Mixtures with other pesticides

Toxaphene has been in use since 1949. It is a complex mixture that consists of at least 670 chlorinated terpenes (Jansson Wideqvist, 1983). It was used as a nonsystemic stomach and contact insecticide. As it is nontoxic to plants (except to cucurbius), it was used to control many insects that inhabited cotton, corn, fruit, vegetables and small grains, and to control the Cussia obtusifola soybean pest. Toxaphene solutions were usually mixed with other pesticides because it can help to solubilise other insecticides with lower water solubility (e.g. DDT, lindane, etc.) (ATSDR, 1996b). 

Bordeaux mixture, in spite of having solved several problems in plant protection at the end of the nineteenth century and at the beginning of the twentieth, has many disadvantageous properties. Its action is not uniform, but depends on the coppier-calcium ratio and on the mode of preparation. Since it is corrosive it cannot be stored in iron or steel containers. Moreover it is incompatible with other pesticides, it scorches the more sensitive plants, and its preparation is elaborate. Thus its use is restricted. Finally, it must be used immediately after its preparation because it crystallises on standing, converting into calcium cuprite, so that its fungicidal action is considerably reduced (Burchfield and Schechtman, 1955). 

Tank mix compatibility. Some chemicals only have limited compatibility with other pesticides this can be due to a problem with the formulations or with the activity of the chemical being affected. To get optimum weed corrtrol in some crops mixtures of chemicals are required or sometimes the use of sequences/ stacking (products applied in close succession) is mote effective. 

In addition to the use of two- or three-way tank mixtures of selected herbicides, herbicides are also used in combinations with other pesticides (e.g., insecticides, fungicides, nematocides) or with auxiliary chemicals such as synergists, safeners, extenders, and adjuvants. 

The GLP requirements for mixtures with carrier (40 CFR 160.113) were originally intended to address problems associated with the incorporation of test and control substances into feed, water, and other media for toxicology studies however, now these same requirements pertain to all other GLP-required studies, including those pertaining to re-entry and worker safety. The requirement involves (1) substantiation of test, control, and reference substance concentration through periodic analyses (2) verification of homogeneity and (3) determination of stability and, if applicable, also solubility. All of these requirements usually require chemical analysis, although bioassay may be necessary for microbial pesticides. 

Dieldrin—which belongs to the 12 POPs banned by the Stockholm convention and is in the same class of other pesticides named drins, such as aldrin and endrin—possesses six aliphatic chlorine atoms on a polycyclic skeleton. The multiphasic dechlorination, in the presence of A336, isooctane, aqueous KOH, Pd/C, and hydrogen, proceeded with a different selectivity and degree of dechlorination, depending on the choice of catalyst system, and base concentration. It always required the base and was favored by the presence of A336. It produced a mixture of products derived from the subsequent removal of chlorines, up to a small percentage of monochlorinated derivative. ... 

These data show that peanut products (peanut butter and dry-roasted peanuts) are contaminated with at least three banned pesticides, while mixed nuts, butter crackers, popcorn, sweet roll, pancake mix, and cornbread were reported to contain banned pesticides. Given the low percentage of imports for these products, the occurrence of these pesticides can be said to be the result of past U.S. agricultural practices. Once again, this suggests that even USDA certified organic peanut products will contain a mixture of banned pesticides. The occurrence of banned pesticides in the other grain-based products may be associated with the occurrence of butter or oils in these mixed products. 

Closed system Mixing the active pesticide ingredient or its formulation with other substances such as water in a closed container as opposed to an open environment and/or loading the pesticide (mixture) into application equipment in a closed environment (such as pumping the pesticide from one closed container to another) (Sielken, Ch. 8). 

Pesticide mixtures have been found to exhibit greater than additive effects when administered together. These enhanced effects may be due to the actions of the pesticides themselves, the presence of so-called inert ingredients in their formulations, synergistic interaction with other environmental pollutants, or combinations of these. 

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