Pesticides is the umbrella term for substances that repel or kill pests that cause harm to plants growing in the garden or landscape. Since fungi and insects are some of the main threats to vegetable crops, farmers and gardeners use fungicides and insecticides in order to save their produce from attack. You must consider the type of vegetables you are growing, potential pests for your region and the pros and cons of using pesticides.

Fungicides
A variety of fungicides are available to homeowners to apply to vegetables infected with fungi that transmit diseases. For example, chlorothalonil is used to treat vegetables infected with early or late blight. It is a contact fungicide, meaning that you apply the substance to the vegetable plant leaf and stems; it serves as a protectant and is not absorbed by the plant's tissues. Also a contact fungicide, mancozeb protects vegetables from diseases like fungal leaf spots, downy mildew, rust and scab. maneb is a contact fungicide particularly useful for infected beans, cucumbers, peppers and tomatoes. Finally, PCNB is effective at treating vegetables infected with diseases like Rhizoctonia rot, southern blight and club root.

Insecticides
Like fungicides, a particular insecticide targets specific insects. The Texas A&M University AgriLife Extension lists a breakdown of common insect pests per vegetable and the appropriate pesticides to use. For example, aphids attack a huge variety of vegetables, from asparagus to peppers. Growers apply insecticides such as malathion, permethrin and bifenthrin to eradicate aphids, but the type to use is vegetable dependent, and you must read the label to see if it applies to your particular crop. Leafminers also attack many vegetables, such as tomatoes, squash, potatoes, peas, peppers and lettuce. In these cases, pesticides like petroleum oil, spinosad and azadirachtin are used.

Last Resort
Since the days of Rachel Carson's "Silent Spring," several pesticides, such as DDT, have been outlawed in the United States due to their fatal effects on the surrounding ecosystem. Especially if you are only growing vegetables in a small garden, rather than on a huge farm, pesticides should be your last option. If you do use pesticides, it is important to read the label and all potential risks. The Oregon State University Extension Toxicology Network recommends using only pesticides that are nonsystemic. This means little to none of the toxins will be ingested by the plants and thus end up in the vegetables you will eventually eat. The University of Illinois Extension states that compared to other vegetables, asparagus, onions, leafy greens, peas, peppers, sweet potatoes and sweet corn do not experience as much life-threatening damage from pests. This means you can avoid using pesticides by planting disease-resistant varieties of these vegetables in fertile, well-drained soil. You can also learn mechanical control techniques to avoid the use of pesticides. For example, you can spray some plants with a high-pressure water hose to remove aphids and place barriers around plant stems to prevent cutworm attacks.

Natural Pesticides
If you still would like to apply pesticides to your vegetable garden, but want to approach it in a more eco-friendly manner, try making some home remedies to repel pests. For example, an insecticidal soap made from 2 tbsp. of soap flakes and 1/2 gallon of warm water can be used to treat plants being attacked by aphids, spider mites and white flies. Mix a homemade fungicide to treat vegetable mildew problems by combining 1 tsp. of baking soda, 1 tsp. of soap flakes and 1/4 gallon of warm water.

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