School Science Lessons
School food gardens for tropical regions
Updated: 2009-09-01
Please send comments to: J.Elfick@uq.edu.au
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Preface
Before teaching this project, discuss the content of the lessons with a field officer of the Ministry of Agriculture and get advice on planting material, planting distances, site for planting, approved mulch, composting, and control of pests and diseases. Use only the procedures, agricultural chemicals and insecticides recommended by the local field officer of the Ministry of Agriculture.
Appendix
Table of contents
16.13.0 Pesticides and herbicides
16.13.1.0 Plant extract insecticides, home-made insecticides
16.13.2.0 Inorganic chemical insecticides
16.13.3.0 Organochlorine insecticides, organochlorides, chlorinated hydrocarbons
16.13.4.0 Organophosphate and carbamate insecticides
16.13.5.0 Acaricides
16.13.6.0 Fungicides
16.13.7.0 Herbicides, weedicides
16.13.8.0 Insect repellents
16.13.8.1 Mineral deficiencies
16.13.8.2 Nematode pests
16.13.8.3 Weeds
16.13.1.0 Plant extract insecticides
16.13.1.1 Pyrethrin
16.13.1.2 Rotenone
16.13.3.0 Organochlorine insecticides, organochlorides, chlorinated hydrocarbons
16.13.3.1 DDT
16.13.3.2 Methoxychlor
16.13.3.2.1 Piperonyl butoxide
16.13.3.3 Lindane, gammexane, BHC benzene hexachloride
16.13.3.4 Chlordane, aldrin, dieldrin, heptachlor
16.13.4.0 Organophosphate and carbamate insecticides
16.13.4.1 Acephate
16.13.4.2 Dimethoate
16.13.4.3 Malathion, maldison
16.13.4.4 Naled
16.13.4.5 Tetrachlorvinphos
16.13.4.6 Trichlorophon
16.13.4.7 Carbamates, carbaryl
16.13.4.8 Carbamates, methiocarb
16.13.6.0 Fungicides
16.13.6.1 Benomyl
16.13.6.2 Bordeaux mixture
16.13.6.3 Captan
16.13.6.4 Copper oxychloride
16.13.6.5 Chlorothalonil
16.13.6.6 Zineb
16.13.6.7 Metam
16.13.6.8 Quintozene
16.13.6.9 Sulfur
16.13.6.10 Lime sulfur
16.13.7.0 Herbicides, weedicides
16.13.7.1 Bifenox
16.13.7.2 Dalapon
16.13.7.3 Glyphosate
16.13.7.4 Paraquat
16.13.7.5 MCPA
16.13.7.6 2,4-D
16.13.7.7 2,4,5-T
16.13.0 Pesticides and herbicides
See websites: Pests and diseases | See 16.13.1.0 Plant extracts | See also 6.9.18.0 Prepare pesticides
Insecticides can be divided into stomach poisons that require ingestion, contact poisons that are absorbed through the cuticle and fumigant gases that must be breathed in.
Pesticides used in schools
1. The contents of this appendix are for information only and do not constitute advice on how any particular agricultural chemical should be used in any school garden. Before using any agricultural chemical in a school garden the supervisor should obtain advice from a Field Officer of the Department of Agriculture and should obtain permission from the school principal. The information in this Appendix may be incorrect in some countries.
2. The following pesticides are too dangerous for use in school food gardens 1. organochlorine compounds: DDT, benzene hexachloride (lindane, gammexane BHC) aldrin (chlordane, dieldrin, heptachlor epoxide, endrin) 2. organophosphorus insecticides: chlorpyrifos, parathion, malathion, dimethoate, dichlorvos, mevinphos
16.13.1.0 Plant extract insecticides, home-made insecticides
1. Chilli spray contain an organic compound which repels insects. Grind chillies, but be careful not to put it in your eyes, and add soapy water or detergent as a sticker. Spray on leafy vegetables. Repeat the spray regularly.
2. Garlic oil may be effective against the larvae of mosquitoes and houseflies.
3. Nicotine
See diagram 16.13.1.0 3.: Nicotine
Nicotine is an organic compound obtained from the leaf of the tobacco plant. It can be made by putting non-filter cigarette butts in hot water. This poison is a stomach poison for many insects. Nicotine chemical is very dangerous to use.
4. White cabbage moth deterrent
Boil lettuce leaves and use the solution on cabbages, cauliflower, Brussels sprout.
5. Sooty mould
Add 5 mL of cooking oil + 5 mL household detergent  + 500 mL of water.  Use solution as a spray.
6. Aphid, slug, beetle deterrent
Mix 3 cloves of macerated garlic + 5 mL of household detergent + 500 mL of water. Use solution as a spray.
7. Black spot on roses
Mix 4 mL of sunflower oil + 10 cc sodium bicarbonate + 1 drop household detergent + 1 litre of water. Use solution as a spray.
16.13.1.1 Pyrethrin
See diagram 16.13.1.1: Pyrethrin
Pyrethrin is an organic compound extracted from the pyrethrum flower Chrysanthemum cinerariaefolium. Pyrethrins have an immediate “knock down” effect on flying insects, but a second poison may be needed to kill them. They have low toxicity to mammals. Allethrin insecticide is an organic compound which is the same as pyrethrin but made in a factory. Permethrin is an organic compound which is similar to Pyrethrin but is made in a factory. Chilli, pyrethrin and permethrin are stomach poisons and contact insecticides. They are safe to use, but some people are made sick by them. They are not persistent and there is no withholding period. These poisons kill most pests quickly and so are called knockdown sprays. They also repel insects, stopping them from coming near plants.
16.13.1.2 Rotenone, derris
See diagram 16.13.1.2: Rotenone
Rotenone is an organic compound obtained from roots of the legume Derris and other local bean plants. This chemical is a contact and stomach poison. Rotenone can be used to repel insects and as an acaracide. It is often used to kill fish. It can also affect pigs. It is effective for short periods only because it is broken down by oxygen and sunlight. It is not persistent and must be sprayed every three days. It does not store well. This is a good insecticide but repeated applications are needed. If applied as "derris dust" the plant leaves must not be too shaded. Insects are never resistant to this poison. It can control beetles, weevils, slugs, looper caterpillars, thrips, flies. Rotenone is also used to poison fish.
16.13.2.0 Inorganic chemicals
These chemicals are persistent stomach poisons that kill chewing insects, e.g. caterpillars but not sucking insects, e.g. aphids, mosquitoes. Other inorganic chemicals are used as attractants, repellents and synergists. Inorganic insecticides are usually heavy metal compounds, particularly of lead, mercury, arsenic and antimony. Also, some are fluoride salts, e.g. NaF, sulfur, polysulfides and borax.
1. Borax (Na2B4O7) is used as a cockroach and ant poison and is slightly toxic to mammals.
2. Copper chrome arsenate (CCA) is used to preserve fence posts and garden furniture giving a green colour. Such treated timber is safe for normal use but the sawdust and smoke from burning may contain dangerous levels of arsenic. The white powder seen on some newly purchased timber is probably harmless sodium sulfate.
3. Copper (II) sulfate and lime is used in Bordeaux mixture. Copper (II) sulfate can causes vomiting.
4. Lead arsenate (PbHAsO4) is a heavy metal compound that is insoluble in water and so not readily absorbed by plants on contact. It is effective only by ingestion. The lead blocks essential sites on enzymes and so it is nonspecific. It is toxic to all living systems and extremely persistent. Sodium arsenite is no longer used as a cattle dip against ticks.
5. Sodium fluoride (NaF) and cryolite (Na3AlF6) liberates fluoride ions to precipitate Mg2+ as fluorophosphate thus affecting magnesium dependent enzymes. It is nonspecific and toxic to animals.
6. Sulfur as elemental sulfur, S, and the soluble lime sulfur (CaS) experiences aerial oxidation to SO2, to act as a safe fungicide and acaricide. It has some use as an insecticide.
7. Petroleum oils, petroleum oil spray (PSO) are also "white oil", and "summer oil", and "winter oil". These chemicals are poisonous to some scale insects. They are fairly safe to use. There should be a 1 day withholding period before harvest of the sprayed crop. their classification is based on the temperature at which 5% of the constituents boil, e.g. C21, C23, C24 oils. The latter has less phytotoxicity. The oil droplets on the plant must all join together to kill all the insect pests. These oils are used in 2 ways: 1. They can control scale insects on citrus trees. 2. They can be mixed with other insecticides such as carbaryl to spread them better on plants. Concentrations: 0.25% = 250 mL oil in 100 L water, 2% = 2 L oil in 100 L water.
16.13.3.0 Organochlorine compounds, organochlorides (chlorinated hydrocarbons)
See also 13.4.0: Chlorine
The insecticides DDT, lindane, chlordane, dieldrin, aldrin and heptachlor, fungicides hexachlorobenzene (HCB) and chlorinated phenols, e.g. pentachlorophenol, and herbicide 2, 4, 5 -T must not be used in schools. Also, the use of almost all of these chemicals is now banned in Australia.
Organochlorines are composed only of carbon, hydrogen and chlorine. They are biologically very active but not easy to breakdown, hence persistent. They have one or more chlorine atoms attached to the carbon atoms, replacing hydrogen. The term organochlorine refers to a wide range of organic chemicals, which contain chlorine and sometimes several other elements that have been used in Australia as herbicides, insecticides, fungicides and industrial chemicals, e.g. polychlorinated biphenyls (PCBs). They are very stable compounds that can be distributed in the environment where they persist long after their original use. They degrade slowly and being fat-soluble, accumulate in the food chain, eventually ending up in the fat of our bodies. Key properties of organochlorines which cause concerns are persistence and toxicity. While organochlorine pesticides were manufactured for their toxicity, the fact that they were also persistent had advantages in that they remained effective against target pests for prolonged periods. used to protect crops, livestock, buildings and households from the damaging effects of insects. Commonly used OCP insecticides were DDT, lindane, chlordane, dieldrin, aldrin and heptachlor. Fungicides included hexachlorobenzene (HCB) and chlorinated phenols such as
pentachlorophenol. Herbicide 2, 4, 5 -T was also used.
Hexachlorobenzene (HCB) used in the past as a fungicide (seed disinfectant, seed paint) but now banned in Australia, appears as a widespread contaminant in many environments. It was deregistered for general use between 1985 and 1987.
Chlorinated phenols such as pentachlorophenol (PCP) have been widely used in Australia to protect softwood timber from decay.
2, 4, 5-T was used in the past as a herbicide against broad-leaved woody plants, as a defoliant. The use of almost all the chemicals mentioned above is now banned in Australia.
16.13.3.1 DDT
The new chemical name is1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane. The old name was dichlorodiphenyltrichloroethane, hence "DDT". DDT is a organochlorine contact insecticide that kills by acting as a nerve poison is a highly effective insecticide, both by contact and by ingestion, and is of very low toxicity to mammals. It is odourless and tasteless, has a high persistence, and is chemically stable. However, insects can develop resistance to DDT by natural selection of surviving members with enzymes that can detoxify it. DDT and its metabolic breakdown product can accumulate in the fat of birds and fish, and even people, at the end of the food chain. It may cause birds to produce thin shell eggs that break easily. So the advantage of it being chemically stable is now seen as a major disadvantage. It was also used in large quantities in the control of mosquitoes which caused malaria in tropical countries. There has been a total ban on the use of DDT in Australia since 1987. the technical product "DDT" which is a mixture of isomers, principally p,p'-DDT, with lesser amounts of o,p'-DDT (isomers are chemicals with the same molecular make-up, but with differing three-dimensional structure). Small amounts of the breakdown products DDD and DDE can also be found in the formulation. Once stored in fatty tissue, DDT residues are sequestrated and stabilized unless they are mobilized either through lactation or significant weight loss, which burns fat DDT, DDD and DDE are all strongly suspected of being environmental endocrine disrupters (chemicals that affect the hormonal system).
16.13.3.2 Methoxychlor
See diagram 7.8.2.2: Methoxychlor
It is an organic compound, containing chlorine. It is a contact and stomach poison, very safe to use, and has long persistence. Methoxychlor is pale yellow powder and has a fruity or musty odour. It is used to kill flies, mosquitoes, cockroaches, chiggers and others. Methoxychlor is a general insecticide for food crops, household pests, farm animals, pets and grain storage. Available as W.P., E.C., dusts and in aerosol cans. Methoxychlor is a biodegradable analogue of DDT. While non-polar compounds, e.g. DDT, stay dissolved in the fat of the body, polar substances, e.g. methoxychlor, are water-soluble and can be excreted to be further attacked by other organisms. DDT and pyrethrins keep open the sodium channel of the insect nerve cell, but not the mammal nerve cell, so sodium ions to leak in causing continuous transmission of nerve impulses and the insect dies of exhaustion. You can observe the frantic activity of house flies sprayed with DDT. When DDT sprays were introduced an advertisement stated “They fly outside to die”. Methoxychlor can enter your body when you breathe contaminated air, eat contaminated food, get it on your skin and use gardening products or pet sprays. High doses of methoxychlor could cause damage to the nervous system but low levels of methoxychlor will leave the body so quickly that this type of damage is not likely. The U.S. Environmental Protection Agency (EPA) has set a reference dose (RfD) for methoxychlor at 0.005 milligrams per day.
16.13.3.2.1 Piperonyl butoxide
See diagram 7.8.2.2: Piperonyl butoxide
DDT, methoxychlor, and pyrethrins are more efficient if piperonyl butoxide is added to the insecticide to give a synergistic effect. This additive is not itself an insecticide but deactivates enzymes for detoxification of the pesticide in the insect.
16.13.3.3 Lindane
See diagram 16.3.3.3
Lindane, gammexane, BHC (benzene hexachloride) is an insecticide with different names made by the addition of chlorine to benzene in light. The 7-isomer is the insecticide of the nine isomers formed. Detoxification is by elimination of HCl. Lindane has been used to treat lice in children. The insecticide Lindane is more than 5-20 times more toxic to insects than DDT. It was mainly used against plant eating insects, but had various medical and veterinary applications in treating skin parasites. More specifically, it was used in the control of insect pests in stored seed to control white grubs in pineapples, against ectoparasites on food, and head lice in humans. It was deregistered for general use in 1985. Lindane is a chemical that kills insects, including head lice. was the active ingredient in lice shampoo, which is no longer sold. Generic lindane is still available by prescription for head lice. Shampoo with lindane can be dangerous if swallowed, especially for children. It appears that lindane is not as effective against lice as it once was. One of the safest and most effective methods for controlling head lice is by combing hair with a good lice comb with 3 or 4 rows of closely-spaced metal teeth.
16.13.3.4 Aldrin
See diagram 16.13.3.4: Chlordane, aldrin, dieldrin, heptachlor, endosulfan
Aldrin, chlordane, dieldrin. heptachlor, and endrin are a closely related group made by the Diels-Alder reaction with alkenes from hexachloro-cyclopentadiene. They are broad-spectrum insecticides, highly toxic to insects and mammals, and with high persistence. They also accumulate in body fats and act on the central nervous system. The compound may itself be non-toxic but is converted to a toxic form in the body. They remain in the mammal body, measured as a half residence time, to be detoxified in the liver and excreted by the kidneys but leaving some stored in body fat to be released during illness, stress and lactation, maternal milk. Aldrin and dieldrin have not been produced in the United States since 1974.
Aldrin was manufactured by the Diels-Alder condensation of hexachlorocyclopentadiene with bicyclo[2.2.1]-2,5-heptadiene.
Dieldrin was manufactured by the epoxidation of aldrin by reacting it either with a peracid to produce dieldrin and an acid by-product, or with hydrogen peroxide and a tungstic oxide catalyst to produce dieldrin and water. Aldrin and dieldrin are active against insects by contact or ingestion. Their primary use was for the control of termites around buildings, corn pests by application to soil and in the citrus industry, termite-proofing of plastic and rubber coverings of electrical and telecommunication. In 1970, the U.S. Department of Agriculture cancelled all uses of aldrin and dieldrin based on the concern that these chemicals could cause severe aquatic environmental change and are potentially carcinogenic. Aldrin and dieldrin are classified as hazardous wastes. That should be incinerated
Chlordane, dieldrin, aldrin and heptachlor, a related group of chlorinated organic compounds, were marketed to complement DDT. Chlordane was used for instance to control termites, various types of ants, borers, lawn beetles, curl grubs, cut worms and black beetles. Dieldrin was widely used against locusts and argentine ants, in the protection of electricity and telephone cable, soil treatment in farm and industrial premises for control of termites, and control of termites in buildings, fences and similar structures. Aldrin was used as a soil treatment, usually pre-planting, for crops such as sugar cane, it was used in ant control as well as subterranean termite control, the protection of power poles from termites, farm, industrial and domestic control of fleas, flies, lice and mites. Heptachlor was used similarly to chlordane. It was also commonly used in soil treatment in crops for control of funnel ants and grubs of the grey-black beetle in cane growing areas, and banana beetle borer in banana plantations.
16.13.4.0 Organophosphate and carbamate insecticides
See diagram 16.13.4.3
High persistence chlorinated pesticides are being replaced by the organophosphorus group that has a range of activity, persistence, specificity and function. Their general formula is (RR'X) P = 0, where R and R' are short chain groups and X is a leaving group that it is easily removed from the molecule either after a reaction in the body so persistence is reduced, e.g. Carbaryl
16.13.4.1 Acephate
See diagram 16.13.4.1: Acephate
Acephate is a contact poison which is also systemic in some plants. It is fairly safe to use. There should be a 7 days withholding period before harvest of the sprayed crop. It persists for some time. It may burn young leaves. Acephate can be used to control many insect pests and some people say it is the best general purpose insecticide for use in the tropics. It can control aphids and thrips, caterpillars, leaf miners, rice hoppers, diamond backed moth on cabbages, cutworms, and many other insects. Acephate is usually available as a wettable powder. It is also available as a dust.
16.13.4.2 Dimethoate
See diagram16.13.4.2: Dimethoate
Dimethoate is a systemic poison that is dangerous if the mist is breathed in or swallowed. There should be a 7 days withholding period before harvest of the sprayed crop. It may damage some fruit trees. Dimethoate can be used to control aphids and all sucking insects but it will not control chewing insects such as grasshoppers. It can control leaf miner in hibiscus cabbage (aibika) cabbages, okra, and sweet potato, aphids and thrips on plants of the pumpkin family, cabbages, spring onions, tomato and bean, Heliothis corn ear worm on bean and plants of the tomato family, mites and red spider on plants of the tomato family, taro, banana, bean and cassava, bean fly, vegetable bugs, pod borer on bean, and fruit fly. When insects are first seen spray a solution of 5 mL of concentrate in 5 litres of water. Make sure that the whole plant is sprayed. Dimethoate is usually available as emulsifiable concentrate (E.C.). It is also available as dusts, wettable powder (W.P.) and granules.
16.13.4.3 Malathion, maldison
See diagram16.13.4.3: Malathion
Malathion, maldison, is a contact poison which is also weakly systemic in some plants. It is fairly safe to use but the concentrate is dangerous if swallowed, breathed in, or allowed to remain on the skin. There should be a 7 days' withholding period before harvest of the sprayed crop. It persists for some time. Malathion can be used to control many different insect pests which eat leaves and stems but some insects have become resistant to it. It can control aphids, mole crickets, grasshoppers, cutworms, scale insects on citrus trees, bugs on plants of the pumpkin family, bean and eggplant, taro leaf hopper, spider mites. When the insects are first seen spray a solution of 10 mL of "Malathion 50" in 4 litres of water, and repeat the spray when necessary. Malathion is usually available as a concentrate. It is also available as aerosols, granules and dusts. For control of scale insects mix with white oil, e.g. Albarol, and water. For control of pests of stored products use as a dust.
16.13.4.4 Naled
See diagram 16.13.4.4: Naled
It is a contact and stomach poison. It is dangerous to use. Naled can be used just before harvest. It can control caterpillars, cutworms, bugs on eggplants, red spider mite on cassava and other crops. Naled is available as an emulsifiable concentrate (E.C.) and a dust.
16.13.4.5 Tetrachlorvinphos
See diagram 16.13.5.0: Tetrachlorvinphos
Tetrachlorvinphos is a contact and stomach poison. It is fairly safe to use. This chemical is not allowed to be used on crops in the U.S.A. Tetrachlorvinphos can be used to control caterpillars and other pests of leafy vegetables but other insecticides are better for this purpose. It can be used to kill parasites of animals and to kill pests in agricultural buildings. Tetrachlorvinphos is usually available as emulsifiable concentrate (E.C.) oil solution and dusts.
16.13.4.6 Trichlorophon
See diagram 16.13.5.0: Trichlorophon
Trichlorphon is a stomach poison and contact insecticide for certain insects. It also is used to kill flies and cockroaches. It is dangerous to use. There should be a 2 days withholding period before harvest of the sprayed crop. Trichlorphon can be used to control cutworm of cabbage and other crops, white fly on taro, corn ear worm, bean fly, bugs, leaf hoppers, banana scale moth. Not effective for control of diamond backed moth. Trichlorphon is available as wettable powder (W.P.) emulsifiable concentrate (E.C.) and dusts.
16.13.4.7 Carbamates, Carbaryl
See diagram 16.13.4.7 Carbaryl, 1-napthyl methylcarbamate, "Sevin", "Carbamine", "Dicamba", "Bugmaster", C12H11NO2
It is a contact poison which is also weakly systemic in some plants. It is fairly safe to use but the concentrate is dangerous if it is swallowed, breathed in or allowed to remain on the skin. There should be a 7 days withholding period before harvest of the sprayed crop. It has a short persistence. It may burn young leaves. Carbaryl can be used to control many different insect pests which eat leaves and stems but you may need a following spray of another insecticide to kill all the insect pests. It can control leaf miner on hibiscus cabbage (aibika) okra, tomato and sweet potato, caterpillar on cabbage and other leafy vegetables, 28-spotted ladybird on plants of the pumpkin family, tomato leaf miner, pod borers in bean, bugs on bean and eggplant, green looper caterpillars on bean and tomato, diamond backed moth on cabbages, taro leaf hopper, white fly on taro and other crops, army worm, pumpkin beetle, moths on fruit trees, potato moths. When the insects are first seen spray a solution of 5 grammes of carbaryl in 4 litres of water, and repeat the spray when necessary. Carbaryl is usually available as a wettable powder. It is also available as granules and dusts. For control of scale insects mix with white oil (petroleum oil).
16.13.4.8 Carbamates, Methiocarb
See diagram 16.13.4.8 Methiocarb, mercaptodimethur, 4 methyl thio-3,5-xylyl methylcarbamate
It is a contact and stomach poison insecticide, acaracide and molluscicide. Also it is a bird repellent. It is dangerous with long residual activity but as no systemic action. Methiocarb is used mainly as snail bait and repellent for snails and slugs. It also controls grasshoppers, mites and many insects.
16.13.5.0 Acaricides
These chemicals are used to kill red spider, mites and other 8-legged pests.
See diagram 16.13.5.0: Dicofol
1. Dicofol, C14H9Cl5O, contains chlorine. It is a contact poison of mites only with long residual action, does not harm insects, is fairly safe, is not systemic, but may burn eggplant (Aubergine) and other fruit. There is a 7 days withholding period. Dicofol can control mites on citrus trees and red spider mite on passionfruit, banana, cassava and other crops, but Dimethoate is better. Highly inflammable, do not smoke near it. Dicofol is available usually as E.C., it is also available as W.P. and dusts.
2. Formaldehyde (formalin) can be used as a soil drench which prevents damping off disease of seedlings. It will irritate eyes and nose.
3. Naled, see Insecticides
4. Dimethoate, see Insecticides
5. Sulfur, Wettable sulfur see Fungicides
6. Benomyl. see Fungicides
7. Methiocarb. see Insecticides
16.13.6.0 Fungicides
16.13.6.1 Benomyl
See diagram: 16.13.6.1
Benomyl, C14H18N4O3, is a carbamate. A systemic poison, very safe to use on fruit, vegetables and field crops but it may irritate the eyes and skin, good residual activity in soil, 5 days withholding period. It can control powdery mildew on plants in the pumpkin family, fungus diseases of tomato and pineapples, and is used as an oil and water emulsion to control black leaf streak and other leaf spots of banana. Sugarcane, pineapple and other planting material can be dipped in it to control many different fungi. Benomyl can control many leaf spots, vegetable rots and white mould diseases. However, there are some fungus diseases it cannot control such as downy mildew and some fungi have developed resistance to it so it should not be used too much. It will control mite eggs but not adult mites and can kill some nematodes. It kills fish. It can stop fungi reproducing. It can be made more active by adding surfactant. It should be stored in a dry place. The container must be kept tightly closed especially in tropical countries. Benomyl is available as a wettable powder (W.P.).
16.13.6.2 Bordeaux mixture, CuSO4.3Cu(OH)2.3CaSO4
Bordeaux mixture is a mixture of copper (II) sulfate, calcium hydroxide, or slaked lime. It is sometimes called "Bordo Mixture". It is a protective fungicide which is safe unless eaten. The two chemicals are often bought separately and mixed in a plastic bucket and used immediately. It may burn leaves and metal and is hard to use properly. Bordeaux mixture can control rots, downy mildew, leaf spots. It repels many insects. It can kill the eggs of mites. copper (II) sulfate may be used by itself to control leaf spots and other diseases.
16.13.6.3 Captan
See diagram: 16.13.6.3
Captan is ethanethiol or ethyl mecaptan. Captan contains chlorine and sulfur. A protective fungicide, safe to use but may irritate the skin, used mainly as a dust on seeds to prevent damping off disease, also used on vegetables and other crops and as a dip for stored products, 1 day withholding period. It is a good all purpose fungicide for controlling mildew and leaf spots and damping off fungus on seeds. Captan can control root and stem rot of bean, fungus diseases in carrots, peanut and sorghum, and leaf spot of yams. It kills fish. Seed which has been dusted with it should not be eaten. Captan is available as dusts and W.P. and in special soil fungicidal products. In 1989 Captan was phased out of general usage as a pesticide in USA.
16.13.6.4 Copper oxychloride, ClCu2H3O3,
Copper oxychloride is made from copper and chlorine. It is a protective fungicide. It is safe to use. There should be a 1 day withholding period before harvest. Copper oxychloride is a good fungicide for leaf diseases. It can control downy mildew, leaf spots, leaf rot and other fungus diseases. Copper oxychloride is available as wettable powder (W.P.) and dusts.
16.13.6.5 Chlorothalonil
See diagram 16.13.6.5: Chlorothalonil
Chlorothalonil, C8Cl4N2, contains chlorine. It is a protective fungicide. It is safe but it makes some people sick. Its effect lasts a long time. This is the best fungicide for fungus diseases of tomato. Chlorothalonil can control leaf spots, powdery mildew, downy mildew and other fungi on plants. It does not kill all soil fungi. It can kill fish. Chlorothalonil is available as wettable powder (W.P.) and tablets.
16.13.6.6 Zineb
See diagram 16.13.6.6: Zineb
Zineb, C4H6N2S4Zn, contains zinc. It is a protective fungicide. It is safe to use but it may cause skin irritation. It may damage young seedlings. There should be a 7 days withholding period before harvest of the sprayed crop. This is the best general purpose fungicide. Zineb can control many vegetable fungus diseases including downy mildew on plants of the pumpkin family, leaf spots and rust diseases. It is available as a wettable powder (W.P.) and as dusts.
16.13.6.7 Metam
See diagram 16.13.6.6: Metam
Metam-Sodium is a carbamate salt containing sodium. It is used to kill fungi, insects, nematode worms and weeds in the soil. It is fairly safe to use but may irritate eyes and mouth.
16.13.6.8 Quintozene
See diagram 16.13.5.0: Quintozene
Quintozene, C6Cl5NO2, is a protective fungicide for seed and soil. It is safe to use but may cause skin irritation. It may burn young leaves. This can be used as a soil drench after planting to control various fungus diseases such as damping off fungus and rots. It is applied to soil before sowing or after sowing to treat both seeds and soil. It can be used to treat soil at transplanting and treat seeds of cabbages. Seeds that have been treated with it must not be eaten. It does not kill many kinds of fungi. It cannot be used to control bacterial wilt. It is available as dusts, granules, and pastes.
16.13.6.9 Sulfur
It is a non-metallic element and is used as "Wettable sulfur". It is a fungicide and acaricide. It is very safe to use but it irritates the eyes and skin. It may damage leaves of plants in the pumpkin family. There is no withholding period. It can control mites on capsicums, citrus hibiscus cabbage and tomato. Also it can control powdery mildew, downy mildew and some rust diseases, but it is not effective for other fungus diseases. sulfur is available as a dust, wettable powder and sulfur paste.
16.13.6.10 Lime sulfur, CaSx
It contains calcium and sulfur. It is a fungicide, acaracide and insecticide which is sprayed or dusted on plants. It can be dangerous to use and causes skin irritation. It may burn leaves and metal. It can control many fungus diseases such as leaf spots and powdery mildew and it can control red spider and mite and scale insects. This is a hard spray to use properly. It may damage plants in the pumpkin family. Lime sulfur is available as a solution or a powder.
16.13.7.0 Herbicides, weedicides
A herbicide is a substance used to destroy plants or to slow down their growth. The formulation is the form in which the pesticide is supplied by the manufacturer for use. The half-life is the time required for half the amount of substance to be reduced by natural processes. The LC50 is the concentration in air, water, or food which will kill 50% of the subjects, usually laboratory rats. Mutagenicity is the ability to cause genetic changes. Non-target animals or plants other than those that the pesticide is intended to kill. Persistence is the tendency of a pesticide to remain active after it is applied. Residual activity is the remaining amount of activity as a pesticide. Bees gathering nectar and pollen may be directly exposed to pesticides or they may carry contaminated pollen back to nests and hives and expose other bees to it. copper (II) sulfate solution, dilute sulfuric acid and dinitro-o-cresol can each kill some weeds without causing injury to crops.
16.13.7.1 Bifenox
See diagram 16.13.5.0: Bifenox
Bifenox, C14H9Cl2NO5, contains chlorine. It is a contact poison. It is fairly safe but irritates the eyes. It remains a long time in the soil.
16.13.7.2 Dalapon, 2,2-dichloropropionic acid, "Dowpon"
See diagram: 16.13.7.2
Dalapon Na is a selective poison which is taken in by the plant and moves through it to kill all parts including the roots. It acts slowly over 2-3 weeks. It is safe to use but causes irritation to the eyes and skin of some people. Dalapon can control most annual and perennial grasses. It will kill every plant it touches. Dalapon is available as a water-soluble powder.
16.13.7.3 Glyphosate, N-(phosphonomethyl) glycine, “Roundup”, “Rodeo”, “Accord”, "Zero"
See diagram: 16.13.7.3
Commercial glyphosate products may contain inert ingredients, i.e. anything added to the product other than an active ingredient, e.g. glyphosate 41%, polyethoxylated tallow amine surfactant 15% and water 44%. It may contain the contaminant N-nitrosoglyphosate (NNG). The registered use status is "General Use". It can control many difficult weeds, e.g. nut grass, couch grass, Johnson grass, paspalum, Kikuyu, blady grass, Guinea grass and purslane. It is used in forestry and noxious weed control to control grasses, herbaceous plants but not all broadleaf woody plants. It is absorbed by leaves and prevents production of an essential amino acid and inhibits plant growth. It is broken down by some plants to mainly aminomethylphosphonic acid. Do not allow spray drift to contact desirable plants! It is safe to operators and has no residual activity in the soil because glyphosate and the surfactants used in commercial formulations are strongly adsorbed by the soil. However it remains unchanged in the soil depending on soil texture and organic matter content until soil micro-organisms break it down. Glyphosate and the surfactant are not absorbed from the soil by plants. It may be slightly toxic to fish but it does not build up, bioaccumulate, in fish. It is usually non-toxic to birds, mammals and bees. In tests in male and female rats, the acute oral LD50 was 4320 mg / kg. It does not cause genetic damage or birth defects, and no noticeable effect on fertility, reproduction, or development.
16.13.7.4 Paraquat
See diagram: 16.13.7.4
Paraquat is a compound which contains chlorine. It is a contact fast action poison.
PARAQUAT IS A VERY DANGEROUS CHEMICAL!
It can kill people if swallowed. It is not poisonous after touching the clay in soils. There is no persistence in soil. There should be a 9 day withholding period before harvest. It controls most broad leaf annual weeds and grasses. It works best when weeds are 2-15 cm high. It is not very effective on perennials with good root system. It kills water weeds. You must keep livestock away when spraying. Paraquat is available as water solution. Mix with water and immediately spray on leaves. The redox indicator methyl viologen, Paraquat. forms a stable, free radical that is very reactive. Paraquat, Diquat and Cyperquat are quaternary ammonium herbicides related to cationic surfactants that kill by contact with the plant foliage and cannot enter the plant via its roots because they are very strongly adsorbed onto clay and soil particles. They are used to kill weeds between crops or just before a crop emerges. They are toxic to humans. The phenoxyacetic acid herbicides 2,4-D and 2,4,5-T and its precursor 2,4,5-trichlorophenol (TCP).
16.13.7.5 MCPA, 4-Chloro-2-methylphenoxyacetic acid, also called 2-Methyl-4-chlorophenoxyacetic acid (MCPA)
See diagram 16.13.7.7: MCPA
Phenoxyacetic acids can mimic the natural auxin, plant hormone, indole acetic acid and are were not destroyed by the plant. They can also be used in setting unfertilized fruits and promoting root growth. When used in excess they can be used as herbicides. For MCPA is used to kill dicotyledon weeds in monocotyledon cereal crops. Equal amounts are absorbed by weeds and cereals but the cereals remain unharmed because of the differences in their growing shoot structure.
16.13.7.6 Herbicide 2,4-D, 2,4-dichlorophenoxy acetic acid
See diagram 16.13.7.7: 2,4-D
The selective herbicide 2,4-D is toxic to broad leafed plants but less harmful to grasses. This hormone weed killer 2,4-dichlorophenoxy acetic acid is an aryloxyalkanoic acid known also as a "phenoxy herbicide", which includes MCPA, mecoprop, triclopyr and 2,4,5-T. Their actions against weeds resembling those of auxins (growth hormones). Absorbed 2,4-D is translocated within the plant and accumulates at the growing points of roots and shoots where it inhibits growth. The principal use is for the control of broad leaf weeds in cereal crops, including wheat, maize, rice, sorghum, grassland and turf areas. It is also widely used in mixtures with other herbicides to provide weed control in forestry, orchards and non-crop areas, and for the control of aquatic weeds. 2,4-D is a WHO Class II "moderately hazardous" pesticide, in the same class as endosulfan, lindane, paraquat and toxaphene. It has an LD50 of 375 mg / kg in the rat with evidence
suggesting a similar level of toxicity in human. Occupational exposure to 2,4-D has produced serious eye and skin irritation, nausea, weakness and fatigue, and inflammation of nerve endings. The various chemical forms of 2,4-D can have different toxic effects. Orthocarboxylic acids, e.g. picloram can behave in a similar manner and is more potent than 2,4-D.
16.13.7.7 Herbicide 2,4,5-T, 2,4,5-trichlorophenoxyacetic acid
See diagram 16.13.7.7: 2,4,5-T | See 16.14.0: Dioxins
It was used to kill noxious weeds, e.g. privet and blackberry. At first it caused birth defects in animals and chloracne rash in workers due to a dioxin impurity TCDD (2,3,7,8-Tetrachlorodibenzo-p-dioxin) but this impurity can be controlled to an acceptable limit. Production of 2,4,5-T was contaminated with the carcinogenic dioxin TCDD. Agent Orange was used first by the UK military in Malaysia and later by the US military to defoliate jungle regions in Vietnam. Abnormal foetal skeletal development, increased foetal mortality and other reproductive effects may be associated with exposure to phenoxy-acid herbicide and their dioxin contaminants. 2,4-D has low soil sorbtion and a high potential for leachability and 2,4-D residues have been recorded in groundwater and surface water. Some formulations of 2,4-D are highly toxic to fish. 2,4,5-T, 2,4,5-Trichlorophenoxyacetic acid, "Weedone", Acetic acid (2,4,5-trichlorophenoxy)-555, C8H5Cl3O3. This herbicide was formerly used for industrial sites, lumber yards and vacant lots, rangeland and rice, lawns and turf, aquatic use, home use, recreation areas, food crops for humans. 2,4,5-T is used postemergence alone or with 2,4-d for the control of shrubs and trees. It is also used for girdling, injection or cut-stump treatment. It has been used as a growth regulator to increase size of citrus fruits and reduce excessive drop of deciduous fruit. The use of 2,4,5-T in the United States has been cancelled since 1985. control in lakes and ponds at 22-45 kg / ha, and along ditches and irrigation networks. It is odourless but is an irritant to eyes, nose, and throat. The persistence of 2,4,5-T does not exceed one full growing season. Biodegradation of 2,4,5-T to 2,4,5-trichlorophenol appears to be the dominant removal mechanisms. 2,4,5-T is was one of the most rapidly decomposed herbicides. 2,4,5-T has been qualitatively identified in drinking water.
16.13.8.0 Insect repellents
See diagram 16.13.8.0: Deet, DMP
Natural insect repellents contained strong-smelling oils, e.g. citronella, that repel insects after contact with the repellent. The most effective insect repellents is deet, NN-diethyl-m-toluamide. Also, DMP, dimethylphthalate, is an effective mosquito repellent but it dissolves the plastic in “watch glass” and spectacles. Other effective repellents are “E-Hex”, ethyl hexanediol, and “Indalone”, butyl 3,4-dihydro-2,2-dimethyl-4-oxo-2H-pyran-6-carboxylate! The best repellent for bush flies and sand flies is di-n-propyl isosinchomeronate with the addition of the pyrethrum synergist N-octyl bicycloheptenedicarboximide, NN diethyltoluamide, di-N-propyl isocinchomeronate. n attractant for pantry moth is "biolure" (2,E)-9, 12-tetradien-1-yl acetate.
16.13.8.1 Mineral deficiencies
Bitter apple calcium deficiency
Blossom end rot of tomato and capsicum, uneven calcium supply
Boron deficiency of  beetroot, celery, cauliflower, apple, pear
Chlorosis, iron deficiency, yellowing of hydrangeas
Fasciation mutation of roses, Celosia
Iron deficiency of citrus, light green to white fading leaves
Magnesium deficiency of citrus, leaves yellow near midrib
Manganese deficirency of citrus, light yellow-green betwen veins
Oedema of camellia
16.13.8.2 Nematode pests
Bulb and stem nematode Ditylenchus dipsaci bulbs, e.g.daffodil, onion
Leaf nematodes in the buds  Aphelenchoides spp. blackcurrant, strawberry
16.13.8.3 Weeds
Dodder Cuscuta lucerne, onion
Devil's twine Cassytha sp.
Dry patch, water-repellent soil