I want to put the biggest “IF” I possibly can on this. If you are going to spray your pastures, CRP, etc., fall is the time to do so. There are times when applying herbicide in grasslands is effective on your target species and there are times when all you are doing is taking a match to your money. Then of course, we have the collateral damage that we don’t think much about, and I believe we should start to consider the cost pertaining to that.
First off, whether you think I’m cuckoo with believing mowing or grazing are better weed control methods, there are definitely times your spray isn’t effective. If you are trying to spray pasture or CRP weeds anytime from the end of June through the middle of September it is a waste of time and money. I know many of you see red when dreaded thistles show up, but often by the time you either see the purple demon, or have time to get after them, it’s too late. They have gone to seed.
At this point, there is no doubt mowing and knocking down those thistles is the most effective control measure. If things get really bad sometimes you just have to do the next best thing, not the optimum thing. You have run out of time by July and it’s just damage control time. Not only is trying to spray after it’s too late to control your noxious weeds ineffective at its goal, but you kill the beneficial warm season plants. It’s not just too late for thistles, pretty much every other noxious weeds like Leafy Spurge and Wormwood Sage are far past any effective application.
Thistles are biannuals, so right now the new crop is starting their life cycles. You are starting to see the rosettes popping out of the ground this time of the year. If you are to spray this is an effective time as they are young (less root growth) and taking in nutrients before winter. Perennial noxious weeds are also busy taking in nutrients before winter. Right now is the start of the optimum window for effective control. If you are interested in mitigating the collateral damage, the later you can wait the better. Obviously, you need the right temperatures for herbicide to work but we can limit the harm to our beneficial plants if they are entering dormancy. The ideal situation would be if we get that normal September frost and then it warms back up.
If you missed the fall window but are on your toes come spring, then the time is early. The first part of May is most effective as your target plants are really trying to take off. This is especially the time you should be after your Wormwood and Spurge if you are going to do so. I’m really starting to doubt we can tame Leafy Spurge with chemical applications. It can look completely toasted and then seem like it comes back even stronger. It may have at one time seemed like a joke that using sheep or goats could be used as effective tools against noxious weeds but I’m a believer.
It’s important to remember that timing is just as crucial with using sheep or goats as it is for spraying, but when it comes to Leafy Spurge they might be our only hope. Sheep producers, do you have Spurge, thistles, or many broadleaf plants in your sheep pastures? Yeah, didn’t think so. Sheep prefer forbs over grass, even spurge, they will pass over the grass to seek out the forbs. If you are a cattle producer, you probably don’t want to decrease your carrying capacity by contracting sheep to go after your spurge. One of the coolest things about it is that it won’t affect your carrying capacity as long as you don’t overgraze the sheep to where they run out of forbs.
The bigger caveat I want to offer here is you don’t have to spray every inch of the field or pasture. If you spray, spot spraying is going to have much lower collateral damage as you are only spraying the problem spots. I know it seems like more work, because it is, but if you want something good you have to work for it. Drone spraying has really taken off, and I think they can be a good thing, if they are spot spraying. Spot spraying and spraying during the effective dates.
At some point, especially with new CRP, we have to learn acceptance that there will be weeds. The law does not require eradication, which if you apply common sense, isn’t possible. We create disturbances with our actions on the landscape; weeds will come as that is their function. Again, mowing is usually the best thing to do, we can mow as many times as we need to. Through patience and time that horrible looking CRP will establish and those plants that are supposed to be out there will out compete the weeds and that is a much better longterm plan than panic spraying every year. We have been spraying for decades now, how has that turned out? Are those weeds gone and never coming back?