Topic Fact Sheet
What are pesticide formulations?
A pesticide formulation is a mixture of chemicals which effectively controls
a pest. Formulating a pesticide involves processing it to improve its storage,
handling, safety, application, or effectiveness.1 See the text box on Some
What makes up a formulation?
- The pesticide formulation is a mixture of active and other
ingredients (previously called inert ingredients). An active
ingredient is a substance that prevents, kills, or repels a pest or
acts as a plant regulator, desiccant, defoliant, synergist, or
nitrogen stabilizer.4 Pesticides come in many different
formulations due to variations in the active ingredient's
solubility, ability to control the pest, and ease of handling and
- Synergists are a type of active ingredient that are sometimes
added to formulations.4 They enhance another active
ingredient's ability to kill the pest while using the minimum
amount of active ingredient, but do not themselves possess pesticidal
properties. For example, insecticides containing the active ingredient
pyrethrins often contain piperonyl butoxide or n-octyl bicycloheptane
dicarboximide as a synergist.
- Other (or inert) ingredients may aid in the application of the
active ingredient. Other ingredients can be solvents, carriers,
adjuvants, or any other compound, besides the active ingredient, which
is intentionally added.4 There are many types of other
ingredients: solvents are liquids that dissolve the active ingredient,
carriers are liquids or solid chemicals that are added to a pesticide
product to aid in the delivery of the active ingredient, and adjuvants
often help make the pesticide stick to or spread out on the
application surface (i.e., leaves).5 Other adjuvants aid in
the mixing of some formulations when they are diluted for application.
What do manufacturers consider when creating a formulation?
- The type of surface, training, equipment, runoff, drift, habits of
the pest, and safety are all considered when a manufacturer designs a
Type of surface
- Some formulations are more effective on certain surfaces than
others. Discoloration or pitting of the surface of plants or other
surfaces may occur with some formulations.6,7
Training and equipment
- Many pesticide products that the public purchases and uses are
ready-to-use (RTU) formulations which require no dilution and can be
applied quickly and conveniently. Examples of ready-to-use
formulations used by homeowners are granules for insect and weed
control and baits for rodent control.
- Many of the formulations used by farmers and commercial
applicators (like pest control companies) need to be applied with
certain equipment. These formulations may also require certification
or training for individuals performing the application. For example,
termiticide applicators may be required by the Department of
Agriculture in each state to complete specific training in the use of
- Some liquid pesticide formulations commonly used by farmers and
commercial applicators are applied with a compressed air sprayer,
fogger, or soil injector.6 Other liquid pesticide
formulations used by farmers may require the use of aircraft, low
pressure boom sprayer, high-pressure sprayer, or ultra-low-volume
- The equipment required for the application is listed on the label.
Runoff or drift
- Rain soon after the application may cause the pesticide to run off
and contaminate lakes, rivers, streams, or ponds.7
- Wind may carry or drift the pesticide during the application onto
adjacent property, bodies of water, people, or animals.
- Specific environmental precautionary statements may be present on
the label describing how to avoid runoff or drift.
Safety to people, animals, and the environment
- Individuals who apply, handle, transport, or dispose of pesticides
should know the proper manner in which to deal with them. Safety gear
is important to minimize potential exposure to pesticides during an
application. An applicator's proper personal protective equipment
(PPE) may include a long sleeve shirt, pants, closed-toe shoes,
chemically resistant rubber gloves, a respirator, and/or eye
protection. The equipment required for an application will be listed
on the label.
- In addition to the safety of those working with pesticides, the
safety of people, pets, and the environment near the site of
application need to be taken into account.7 To facilitate
this, the label often has precautionary statements to protect wildlife
and other non-target species.
Habits of the pest
- The pest needs to be identified. Information on how the pest
feeds, its reproductive habits, and its life cycle will help the
manufacturer determine which formulation would be the most
Can pesticides be mixed together?
- The pesticide product label will list any chemicals that it should
not be mixed with (i.e., incompatible with) or containers that it
should not be mixed in.4 For example, wettable sulfur
should not be mixed with Lorsban or Morestan because they are
- Some pesticides can be mixed together (i.e., they are compatible
with each other).
- Not all pesticides can be mixed together (incompatible) because
they separate out of the solution, gel, curdle, or clog the equipment
- Pesticides that are physically different (i.e., dust versus
liquid) are typically incompatible.
How are incompatibilities avoided?
- Verify with the pesticide label what types of pesticide
formulations to avoid mixing. Formulated pesticide products that are
ready-to-use (RTU) liquids and concentrated liquids that have been
diluted according to label instructions can be mixed
together. However, undiluted liquid concentrations should not be
- To reduce incompatibilities of flowable, wettable powder, and
water-dispersible granule formulations, regular shaking is
- If you have questions about compatibility or other
pesticide-related issues contact your State Department of Agriculture
or your local County Cooperative Extension Service for more
Date Reviewed: December 1999
- Ware, G.W. The Pesticide Book, 4th ed; W.H. Freeman: Fresno, CA, 1994.
- University of Nebraska Cooperative Extension Service. A guide for private and commercial applicators: Applying pesticides
correctly. National pesticide applicator training core manual, University of Nebraska: Lincoln, 1992.
- Oregon Pesticide Applicator's Manual: a guide to the safe use and handling of pesticides; Miller, T.L, ed. Oregon State
University Extension Service: Corvallis, 1993.
- Label Review Manual; U.S. Environmental Protection Agency, Office of Pesticide Programs, U.S. Government Printing
Office: Washington, DC, 1998. http://www.epa.gov/oppfead1/labeling/lrm/
- Terms of the Environment; U.S. Environmental Protection Agency, Office of Pesticide Programs, U.S. Government Printing
Office: Washington, DC, 1997. http://www.epa.gov/OCEPAterms/
- Bohmont, B.L. The standard pesticide user's guide (revised). Prentice Hall: Princeton, NJ, 1990.
- Farm Chemicals Handbook 1997; Meister Publishing Company, Willoughby, OH, 1997.
NPIC fact sheets are designed to answer questions that are commonly
asked by the general public about pesticides that are regulated by the
U.S. Environmental Protection Agency (U.S. EPA). This document is
intended to be educational in nature and helpful to consumers for
making decisions about pesticide use.