Mixes and Rain Fastness of Product

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I have had several questions within the last day or so on rain fastness of products. Labels often address this but not all the time, and often times you are mixing more than one product and that makes it challenging.

I am going to attach the Apogee label and it states for peanuts that 8 hours is needed. I think it states 1 hour for grass seed crops. You are spending $30/acre for one application so I would be careful. But too, if you spray and get rain much closer to the application I would be reluctant to go back and spray immediately. You simply may have to come back with the second spray sooner than you would like to. Yes, this is almost an “I don’t know what to tell you” answer. If we are in a pattern of afternoon showers I would spray it in the morning as soon as I could and then you will probably get 3 or more hours. That is well below the 8 hours if a shower comes up but I suspect you will get decent activity.

For grass herbicides like clethodim (Select) if you can get 30 minutes you will probably be okay. The crop oil really helps here. The label will have a longer rain fastness but this product gets in quickly. You can always come back with more if it is apparent in 4 or 5 days or week that nothing is going on. You can use the upper end of the rate for clethodim if you are worried about control and wash off. But too, if you are having trouble getting in the field due to wet conditions, clethodim is going to work really well because the grass is not at all stressed. PPO inhibitors (Cobra, Storm, Ultra Blazer) need at least 1 hour (see table 4-9 in Peanut Information…I have not looked at labels in a while for this but at one time this was on the label. Note some products do not list a time, but I would think Ultra Blazer and Storm would fall in the same category with Cobra.) Also, Cadre will probably work better with the rains we have had recently. A considerable amount of Cadre applied post emergence is actually absorbed by roots. Some of you will recall the days of Scepter in soybeans. York’s group did some early work comparing soil, foliage and soil + foliage application to emerged sicklepod under greenhouse conditions and found that soil only was as good as foliar only. Dr. Wilcut did similar work with Cadre while he was at Georgia way back in the early 1990s and I think he saw the same thing on several weeds. I did some work in graduate school with Staple and found similar results. Whenever you have a herbicide that can be applied preemergence or one with known residual activity after application, you will get some activity even if you get some wash off. The Cadre label has 3 hours listed but if you get 1 hour I suspect you will get decent control and maybe even better residual control on weeds that are going to come up (do not repeat the application because of carryover potential, possible long-term stunting of peanut, and budget.) With PPO inhibitors you will know within a few days if you are going to get some control. If you are worried about it and just feel like you need to turn around and spray again (but seldom will you get rain within one hour in all of your fields) I would use another product just to make sure you are not getting a 1.5x rate of a single product out there at one time. So, if you just have to spray because you are worried (and the 1 hour gives you a good bit of flexibility) I would follow Blazer with Cobra or Cobra with Blazer, etc.

The Apogee label has information on adjuvants when mixed with other products. But with the investment I would make it a standalone application and always have crop oil and UAN or AMS in the tank. Clethodim (various formulations) requires crop oil and UAN or AMS can in some cases help

clethodim performance. So, applying clethodim with Apogee is okay because the adjuvant system matches up well for both products. We have never seen clethodim reduce Apogee performance or Apogee reduce grass control by clethodim.

Barbara has discussed rain fastness of fungicide sprays recently at the training session and it is hard to make a general recommendation. One thing that is helpful is the fact that you are coming back soon with another spray. This is not to say our fungicides are overly curative but you have another spray coming to fight back epidemics. The stem rot activity may be greater with the rain but the leaf spot control less. Fortunately the leaf spot control programs are inexpensive and not too hard to swallow if you get a lot of rain right after an application and need to come back almost immediately.

Hope these comments help.

Article first appeared as North Carolina Peanut Note (PNNC-2013-048)