Crop protection products; referred to as Pesticides are among the widely used and the most effective and efficient control tools for various types of pests; such as weeds, insects, and disease causing organisms like fungi.
Of great concern and challenge to all growers is precaution that comes with the need to mix several types of pesticides in order to save on cost of spraying, time and to enhance the control of more than one pest problem in a given time, a typical and practical scenario of crop protection. Other concerns are ensuring that the individual pesticide properties in a mix remain intact and effective on the intended problem without any antagonism and or toxicity effects on crop being sprayed.
It is important for every farmer to note that pesticide can either be chemically or physically incompatible and that certain pesticide labels contain compatibility information which every farmer should read before use.
Chemical incompatibility is when even with products that seem to physically mix well, such a mix or mixes reduces or increases the effectiveness of individual product(s) thus reducing effectiveness of target or on the contrary increased effectiveness that sometimes result to toxicities in crops sprayed.
Physical incompatibility or improper mixing of pesticides is when a mix of two or more pesticides forms solids, sludge or separate layers even with constant agitation and which sometimes results to clogging of nozzles, unwanted residues on crops and ineffectiveness.
As a general rule, performing a compatibility test in a jar is key to determine chemical and physical compatibility, normally if the test is positive, it is important for growers to undertake spraying of the mix on to a small area with crop to rule out any toxicity and to assess effectiveness on target pest.
Water quality is key to compatibility of pesticides and growers are always advised to use the best water available for preparing a pesticide tank mix; Clean with no soil particles or organic matter, where possible the Water pH should be between 5-7, and not hard water.
Considering information contained on every product label on usage and different product formulations, a general sequence or procedure is achieved by addition of water to about half tank, addition of Solid formulations with agitation, addition of water to three quarter full, addition of liquid formulations filling up the tank with agitation for uniformity. Using some common pesticide formulations; Wettable Powders and Dry flowable or Water Dispersible granules (WPs, DF and WDG) should be added first, followed by Flowables (F, FL), Micro Encapsulated (ME) formulations and Suspension Concentrates (SC), this is followed by Emulsifiable Concentrates (EC) followed by Solutions (S) and or Soluble powders normally of fertilizers, Adjuvants or oils should be added last. Constant agitation with every addition is necessary for uniform mix. Pre slurring of all dry formulations, SC and EC s before adding to the Tank Mix is important for uniform mix.
Once this is achieved, key precaution is to ensure that spray mixes are not left in direct sunlight where there is exposure to UV light and resulting high spray mix temperatures that result in faster breakdown of pesticides and that all spray mix is used and not left overnight for pesticides in mix break down with the passing of time.