Situation 1. Lots of weeds and they’re growing fast. Recent rainfall events have lots of weeds germinating. Established weeds that were missed earlier in the season are getting bigger by the day. In this situation, the field would probably benefit from one spray at the full rate versus two sprays at the low rate. This is the preferred option because good timely control of these earlier weeds is essential.
Situation 2. Spraying at night to dodge heavy winds. Night may be the only time when winds are below 15 to 20 km/h. Overnight can be a reasonable second choice if day time applications are just not working out. Forecast apps like Windy.com can provide a 10-day prediction of wind patterns. Article on spraying at night. If you’re in the situation of wind-delayed spraying, you may also want our tips for spraying in the wind. Finally, while nights are often less windy, you don’t want to spray when there’s no wind or an inversion risk.
Situation 3. Scouting shows escapes or efficacy issues. Did you find healthy weeds that should have been controlled – based on the product applied and the timing? These could be herbicide-resistant escapes. Labs can test weeds for herbicide resistance.
Situation 4. Tank mix makes a mess of the sprayer. Sometimes things together into a tank mix can cause clogging lumps. It can take hours to clean up when you probably don’t have time for something like that. A “jar test” of new tank mixes can help prevent such a situation. Talk to retailers about a new tank mix and ask about risks and mixing order. Also check labels for any restrictions or recommendations when it comes to tank mixes or mixing order. This article has tips on how to test a mix.