Rainy weather weed control considerations

I don’t have to tell many people how wet it is out there right now. Much of our cotton that has not received a residual herbicide treatment is beginning to get woolly. Cotton fields may not be necessarily “grown up” with weeds, but there is considerable weed pressure showing up. In some cases, the RR cotton is approaching five to six leaves, and is too late for over-the-top (OT) glyphosate applications. Producers should avoid OT glyphosate treatments on these fields. I haven’t seen anything that I would consider to be a salvage situation just yet.

What is the best option for weed control if you’re in this situation? There are numerous weed management strategies available for producers. Probably one of the most broad-spectrum tank-mixes will be Staple plus Assure II. There is likely to be some grass control antagonism, but, if you want to avoid it, apply the two treatments in separate applications three days apart, making the graminicide application first. This recipe will be effective in conventional, Roundup Ready and Liberty Link cotton.

Envoke is another option that will provide some sedge and broadleaf control in over-the-top applications. In earlier articles, we stressed the need for the five leaf plus cotton stage before making OT applications. Another situation that producers will need to consider with this product is stressed cotton, especially from excess moisture. If you choose to use Envoke, allow those fields to dry before making the applications. Be aware that Envoke does not have an aerial application label, and cannot be applied with anything other than surfactant, in the tank. So grass control must be done in a separate application. Similar to Staple, Envoke will antagonize grass control with our graminicides, but we’re a little more restrictive in regards to timing. A graminicide cannot be applied within seven days before or after an Envoke application. However, Envoke will not antagonize glyphosate activity.

Of course there is older chemistry available for weed management. MSMA tank-mixes with Staple, Cotoran, Aim (watch that cotton size), and others can bail us out of some potentially hairy situations without compromising crop health and fruiting patterns. Hooded sprayers are another option. If you don’t like post-directing glyphosate under cotton plants, applying glyphosate under the hood and post-directing conventional mixes under plants is another option.

With Liberty-Link cotton, there is a little more flexibility. We’re not concerned with cotton stage because of no fruiting disruption, but rather spray coverage of the weeds. We need to closely monitor weed stages. These weeds are going to take off over the next few days, so when you finally get into the field be ready to pull the trigger with these applications. Of course it’s difficult to address every weed situation or control option in this brief article. If you’ve been in this situation before and have something that works, by all means use your tried and true methods. Also, let me know, I’m still learning.

Steve Kelly is Extension cotton weed specialist with the LSU AgCenter.

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