Pesticide Handling & Storage

Pesticide Mixing 

Formulations

Pesticide products consist of their active ingredient(s) and other inert ingredients that are added to serve as carriers for the AI. This mixture is called a formulation. There may be different product formulations that include the same AI. The appropriate formulation to choose may be dependent upon several factors, including the equipment available, the cost of the product, the pest(s) to be controlled, and both user and environmental safety. The formulation of a product is often indicated by a suffix to the trade name. 

Dry or Solid Formulations

• Dusts (D) – used dry
• Granules (G) – used dry; similar to dust, but larger particles that are easier to handle and apply
• Pellets (P or PS) – used dry; large, uniform particles can be applied with more precision than granules
• Soluble Powders (SP or WSP) – dissolve in solution
• Wettable Powders (WP or W) – suspend in solution, must be agitated; abrasive, may cause wear to spray equipment
• Water-Dispersible Granules (WDG) or Dry Flowables (DF) – similar to wettable powder, but granular for easier handling; suspend in solution, must be agitated

Liquid Formulations

• Emulsifiable Concentrates (EC or E) – liquid AI plus petroleum-based solvent and emulsifier; oil base may contribute to phytotoxicity
• Solutions (S) – soluble AI plus carrier
• Suspension concentrates (SC), Flowables (F)/Liquids (L) – solid AI combined with carrier (e.g., clay) and ground to a powder, suspended in liquid; similar texture to latex paint; settle in container and require agitation

Tank Mixing

When using more than one pesticide, you may be able to tank mix products and apply them at the same time. See each label to determine which products can be mixed and if there are specific instructions or restrictions, as well as if any adjuvants are recommended or prohibited. When tank mixing products, always add water to the tank first—at least one quarter of the way full—and add products in the proper order according to their formulations: 

1. Wettable Powders (W or WP)
2. Water Dispersible Granules (WDG), dry flowables, (DF)
3. Flowables (F), suspension concentrates (SC)
4. Emulsifiable Concentrates (EC)
5. Solutions (S)

Adjuvants

Adjuvants are non-pesticide chemicals that are added to pesticides or to pesticide spray mixtures to improve their chemical or physical characteristics. The most common types of adjuvants are nonionic surfactants, crop oil concentrates, spreader/stickers, drift control agents, buffering agents, compatibility agents, and foam-reducing agents. Adjuvants can reduce or eliminate many spray application problems by performing specific functions. These functions include spreading, wetting, sticking, reducing drift, buffering, improving compatibility, reducing foaming, and improving the effectiveness of certain pesticides. Non-ionic surfactants are usually best for improving mixing of pesticides, for enhancing coverage of leaf surfaces, and for improving retention of the pesticide on the crop or weed. Although several adjuvants perform more than one function, no one adjuvant can perform all of these functions.

The most important source of information you have to determine whether to use an adjuvant and when to add it to a tank mix is the pesticide label. Some prohibit the use of adjuvants due to the potential for severe crop injury or loss. Surfactants can increase the potential for crop injury by enhancing penetration of pesticides into the foliage or by causing burning on their own. High temperature and humidity enhance this potential injury. Avoid spraying in the mornings or during the day when the temperature (ºF) plus the % humidity together sum to 150 or more.

It is best to avoid silicone-based or ionic surfactants unless you have a specific purpose for using them. If a label does not list a certain tank mix that you want to use AND, at the same time, does not preclude it, you may make the tank mix. Remember, however, that you should first conduct a “jar test” and try the mix on a small scale first to make sure that there will be no problems.

If a label provides no mention of adjuvants, consult the manufacturer or pesticide dealer.

Know Your Water

Many pesticides remain stable only when mixed with slightly acidic to neutral water, typically within a pH range of 5.0 to 6.5. When pesticides are mixed with alkaline water (with a pH above 7) they can undergo a chemical breakdown known as hydrolysis which may reduce the pesticide’s effectiveness, in some cases within just a few minutes of mixing. As a result, pest control is compromised, product is wasted, and costs increase due to the need for additional applications. If your water pH is higher than 7.0, you may want to consider using an acidifying agent such as citric acid to lower the pH in the tank. Many of the pH-sensitive pesticides have acidifying agents in the formulation that moderate the effect of alkaline water. However, growers who suspect a pH problem should test their water using a handheld pH meter or paper test strips. Also, organic matter can tie up certain pesticides or clog nozzles, so be sure to use water that is free of organic debris.

Guidelines for Mixing Safely

• Obtain the proper training before mixing pesticides. 
• Calculate the amount of pesticide and water needed for the application. 
• Mix during daylight hours if possible.
• Wear appropriate personal protective equipment (PPE), as specified on the label.
• Dispense and mix in a well-ventilated area.
• Measure using appropriate tools, e.g., a scale or measuring cup that will dispense an accurate amount of product. Use tools designated for pesticide measuring, not household items that have other uses. 
• Always add water to the tank first—at least one quarter of the way full.
• Pour pesticide down the side of the tank to avoid splashing.
• Make sure you have a solid footing while pouring.
• Additional water should be carefully added to the pesticide mix by pouring down the side of the tank.
• Do not submerge the end of the water supply hose into the pesticide mix as it could back siphon. Pipe or hosing should be suspended over the opening of the tank.
• Wash gloves before removing them; clean and/or dispose of all PPE appropriately.

Personal Protective Equipment

Appropriate personal protective equipment (PPE) should be worn before opening a pesticide container. The label should be checked for Agricultural Use Requirements. PPE should include chemical resistant gloves and front protection such as a bib-top apron made of butyl, nitrile, or foil laminate material. A face shield, shielded safety glasses, or goggles should be worn. When pouring any pesticide from its container, the container and pesticide should be kept below face level. Ideally your waist should be even with the opening of the tank. A respirator will ensure protection against dusts or vapors. A tank should never be left unattended while it is being filled. If the pesticide user should splash or spill pesticides on themselves, they should stop the operation, wash thoroughly with a mild liquid detergent and water, put on clean PPE, and clean up the spill.

Pesticide Mixing and Loading Sites

Mixing should be avoided in areas where a spill, leak, or overflow could allow pesticides to get into water systems. The mixing and/or loading of pesticides should not occur within four hundred feet of any private or public drinking water supply or two hundred feet of surface water. No pesticide application equipment or mix tank should be filled directly from any source waters unless a backflow prevention device is present. Mixing should not occur on gravel or other surfaces that allow spills to move quickly through the soil.

All transfers of pesticides between containers, including mixing, loading, and equipment cleaning, should be conducted over a spill containment surface designed to intercept, retain, and recover spillage, leakage, and wash water.  Containment needs depend on the quantities of pesticides that are being mixed and loaded. If mixing small quantities, a tarp can be sufficient to contain any spills. Spills can then be cleaned up with an absorbent material. If mixing large quantities regularly, constructing a designated mixing/loading pad is optimal. 

Absorbent material such as re-usable gelling agents, vermiculite, clay, pet litter, or activated charcoal should be on hand along with a garbage can and shovel to quickly contain and clean up any spills. The spilled pesticide should be contained—it should not be hosed down. Absorbent materials should be used to soak up the pesticide, which can then be shoveled into a leak-proof drum. 

Washing and Rinsing Operations

Washing and rinsing of pesticide residues from application equipment, mixing equipment, or other items used in storing, handling, or transporting pesticides should occur on a pad.  In order to reduce the need to frequently wash the application equipment and to avoid cross contamination, application equipment should be dedicated for use for certain types of pesticides.  For example, if a backpack sprayer is used only for applying herbicides it would not necessarily need to be washed after each use.  On the other hand, if the backpack sprayer was used to apply both herbicides and insecticides it would be necessary to always clean the equipment to avoid cross-contamination.

Pesticide Storage 

Pesticides should always be stored in their original containers with their original labels and kept tightly closed. Pesticide products must have label instructions under the heading ‘Storage and Disposal’ for the storage, residue removal, and disposal of pesticides and pesticide containers. Consult the label when you purchase a new pesticide and ensure that these instructions are followed. 

Storage Location

Pesticide storage should be restricted to a first story room or area which has direct access to the outside and is well ventilated. Pesticides should not be stored in basements or outdoors. The area should be located away from water supplies and from areas prone to flooding, and should be protected from direct sunlight, freezing temperatures, and extreme heat. Pesticides should also be stored away from food, animal feed, PPE, seeds, crop packing materials, or other materials that you do not want to risk being contaminated. 

Smaller quantities of pesticides can be stored in cabinets within buildings. Double-walled pesticide cabinets with locks are commercially available. 

If possible, storage areas should be located close to where pesticides will be mixed to avoid having to transport containers. 

Storage areas should be posted as ‘Pesticide Storage’ and kept securely locked. Keep your local fire department informed of the location of all pesticide storage areas. Firefighters should be cautioned to avoid breathing any smoke from a fire that includes smoke from burning pesticides. A fire in a pesticide storage area may also endanger people in the immediate area or community and may require that those potentially affected be evacuated.

Storage Practices

Maintain an inventory outside or away from the storage site of the contents of the storage facility that includes product names, AIs, and dates that products were received, and write the date received on the pesticide container. Unless otherwise marked, most pesticide products have a shelf life of about 2 years. 

Rotate your stocks and use the oldest products first. 

Store pesticide containers right-side up. Store dry chemicals above liquids, and keep liquid containers in an additional tray or tub to catch leaks. 

Separate pesticides by hazard and function. Flammable pesticides should be stored separately from non-flammable pesticides, in a fireproof cabinet. Fungicides, herbicides, and insecticides should be stored in separate locations of the storage area to prevent cross-contamination and accidental misuse. Herbicides, especially hormone-like weed killers such as 2,4-D, should not be stored with other pesticides (primarily insecticides and fungicides) as they can volatize and be absorbed by other products.

If any pesticide has to be stored in other than its original container, that container must be labeled with the name and concentration of the active ingredient and the signal word and warning statements for the pesticide along with a copy of the label. 

Make available to personnel at all times: a respirator with chemical cartridge, gas mask with canister, goggles, rubber gloves and aprons, fire extinguisher, and a detoxicant for spilled materials suggested by your local fire department. Instruct all personnel on proper use of the above equipment and on what to do in case of emergency. A shower stall with plenty of soap should be made available on the premises. Prompt washing in case of accidental spillage may be a matter of life and death.

Winter Storage of Pesticides

Plan pesticide purchases so that supplies are used by the end of the growing season. When pesticides are stored for the winter, keep them at temperatures above freezing, under dry conditions, and out of direct sunlight. If a pesticide does freeze, place it in warm storage (50º-80º F) to thaw, checking to make sure the container is still intact and placing it in a secondary container, such as a waterproof tub, to catch any spillage in case there’s a crack. Shake or roll the container every few hours to mix product or eliminate layering and invert it to make sure the produce is completely mixed. If layering persists or if all crystals do not completely dissolve, do not use the product. If in doubt, call the manufacturer.

Look for these signs of product deterioration before using pesticides after they’ve been stored:

Pesticide Disposal 

Consult the label for disposal instructions. Generally, the safest way to dispose of pesticides is to use them up, applying them to their intended targets according to the label’s instructions.

For current instructions on regulations and guidelines pertaining to the disposal of chemicals, contact the appropriate agency in your state, either the state Department of Agriculture or Environmental Protection. The Pesticide Stewardship Alliance has a pesticide disposal database with resources for each state. Visit their website at https://tpsalliance.org/resources/state-disposal-map  

Triple-rinse empty liquid pesticide containers. The rinse material should be poured into a spray tank and applied to a registered site. Triple-rinsed containers are considered non-hazardous and should be disposed of according to state recommendations. Never reuse an empty pesticide container. If an empty, triple-rinsed container cannot be disposed of immediately, store it in a safe, locked area. Before throwing out powders or granular pesticide containers, be sure to remove all contents from the containers.

A pesticide product that can no longer be used according to the label instructions because it is no longer registered or is otherwise unusable is considered hazardous waste. Applicators are advised to use pesticides in the same year of purchase and to store pesticides properly in order to avoid the accumulation of unusable pesticide products. It may be necessary to contract a licensed hazardous waste facility to dispose of unregistered or otherwise unusable pesticides.