Flashcards in PESTICIDES IN IPM Deck (20):
Factors to Consider
1.) Client Philosophy
2.) Location and Commodity
Product contract limitations such as 'organic'
Application near dwellings, schools, hospitals, parks, playgrounds, commercial lots, and other areas of public domain may impose limitations or prohibit the use of certain pesticides.
Adjacent crops can also be a determining factor, especially when dealing with pesticides that our prone to 'drift'.
Proximity to endangered species, wildlife reserves, lakes, ponds, and irrigation canals can influence pesticide selection.
Consideration of the commodity is primary.
The pesticide must be registered for use on the commodity and crop growth stage from the application.
Although a pesticide may be registered for one crop against a pest, it may not be registered for another crop despite having the same pest problem.
Considerations for Pesticides
2.)Mode of Action
3.)Site of Action
Pesticides are available in many different formulations including, liquid, dust, granules, baits, etc.
When more than one formulation is available for pest control, consider how it may affect the host plant, people, non-target organisms, and the environment.
Formulations that have the longest residual activity will more likely control a larger portion of the pest population however, tend to be more destructive to natural enemies and other non-target organisms/ or toward the environment.
Be sure the formulation is compatible with application equipment.
Worker Safety can also be a large consideration for choosing certain kinds of pesticides.
Mode of Action (MOA)
The Mechanism by which the pesticide kills or controls the target organism.
Most pesticides act through interference with metabolic processes.
Some cause physical damage.
Pesticides in the same class, generally, have similar modes of action. (All organophosphate insecticides, attack the nervous system)
MOA can provide clues to which non-target organisms may be affected along with other pests.
MOA may be more effective in certain life stages than others.
It is helpful to rotate pesticides with different MOA's in order to avoid resistance.
Systemic materials, on the other hand, move within the plant; applied to the media they will move throughout the entire plant, including new shoots. However, systemics take time to move up to the new shoots and control doesn’t happen until the toxic material is present where the insects or mites are feeding (unless applied on weeds).
Contact materials cover only the plant’s surface and insects or mites must directly contact the active ingredient for control. Good coverage is important – any surface not covered isn’t toxic, including new shoots and the newest leaves in the growing tip.
Translaminar materials don’t have surface residues but move into the leaf where a reservoir of active ingredient remains for a period of time providing longer control. As opposed to systemics – translaminars move only short distances, not through the entire plant.
Site of Action (SOA)
Refers to the specific enzymatic, metabolic, or physical reaction caused by the pesticide. For many pesticides the exact location is not known.
Indicate the amount of time it takes for a pesticide to degrade and is measured in terms of half-life.
As mentioned earlier, greater persistence is a good indicator of greater pest control, however can be a hazard to people, wildlife, beneficials, honeybees, and the env. overall.
As a PCA there are strict rules on how much pesticide can be applied based on potency.
The range of organisms and the respective life stages affected by a pesticide.
Broad-Spectrum: Kills a wide range of pests and non-targets.
Selective: Target Controls a smaller group of closely related organisms targeting chemical processes unique to a pest group. (Often desired in IPM).
The capacity of a material to cause injury to organisms.
A toxicity rating on the pesticide label suggest's the relative hazard the pesticide has toward people and the environment.
Many times persistence is a function of pesticide toxicity.
Types of Pesticides
By Pest: Insecticides, herbicides, fungicides, rodenticides, and nematicides.
Materials added to a pesticide formulation to enhance performance, customize the application to site-specific needs, or compensate for local conditions.
Spray adjuvants are packaged separately from the pesticide, whilst
Formulation adjuvants are mixed with the pesticide.
Directly enhance pesticide performance once the spray reaches the plant and include humectants (moisture retention promoters), penetrants, stickers, and wetter-stickers.
Help the spray application process and include acidifiers, buffers, colorants, defoamers, deposition aids, drift control agents, and water conditioners.
Some adjuvants can act as both.
Begins with a genetic trait that allows a pest individual to survive an application of a pesticide, whilst most other individuals in the population are killed off. After surviving the first application, the resistant individual then passes the gene(s) for resistance onto the next generation. The more the pesticide is used, the more susceptible individuals are eliminated and the larger the proportion of resistant individuals grows (with every passing application and every passing generation) until the pest population is no longer effectively controlled.
Frequently, resistance develops only in certain local-statewide- population (biotypes) of a species.
Factor Influencing Pesticide Resistance
Cross-Resistance vs. Multiple Resistance
Mechanisms for resistance include biochemical responses that decrease the sensitivity of the target site (such as nerves), detoxification of the pesticide by enzymes, and reduced penetration of the pesticide through plant epidermis.
Cross resistance occurs when the pest is resistant to two or more pesticides. Because the pesticides tend to be in the same or similar class; the resistance tends to be mediated through one or the same group of genes.
Multiple resistance describes when a pest is able to tolerate several classes of pesticides, that are unrelated to each other chemically. (multile genes typically mediate multiple resistances)
Populations of resistant individuls within a specieas are called a resistant strain or resistant biotype.
Characteristics for insect and diseases include; lifespan, reproductive capabilities, and mobility. Typically a short-lived pest with a high reproduction rate and immobility will show signs of resistance.
For weed species resistance is favored by high rates of seed production and germination.