulted was numerous instances of damage and law suits caused by herbicide drift.
Fast forward to this year – BASF registered a low volatile formulation of dicamba containing BAMPA salts in hopes of eliminating the drift issue. They market this product as Engeria herbicide. Monsanto has registered XtendMax, and Dupont has added FeXapa to the list of registered dicamba products for use on Xtend soybeans. These two products are DCA-based products containing VaporGrip technology that reduces the volatility of the dicamba spray mix. These products, along with rigorous spraying restrictions including temperature, wind speed and nozzle guidelines, were expected to eliminate the drift issues reported last year. This does not appear to have occurred.
By mid June, there have been many reported drift issues in the southern and south-eastern states where spraying has been completed. State and local officials are investigating along with many of the nation’s leading weed and sprayer technology researchers.
While the investigations continue, there are several considerations for growers who have yet to spray their Xtend crops. Firstly, only use a registered dicamba herbicide (listed above) on Xtend crops. Secondly, do not use any form of aircraft to apply these products! Thirdly, read and follow the label instructions for application. This includes spraying only when the wind speeds are below 15 mph (ideally 2 – 10 mph) and when temperatures are below 85oF. On-farm weather stations are best for providing you with real-time weather information about your fields. In addition, only approved nozzles operated at prescribed pressures are allowed for application. Spraying should never be done when the wind direction is moving towards a susceptible crop, such as conventional soybeans. Observe all buffering restrictions regarding spraying next to susceptible crops.
Figure 1: Spray Times
To avoid spray drift, most labels specify to not apply when wind speed exceeds 10 to 15 mph. To avoid conditions that are associated with temperature inversions or evaporation, spraying is not recommended when wind speeds are less than 2 to 3 mph, relative humidity is below 40%, or temperature is above 75°F to 85°F. Be sure to read and follow actual labels.
Weather Manager in FarmCommand provides an hourly forecast of temperature, relative humidity, rain, wind speed, and wind direction to determine when conditions are likely to be suitable for spraying.
Figure 2: Current Weather Conditions
Current conditions from nearby weather stations provide near-real-time updates of actual conditions.
The final discussion point is around what happens when your fields have been drifted on or have drifted on a neighbouring field. Damage can vary from slight to significant depending on the stage of the crop and the amount of the damage. Unfortunately, there is nothing you can do on injured soybeans to reduce the potential yield loss. It should be noted that the damage often looks worse four to seven days following application and can often outgrow much of the damage.
Here are a few suggestions if you run into a drift situation:
- Assess the extent and size of drift damage. The easiest and quickest way to do that is to utilize innovative decision-support tools that collect and analyze your field-centric data. Farmers Edge, a global leader in decision ag, provides all growers with professionally installed on-farm weather stations along with access to the fastest growing network of on-farm weather stations. Growers also receive high-frequency, high-resolution satellite imagery that can be accessedas processed maps in FarmCommand – an all-in-one farm management platform. Field Variability Maps aid in determining the extent of the damage and Crop Health Maps help to estimate a range of expected yield loss. Field-centric weather data helps to confirm where the drift originated.
- Armed with this data, contact your neighbour – either the “drifter” or “driftee.” Show him the data available or visit the field with him if you don’t have access to data.
- Contact local or state representatives to notify them of the issue. If you are the drifter, have all your application and weather information in front of you. This is very easy to do for Farmers Edge growers. They have all their as-applied data stored in FarmCommand. This data is collected through in-field telematics and data transfer devices which are installed prior to each field operation. With FarmCommand, growers can easily access all as-applied, crop health, field variability and weather data from one platform.
- Get an estimate of the damage. If the damage is small – below $1500 – $2000, try to settle with your neighbour directly. Matters are often settled by the drifter purchasing herbicide or fungicide for the agreed upon amount and giving it to the “driftee.” If it appears there is significant loss potential, the drifter should contact his/her liability insurer and have a claim initiated. All you need to have is your field-centric data easily accessible as It will assist you in your liability investigation for drift claims.
We’ve had couple of cases this year so far. In the first instance, a retailer was accused of drift damage. We used FarmCommand to search historical weather data with wind speed/direction at 15 minute intervals and could prove that the retailer wasn’t the one who actually caused the drift.
In the second instance, a grower issued a chemical claim stating the chemicals he used were not effective on his crop. The chemical company blamed the weather. The grower was able to search his field-centric historical weather data to show temperature, wind speeds, GDD and rainfall data proving neither rainfall nor temperature played a role in the poor performance of the chemical. The grower was credited for respray.
These are just some of the examples of how having field-centric data at your fingertips helps you work through complaints to an acceptable outcome.
To learn more about Farmers Edge, visit FarmersEdge.ca.au
