| Objectives for Today's Class | ||
|---|---|---|
| References | Mastery Topics |
MODE OF ACTION OF FUNGICIDES
The action of most fungicides takes place outside the host and is called "protection". A fungicide that acts outside the host is called a ""protectant fungicide." Most older fungicides sprayed on leaves and fruit are of this type. "Therapy" is chemical action inside the host. Triadimefon (Bayleton) has several days therapeutic action against wheat leaf rust and also reduces the production of viable spores, that is, spores capable of growing. Propiconazole (Tilt) has several days therapeutic action against wheat leaf rust, tan spot and several other diseases and reduces the production of viable spores.
Most protectant fungicides are relatively stable by themselves. Generally they are relatively insoluble in water and resist removal or chemical change by water, yet must be toxic to fungi. Often a chemical change is brought about by the fungus, the host, or the environment before toxicity occurs. Toxicity simply means the ability to do damage to the fungus cells.
Fungicides may act to produce a toxic reaction in the fungus in several different ways. (l) Some may inhibit (slow down or stop) cell wall formation. Propiconazole and triadimefon act this way on cereal rusts. (2) The permeability of the cell wall may be affected, causing a leaking of nutrient materials from the cell. (3) Some fungicides may combine with essential metals in a way that they become unavailable for normal cell functions, including the functioning of essential enzymes. (4) Other fungicides may inhibit respiration, or nuclear division, or may break dormancy of spores.
Some fungicides may also be toxic to plants if applied at too high rates, or if applied under unfavorable environmental conditions. This is called phytotoxicity. Formulations of maneb + zinc are less phytotoxic to many vegetables than formulations that contain only maneb. Sometimes the method of formulation may make a fungicide less phytotoxic.
| Aliphatic Nitrogen Fungicides | ||
| Name | Structure | Trade Names |
| Dodine |  |
AC 5223, Apadodine, Carpene, Curitan, Cyprex, Efuzin, Melprex, Sulgen, Syllit, Tebulan, Vandodine, and Venturol. |
| amide fungicides | ||
| Triflorine |  |
Brolly, Denarin, Funginex, Nimrod T, Saprol, and Triforine DC |
| anilide fungicides | ||
| Benalaxyl |  |
Benalaxyl-M |
| antibiotic fungicides | ||
| Blasticidin-S |  |
Blasticidin-S |
| Cycloheximide |  |
Cycloheximide |
| Griseofulvin |  |
Griseofulvin |
| Streptomycin |  |
|
| aromatic fungicides | ||
| benzimidazole fungicides | ||
| benzimidazole precursor fungicides | ||
| carbamate fungicides | ||
| conazole fungicides | ||
| copper fungicides | ||
| dicarboximide fungicides | ||
| dinitrophenol fungicides | ||
| dithiocarbamate fungicides | ||
| imidazole fungicides | ||
| inorganic fungicides | ||
| mercury fungicides | ||
| morpholine fungicides | ||
| organophosphorus fungicides | ||
| organotin fungicides | ||
| oxazole fungicides | ||
| phenylsulfamide fungicides | ||
| phenylurea fungicides | ||
| pyridine fungicides | ||
| pyrimidine fungicides | ||
| pyrrole fungicides | ||
| quinoline fungicides | ||
| quinone fungicides | ||
| quinoxaline fungicides | ||
| thiazole fungicides | ||
| thiocarbamate fungicides | ||
| triazole fungicides | ||
| xylylalanine fungicides | ||
| unclassified / unclassified fungicides | ||
Questions, Comments, Complaints and Complements?
This page is authored and maintained by:
Dr. J.E. Partridge, Department of Plant Pathology, University of Nebraska-Lincoln
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Copyright (C) 2008 J.E. Partridge, University of Nebraska-Lincoln. All Rights Reserved.