Here are three potential past paper questions based on the information provided:
1. Explain the difference between a selective and non-selective herbicide.
2. Describe two methods of pest control other than chemical control and provide an example of each.
3. Explain the advantages of using biopesticides compared to conventional pesticides.
Here are three potential past paper questions based on the information provided:
1. Explain the difference between a selective and non-selective herbicide.
2. Describe two methods of pest control other than chemical control and provide an example of each.
3. Explain the advantages of using biopesticides compared to conventional pesticides.
Here are three potential past paper questions based on the information provided:
1. Explain the difference between a selective and non-selective herbicide.
2. Describe two methods of pest control other than chemical control and provide an example of each.
3. Explain the advantages of using biopesticides compared to conventional pesticides.
Here are three potential past paper questions based on the information provided:
1. Explain the difference between a selective and non-selective herbicide.
2. Describe two methods of pest control other than chemical control and provide an example of each.
3. Explain the advantages of using biopesticides compared to conventional pesticides.
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CROP PROTECTION
Basic Principles of Protection from Weeds and Pests
WHAT IS A WEED? • A Weed is ANY plant that is growing where it is not wanted! THE EFFECTS OF WEEDS ON CROPS • Weeds compete with crops for sunlight, water, nutrients and lowers production. • Weeds harbor pests that can attack crops. • Weeds can secrete poisonous substances e.g. milkweed • Weeds can be parasitic to plants e.g. love vine • Weeds can contaminate the harvested crop e.g. weed seeds in rice METHODS OF WEED CONTROL • Cultural control – crop rotation, crop competition, mulching, using preventative measures. • Mechanical control – hand pulling, hoeing, tillage, flooding, burning, harrowing, ploughing, brush cutting. • Biological control – using other organisms to control weed growth. • Chemical control – the use of herbicides. • Integrated control – combining two or more methods of control for a particular crop CHEMICAL WEED CONTROL Herbicides are chemicals that kill or alter the normal growth of weeds. They can be divided into two main groups: selective and nonselective. • Selective herbicides are those that control the target weed(s) without damaging other species. • Nonselective herbicides kill all vegetation. Herbicides can be further divided into pre-emergence and post-emergence categories. • Pre-emergence herbicides are applied prior to germination and emergence of weeds. • Post-emergence herbicides are used for controlling weeds that have already emerged from the soil. They are either contact or systemic in nature. • Contact herbicides affect only those plant parts that they contact and are not translocated to other portions of the plant. • Systemic herbicides are translocated throughout the plant and destroys the entire plant system WHAT IS A PEST? • A pest is any organism that is harmful, undesirable or injurious to crops or livestock THE EFFECTS OF PESTS ON CROPS • Pests cause a decrease in production • Pests transmit diseases • Pests cause damage to stored produce e.g. weevils • Pests cost the farmer money to control PLANT DISEASES Plant diseases can be caused by;- • Fungi • Bacteria • Viruses • Nematodes • Insects and several other organisms. These are called pathogens. Various organisms can transport (vector) pathogens from infected to healthy plants. SMUT ON CORN – FUNGAL INFECTION TOMATO MOSAIC VIRUS BACTERIAL WILT IN BANANA ROOT KNOTS CAUSED BY NEMATODES INSECT PESTS • There is a whole range of pests, most of them being insects. Their mouth parts may be modified for piercing, sucking or biting the plant MODES of DAMAGE NAME MODE of FEEDING NATURE of DAMAGE CONTROL Aphid Piercing and sucking They suck the sap from the Use a systemic insecticide leaves and produce honey such as Malathion dew which encourages the growth of sooty mold Weevil Boring Larvae bore into the stems Pre harvest control and of plants proper post harvest techniques Army worm Biting and chewing Swarms of larvae invade Use a contact or stomach and strip of foliage poison Cutworm Biting They cut plants to ground Soil treatment with level Chlordane Leafminer Tunneling They tunnel into the leaves Use a systemic insecticide of plants leaving white such as Lannate streaks on the leaf surface Mite Sucking They suck the sap from Use a miticide e.g. Vydate leaves and leave a white web on plants THE LIFE CYCLE OF THE INSECT Insects usually have 4 stages in their life cycle and is called complete metamorphosis as opposed to incomplete metamorphosis which do not have a larval stage
COMPLETE METAMORPHOSIS INCOMPLETE METAMORPHOSIS
METHODS of PEST CONTROL • Mechanical / physical control – hand picking, use of traps, use of mechanical barriers. • Cultural control – crop rotation, sanitation, selection of resistant varieties, rogueing, change of locality, correct planting spaces, use disease free seeds • Biological control – the use of parasites/predators that attack the pest e.g. ladybird beetles eat aphids, wasps kill mealy bugs • Chemical control – the use of stomach poisons, contact insecticides and fumigants • Integrated Pest Management (IPM) – the use of biological, cultural and mechanical methods in combination. Chemical control is used as a last resort Effects of indiscriminate use of chemicals in the environment • Use of the wrong chemical will have a harmful effect on plants • Chemicals destroy beneficial organisms • Chemicals may cause certain pests to build resistance requiring stronger chemicals • Chemicals can wash off plants, soak into the soil and enter waterways • Chemicals can enter the food chain and become concentrated causing destruction • Artificial fertilisers wash into waterways and cause ‘algal bloom’ resulting in eutrophication causing deoxygenation of water and the death of aquatic life BIOPESTICIDES Biopesticides are certain types of pesticides derived from such natural materials as animals, plants, bacteria, and certain minerals. For example, canola oil and baking soda have pesticidal applications and are considered biopesticides.
Biopesticides fall into three major classes:
o Biochemical pesticides are naturally occurring substances that control pests by non-toxic mechanisms o Microbial pesticides consist of a microorganism (e.g., a bacterium, fungus, virus or protozoan) as the active ingredient. o Plant-Incorporated-Protectants (PIPs) are pesticidal substances that plants produce from genetic material that has been added to the plant WHAT ARE THE ADVANTAGES OF USING BIOPESTICIDES? • Biopesticides are usually inherently less toxic than conventional pesticides. • Biopesticides generally affect only the target pest and closely related organisms, whereas broad spectrum, conventional pesticides may affect organisms as different as birds, insects and mammals. • Biopesticides often are effective in very small quantities and often decompose quickly, resulting in lower exposures and largely avoiding the pollution problems caused by conventional pesticides. • When used as a component of Integrated Pest Management (IPM) programs, biopesticides can greatly reduce the use of conventional pesticides, while crop yields remain high. PAST PAPER QUESTIONS USE THE INFORMATION FROM THE PREVIOUS SLIDE TO ANSWER THIS QUESTION