Damage from herbicide drift is sure to be reported in some part of the peanut belt in 2010 because of the close proximity of peanut fields to either Roundup Ready cotton, corn or soybean fields and other small grain and horticultural crops.
To help minimize spray drift, use the tips as follows:
Avoid Spraying In Windy Conditions
High wind speed is the number one cause of herbicide drift. When wind speed doubles, the horizontal distance spray droplets travel will also double. Conversely, do not spray when winds are extremely calm because of potential herbicide movement due to temperature inversion.
Apply Larger Droplets
The smaller the droplet, the longer the time it takes to travel from spray tips to the target (weeds or soil) and the farther it will drift. Larger and more uniform droplets reduce the potential for drift.
The ideal droplet size is 400 to 800 microns. Smaller droplets also evaporate faster, and herbicide efficacy will be reduced. Therefore, use a larger nozzle orifice size. Larger orifice nozzles with high delivery rates produce a thicker sheet of spray solution and larger droplets than nozzles with a small orifice size.
Increase Carrier Volume
The driving force behind herbicide uptake into plant leaves is the concentration gradient.
Increasing the carrier volume will decrease the water droplet concentration, minimizing the risk of drift damage. Increasing the carrier volume may help improve the efficacy of some herbicides (e.g. Ignite), but decrease the activity of other herbicides (e.g. Roundup).
Decrease Spray Pressure
Increased spray pressure can cause the spray sheet to be thinner. This thinner sheet will break into smaller droplets than a thicker sheet produced at lower pressure.
Use Drift-Reducing Nozzles
Many nozzles on the market today that are designed to produce a higher percentage of large spray droplets and lower percentage of spray “fines.” Select nozzles that work best with your sprayer and production practice.
Use A Drift-Reducing Agent
There are several drift retardant producers that can be added to spray mixtures to reduce the percentage of “fines” in herbicide applications. Check labels and make sure that these products are compatible with the spray mixture. It is generally not recommended to use both reduction tips and retardant agents at the same time.
Lower Boom Height
When the boom height is set too high, droplets must fall further, increasing the chances for drift. Setting the boom at the lowest possible height while maintaining proper spray overlap will reduce the risk from herbicide drift.
Weather conditions can affect the potential for herbicide drift. The optimum conditions for low risk are higher humidity levels and lower temperatures. Droplet evaporation is most severe when conditions are hot and dry.
Avoid Temperature Inversions
A temperature inversion occurs when a layer of warm air gets trapped between two layers of cooler air. Spray particles can get caught in a layer of warm air and move offsite for long distances.
Be Cautious Around Sensitive Plants
Make applications when sensitive plants are not present, avoid applications near sensitive plants by using unsprayed buffer rows, and spray when the wind is moving away from sensitive plants. Use a shielded sprayer. Avoid aerial applications near sensitive areas.
All herbicides have the potential to move by means of physical drift. Over-the-top applications of Roundup in Roundup Ready crops have the potential to damage adjacent crops including peanut. Conversely, applications of Cadre, Pursuit, Cobra and 2,4-DB made to peanut can damage adjacent cotton fields.
Always read and follow herbicide label instructions to maximize herbicide effectiveness and minimize herbicide movement to non-target plants.
Information provided by Peter Dotray, Todd Baughman, James Grichar, Texas AgriLIFE Research and Extension Service.