Horticulture Science Lesson 32 Determining the Kinds of Pesticides

Interest Approach Ask the students, “If given a choice, would you prefer eating an apple or other produce that displays insect damage over damage-free produce?” Tell them that most Americans reject produce that has evidence of insect damage. Ask if they feel the same about potted flowering plants, cut flowers, or bedding plants they might buy. Once it has been established that pest control is important, present the objectives of the lesson.

Student Learning Objectives Identify the major classifications of pesticides. Describe the major classifications of herbicides. Explain the major classifications of insecticides.

Terms contact herbicide contact insecticide fumigant fungicides herbicides insect insecticides miticides

Terms mode of action molluscicides nematocides nematodes nonselective herbicide pesticide

Terms postemergence applications preemergence applications preplanting applications respiratory insecticide rodenticides selective herbicide stomach insecticide systemic herbicide

What are the major classifications of pesticides? Pesticides are the materials used to control pests. These chemicals may be natural or man-made. Although once used almost exclusively, is now viewed as only one component of an IPM program. In fact, use of chemical pesticides is now often done only when absolutely necessary. Application of pesticides must be done safely to reduce potential injury to people and the environment.

What are the major classifications of pesticides? Insecticides are used to control insects, which are a group of animals with an exoskeleton and three body parts. Most insects have six legs and four wings. Insects are killed by body contact with the chemical, by swallowing the insecticide, or by insecticides that enter through the respiratory system.

What are the major classifications of pesticides? Miticides are used to control mites and ticks. They are usually killed by coming in contact with the chemical.

What are the major classifications of pesticides? Fungicides are used to control fungal disease. Fungicides are used to prevent a plant from becoming infected. Therefore, they are applied before the disease is present.

What are the major classifications of pesticides? Herbicides are used to kill unwanted plants. Rodenticides kill rodents, such as rats and mice. These chemicals are usually applied as bait. Eating the chemical poisons the rodents.

What are the major classifications of pesticides? Nematocides kill nematodes, which are tiny hair-like roundworms that feed on the roots of plants. Nematocides are usually applied in the form of a fumigant, which is a substance that produces a smoke, vapor, or gas when applied.

What are the major classifications of pesticides? Molluscicides are used to kill slugs and snails. These chemicals are usually applied as bait, which attracts the slugs and snails and poisons them.

What are the major classifications of herbicides? Herbicides are classified by selectivity, contact versus translocation, timing, and mode of action. Herbicides are classified as being selective or nonselective. Selective herbicides act on certain plant species and not others. Nonselective herbicides kill all vegetation.

What are the major classifications of herbicides? Herbicides may act on contact with plants or be translocated in the plant. Contact herbicides kill the parts of a plant to which it is applied. Translocated or systemic herbicides are absorbed by the roots or other plant parts and moved throughout the plant by vascular tissues. Translocated herbicides are particularly effective with perennial plants.

What are the major classifications of herbicides? Timing refers to the stage of the crop or weed development. Preplanting applications are made before the crop is planted to control annual weeds. Preemergence applications are made before the crop or weeds emerge. Postemergence applications are completed after the crop or weeds have emerged.

What are the major classifications of herbicides? Mode of action refers to how herbicides kill weeds. The mode of action is the effect on metabolic processes or enzyme systems that result in a lethal or toxic action in the plant. Herbicides may have a single mode of action or a multiple mode of action.

What are the major classifications of insecticides? Insecticides are classified by how they enter an insect’s body. Three general groups of insecticides are contact, stomach, and respiratory. Contact insecticide is absorbed through the skin or exterior of an insect. The chemical must be applied directly on the insect and is normally used with sucking insects.

What are the major classifications of insecticides? Stomach insecticide is effective when eaten. The chemical is applied to the plant parts, which are eaten by the insect. This type of insecticide is most effective on chewing insects. Respiratory insecticide is an insecticide that enters the respiratory system of the insect. It is commonly called a fumigant. This type of insecticide is used in enclosed places.

Review/Summary What are the major classifications of pesticides? What are the major classifications of herbicides? What are the major classifications of insecticides?