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GRAANGIDS
2017
GRAIN GUIDE
Tank mixtures can affect the
effectiveness of weed control
Most of the time producers underestimate the impact a tank mixture of agrochemicals has on
crop production.
The seed of most seed companies is treated with fungicide and/or insecticide or both and is sold
like that to producers. There are also various products on the market that can be used as plant
growth regulators to promote emergence and arrangement. Furthermore it is a common practice
among maize producers to plant with pre-emergence herbicides. Therefore, several instances can
arise where different agrochemicals are mixed with one another.
However, these products must
be mixed strictly according to registration prescriptions. Product labels of herbicides contain
a section where the “mixability” is addressed to prevent agrochemicals from being mixed
together randomly.
Disadvantages of unregistered tank mixtures:
• Products are inconsistent and precipitate, foam and/or thicken.
• This causes clogging of spray equipment.
• Herbicide is not a homogenous solution.
• Herbicide dosage is affected (too high or too low).
• Too little herbicide reaches the target plant (weed).
• Ineffective weed control.
• Crop damage right after administration.
• Delayed effect on crop - probably only visible later in season (yield losses/quality of
yield influenced)
• Extended aftereffect in soil.
• Risk of any damage borne by the producer himself.
Important to remember:
• Tank water must be corrected if pH is too low or too high.
• ‘Hard water’ (e.g. high sodium and/or calcium levels in water) can prevent herbicide for
dissolving effectively in water.
• Sequence in which agrochemicals must be mixed in tank mixtures:
WG>GR>WP>SC>CS>EC>SL
• The formulation of a herbicide is an indication of the solubility of a product in water.
• Where products are mixed, first dissolve small amounts of the products in water and mix well
before mixing with the rest of the tank water (already prepared) (particularly granular
formulae).
• Certain herbicides can be successfully (and in accordance with registration) mixed with an
insecticide, but as a rule fungicides cannot be mixed with herbicides.
• The addition of any other products like growth regulators and additives (penetrators, wetting
agents) must be done very carefully.
• Only registered products with indications on their labels may be added and mixing instructions
must be followed at all times.
For further enquiries, contact Elbé Hugo at 018 299 6298 or send an email to
HugoE@arc.agric.za.
Elbé Hugo, ARC-GCI