News & Events
Featured Stories
Current Featured Stories Archived Featured Stories

Using Tank Mixes to Control Pests and Diseases

October 29, 2012

Many growers apply various tank mixes, or combinations of two or more chemicals within the same stock tank. Tank mixes are frequently applied to control difficult pests and diseases, to control one or more pests with a single application, or as part of a resistance management strategy.  Another common practice is to mix insecticides with fungicides to reduce the number of individual applications that would otherwise be applied.

Tank mixes can be applied to control a single pest using products effective at controlling differing life cycles such as when mixing an ovicide for controlling eggs and an adulticide for controlling adults.  Mixing two or more pesticides together is also an effective strategy for controlling a single pest using products from different chemical classes with differing modes of action.  Some growers apply two or more products from different chemical classes as a resistance management tool; this is useful for controlling difficult to control pests or pathogens or to control multiple pests simultaneously.

In many instances, growers combine pesticides with differing modes of action for controlling the same pest or to manage multiple pests simultaneously with a single application.  Tank mixes can effectively be used to control similar types of pests (either insects or diseases) or to target different types of pests (both insects and diseases) simultaneously.  Tank mixes targeting multiple pests can greatly reduce the time, labor, and application costs usually associated with controlling multiple pests separately.

Growers should always refer to each chemical’s label prior to mixing with other products.  It is illegal to mix pesticides with other products when tank mixes are expressly prohibited on the label.  In many instances, chemical labels do not prohibit tank mixes and may provide guidance as to which combinations are safe and acceptable.  Chemical labels may provide an indication of which formulations are compatible and the order they must be added when mixing.  Any tank mixes must be prepared consistent to the instructions provided in the label.

When multiple chemicals can be safely mixed and applied in combination without affecting the physical properties of the spray solution or causing injury to the targeted crops, they are considered compatible.  When two of more ingredients of a solution are incompatible, growers applying these mixtures are likely to observe residues in the stock tank, clogging of equipment, loss of effectiveness against the target species, and increased damage to both target and non-target plants.  

Growers should always test the physical and chemical compatibilities of a tank mix before making applications over an entire crop by conducting a jar test.  A jar test entails mixing the appropriate quantity of each chemical in a small volume of water in a one quart jar or one gallon container. Add each of the products into the jar (or jug) of water in the following order (unless specified differently on the product labels).  Each component should be thoroughly mixed before the addition of a new ingredient.

1st     compatibility agents, activators, or surfactants
2nd     wettable powders or dry flowable formulations
3rd     water soluble concentrates or solutions
4th     emulsifiable concentrates or flowables
5th     soluble powder formulations
6th     any additional spreaders or stickers

After all of the chemicals have been added, close the lid on the container tightly and invert 10 times.  Observe the solution immediately after mixing and again 30 minutes later.  The presence of clumps, gums, or sludge indicates an incompatibility, and this particular combination should not be applied to your crops.  A minor amount of separation that remixes easily with agitation is acceptable. Compatibility testing only demonstrates the stability of the mixture and does not demonstrate whether the combination has any pest control activity or is safe to apply to crops.  

The potential for increased risk of phytotoxicity, or chemical burn, on target and non-target crops is another concern with tank mixes.  Tank mixes should be tested on a small scale, making an application to only a few plants of each desirable species.  Observe the test blocks several days after application for any signs of injury symptoms.  When no phytotoxicity is observed, it is safe to make larger scale applications of the tank combination.

Spray solutions of tank mixes should be mixed with at least half the desired amount of water in the tank prior to adding any of the individual components.  The agitation system should also be operating to attain thorough mixing of the products as they are added.  It is important to add the products to the stock tank in the order described above (jar test) to avoid dilution problems.  After all of the products have been added, fill the spray tank with the desired amount of water and agitate it well before applying to the crops.  Always test tank mixes that are new or being applied to new crops on a small scale before making applications to large blocks of plants.

Paul Pilon
Perennial Solutions Consulting



©2018 BASF Corporation