Horticulture Science Lesson 32

Determining the Kinds of Pesticides

Horticulture Science Lesson 32

Determining the Kinds of Pesticides

Interest ApproachInterest ApproachAsk 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 thatmost Americans reject produce that has evidence of insect damage. Ask if they feel the same about potted flowering plants, cut flowers, or bedding plants theymight buy. Once it has been established that pest control is important, present the objectives of the lesson.

Student Learning ObjectivesStudent Learning Objectives•Identify the major classifications of pesticides.

•Describe the major classifications of herbicides.

•Explain the major classifications of insecticides.

TermsTerms• contact herbicide• contact insecticide• fumigant• fungicides• herbicides• insect• insecticides• miticides

TermsTerms• mode of action• molluscicides• nematocides• nematodes• nonselective herbicide• pesticide

TermsTerms• 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/SummaryReview/Summary•What are the major classifications of pesticides?

•What are the major classifications of herbicides?

•What are the major classifications of insecticides?