- - AGRICULTURE CORE CURRICULUM - - (CLF7000) Advanced Core Cluster: PLANT AND SOIL SCIENCE (CLF7350) Unit Title: PLANT PATHOGENS AND PESTS ____________________________________________________________________________ (CLF7353) Topic: INSECT BIOLOGY Time Taught in Year(s) 5 hours 3 AND 4 ____________________________________________________________________________ Topic Objectives: Upon completion of this lesson the student will be able to: Learning Outcome #: (F-8) - Summarize the use of insect pheromone traps as indicators for spray programs. (F-9) - Collect and mount three beneficial insects and discuss how they are helpful. (F-10) - Collect and mount five harmful insects and list the crops they infest. (F-11) - Draw and label the parts of an insect. (F-11) - Draw and label the parts of a mite, spider or tick. (F-12) - Draw and label the four stages of growth of an insect species which goes through a complete metamorphosis (holometabolis; e.g., bee, moth, etc.). (F-13) - Briefly discuss why holometabolic insects tend to be the most damaging to plants and give one example. Special Materials and Equipment: Collected insects and mites, killing jars, ethyl acetate, plaster of paris, spreading boards, size 00 vials, mothballs or moth crystals, hand lenses and/or microscopes. References: Davidson. Insect Pests. pg 1-20. Swan and Papp. THE COMMON INSECTS OF NORTH AMERICA. Powell and Hogue. CALIFORNIA INSECTS. Evaluation: Unit Examination TOPIC PRESENTATION: INSECT CONTROL INTRODUCTION A. Insects are the most abundant form of animal life on earth. B. They are found nearly everywhere except in the polar regions and the open sea. C. Several hundred thousand kinds of insects have been described, over one million species are known. 1. This is three times the number in the rest of the animal kingdom. 2. Over 1,000 kinds may be found in an average sized backyard. 3. They often number many million to the acre. INSECT CONTROL A. Insects provide many benefits to man. 1. Their pollination activities make possible the increased yield of many agricultural crops. 2. They provide us with products such as silk, honey, beeswax, shellac, and permanent inks and dyes. 3. They serve as food for fish, birds, and other wildlife. 4. Insects perform valuable services as scavengers. 5. They help to control harmful animals (especially other insect pests) and plants. 6. They have medicinal value (i.e., honeybee venom for treating arthritis). 7. They serve as objects of art and ornamentation. B. Insects cause many harmful effects and economic losses. 1. They damage and destroy agricultural crops and other plants. 2. They aid in the spread of diseases in man, animals, and plants. 3. Insects annoy man and animals in various ways. 4. They destroy or lower the value of stored foods. 5. They destroy homes, timber resources, and other goods. C. How can we recognize an insect? 1. The body of an adult insect is divided into three distinct parts - the head, thorax, and abdomen. 2. Adults have three pairs of jointed legs. 3. They have one pair of antennae (feelers). 4. The eyes of adult insects are usually compound. 5. Adult insects commonly have two pairs of wings, flies, however, have only one pair of fully formed wings and a pair of small club shaped structures in place of the second pair of wings and a few groups have no wings as adults. D. How do spiders, mites, and ticks compare to insects? 1. They have two main body regions (head and thorax are fused together). 2. They have four pairs of jointed legs. 3. They lack both antennae and wings. 4. They have only simple eyes. E. Insects may develop from egg to adult with only slight or major changes in form depending on their species. Some shed their skin (molt) as they grow larger. 1. Some insects change only in size as they develop (without metamorphosis). a. The adult lays eggs. b. A nymph, which looks like a tiny adult, hatches from the egg and molts several times. c. The final stage is the wingless adult. 2. Some insects change form slightly. (Simple metamorphosis.) a. Their nymphs hatch from eggs. b. These nymphs, which have no wings, molt and go through several growing stages (instars) often gradually developing wing pads in the last instars. c. The final stage is the winged adult. 3. Other insects change completely (complete metamorphosis) in a four step process: a. the larva (worm, caterpillar, grub, or maggot) hatches from an egg, b. in this larval stage they grow the most and often do the most damage, c. when full grown the larva changes into a pupa (inactive stage), d. during the pupal stage it changes into an adult, and e. the adult stage usually has wings. F. Insects have several characteristics which can be used for identification. 1. Look first at the type of mouth parts. a. Sucking (piercing) and chewing mouth parts are found. b. There are variations of mouth parts within each of these. 2. Wings are a more noticeable part of the insect. a. Most adult insects have two pairs of wings. b. Some have one pair, and some are wingless. c. Wings can be membranous (like cellophane), hardened (like armored covering or bear tiny hairs or scales. d. The number and arrangement of wing veins are of great value in identification. 3. Legs may differ in relative size and shape of the various segments. a. Specializations in legs include those designed for running, jumping, attacking, digging, and swimming. b. Each of these can be recognized by their individual characteristics. 4. Insects have two types of eyes. a. Simple eyes (ocelli) number from 0 to 3. b. Compound eyes are most commonly found as a pair. (None on spiders or mites.) 5. Antennae are appendages arising from the head. a. They are found in pairs and usually only on adults. b. They are nearly always jointed. (None on spiders or mites.) 6. The type of metamorphosis is also very helpful in placing an insect in their proper order. G. Insects which go through a complete metamorphosis are often the most damaging to plants. 1. Both the larval stage and adult stages do damage. (More common with holometabolous insects.) 2. The granary weevil is a good example, both adult and larvae consume stored grains. H. Pheromones are unique chemicals that attract members of the same species of insects. 1. These chemical are naturally secreted by insects in extremely minute quantities to attract their mates and for other communicating purposes. 2. Artificial insect pheromones are used in pest control as tools for: a. detecting or monitoring insect activity, b. timing insecticide applications, and c. to attract insect to poisoned baits. 3. Synthetic pheromones are often used with sticky traps and are very helpful in monitoring insect activity in integrated pest management programs. ___________________________________________________________ ACTIVITY: 1. Have students catch insects, then draw and label 3 body parts, head, abdomen, and thorax. 2. Have students catch a mite, spider, or tick and draw and label the head and body. 3. Discuss other differences between insects and mites, spiders and ticks, as covered in topic outline, while students have these in view. 4. Have each student collect 3 beneficial insects and explain why they are helpful. (Please see attached explanation "How to collect and preserve insects" and brief list of insects to help complete activities 4 and 5.) 5. Have each student collect 5 harmful insects and list the crops they infest. 6. Give each student a cricket or grasshopper and have them observe through a hand lens or a microscope one mouthpart, wing, leg, compound eye, and antenna. 7. Using information discussed in the topic outline, draw and label the four stages of growth of an insect specie which goes through complete metamorphosis. Note: Bees, wasps, ants, butterflies, moths, flies, (including mosquitoes), beetles, (including weevils) all have complete metamorphosis. ___________________________________________________________ ============================================================================ HOW TO COLLECT AND PRESERVE INSECTS COLLECTING: 1. Insects can be caught by sweeping with an insect net through grassy areas and branches. 2. Turn over logs, rocks and other debris to find more insects. 3. Lights attract many insects. Collect them at night at street or porch lights. KILLING: 1. After insects are collected they must be killed quickly. 2. To make a killing jar: a. Use any heavy glass jar with a wide mouth and tight screw cap. b. Pour 1/2 inch of plaster of paris into the jar and allow it to harden. c. Dry it thoroughly in the oven. d. Pour ethyl acetate into the jar. e. Pour off the excess fluid. f. The jar is ready to use and will last for weeks if it is kept tightly closed. g. When it no longer kills insects recharge with ethyl acetate. MOUNTING: 1. Use a spreading board for moths butterflies and other large winged insects. 2. Pin most insects through the thorax and arrange them in neat rows into a collection box (cigar box works well). 3. Soft bodied insects can be preserved immediately in size 00 vials filled with 70 percent rubbing alcohol. 4. Proper labeling, neatness, and uniformity will make an attractive collection. 5. A mothball or moth crystals should be placed in the collection box. This helps prevent destruction of preserved insect specimen by scavenger insects. BRIEF LIST OF INSECTS 1.BENEFICIAL INSECT USEFUL PRODUCT, SERVICE Silkworm Moth Silk Honeybees Honey, Beeswax, Pollination Scale and Gall Insects Pigments and Dyes Fig Wasp Pollinate Figs Wasps Parasites, Predators Beetles Predators, Natural Control of Weeds Lacewings Predators 2.HARMFUL INSECTS TYPE OF DAMAGE Caterpillars Chewing on leaves Beetles Chewing on Leaves, Boring, Feed on Fruit Grasshoppers Chewing on leaves" Twig Borers Boring into Leaves Stems and Fruit Leafminers " " " Aphids Sucking Plant Juices Scale " " Thrips " " Plant Bugs " " Moth Larvae Feeding on Fruits, Nuts & Berries Earwigs " " " Aphids Transmitting Diseases Mites " " Leafhoppers " " Termites Feed on structural timber Scale Insects Shellac Fruit Flies Used in Scientific Studies Flies Parasites, Predators House Flies Spread Disease Mosquitoes Bite Humans, Spread Disease Fleas Bite Humans and Animals 7/24/90 sg #%&C