Use of pesticides by inexperienced persons can do a lot of harm. They are poisons, and any pesticides will be harmful if enough of the material is inhaled, swallowed or absorbed through the skin. Some are more dangerous than others. Insecticides are for control of insects, fungicides are for prevention or cure of plant diseases, and herbicides are for killing or preventing weeds.
A study at Penn State University indicates that everyone who handles insecticides should wear rubber or plastic gloves. If you get insecticides on your hands, traces may persist for a long time. A former pest control operator still had traces two years later.
A fruit and vegetable grower had methoxychlor, captan and malathion traces on his hands seven days later; parathion was found on the hands of one man two months after his last known contact. Endosulfan, TDE, kelthane, dacthal, trithion, and guthion may have persisted on the hands of some exposed workers up to 112 days.
Before using an insecticide, it is important to determine exactly what the problem is and its cause. It is especially important to determine if the cause is a physiological problem, such as air pollution or a nutrient deficiency, or if it is a pest problem, such as a disease, weed, insect or rodent.
A new gardener is likely to react more sharply to insect attack than an old hand. The spray may be of greater strength than it should be -- a little bit extra for good measure.
Used improperly, sprays can be harmful to human beings, pets, fish and other wild life. Used properly, they can be beneficial, destroying marauding insects without contaminating the vegetables to be used as food.
Read label information carefully each time before using any such material. Make sure the insecticide is safe to use on that particular plant. If the correct dilution is used, if you wait the specified length of time before harvesting, and if the crop is washed thoroughly before being stored or cooked, the vegetable can be used.
If the spray was too strong, or if you harvest the crop too soon after spraying, you may do harm to yourself, your family and friends.
Some insects eat other insects. Ladybird beetles have been used very successfully to control plant lice (aphids) in greenhouses. Often they have not done much when turned loose in aphid-infested fields since they rarely stay put in the problem area. Also, it is difficult to establish a large enough ladybird beetle population to control the insects they are supposed to control.
Researchers at the University of California have found that soap and water or detergent and water sprays can keep pest insects at nondamaging levels. In the home garden, where 100 percent insect control is seldom necessary, these sprays were found to be effective against insects, crustaceans, arachnids and myriapods.
A 1- or 2-percent liquid dishwashing detergent and water, for example, applied as a coarse spray until runoff, was effective.
Soap sprays are known primarily for their ability to physically dislodge insects from plants when applied at high pressure.Other researchers have suggested that insects might be asphyxiated by soap sprays.
The label on each package of insecticide approved for use on food crops must state the correct (safe) dilution (the amount to mix in water) and the number of days to wait before harvesting from the plant that has been sprayed. Do not use an insecticide on a food plant unless the label states the length of time to wait before harvesting.
If the label says use two tablespoons per three gallons of water, it means level tablespoonfuls. Using the insecticide at less than the recommended strength will be ineffective and using it too strong will be harmful.
Diseases can be prevented to a considerable degree by planting disease resistant varieties. Rotation (planting the vegetables in a different place each year) helps but it is impractical for most gardeners.
Each fungicide is specific for certain diseases and certain plants and should not be used unless the disease has been definitely identified and the label states it can be used effectively. It is difficult for most gardeners to identify most plant diseases or to know what to use. Unless the information can be obtained from a reliable source, it is better not to use a fungicide.
In many cases, a condition that looks like it might be a disease can be due to fertilizer burn, poor drainage, need for water or pollution. A fungicide will not help in these circumstances.
A certain amount of pest damage is inevitable, so do not demand or even expect total eradication of pests. Control to an acceptable degree is what you should seek.