By Bob Koch and Dave Nicolai et.al
Insecticides continue to be important tools for management of key insect pests of several of our crops. We must use these insecticides wisely to prevent unintended impacts and to reduce the risk of losing access to these insecticides due to regulations.
Repeated detections of pesticide above certain concentrations can lead to increased regulation. The Minnesota Department of Agriculture (MDA)performs extensive monitoring for pesticide residues in groundwater and surface waters of Minnesota.
One insecticide, chlorpyrifos (e.g., Lorsban), continues to be detected each summer in surface waters and has been declared a "Surface Water Pesticide of Concern" in Minnesota. Also of concern are the increasing detections of neonicotinoid and pyrethroid insecticides in surface waters. These are highly toxic to aquatic species.
Several pathways exist for insecticides to enter surface waters, but one common route is drift. In addition, drift of an insecticide off a targeted crop and into some other habitat can leave an overall reduced rate of insecticide on the targeted crop, which can increase the risk for development of insecticide resistance by the pests in that crop.
We encourage you to use scouting and economic thresholds to determine when and where to apply insecticides. When those insecticides are applied, please keep in mind the following recommendations for drift prevention from the Minnesota Department of Agriculture:
Monitor wind speed and direction
Make applications only when wind is blowing at low speed, preferably between 3 to 10 mph. High wind velocities or calm conditions are not good for application. Avoid applications when the wind is blowing toward sensitive landscape regardless of the wind speed. Many product labels have specific language about wind speed and direction. A handy wind meter can be a good investment to check onsite wind direction and velocity.
Avoid applications during temperature inversions
Temperature inversions also can cause pesticides to move off target and cause damage outside of our fields. Inversions occur when warm air, which is light, rises upward into the atmosphere and cool air, which is heavy, settles near the ground. These conditions do not allow mixing of the air and provide near ideal conditions for suspended droplets to drift away from the target.
Indications that a temperature inversion is likely to occur include
- clear nights
- a calm day (wind speed < 3 mph)
- dew or frost present on the ground, or
- ground fog in low-lying areas.
Consulting inversion detection apps/websites (e.g. NDAWN Inversion app) can be helpful prior to making applications.
Be a good neighbor
Maintaining good relationships with our neighbors goes a long way towards knowing what lies around our fields. Unfortunately, that’s not always an option, so two great resources that can also help are Driftwatch.org and Beecheck.org.
These websites allow us to see if any organic/specialty crops or apiaries are near our fields, and then plan our treatments accordingly. Prior to application, survey the area around the field to be treated for presence of sensitive crops, water bodies, apiaries, residences, playgrounds, school, etc. Do not spray when wind is blowing towards sensitive areas regardless of wind speed. Be a good neighbor; learn what lies around the (or your client’s) field and avoid making applications when conditions favor drift.
Maintain application setbacks
Chlorpyrifos and some other insecticides require application setbacks from water bodies, such as lakes, rivers, streams, ponds and marshes. Maintain the required application setbacks to prevent insecticides from the target field to reach nearby water bodies. When using insecticide premixes or tank-mixes, always use the most restrictive setbacks. MDA's chlorpyrifos label setbacks guidance document provides information about these requirements.
- Additionally, our equipment allows us to minimize the risk of off-target drift by choosing the most appropriate gear and settings when operating our rig. Always remember that you have control over:
- Nozzle selection
- Spray pressure
- Spray boom height
- Spray volume
- Spray equipment ground speed
- Tank-mix partners
Granted, the product’s label will usually be specific in what your options are, but by following the label and making sound decisions when the choice is yours, you increase the odds of a successful application based on your unique situation.
The MDA Pesticide Best Management Practices and Environmental Protection Agency’s drift webpages are good places to learn more about how to reduce the odds of experiencing pesticide drift. Also see UM Extension's article, When is it too windy to spray?Source : umn.edu