The start of the growing season means the arrival of warmer weather, new roses and many of the pests that plague the grower and exhibitor alike. Fungal infections must be prevented or controlled along with the insects that can devour foliage and damage blooms. Warmer summer weather brings on the spider mites that can defoliate a rose bush in a few days if left unchecked. To prevent or control these pests, many rosarians depend on chemical pesticides to keep their roses healthy.

Pesticides do a good job of protecting our roses from a wide variety of pests, but pesticides also have the potential to be harmful to humans, pets and the environment if not used wisely. The term pest-i-cide could be interpreted as a substance that I use to kill (cide) pests. It isn’t really surprising that something used to kill pests would have the potential to harm humans, and therefore, should be handled carefully. In fact, any substance can be harmful to humans, if we are exposed to too much. Even water, oxygen or vitamins, which are essential for life, or life-saving drugs can be harmful (toxic) if we are exposed to too high an amount for too long a period of time. Although any chemical pesticide has the potential to be toxic to humans, there are harmless ways to handle pesticides. The proper use of pesticides includes a basic knowledge about pesticides, awareness of what you are doing, respect for the effects of pesticides, the use of personal protection and a little common sense.

Knowledge about pesticide use starts with an understanding of the intended uses of the specific pesticides that will be used. For example, malathion is an insecticide and should be used to kill insects, while Avid is a miticide used to kill spider mites. Fungicides like triforine or manzate are good at preventing blackspot, but aren't useful as insecticides or miticides. While not the focus of this article, selecting the right pesticide for the intended use is an important first step in using pesticides properly.

How toxic is toxic?

One important aspect of understanding chemical safety is recognizing the differences in the toxic potential of pesticides. Pesticides are grouped into four subgroups based on their ability to cause lethality (death) or to damage the eyes or skin. The standard measure of lethality is known as the lethal dose 50 (LD50). The LD50 value for a pesticide is the dose (grams/kilograms of body weight) of the pesticide that will kill 50% of an exposed population. The lower the LD50 value, the more toxic the pesticide.

The most toxic pesticides carry the word DANGER on the label, are listed as highly toxic and are classified by the Environmental Protection Agency as Category I pesticides. Based on lethality information, it would only take ingestion of a few drops of a liquid or about 3.5 grams (remember that there are 454 grams per pound) of a solid to kill a 150 lb man. Category I pesticides with this lethality potential can only be applied by licensed applicators, and are not available for general use by the home gardener. However, some pesticides available to the home gardener are listed as Category I pesticides based on their ability to produce severe skin and/or eye damage. These pesticides include: Orthenex, Vendex, Isotox, Mavrik 2E, Captan dust or powder, Triforine EC, Lime Sulfur and Copper Sulfate (99%+).

The next most toxic pesticides carry the word WARNING on the label, are listed as moderately toxic and are classified as Category II pesticides. It would take ingestion of 1 teaspoon to 1 ounce of a liquid or between 3.5 grams to 35 grams of a solid Category II pesticide to kill a 150 lb man. Pesticides in this category include: Cygon 2E, Daconil 2787, Diazinon 25%, Metalaxyl (Subdue 2E or Ridomil), Rubigan (some preparations), Permethrin and Nicotine.

Members of the third most toxic group of pesticides carry the word CAUTION on the label, are listed as slightly toxic and are classified as Category III pesticides. These pesticides require ingestion of between 1 ounce to a pint of a liquid or 35 to 350 grams of a solid to be lethal to a 150 lb man. Pesticides in this category include: Avid, Carbaryl, Mavrik Aqua Flow, Captan 50W, Immunox, Maneb, Mancozeb, Manzate, Rubigan (WP, EC), Sentinel (cyproconazole), Pyrethrin, Acephate (Orthene) and Malathion.

The least toxic group of pesticides also has the word CAUTION on the label, but is listed as toxic and classified as Category IV pesticides. These pesticides require amounts greater than a pint for a liquid or greater than 350 grams for a solid to cause death in a 150 lb man. Pesticides in this group include: Benomyl, Copper Sulfate solutions, Diatomaceous Earth, Sulfur WP, Neem Oil and Safer Soap.

It is important to note that none of the categories are listed as nontoxic. That means that even though a pesticide has only a small likelihood of being harmful, caution should always be used when handling these chemicals. For example, diatomaceous earth, which is used to kill soft-bodied insects, has been placed in the least toxic category for pesticides. However, under a microscope you can see that the particles that make up diatomaceous earth have little pointed crystals that puncture the bodies of the insects and provide the insecticidal action. Inhalation of diatomaceous earth is very irritating to human lungs and the respiratory tract, and you should be especially careful if you are an asthmatic.

Protective Gear

When a decision is made to use pesticides in the garden, it is important to protect ourselves from being exposed to the pesticides that we are going to use. By reducing exposure to the pesticides, the pesticides can be used safely. Protective clothing includes shoes, long-sleeved shirt and long pants, hat, gloves, eye protection and a respirator. Since most pesticides induce harmful effects by being inhaled, absorbed through the skin or getting into the eyes or on the skin, it is important to make sure that these areas of the body are adequately protected.

Clothing: Make sure that you wear shoes and socks, not sandals, when spraying pesticides. Shoes should be made of rubber (not canvas or other porous materials) to provide the best coverage. Long-sleeved shirts will cover the arms and long pants will cover the legs to prevent spray material from affecting the skin and being absorbed from the arms and legs. A wide brimmed hat to cover the head is also important. Many pesticides can readily be absorbed into the body through the scalp, so protection here is necessary. The wide brim will also help protect the face and eyes from exposure. Don’t wear mesh caps, as the spray can easily pass through the mesh and reach the scalp.

Gloves: Gloves used for spraying should be made of rubber, not cloth or leather. Since you will be handling the concentrated form of the pesticide to make spray solutions, you especially want to make sure that your hands are not exposed. Liquid formulations can readily soak through cloth or leather gloves, so use either rubber dish washing/cleaning gloves or buy a pair of chemical resistant gloves at the hardware store.

Goggles: There are several types of glasses and goggles on the market for home use. However, few of these provide adequate eye protection from chemical pesticide sprays. Shop or safety glasses have large gaps on the top and sides and allow spray material to easily reach the eyes and should not be used when spraying. Shop goggles may appear to provide better eye coverage, but the numerous holes in the sides for airflow also allow spray material to reach the eyes. Look for goggles with covered vents on the sides and top as these goggles provide the best protection. These goggles can often be found in hardware stores, college bookstores or farm supply stores. Vented goggles are worn by students in chemistry classes and properly protect the eyes while spraying. Remember that Category I pesticides used by the home gardener have the potential to cause severe eye damage, and any chemical spray or dust has the potential to cause eye irritation or injury.

Respirators: Paint or pesticide respirators should also be worn to prevent inhaling dusts, powders, vapors and spray droplets. The respirator should fit snugly on the face, and if you can smell the pesticides, the respirator is either too loose or the cartridges need to be replaced. Cartridges don’t last forever and should be replaced after about 8 hours of use. These respirators are readily available at hardware stores and home improvement centers. Dust respirators or dust masks offer some protection from the solid form of pesticides, but offer little protection from vapors or liquid forms of the pesticides, and are not recommended for use

Basic Principles of Spray Safety

There are also some basic principles to using pesticides at home that will help insure that no harmful effects come to the user or anyone else. Most of these items are common sense items, but it never hurts to be reminded about them.

Before you spray

Put on your protective clothing, gloves, goggles and respirator before you mix spray material.

Use pesticides only for their recommended use.

Use only the recommended amount. More is not always better and can be harmful.

Read the pesticide label BEFORE use. It is better to spend a little time to become knowledgeable about the pesticide that you want to use than having to react to a problem.

Keep pesticides in their original containers and safely out of reach of children and pets.

Be especially careful when handling the concentrated form of any pesticide, as the concentrated form is the most toxic form.

Prepare spray materials in a well-ventilated area.

Remove pet bowls, children’s toys, etc. from the area to be sprayed and nearby areas.

 

When you spray

Avoid spraying on windy days and never spray into the wind.

Do not smoke, drink or eat while spraying or mixing pesticides. Wait until you have finished spraying and cleaned up to smoke or eat.

Keep children, pets and other adults indoors or away from the garden during spraying.

After you spray

Clean up spray equipment, gloves and goggles after spraying.

Wash spray clothes separately from other clothing.

Shower and shampoo immediately after spraying to remove any residue from skin and hair.

 

Any chemical pesticide available to the home gardener can be used safely without harm to the applicator, family members, pets, neighbors or the environment. Simply be aware and knowledgeable about what you are doing, use proper protective clothing and gear, have respect for the pesticides and their effects, and use a little common sense. By following these basic guidelines, you can have beautiful roses and be able to enjoy them.