April 1, 2021-
As we gear up for transplanting and general field work, we also find ourselves making a number of crop management decisions. Many of the decisions we make revolve around pesticide selection, and these are often conversations that Cooperative Extension is heavily involved with. Sometimes these are easy conversations to have and sometimes they require in-depth dialogue in order to fully understand what pesticides may or may not be acceptable by industry. Last year we posted an article about specific issues that deserved special attention. We’re reposting this article because much of it rings true in 2021 as well. Below are specific items that we’ll be considering again in 2021, and we strongly feel that you should as well:
1.) FOLLOW YOUR CONTRACT! There is usually information in a tobacco contract that outlines specific pesticides that cannot be used to grow a crop. Unfortunately, we find that there are major differences in what various buying companies have deemed acceptable for application, so there is no longer a “one size fits all approach” for our recommendations. This is where it’s important to remember that just because a pesticide is labeled for tobacco does not mean it can be used in each situation. Remember, you as a farmer have direct access to your contract and the representatives from your buying company – we in Extension do not.
2.) Some insecticides are still labeled for use in tobacco production but are no longer approved for use by some purchasers. Two great examples of this are chlorpyrifos (Warhawk and Lorsban Advance) and acephate (Orthene 97, Acephate 90 WSP, and many others). Dr. Burrack recently posted a great article outlining the chemical alternatives to chlorpyrifos, so be sure to give it a look if you contract with a company that has prohibited its use. We are also fortunate to have chemical alternatives that offer similar or better insect control than acephate (see pg. 150 of the 2021 Tobacco Production Guide). As was mentioned in point number one, this why it is so important to read your contract and consult with your buyers for further clarification.
3.) Our options are very limited when it comes to herbicide selection, and it appears that for some growers those options just became even more limited. For the last few years, we have strongly encouraged producers to consider using pendimethalin (Prowl H2O, Prowl 3.3 EC, and many others) at layby as a way to extend residual weed control and reduce the resistance pressure that we are placing on sulfentrazone and clomazone. Back to point one, this is where reading your contract and having a discussion with your buyer(s) can be useful because some growers can make this application and some cannot. We are fortunate that napropamide (Devrinol 2XT and Devrinol DF-XT) is also labeled for a layby application and is a different chemistry than other herbicides that are used. We have been told that napropamide will be a suitable material for layby application where pendimethalin is not. The application rate for napropamide will vary depending on whether or not it was applied before transplanting or over-the-top after transplanting. If it was not, then 3 qts or 3 lbs per acre would be my targeted rate (depending on formulation). You may only apply a maximum of 4 qts or 4 lbs per acre per season, so remember that total if multiple applications will be used.
4.) Remember certain guidelines for pesticide applications. I specifically think about chlorantraniliprole (Coragen) in this situation. Back around 2017, some buyers began dictating the crop stage at which the final application of this insecticide could be made (no applications after layby, for example). Previous guidelines for acephate application had also been outlined (no applications post-topping).
5.) READ EACH PESTICIDE LABEL!! We cannot stress this enough. It’s important to read and understand these labels as it ensures you know what you are applying to the crop. Certainly, this helps to control target organisms in a safe and environmentally sound manner, but it also helps prevent the application of active ingredients that are not labeled for tobacco. One good example is Quadris Flowable (which is labeled for tobacco) and Quadris Top (which is NOT labeled for tobacco) (Fig. 1). Both fungicides contain the active ingredient azoxystrobin, but Quadris Top also contains difenoconazole – which is not approved for application in US tobacco production. Collectively, this means that an application of Quadris Top to tobacco is an illegal activity and can result in your contract being canceled. This specific point has gained traction because difenoconazole has been added to a number of pesticide residue testing lists, which means an honest mistake may wind up costing you big time. This particular issue is not limited to Quadris as it also applies to multiple herbicides and insecticides. So again, please take the time to read each chemical label.
