Core Topic: Pesticide Formulations-Tank Mixing/Compatibility
Once your group has a pretty good grasp of the property's of formulations why pesticides are formulated, what the pros and cons of different ones are then there's a bunch of other things you can use to build on that information one is about tank mixing incompatibility many times you will have a group of clients be they corn farmers or golf course superintendents that want to apply several products to the cornfield fairway and rather than make three trips they wanna make one but in order to do that they have to put three products in the tank and those products have to basically play nicer or it ain't gonna work right and many labels give you some support about that one thing that I'll do when I'm preparing to teach about incompatibility is I'll have sample labels that the people would use and I will ask them number one to find the instructions about compatibility, proper mixing, doing are compatibility test and that them as to whether they find them helpful or not there are some labels that are quite helpful and tell you what products they do mix with, or what products commonly cause problems there are other labels that are unfortunately pretty skimpy and maybe make reference to a compatibility chart which very few exist or refer you to your extension agent or educator and it's a reach to expect those people to know every single possible combination that every kind pesticide applicator in their area would use. so back to the point if they can have their hands on experience with some labels and find this information it's real helpful but it also helps I think if you can use these common materials to show what happens when materials aren't compatible it'll give folks something to hang their hat on when they're trying to do these tank mixes or do these compatibility tests in preparation for making a tank mix. now here for example would be a physical incompatibility there's plenty of instructions and you can reference your resource materials from Penn State for this but a good example that I'm not gonna show is oil and water if you pour corn oil into water it's not gonna mix its gonna layer if you put a little dishwashing detergent in there and shake it up you can kinda keep a mixture somewhat uniform but the minute you stop shaking or let that stand it's gonna layer back again. so that would be an example a physical incompatibility another one would be this. I'm gonna take some strong tea which is a solution and I'm gonna add some lemon juice which a lot of people do to their tea and then add cream and if you do this you need creamer whole milk at least can't get by with the skinny stuff and when you mix these materials you no longer have a clear solution and if you look at this closely you'll see that there's clots or lumps forming in it and that would be very difficult to spray without plugging nozzles that would be very difficult without agitation to keep it uniform and here's some that I mixed up a several hours before and you can see what's beginning to happen. in your resource materials you find many examples so both physical incompatibility and chemical incompatible here's a cheap inexpensive way to demonstrate chemical incompatibility and also play on what students have probably learned in biology class if they ever did the starch test now we're gonna start with a weak suspension of cornstarch and you can tell it's a suspension because it's cloudy and also a weak solution, true solution of iodine.
now one would think if you mix cloudy white in clear orange you're going to get a lighter orange. however, if you put these together you gonna find that's not the case and in this case you've got something purple and what you have you don't know in fact like I said this is the positive test for starch iodine onto starch but the fact is that is an applicator you can clearly see you don't have what you started with you don't necessarily know what you have could you spray this. certainly. would you want to I wouldn't because I don't know what I have and I don't know if it has the same properties as what I intended to apply will it have the same effect will it burn up the plant will it work at all will it affect the insect or disease I'm trying to control who knows so this is an example of formation a new substance which is indicative of a chemical change which tells me I probably don't want full with this stuff. okay, as a suggestion if I were you I would use three jars rather than poor one into the other if you use the three jars third for the combination you can compare what you started with to what you end up with same thing with the precipitate formation and the fiscal incompatibility