Fungicide

Tiny things called fungi can hurt plants.

They can ruin crops and food. People use special sprays to stop them. These sprays are called fungicides.

Some sprays stay on the outside of a leaf. Other sprays move through the plant. This helps the spray reach more parts.

Some sprays use things like sulfur. Other sprays use oils from plants. These help keep plants healthy.

Sometimes, the fungi learn to fight the spray. This makes the spray stop working.

We must use these sprays very carefully. They can be bad for people too. We want to keep our food safe.

Fungi can hurt many living things. They can damage crops and food. To stop them, people use fungicides. These are special tools to kill fungi or their spores.

There are different ways fungicides work. Some are contact sprays. They only protect the spot where they land. Other sprays move through the plant. We call these systemic fungicides. They travel through tiny tubes in the plant. This helps them reach more parts.

Some fungicides are very simple. They use things like sulfur or copper. These can be cheap but must be used often. Other kinds use oils from plants, like neem oil. Some even use tiny living things to fight the fungi.

Sometimes, fungi learn to fight back. This is called resistance. The fungi change so the spray no longer works. They might even pump the spray out of their cells.

We must use these sprays with care. Some can be bad for humans. In the United States, a group called the EPA studies them. They make sure the sprays are safe for our food and the Earth.

Fungicides are special tools used to kill parasitic fungi or their spores. Fungi can cause big problems in farming by hurting the quality and amount of food grown.

People use these tools in agriculture and to fight fungal infections in animals and humans. They even work on oomycetes, which are not true fungi but infect plants in a similar way. Some fungicides are contact types that only protect the exact spot where they land. Others are translaminar, meaning they move from the top of a leaf to the bottom. Systemic fungicides are even more active because they travel through the plant's xylem vessels.

There are many different ways these tools work. Some are nonspecific, meaning they work in a general way to stop fungi. In the 1930s, the first organic ones called dithiocarbamates became available. These include names like zineb and mancozeb. Other types are specific and target one single biological process. For example, some target how a fungus uses energy or builds its cell walls.

Some even target how a fungus makes proteins or moves parts inside its cells. This variety helps farmers choose the right tool for the job.

History shows how our science has changed over time. Traditional fungicides were simple inorganic compounds like sulfur or copper salts. These were cheap to make but did not work very well. They had to be used over and over again to stay effective.

Later, scientists developed more complex organic chemicals. Today, we even use things like neem oil or helpful bacteria to fight bad fungi. Some people even look at mycoviruses, which are tiny viruses that live inside fungi, as a way to control them.

Fungi are very smart and can learn to fight back. This is called resistance. When a fungus is exposed to a spray, it might change so the spray no longer works.

One fungus, called Botrytis cinerea, has learned to resist two different types of chemicals. Another fungus called Black Sigatoka changed just one tiny part of its protein to stay safe. Some fungi even develop tiny pumps to push the chemicals out of their cells. This is a hard job for farmers to manage.

Because these tools can be strong, we must use them safely. Some fungicides can be dangerous to humans if they are not handled right. For example, ziram is toxic if a person swallows it. In the United States, a group called the EPA manages these rules.

They check data on how chemicals affect the environment and human health. They also set limits on how much of a chemical can stay on food. This helps keep our food and our world safe.

Fungicides are specialized pesticides designed to kill parasitic fungi or their spores. These substances are vital because fungi can cause severe damage in agriculture by reducing crop yields and quality. Beyond farming, fungicides are used to treat fungal infections in animals and humans. They are also used to control oomycetes. While oomycetes are not genetically classified as true fungi, they share similar methods of infecting plants.

How a fungicide moves through a plant determines its type. Contact fungicides stay on the surface where they are sprayed and do not enter plant tissue. Translaminar fungicides are different because they redistribute from the upper, sprayed surface of a leaf to the lower, unsprayed side. Systemic fungicides are the most mobile. They are taken up by the plant and redistributed through the xylem vessels, which are the plant's internal transport tubes. Some systemic fungicides move only upward or stay local, but few move to every part of the plant.

Scientists classify fungicides in several ways as the underlying science has evolved. One method is by chemical makeup, such as inorganic compounds like elemental sulfur or copper salts versus organic compounds. Another way is by chemical structure, such as dithiocarbamates or phthalimides. The most successful classification is by the mechanism of action (MOA). This refers to the specific biological process the fungicide disrupts within the fungus.

Fungicides can be categorized as either nonspecific or specific. Nonspecific fungicides, such as dithiocarbamates and N-substituted phthalimides, work in a general way. Dithiocarbamates like mancozeb and zineb are thought to inhibit cysteine-based protease enzymes. Specific fungicides target a single, precise biological process. These include those that target nucleic acid metabolism, such as metalaxyl. Others target the cytoskeleton, which provides structure to cells. Some target respiration by inhibiting enzymes like succinate dehydrogenase. Other specific types interfere with amino acid synthesis, signal transduction, lipid synthesis, or cell wall biosynthesis.

The history of these tools shows a move from simple to complex chemistry. Traditional fungicides were simple inorganic compounds like sulfur. While these were cheap, they were relatively ineffective and required repeated applications. In the 1930s, the first organic compounds, the dithiocarbamates, became available. Modern science also explores biological alternatives. These include neem oil, rosemary oil, and even beneficial organisms like the bacterium Bacillus subtilis or the fungus Ulocladium oudemansii. Scientists are also studying mycoviruses, which are viruses that live inside fungi, as potential biocontrols.

Fungi can develop resistance to fungicides, which is a major challenge for agriculture. This occurs when high doses of a fungicide create selection pressure, allowing resistant pathogens to survive. One form is cross resistance, where a pathogen becomes resistant to multiple fungicides that share a similar mechanism of action. For example, the fungus Botrytis cinerea is resistant to both azoles and dicarboximide fungicides. Resistance can happen through several biological changes. A pathogen might alter its target enzyme, as seen in Black Sigatoka, which changed a single amino acid in its cytochrome b protein. Other fungi use "efflux," where they use transporters to pump the toxic chemicals out of their cells.

To manage these risks, organizations like the Fungicide Resistance Action Committee (FRAC) provide guidance. They classify compounds by structure and mechanism of action to help prevent resistance. Safety is also a primary concern because some fungicides pose risks to humans. For example, ziram is toxic to humans with long-term exposure and is fatal if ingested. In the United States, the Environmental Protection Agency (EPA) regulates these substances under the Federal Insecticide, Fungicide, and Roderticide Act (FIFRA). The EPA requires detailed data on toxicology and environmental impact before a product is registered. They also set legal tolerances, or maximum residue limits, for chemicals found on food crops to ensure safety.