Herbicides are grouped according to family (e.g., triazines), the target site of action or mechanism of action (e.g., Group 5), and mode of action (e.g., Photosynthesis Inhibitor). Herbicides within a family have similar chemical structures and typically the same site or mechanism of action (MOA). Knowing the chemical family and MOA group to which an […]
Resistance
How to Manage Herbicide Resistance
If herbicide resistance is confirmed or highly suspected, diverse approaches to managing herbicide resistance need to be incorporated into weed management strategies immediately for the species in question. It is best to stop using the herbicide in question and other herbicides with the same mechanism of action. However, in many cases, the herbicide continues to […]
Proactive Herbicide Resistance Management
Early detection of resistance means management will be easier, and it increases the potential to avoid the spread of the resistant biotype. Unfortunately, because resistant plants and susceptible plants look alike, resistance often is not detected until the resistant biotype has spread to 30% or more of the field and perhaps to surrounding fields. Therefore, […]
Mechanisms of Herbicide Resistance
What occurs within a resistant plant that allows it to survive after an herbicide application? What characteristics do the resistant plants possess that the susceptible plants lack? The four known mechanisms of resistance to herbicides are: Altered target site: An herbicide has a specific site (target site of action) where it acts to disrupt a […]
Herbicide Resistance Terms to Know
Susceptibility and Tolerance Herbicide susceptibility is the degree to which a plant is subject to injury or death due to a particular herbicide. Herbicide tolerance is the inherited ability of a species to survive and reproduce following herbicide treatment. There was no selection to make the plants tolerant; those plants simply possess a natural tolerance. […]
Raised Resistance Risks
The likelihood and speed of resistance development largely depends upon whether the fungicide affects a single metabolic site (single-site) within the fungus or multiple sites (multi-site). A single gene mutation is all that is required for a fungus to overcome the toxic effects of a single-site fungicide. With single gene mutations governing resistance development, the […]
Mechanisms of Fungicide Resistance
There are several ways that populations of fungi can become resistant to fungicides, these include: 1. Altered target site. A fungicide has a specific target site where it acts to disrupt a particular biochemical process or function. If this target site is somewhat altered, the fungicide no longer binds to the site of action and […]
Is Fungicide Resistance to Blame?
Most fungicide failures are not due to resistance. Before assuming a pathogen surviving a fungicide application is resistant, eliminate other possible causes of poor control: Fungicide application Inadequate rate Poor spray coverage (illustrated below) Improper timing of application Antagonism between two or more products (wrong tank-mix partner) Environmental and plant growth conditions Excessively wet or […]
Fungicide Resistance
Fungicides are important tools for preventing and managing plant disease. Unlike insecticides and some herbicides which kill established insects or weeds, fungicides are most commonly applied to protect healthy plants before infection occurs. Resistance to fungicides is one of many possible causes of poor disease control (see Is Resistance to Blame?). Resistance refers to a […]
Herbicide Resistance
Herbicide resistance is the inherited ability of a biotype of a weed to survive an herbicide application to which the original population was susceptible. A biotype is a group of plants within a species that has biological traits (such as resistance to a particular herbicide) not common to the population as a whole. In simple […]