Fungicide Use in Field Crops Web Book

What is a fungicide? A fungicide is a chemical used for killing or limiting the development of fungi or organisms similar to fungi (i.e., oomycetes). Fungicides are used to preserve yield and quality in field crops by mitigating the potential impact of disease on plants. Fungicides in field crops are applied in a variety of ways that include soil applications, seed treatments, or foliar sprays.

Fungicides are an important group of tools used in modern agricultural production. Proper use of these chemicals decreases risk of fungal diseases that can cause economic and yield variability in crop production. The organisms that cause fungal diseases threaten crop production every year, and can be particularly destructive during some seasons. Fungal disease development is strongly impacted by the environment and it can be difficult to predict which disease will be problematic in any given year. For this reason, having fungicide management tools ready to use is of great importance. Fungal organisms are continually changing through genetic mutation, and spread from region to region by the activities of humans or fluctuations in the environment. Sometimes, this can result in situations where fungicides may be the only way to preserve a crop. An example of this occurred when the pathogen that causes soybean rust began to move into U.S. soybean producing regions (Gallery 1.1). Soybeans grown in these areas did not have genetic resistance to this pathogen, thus fungicide application was the only option for control of this disease. Emergency labeling of certain fungicides to manage soybean rust occurred, but fortunately the threat to soybeans, at least in the primary soybean growing regions of the U.S., did not materialize. Without fungicides, an outbreak of this or another disease may have disastrous consequences for crops and those who manage them.

Fungicide use is not a cure-all, and overuse will often cause them to become ineffective. Fungicides are only one group of tools for effective disease management and are best used as part of an overall strategy that includes field scouting, variety selection, crop rotation, and many other strategies. There is no doubt that fungicides have become an important part of modern farming to preserve yield potential, protect seed and grain quality, and reduce toxins in food and feed.