Pesticide Safety and Use

Who can apply pesticides

Except in the state of Maine, farmers do not need a license to apply general use pesticides and a pesticide license is only required when using restricted use pesticides.  Also, workers who help someone who is licensed or certified to apply restricted-use materials may also need a license to assist.  Usually, commercial applicators follow a different set of rules that are more restrictive.  It is important to check with your state lead agency to determine what is appropriate in your state.  Please note that the requirements of the EPA Worker Protection Standards (WPS) must still be followed regardless of whether a pesticide license or certification is required.  See the section on WPS below.  As of this printing, following are contacts in each state who can provide information on specific requirements for pesticide licenses and certification when necessary.  If more information is needed, go directly to the web site for each state.

Connecticut:  Linda Schmidt,, 860-424-3369,

Maine: Gary Fish,, 207-287-2731,

Massachusetts: Hoang Vo,, 617-626-1818,

New Hampshire:  603-271-3694,

Rhode Island:  Robin Mooney,, 401-222-2781 Extension 4513,

Vermont:, 802-828-2431,

Warning! Pesticides are poisonous.  Read and follow all directions and safety precautions on labels.  Handle carefully and store in original labeled containers out of reach of children, pets and livestock.  Do not use concentrations greater than stated on the label.  Do not apply more pesticide per acre or more frequently than the fewest number of days between applications recommended by the label.  Remember that the pesticide label is a legal document. If you do not follow the label directions implicitly, you could lose your applicator's license or be fined by the State Lead Agency (SLA).

Pesticide Registration

Pesticides require both federal and state registration. Pesticides in this publication have been reviewed for federal registration status and are current at the time of publication. State registration status has been reviewed for most products, but state registrations are renewed annually and may be subject to change. Each New England state maintains a registration database, which can be found at the following websites:

Maine Board of Pesticides Control
Searchable database

New Hampshire
Division of Pesticide Control
Contact Director of Division of Pesticide Control for information

Vermont Agency of Agriculture, Food, and Markets
Searchable database

Massachusetts Pesticide Product Registration Information
Searchable database

Connecticut Department of Energy and Environmental Protection
Searchable database

Rhode Island
Department of Environmental Management
Searchable Database
Select 'Registered Pesticides' link for list

Understanding Pesticide Labels

A pesticide is referred to: (1) by a common name, which is also the name of the active ingredient (AI) or (2) by a trade or brand name (trade names are capitalized in this guide).  Trade names are used in the guide for identification only; no product endorsement is implied, nor is discrimination intended against similar materials.

Labels are for your protection and information: Look for the percentage (by weight) or amount of material in the formulation.  Compare costs of two similar products on the basis of effectiveness, the amount of actual pesticide contained and the quantity of the formulations needed/acre.

Labeled Formulations: The examples of pesticide products that are listed under each crop within this publication give only one formulation and one trade name.  Often there are other formulations and trade names with the same active ingredient. Growers should be aware of other formulations and products. Consult the tables in Weed, Insect and Disease Management Sections (Tables 25 [ ], 28 [ ], and 29 [ ]) for lists of formulations and products.  The rates to be applied are on the label.

  • Emulsifiable concentrates (EC) are less troublesome to spray equipment than wettable powders (WP). The water-based flowable concentrates and wettable powders are less likely to cause plant injury than oil-based concentrates of similar materials.
  • Wettable powders/suspendable powders (WP) are less likely than ECs to cause injury to sensitive plants or to cause trouble when mixed with fungicides or other pesticides.
  • Dry flowables (DF) are similar to wettable powders in their formulation but are pelletized to minimize dust.
  • Flowables (F) are liquid formulations with similar properties to latex paint. Clean equipment immediately after use.

Note: There may be several products registered with the same active ingredient.  Each label is different, and some crops may be listed on some labels but not on others.  Always be certain the crop is listed on the product label before ordering or using the product.

Restricted-Use Pesticides:  In accordance with federal and state pesticide regulations, those pesticides that are highly toxic and those that persist and accumulate in the environment are placed on a restricted-use list and shall be sold and used only by certified applicators.  For information about training for certified applicators contact your Extension Specialist or the offices listed above.  In some instances, states may require additional permits for certain pesticide users.

Control of target pest not on the label: Always be certain the crop is on the label before using a pesticide on that crop. Target pests not listed on the label may not be effectively controlled by that product.

Tank mixture and aerial application: Check the label and consult your state pesticide regulatory agency.

To avoid illegal residues: Adhere strictly to days to harvest (dh). Accurately calibrate your equipment; never exceed label recommendations. Prevent drift to adjacent properties or crops, or contamination of bodies of water. The applicator is held responsible for problems caused by drift or contamination. High-volume, low-pressure, ground applications cause less drift than low-volume, high-pressure, air-blast, ground applications, aerial applications or dust.

Disposal of pesticides: Read label.  For current instructions on regulations and guidelines pertaining to the disposal of chemicals, contact your State Lead Agency (SLA) for pesticide regulation located in either the state Department of Agriculture or state Department of Environmental Protection.  Triple rinse empty containers; dispose of them carefully and properly.

It is the responsibility of the user to read the label and be sure that the material selected is labeled for the proposed use.  Similar pesticide products may not have the same crop uses.

Pesticide Toxicity

All pesticides are poisonous.  However, some are more toxic than others.  The toxicity of the pesticide is usually stated in the precaution label.  For example, a skull and crossbones figure and the signal word "Danger" are always found on the label of highly toxic (Toxicity Class I) materials.  Those of medium toxicity (Toxicity Class II) carry the signal word "Warning".  The least toxic materials (Toxicity Class III) have the signal word "Caution".  The toxicity of a pesticide is expressed in terms of oral and dermal LD50.  LD50 (lethal dose 50) is the dosage of active ingredient that kills 50% of test animals (usually rats or rabbits) with a single application of the pure pesticide for a given weight of the animal (mg/kg of body weight).  The lower the LD50 value, the more toxic the material.  Oral LD50 is the measure of the toxicity of pure active ingredient when administered internally to test animals.  Dermal LD50 is the measure of the toxicity of pure active ingredient applied to the skin of test animals.  Generally, an oral application is more toxic than a dermal one.

Pesticide Characteristics

Solubility is the ability of a chemical to dissolve in a solvent.  Pesticides that are highly soluble in water are often desirable from an applicator's perspective because they are less likely to clump and/or separate.  However, they also pose potential water quality issues as they can easily leach into the groundwater supply.  If practical, use the least soluble material at the lowest effective rate.

Adsorption is the binding of a chemical to the surfaces of soil particles and organic matter. Some chemicals are tightly adsorbed and do not easily leach from soils; however, they have a higher risk of moving with soil when there is surface erosion. Others have low adsorption, and will leach more easily.

Persistence refers to the amount of time a chemical will stay in the environment before being broken down into nontoxic substances.  The rate of breakdown is affected by sunlight, temperature, soil pH, moisture and microbial activity.  Pesticide persistence is measured in terms of half-life, which is the length of time needed for one-half of the amount applied to break down.  Persistent chemicals break down slowly, increasing the chance for them to leach into the soil.  Conversely, short-lived materials may be degraded before significant leaching occurs.  Many pesticides are broken down by sunlight (photodegradation) and/or microbial action. Incorporation of pesticides into the soil reduces or eliminates photodegradation.  As depth in the soil increases, there is less microbial degradation.  Any practice that slows degradation increases persistence and the likelihood of leaching.  Generally, foliar applied materials are more likely to break down before significant leaching occurs than those that are applied to the soil.


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 or not to use an adjuvant 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 middle of days when you can add the temperature and humidity together and get 150 or more.  

It is best to avoid silicone-based surfactants, ionic surfactants, or others that you are not familiar with 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 try it on a small scale first to make sure that there will be no problems.

Some labels provide no mention of adjuvants; in this case, consult the manufacturer or pesticide dealer.

Know Your Water

The pH of the water in your tank mix can sometimes affect the efficacy of pesticides.  Insecticides, in particular, have a tendency to break down (hydrolize) rapidly in alkaline water.  Water pH can vary, depending on the source, from 5.0 to 9.5.  Neutral water has a pH of 7.0, while alkaline water is higher than 7.0.  If your water pH is much higher than 8.0, you may want to consider using an acidifying agent such as vinegar 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 have their water tested.  This can be done on the farm with pH test kits.  Also, organic matter can tie up certain pesticides or clog nozzles, so be sure to use water that is free of organic debris.

The Worker Protection Standard and Who Must Comply

Pesticides can be useful tools for farmers.  They can also be deadly.  Exposure to pesticides can cause physical harm, debilitation, and even death.  Not only applicators are at risk.  Family members and workers can also be harmed due to improper storage and use of pesticides.  

For this reason, the EPA has developed the Agricultural Worker Protection Standard (WPS) for Pesticides (US EPA regulation, 40 CFR Part 170).  The WPS applies to all pesticides that are used in the production of agricultural plants on farms, forests, nurseries, and greenhouses.  This includes general use pesticides including those allowed in organic production (OMRI-approved), as well as restricted-use pesticides.  Also, even if a pesticide license is not required, employees and handlers must still receive education in and comply with the WPS.

The WPS requires the owner or employer to take steps to reduce the risk of pesticide-related illness and injury: 1) if pesticides are used on the farm or 2) workers or pesticide handlers are employed who may be exposed to such pesticides.

You will know a pesticide product is covered by the WPS if you see the following statement in the "Directions for Use" section of the pesticide labeling:

Agricultural Use Requirements

Use this product only in accordance with its labeling and with the Worker Protection Standard, 40 CFR Part 170. This standard contains requirements for the protection of agricultural workers on farms, forests, nurseries, and greenhouses, and handlers of agricultural pesticides. It contains requirements for training, decontamination, notification, and emergency assistance. It also contains specific instructions and exceptions pertaining to the statements on this label about personal protective equipment, notification of workers, and restricted-entry intervals.

The primary WPS resource is the How to Comply manual (, developed by EPA.  The manual is available from your State Lead Agency (SLA), pesticide education office of the Cooperative Extension Service, the EPA Region 1 office and EPA's National Agricultural Compliance Assistance Center.  Every agricultural producer should have a copy of the EPA How to Comply manual.

Key Elements of the Worker Protection Standard

The following is a brief summary of the major elements of the WPS.  Each of these categories is described in greater detail in the EPA How to Comply manual.  Producers should refer to the How to Comply manual for complete details and explanations of the requirements of the Worker Protection Standard.

Information and Education. To ensure employees will be informed about exposure to pesticides, the WPS requires:

  • Pesticide safety training for workers and handlers,
  • Pesticide safety poster to be displayed for workers and handlers
  • Access to labeling information for pesticide handlers and early-entry workers
  • Access to specific information a centrally-located Application List of pesticide treatments on the establishment

Protection. To ensure employees will be protected from exposures to pesticides, the WPS requires employers to:

  • Prohibit handlers from applying a pesticide in a way that will expose workers or other persons
  • Exclude workers from areas being treated with pesticides
  • Exclude workers from areas that remain under a restricted entry interval (REI) with narrow exceptions
  • Protect early-entry workers who are doing permitted tasks in treated areas during an REI requirements include special instructions and duties related to correct use of Personal Protective Equipment (PPE)
  • Notify workers about treated areas so they can avoid inadvertent exposures
  • Protect handlers during handling tasks requirements include monitoring while handling highly toxic pesticides and duties related to correct use of PPE.

Mitigation. To mitigate exposures that employees receive, the WPS requires:

  • Decontamination sites that provide handlers and workers an ample supply of water, soap and towels for routine washing and emergency decontamination,
  • Emergency assistance that provides transportation to a medical care facility if an agricultural worker or handler may have been poisoned or injured by a pesticide and providing information about the pesticide(s) to which the person may have been exposed.

Agricultural Owner Exemptions. Even if you are the owner of the farm, forest, nursery, or greenhouse and you or members of your family do all the work there, you are a "WPS employer."  You must comply with SOME of the WPS requirements, such as adhering to restricted entry intervals, personal protective equipment (PPE) and ALL the specific requirements listed in the pesticide labeling.

If you hire commercial handlers, certain information must be given from you (the operator) to the commercial handler employer.

  • Specific location and description of any areas that may be treated with a pesticide or be under an REI while handler is there, or that the commercial handlers may be in (or walk within 1/4 mile of),
  • Restrictions on entering those areas.

Crop Advisors. The WPS requires employers to provide certain protections to their employees who are working as crop advisors. Examples of crop advisors are crop consultants, scouts, and integrated pest management monitors. An independent or commercial crop advisor is any person working as a crop advisor who is employed (including self-employed) by anyone other than the agricultural establishment on which the work is being done. Certain provisions of the WPS apply to crop advisors depending on when the advisor is on the farm and when the pesticide has been applied.

Commercial Handlers. Employers of commercial handlers must make sure that their customer the operator of the farm, forest, nursery or greenhouse, knows certain information such as: specific location and description of the area treated with the pesticide, time and date pesticide is to be applied, product name, EPA registration number, active ingredient(s), REI for the pesticide, whether the labeling requires treated area posting and oral notification and any other specific requirements on the pesticide labeling concerning protection of workers and other persons during or after application.

For more information on the WPS, contact your Cooperative Extension Pesticide Safety Education Coordinator, SLA or EPA Region 1 office.  Web Site for WPS:

Pesticide Storage

Pesticides should always be stored in their original containers and kept tightly closed. For the protection of others, especially firefighters, the storage area should be posted as Pesticide Storage and kept securely locked.

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 pesticides.

Store pesticides in a cool (between 40° and 80°F), dry, well ventilated area that is not accessible to children and others who do not know or understand the safe and proper use of pesticides.

Any restricted pesticide or container contaminated by restricted pesticides must be stored in a secure, locked enclosure while unattended.  That enclosure must bear a "pesticide storage" warning sign readable at a distance of 20'.  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.  Keep an inventory of all pesticides stored in an area away from the storage site, so that it may be referred to in case of an emergency at the storage site.

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.

Keep your local fire department informed of the location of all pesticide storage areas.  Fighting a fire that includes smoke from burning pesticides can be extremely hazardous.  Firefighters should be cautioned to avoid breathing any smoke from such a fire.  A fire with smoke from burning pesticides may endanger people in the immediate area or community.  They may have to be evacuated if the smoke from a pesticide fire drifts in their direction.

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.  The following points should be observed:

  • Read the label.  Special storage recommendations or restrictions will be printed on the label.
  • Write the purchase or delivery date of the product on the label with waterproof ink.  Products may lose their effectiveness over several years.
  • Ventilation is important for storage of most pesticides.
  • Store herbicides separately from other pesticides to avoid cross contamination.  Below are signs of quality deterioration:


General Signs of Deterioration


Evidence of separation of components such as sludge or sediment.  Milky appearance does not occur when water is added. 


Milky appearance does not occur when water is added. 


Excessive lumping; powder does not suspend in water. 

D, G

Excessive lumping or caking 


After freezing, place pesticides in warm storage (50° to 80°F, or 10° to 26.7°C).  Shake or roll container every few hours to mix product or eliminate layering.  If layering persists or if all crystals do not completely dissolve, do not use product.  If in doubt, call the manufacturer.

Emergency Information

Human Exposure. If someone has swallowed or inhaled a pesticide or gotten it in the eye or on the skin:

  • Call 911 if the person in unconscious, having trouble breathing, or having convulsions.
  • Check the label for directions on how to give first aid.
  • Call the Poison Control Center at 1-(800)-222-1222 for help with first aid information.

The National Pesticide Information Center (NPIC) 1-(800)-858-7378 can also provide information about pesticide products and their toxicity.

Poisoning Information (Adapted from Ohio Vegetable Production Guide)

Make sure your doctor has a copy of the Note to Physicians that is placed on the labels of dangerous pesticides.

Treatment for pesticide poisoning is very precise. The antidotes can vary for the different pesticides. In an emergency, call your doctor and provide specific information on the trade name and common name of the pesticide exposed to. Your doctor will then consult the center if necessary.

Tables 25, 28, and 29 list restricted herbicides, insecticides, and fungicides that are commonly recommended for vegetable weed, insect, and disease control along with their oral and dermal LD50 values. Materials with an LD50 value of less than 100 should be considered highly toxic and handled with extreme caution.

Spills. The National Response Center can help you decide how to respond to a spill. They can be reached at: 1-(800)-424-8802. In addition, CHEMTREC maintains a large database of Material Safety Data Sheets, chemical information references, resources, and networks of chemical and hazardous material experts. CHEMTREC provides access to technical information regarding chemical products as well as telephone access to product specialists, chemists, or other experts. (1-800-424-9300 in the U.S. or 703-527-3887 outside the U.S.)

The Comprehensive Environmental Response, Compensations, and Liability Act (CERCLA) requires that all releases of hazardous substances (including radionuclides) exceeding reportable quantities be reported by the responsible party to the National Response Center (NRC). Title 40 of the Code of Federal Regulations Part 302 promulgates reportable quantities and reporting criteria. All the Extremely Hazardous Chemicals (EHS) that overlap with the CERCLA listed chemicals table (40 CFR Part 302.4) should be reported to NRC as well as to the LEPC and SERC.

For small pesticide spills or for more information, call the pesticide manufacturer or the National Pesticide Information Center (NPIC) at 1-800-858-7378.

Reporting a Spill: The National Response Center (NRC) is the sole federal point of contact for reporting oil and chemical spills. If you have a spill to report, contact NRC at 1-800-424-8802 (toll-free) or check out their Web site for additional information on reporting requirements and procedures. For those without 800 access, please contact the NRC at 202-267-2675.

Producers should be aware that they may be required to report spills to their state Lead Agency (SLA)  or their state Department of Environmental Protection.

For more Information: contact the National Pesticide Information Center (NPIC) at 1-800-858-7378.  

Calibration of Pesticide Application Equipment

(Adapted from 2011 Rutgers Commercial Vegetable Production Guide,

Calibration is the process of measuring and adjusting the amount of pesticide your equipment will apply over a target area. Periodic calibrations of sprayers, dusters, and granule distributors are necessary to ensure accurate delivery rates of pesticides per acre. Calibrations are made by measuring the total gallons of water applied per acre, in the case of sprayers, and the total pounds of dust or granules applied per acre, in the case of dust and granule distributors. Too little spray or dust applied results in inadequate distribution of toxicant over plant surfaces. Control is usually poor, and additional applications are required. Too much per acre is hazardous for the applicator, is frequently injurious to plants (phytotoxic), and could lead to excessive residues if applied close to harvest.

Selection of sprayer tips

The selection of proper sprayer tips for use with various pesticides is very important. Nozzle tips must be selected according to the spray coverage, droplet size, and application volume desired. Flat fan-spray tips are designed for preemergence and postemergence application of herbicides. These nozzles produce a tapered-edge spray pattern that overlaps for uniform coverage when properly mounted on a boom. Standard flat fan-spray tips are designed to operate at low pressures (30-60 psi) to produce small- to medium-sized droplets that do not have excessive drift.  Flood-type nozzle tips are generally used for complete fertilizer, liquid N, etc., and sometimes for spraying herbicides onto the soil surface prior to incorporation.

Full and hollow-cone nozzles deliver circular spray patterns and are used for application of insecticides or fungicides to crops where thorough coverage of the leaf surfaces is extremely important and where spray drift will not result in crop injury of nearby plants. They are used when higher water volumes and spray pressures are recommended. With cone nozzles, the disk size and the number of holes in the whirl plate affect the output rate. Various combinations of disks and whirl plates can be used to achieve the desired spray coverage.

Calibration for Field Sprayers

Width of Boom. The width of boom must be expressed in feet. The boom coverage is equal to the number of nozzles multiplied by the space between nozzles.

Ground Speed (mph). Careful control of ground speed is very important for accurate spray application. Select a gear and throttle setting to maintain constant speed. A speed of 2 to 3 miles per hour is desirable. From a "running start," mark off the beginning and ending of a 30 second run. The distance traveled in this 30 second period divided by 44 will equal the speed in miles per hour.  Example: At a tractor speed of 1 mile per hour, you would travel 88'  in 1 minute, 44' in 30 seconds or 500' in 5 minutes and 41 seconds.

Sprayer Discharge (gpm). Run the sprayer at a certain pressure, and catch the discharge from each nozzle for a known length of time. Collect all the discharge, measure the total volume and convert the volume to gallons. Divide this volume by the time in minutes to determine discharge in gallons per minute. Catching the discharge from each nozzle checks the performance of the individual nozzle which is a critical step in calibration. If there is more than 10% variation between any nozzles, all the tips should be replaced. When it is not convenient to catch the discharge from each nozzle, a trough may be used to catch the total discharge.

Before Calibrating. Review and complete the following checklist:

1. Thoroughly clean all nozzles, screens, etc., to ensure proper operation.
2. Check to be sure that all nozzles are the same, are made by one manufacturer, and have the same part number.
3. Check the spray patterns of all nozzles for uniformity. Check the volume of delivery by placing similar containers under each nozzle. All containers should fill at the same rate. Replace nozzles that do not have uniform patterns or do not fill containers at the same rate.
4. Select an operating speed. Note the tachometer reading or mark the throttle setting. When spraying, be sure to use the same speed as used for calibrating.
5. Select an operating pressure. Adjust pressure to desired psi according to the nozzle manufacture. Do this while pump is operating at normal speed and water is actually flowing through the nozzles. This pressure should be the same during calibration and field spraying.

Calibration Using the Jar Method.  Any 1-quart or larger container, such as a jar or measuring cup, if calibrated in fluid ounces, can easily be used following the steps below. A specially designed calibration jar can be used; if you buy one, follow the manufacturer's instructions. Make accurate speed and pressure readings and jar measurements. Make several checks. Keep in mind that you are collecting less than a quart of liquid to measure an application rate of several gallons per acre for many acres.

1. Measure a course on the same type of surface (sod, plowed, etc.) and same type of terrain (hilly, level, etc.) as that to be sprayed, according to nozzle spacing as follows:

Nozzle Spacing  (in) 








Course length (ft)








This area will be equal to 1/128 of an acre.

2. Time the seconds it takes the sprayer to cover the measured distance at the desired speed. Average several runs. This is the time required to cover 1/128 acre.
3. With the sprayer standing still, operate at selected pressure and pump speed. Catch the water from several nozzles for the number of seconds measured in step 2.
4. Determine the average output per nozzle in ounces. The ounces per nozzle equal the gallons per acre applied by one nozzle per spacing.

Calibration for Boom or Airblast Sprayer. The following applies to any pesticide that is applied as a liquid spray.

1. Fill sprayer with water.
2. Spray a measured area (width of area covered x distance traveled) at constant speed and pressure selected from manufacturer's information.
3. Measure amount of water necessary to refill tank (gallons used).
4. Multiply gallons used by 43,560, and divide by the number of square feet in area sprayed. This gives gallons per acre.
5. Add correct amount of spray material to tank to give the recommended rate per acre.

      10 gal of water used to spray an area 660 ft long and 20 ft wide
      Tank size - 100 gal
      Spray material - 2 lb formulated product/A

      gal used x 43,560       =       10 x 43,560       =        33 gal/A
          area sprayed                        660x 20                      
       tank capacity            
=        100 (tank size)   =        3.03 acres sprayed
gal/A                                   33                                 per tank
       3.03 x 2 (lb/A) = 6.06 lb material per tank

Calibration for Granular Applications

The application equipment for granular fertilizer, herbicides, insecticides, etc. in many cases was not designed as precision equipment; therefore, extra care must be taken in calibration to get the results desired. Application rates of granular application equipment are affected by several factors: gate openings or settings, ground speed of the applicator, shape and size of granular material, and roughness of the ground. It takes a conscientious operator, effort, knowledge of equipment, and calibration to achieve accurate application rates. The first step to good application is to be sure the equipment is prepared for operation. Be sure all controls are free and work properly. Check and lubricate moving parts as necessary, remove corrosion, and tighten loose nuts and bolts.

Broadcast Applicators (Gravity-Drop or Spinner Applicators)

1. From the label, determine the application rate.
2. From the operators manual, set dial or feed gate to apply desired rate.
3. On a level surface, fill hopper to a given level and mark this level.
4. Measure test area - length of run will depend on size of equipment. It need not be one long run but can be multiple runs at shorter distances.
5. Apply material to measured area, operating at the speed applicator will travel during application.
6. Weigh amount of material required to refill hopper to the marked level.
7. Determine application rate:
                                                 number    x        length of      X       width of
      Area covered      
=              of runs ______  run (ft)________application (ft)
           (acres)                                                       43,560


     Application    =       amount applied (pounds to refill hopper)   
        rate (lb/A)                          area covered (acres)                             

Note: Width of application is width of the spreader for drop or gravity spreaders. For spinner applicators, it is the working width (distance between runs). Check operator's manual for recommendations, generally one-half to three fourths of overall width spread.

Assume: 50 lb/A rate
              Test run-200 ft
              Four runs made
              Application width-12 ft
              11.5 lb to refill hopper
      Area covered    =   4 x 200 x 12     =     0.22A

      Application rate =       11.5              =     52.27 lb/A

8. If application rate is not correct, adjust feed gate opening and recheck.

Calibration for Band Applicators

1. From the label, determine application rate.
2. From the operator's manual, determine applicator setting and adjust accordingly.
3. Fill hopper half full.
4. Operate applicator until all units are feeding.
5. Stop applicator; remove feed tubes at hopper.
6. Attach paper or plastic bag over hopper openings.
7. Operate applicator over measured distance at the speed equipment will be operated.
8. Weigh and record amount delivered from each hopper. (Be sure all hoppers and all tubes deliver the same amount.)
9. Calculate application rate:

Area covered in bands (acres) = 

      number                     length of                        band
     of bands       
           run (ft)           x           width (ft)

Application rate:

     Rate applied in bands (lb/A)      =     total amount collected (lb)
                                                            area covered in bands (acres)

10. If not correct, readjust and recheck.

Calibration for Changing from Broadcast to Band Application.  Within a field, the treated area may be only a fraction of the total land area. Calculate application rates for portion of the field that is treated, using the ratio of band width to row spacing, as follows:

   Band width                      broadcast                              amount needed
   __in inches              x          rate                    
=                    per acre                              
   row spacing                      per acre                                        of field
       in inches

Calibration for Backpack Sprayers

Growers with diverse crops and small plantings often need to be able to apply pesticide to beds or plots of several hundred square feet. It is important to use the correct amount of insecticide in your backpack sprayer when spraying a small area, to mix and spray safely, and to follow the label instructions.

All measuring and mixing utensils used with pesticides or other chemicals should be clearly labeled with warnings that they are only to be used for measuring and mixing pesticides. Measuring equipment should be locked in the pesticide storage area. All equipment calibration should be done on the same surface to which the pesticide will be applied and at the same speed, pressure, etc.

Maintaining constant pressure can be difficult with sprayers that depend on continual hand pumping. To help with backpack sprayer calibration and application, constant flow nozzles are available.  G.A.T.E. LLC manufactures a CF Valve that delivers a constant 14.9 psi recommended for spraying herbicides and a 21 psi for insecticides and fungicides.  These are designed to deliver the same pressure and flow rate no matter what the pressure in the tank is above the designated pressure and shut off if the pressure in the tank falls below the designated pressure.  SOLO makes a "pressure limiting valve" that actually has three settings of 5, 10 and 15 psi for their backpack sprayers that does the same thing. 

Calibration will vary with the crop, crop stage, amount of canopy, and location of target pest in the crop. Seedlings will require far less material than a fully grown canopy. Match the amount of pesticide to the amount of water needed to spray the crop area at the target crop stage.

For products with rates listed in amount/acre: 

1. Calculate what portion of an acre is being sprayed. Determine sq ft of area to be sprayed (multiply bed or canopy width by row length by number of rows). Calculate what proportion of an acre this is (it may be a small fraction of an acre):

     Proportion of an acre to be sprayed     =     number of sq ft. to spray

                                                                         43,560 sq ft. per acre

2. Calculate how much pesticide to use.  Multiply the label rate per acre for the crop and pest times the proportion of an acre to be sprayed.   

     Amount of pesticide needed      =      amount per acre      X     proportion of acre to be sprayed

3. Measure water needed per sq. ft. of crop. Add a known amount of water (eg 1 or 2 gallons) to the tank. Spray the water as if you were actually spraying your field. Remember, you must maintain constant pressure, constant walking speed, and consistent nozzle height and boom setup or wand motion to achieve the coverage you need. This amount will change with different crops and size of crop canopy. When the water is gone, stop and mark the spot. Measure the area you sprayed and calculate square feet (length of swath x width). Calculate how many gallons (or fluid ounces, for smaller areas) needed per sq ft.

      Gallon per sq ft     =      number of gallons used    

                                          number of sq ft sprayed

This can also be calculated by timing how long it takes to spray a known area, then collecting the output for the same amount of time, at the same pressure. Divide the amount used by the area sprayed. 

4. Determine total water needed:

     Gallons of water needed     = gal. per sq ft        X      number of sq ft to be sprayed

5. Mix the required amount of pesticide in required amount of water. Most commonly, it is best to add half the water, add the pesticide, agitate, then add the remaining water. Spray, using the walking speed, pressure, nozzle and boom setup or wand motion that you used for calibrating. 

For products that give rates for backpack sprayers: Some pesticide label provide a rate of product to use per gallon, for backpack sprayers or smaller areas. If this is given, it is still important to calibrate to determine the amount of water used per unit area (sq. ft.).  Add the labeled rate pesticide per gallon of water, adjusting the rate to match the fraction or number of gallons that will be used.