Pesticide Safety Education Newsletter

for Hawaii's Certified Pesticide Applicators

July 2019




  • Earning Recertification Credits
  • Oregon's "Stop Sale, Use and Removal" order
  • Pesticides in Our Environment (recertification article)
  • Mandatory and Advisory Statements on Pesticide Labels (recertification article)
  • New Changes to Paraquat Label (recertification article)
  • Paraquat Dichloride: One Sip Can Kill (recertification article)

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Earning Recertification Credits

Hawaii-certified “commercial” or “private” pesticide applicators may earn recertification credits by scoring at least 70% on the open-book quiz about certain articles in this newsletter issue. The articles have titles followed by “(recertification article).” Some of the articles are actually stories on other websites, so click the link below the article’s title to view the story.

Recertification credits--also called "continuing education training" or "CET" units--may not necessarily apply to the following certification categories: Private 2, Private 3, Commercial 7f, and Commercial 11.

The quizzes are administered by the Hawaii Department of Agriculture’s staff. There is a link to the Department’s “List of Available Quizzes” at the bottom of the Department’s webpage:

Also on that webpage are the procedures for certification and recertification. For help, call one of the Department’s phone numbers for the Pesticide Branch’s Education Section:

Kaua’i – 1-808-241-7140 (Lihue)

Oahu – 1-808-973-9424 or -9409 (Honolulu)

Maui, Molokai or Lanai – 1-808-873-3078 (Kahului)

Hawai’i – 1-808-974-4143 (Hilo)

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Oregon's "Stop Use, Sale and Removal" Order

To read the Oregon Department of Agriculture's news release "Complaint leads ODA to issue Stop Sale, Use and Removal orders for six over the counter pesticide products claiming to be organic" (June 20, 2019), view the Department's webpage at

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Pesticides in Our Environment (recertification article)

Applicators and the public share concerns about how pesticides may harm the environment.

What is the Environment?

The environment is everything around us. “Natural” elements, such as air, soil, water and wildlife are part of our environment. Other elements of the environment are people, domestic plants and animals and the manufactured parts in which we live and work, including our homes, restaurants, office buildings, factories and all that they contain.

The "target site" is the area we plan to treat with the pesticide because we know pest is there or we expect it to be there. Either the target site itself or a "sensitive area"—like a nearby school, a wildlife preserve or fishpond, or a crop, landscape or garden—may be occupied by a "nontarget organisms", the living things that should not be harmed by the pesticide treatment.

Types of Pests

A target pest is the living microorganism, plant or animal that we want to control when we apply a pesticide. We can think of it as either a key pest, a secondary pest or an occasional pest.

"Key pests" may cause major damage or harm on a regular basis unless they are controlled. Many weeds, for example, are key pests because they compete with our valuable plants for water, sunlight and nutrients. Tall weeds can be key pests when they block a driver’s view of an intersection or driveway. Cockroaches and rodents also can be key pests because their waste and body coverings can trigger asthma in some people. (Skins shed by cockroaches when they molt and rodent hairs are examples of body coverings).


[insert photo of car at an intersection here.]

[caption]]Due to excessive vegetation in the corner sight triangle, drivers are not able to see traffic approaching from the left in time to enter or cross the intersection safely.


"Secondary pests" become a problem after a key pest is controlled or absent. For example, some weed species become pests only after the more competitive key weeds are controlled.

"Occasional pests" become troublesome only once in a while because of their life cycles, environmental influences, or as a result of human activities. For instance, large numbers of the house mouse (Mus musculus) are known to move indoors for food or water during a drought, which reduces their outdoor sources of food and water.

[caption]House mouse (Mus musculus).

Chemical Characteristics of Pesticides

Anyone who uses a pesticide—indoors or outdoors, in a city or on a farm—must consider how the chemical may affect the environment. Its effects vary according to four physical and chemical characteristics of the pesticide: solubility, adsorption, persistence, and volatility.

SOLUBILITY is a measure of the maximum amount of a pesticide that can dissolve in a solvent, usually water. Pesticides rated as highly water-soluble dissolve easily. These chemicals, compared to those with low water-solubility, are more likely to be carried away by water running over the surface of an object or the ground or through a mass of soil.

VOLATILITY is the tendency of a pesticide to turn into a gas or vapor. Some pesticides are more volatile than others. The chance of volatilization increases when the atmosphere is drier (i.e., has a lower relative humidity), warmer or windier. "Co-distillation" is a two-stage process that causes residue of certain chemicals applied on very warm, wet soil to become airborne and later settle somewhere else. It begins with rapid volatilization of the herbicidal residue along with water that is also evaporating off the soil surface. The airborne combination of water vapor and herbicide vapor may then condense on leaves of crop plants and later damage the leaves. Labels of these herbicides give warnings like these two:

"Do not apply in greenhouses as plant injury may result from co distillation of Ronstar G Herbicide active ingredient onto leaf surfaces in condensate."

"Off-Site Movement Under California Growing Conditions: Current research indicates a propensity for off-site movement of certain soil-applied pesticides in California's unique growing conditions. Pesticides, such as Dacthal Flowable, may be moved off-site through a process called co-distillation. This phenomenon has been shown to occur where bare soil is treated (crops not present) and the soil surface is very hot. The pesticides, though not highly volatile, appear to be carried from the soil surface with water molecules during rapid evaporation that occurs immediately after irrigation."


ADSORPTION is the process that causes a pesticide to bind to soil particles. It is the result of an attraction between the chemical molecules and the surfaces of soil particles. Once adsorbed to soil particles, the pesticide is less likely to be carried away with water flowing over the surface of soil or through the soil mass. Clay particles and organic matter are the two components of soil that typically attract oil-soluble pesticides more than water-soluble pesticides. Also, pesticide molecules with a positive charge are more tightly adsorbed to negatively charged soil particles.

PERSISTENCE is the tendency of a pesticide to resist being carried away (by an air current or flowing water) as well as breaking down for a relatively long time. This allows it to maintain its original form over an extended period during which it can continuously control the pest. A chemical’s persistence is described in terms of its half-life, that is, the number of hours or days needed to breakdown or degrade 50% of a measured amount of chemical residue. For example, on plant surfaces, the half-life of the insecticide permethrin ranges from 1–3 weeks, depending on the plant species. In other words, if there is now 20 grams of permethrin on plants in a field, we would predict that there be just 10 grams remaining 1–3 weeks later. In other words, the longer the half-life, the more persistent the pesticide. The pesticide remaining on a surface or on a plant, animal or object after an application or spill is called residue. Sometimes applying a pesticide with a long half-life is desirable because its residue provides long-term pest control and so lessens the need for repeated applications. However, before the residue disappears, it may harm people, animals, plants and microorganisms that are sensitive to the chemical. Therefore, it is especially important to handle and apply persistent pesticides by using equipment and techniques that keep them from drifting, leaching or running off into nontarget sites with nontarget organisms.

Besides presenting a hazard to people and other nontarget organisms, carelessly applying persistent pesticides to an initial crop may result in having illegal residues on a second food or feed crop planted in the same field. To protect consumers from illegals residues, the U.S. Environmental Protection Agency sets a tolerance for each combination of a pesticide ingredient and a crop. The "tolerance" is a legal limit to the concentration of the residual ingredient that may remain in or on a specific food, feed or other agricultural commodity to be sold for food or livestock feed. A grower should check the pesticide label for warnings about the persistence of the residue or a "plantback interval," which says how many days to delay replanting in the treated field after the last application of the pesticide. Here’s a simplified example for an insecticide:

"Treated areas may be replanted with any crop specified on labels of products with the same active ingredient in this product, or any crop for which a tolerance exists for the active ingredient, as soon as practical following the last application. The following plantback intervals must be observed for crops listed here: 30-day plantback for rice or buckwheat."

Persistent residue in fields treated with certain herbicides is also a potential problem. For example, it is possible for the herbicidal residue in the field’s soil to damage a follow-up crop that cannot tolerate the herbicide. The label may give a warning like this:

"Do not plant cotton after the last application of this product, without following the plantback intervals, or injury may result: 3 months interval for wheat, 12 months interval for other crops not on listed on this label."

Breakdown or degradation

Breakdown or "degradation" is one of the processes that cause pesticide residue on a treated or contaminated surface to disappear or dissipate. Several processes degrade most pesticides into simpler and often less toxic chemicals.


[Insert Figure 7.1 here.]

[caption]Breakdown or degradation of pesticides by microbes, chemical reactions and sunlight.


Some pesticides degrade very rapidly—in a matter of days or even hours. Others linger in the environment for a year or more. Pesticides are degraded by these three processes:
•    Microbial action—the break-down of chemicals by soil microorganisms, such as fungi or bacteria.
•    Chemical degradation—the breakdown of chemicals that does not involve living organisms, usually by a chemical reaction with water.
•    Photodegradation—the break-down of chemicals resulting from exposure to sunlight.
Water and temperature both affect degradation. Warm, wet conditions will speed it up of a chemical; cool, dry conditions will slow it down.


Another process that causes residue to dissipate is "transport," which is movement of residue from the target site with air currents, flowing water or with soil particles or objects bearing pesticide residues. Residues may degrade during transport.


[Insert Figure 7.2 here.]

[caption]Movement of pesticides in the environment.
MOVEMENT WITH AIR CURRENTS. Pesticides may move offsite in the form of spray droplets, vapors, dusts or solid particles, and even as residue on wind-borne soil particles. Movement away from a target site by an air current is called drift if it happens during or soon after applying the pesticide. People who apply pesticides outdoors as dusts or sprays are usually aware of how easily pesticides may drift offsite. But those who handle pesticides indoors may not realize how readily some gases, dusts or fine sprays move offsite in air currents created by ventilation systems and forced-air heating and cooling systems. 
Studies have shown that a sizable percentage of pesticides may never reach the target site because of drift. Significant drift can damage or contaminate sensitive crops, poison bees, pose health risks to humans and animals, and contaminate soil and water in adjacent areas. It is impossible to eliminate drift, but it is possible to reduce it to a tolerable level.

MOVEMENT WITH WATER. Falling rain or irrigation water may wash residue off treated surfaces and carry it away. Most pesticide movement with water is by runoff over the ground or by leaching (downward) into and through the soil mass. Runoff and leaching may also occur in three situations: when highly water-soluble or persistent pesticides are used; when too much pesticide is applied or spilled onto a surface; or when too much rain or irrigation moves pesticide through the soil out of the target site or into nearby bodies of surface water or groundwater.
Runoff water in an outdoor environment may move residue into drainage systems, streams, ponds, or other surface water, where the pesticides can travel great distances. Pesticides that leach easily may move downward through the soil deeply enough to get into bodies of groundwater used for drinking and other domestic purposes.
Some pesticides can leach indoors, too. In a greenhouse, for example, pesticide residue may leach through the soil or other planting medium and contaminate greenhouse floors. And, water containing pesticides can runoff into floor drains and contaminate water systems. A careless act, such as dumping a pesticide or rinsate into a sink or toilet may contaminate an entire sewage or water-treatment facility.
Look for special instructions on the label that warn of hazards caused by the movement of pesticides in water. Sometimes labels require buffers or setbacks from wells and bodies of water.

MOVEMENT WITH OBJECTS. Residue of pesticides on or in treated object can be moved from the target site when we move those objects offsite. Here are three examples:
•    We send treated lumber from the wood treatment facility to a lumber distributor’s storage and then to a construction site.
•    The treated agricultural commodities grown for food are carried from farm to market to a consumer’s home.
•    If a pesticide handler drives home while wearing clothing that was contaminated on the job, small amounts of pesticide residue may rub off onto a car seat or the carpeting or furniture at home.

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SOURCE. The preceding article “Pesticides in Our Environment” is based on two sources:
(1) National Pesticide Information Center’s Topic Fact Sheet “Pesticide Half-life.” (as viewed on 7/31/19)
(2) Chapter 1 "Pest Management" in the booklet "National Pesticide Applicator Certification Core Manual, second edition, 2014" published by the National Association of State Departments of Agriculture Research Foundation. (as viewed on 7/22/19) (as viewed on 7/30/19)

The two drawings, Figures 7.1 and 7.2, are from the same guide.

Photo of a house mouse is from the webpage "Rats in the Compost Bin?" on the website for the "Official Blog of the UC Master Gardener Program of Contra Costa County" published July 11, 2016. (as viewed on 7/31/19)

Photo (with caption) of a car at an intersection is from the guide “Vegetation Control for Safety: A Guide for Local Highway and Street Maintenance Personnel" revised August 2008 and published by the U.S. Department of Transportation, Federal Highway Administration. (as viewed on 7/30/19).


Mandatory and Advisory Statements on Pesticide Labels (Recertification Article)

Statements on pesticide labels give good-to-know information, advice, and enforceable instructions to owners, handlers and users of the products. They are not only about application of the pesticides. The statements also cover preparations before application or following up afterward; transport of containers after they have been opened; and storage or disposal of the container or unused product or dilution. Those types of statements are either mandatory or advisory.

Mandatory statements tell you to take or avoid specific actions in order to legally handle or use your pesticide, like these four examples:

  • "Wear chemical-resistant gloves."
  • "If swallowed, call a doctor."
  • "Do not apply within 66 feet of wells."
  • "Keep away from heat, sparks, and open flame."

These are the do’s and don’t’s that tell you where, when and how to handle or apply a pesticide. Pesticide manufacturers put those kinds of statements on their products' labels to lessen the risk of polluting our air, soil or water; harming wildlife, pets, livestock or valuable plants; and, of course, yourself, your workers and neighbors.

Mandatory statements are not merely suggestions or recommendations. Pesticide regulators will take into account each statement when enforcing pesticide laws and regulations. They will compare the actions or inactions of the owner, handler or user of a pesticide to its mandatory statements. In effect, a pesticide’s label becomes the set of rules for that product. To remind you of this, every pesticide label shows the "misuse statement":

“It is a violation of Federal law to use this product in a manner inconsistent with its labeling.”

Advisory statements, however, are recommendations or best management practices that the manufacturer has determined may result in better product performance or improved safety. Older pesticide labels may say that an action is “recommended” or that the action “should” or “may” be taken. But those words may cause some confusion. “Recommended” and “should” suggest that the action is a requirement, though it might have been intended as an option or a choice. Conversely, “may” suggests that the action is an option or choice, though it might have been intended as a requirement . Instead of using those words, some of the newer labels phrase advisory statements to explain the purpose or benefit of doing something. Here are three examples:

• "Latex gloves provide the best protection."
(instead of "Latex gloves are recommended.")

• "Applying the product immediately after preparation will help to ensure that it is in suspension. If application is delayed, agitation to remix the products and checking for resuspension will ensure proper blending."
(instead of "Tank mixtures should be applied immediately after preparation. If for any reason this is not possible, ensure that sufficient agitation has been provided to remix all products and check for complete resuspension prior to application.")

• "Directing the spray mixture around the base of the cotton plants and using leaf lifters and shields on application equipment will help minimize foliage contact and plant injury."
(Instead of "The spray mixture should be directed to the soil around the base of the cotton plants. Care should be taken to prevent the spray from striking the cotton leaves as injury will occur. The use of leaf lifters or shields on application equipment is recommended to avoid spraying the cotton foliage.")

But when the U.S. Environmental Protection Agency reviews labels awaiting approval or registration, it allows “recommended,” “should,” “may” or similar terms on a case-by-case basis, as long as they are unambiguous and do not appear to cause problems.

To get help interpreting statements on your pesticide’s label, ask the Hawaii Department of Agriculture’s Pesticides Branch for clarification. The telephone numbers for the Branch’s Education Section are for Kauai (808) 241‑7140; for Oahu (808) 973‑9424 or ‑9409; for Maui (808) 873‑3078; and for the Big Island (808) 974‑4143.

Your pesticide label provides a wealth of information about making the most of a pesticide while preventing problems. Failure to follow the label’s mandatory statements may cause a serious pesticide accident. It may also constitute a legal violation subject to civil or criminal penalties and you can be liable for any personal injury, crop or site damage, or pollution that occurs resulting from misuse. Always remember: The label is a legal document.

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SOURCE. The preceding article, "Mandatory and Advisory Statements on Pesticide Labels," is based on two sources

 "Mahalo" to staff of the Hawaii Department of Agriculture’s Pesticides Branch for their comments and suggestions.


Paraquat Certified Applicator Training to Prevent Poisonings Now Available (recertification article)

March 2019

A new certified applicator training module for “paraquat dichloride” (also known as “paraquat”) is now available. The training was developed by paraquat manufacturers as part of EPA’s 2016 risk mitigation requirements and approved by EPA.

Paraquat is one of the most widely used herbicides in the U.S. for the control of weeds in many agricultural and non‐agricultural settings and is also used as a defoliant on crops such as cotton prior to harvest. Paraquat is a restricted use pesticide for use only by a certified applicator. The restriction applies to mixing, loading, and applying paraquat, as well as other pesticide handling activities.

Since 2000, 17 deaths have been caused by accidental ingestion of paraquat. Many of these deaths resulted from people illegally transferring the pesticide to beverage containers and the victim later mistaking it for a drink. A single sip can be fatal. In addition to the deaths by accidental ingestion, since 2000, three more deaths and many severe injuries have been caused by the pesticide getting onto the skin or into the eyes of those working with it.

To help prevent these tragedies, certified applicators must now take paraquat‐specific training before use, to emphasize that the chemical must not be transferred to or stored in improper containers. The training also covers paraquat toxicity, new label requirements and restrictions, consequences of misuse, and other important information.

The requirement for training is only one of several actions EPA has taken to prevent poisonings, including making label changes, restricting the use of all paraquat products to certified applicators only, and requiring closed‐system packaging for all non‐bulk (less than 120 gallon) end use product containers of paraquat.

See details of EPA’s regulatory actions in the article “Paraquat Dichloride: One Sip Can Kill” (recertification article)” in this issue.

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SOURCE. The preceding article "Paraquat Certified Applicator Training to Prevent Poisonings Now Available" is a slightly modified version of an email message dated 3/18/19 from Kerry Richards, PhD, Pesticide Safety Education Program Coordinator, University of Delaware.



Paraquat Dichloride: One Sip Can Kill (recertification article)

 To read the US Environmental Protection Agency's webpage, Paraquat Dichloride: One Sip Can Kill, view the Agency's webpage at

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