When fungicide resistance results from modification of one major gene, pathogen subpopulations are either sensitive or highly proof against the pesticide. Resistance in this case is seen as complete loss of disease management that cannot be regained by using higher rates or more frequent fungicide applications. This type of resistance is often referred to as "qualitative resistance."
When fungicide resistance results from modification of many interacting genes, pathogen isolates exhibit a range in sensitivity to the fungicide depending on the amount of gene changes. Variation in sensitivity inside the population is continuous. Resistance in this case is seen as an erosion of disease management that may be regained by using higher rates or more frequent applications. Long-term selection for resistance within the pathogen by repeated applications could eventually end in the best labeled rates and/or shortest application intervals not being able to adequately management the disease. This type of fungicide resistance is often referred to as "quantitative resistance.
Fungal isolates that are proof against one fungicide are often additionally proof against other closely-related fungicides, even once they have not been exposed to these other fungicides, as a result of these fungicides all have similar mode of action. This is often referred to as cross resistance. Fungicides with a similar group Code are probably to exhibit cross resistance. Often negative cross resistance occurs between unrelated fungicides as a result of the genetic modification that confers resistance to 1 fungicide makes the resistant isolate more sensitive to a different fungicide.
Managing fungicide resistance is critically necessary to extend the amount of your time that an at-risk fungicide is effective. The primary goal of resistance management is to delay its development instead of to manage resistant fungal strains after they have been selected. Therefore, resistance management programs have to be compelled to be implemented when at-risk fungicides first become available for commercial use. The objective of resistance management is to minimize use of the at-risk fungicide without sacrificing disease management. This is often accomplished by using the at-risk fungicide with other fungicides and with non-chemical management measures, such as disease resistant cultivars, in an integrated disease management program.
It is important to use an effective disease management program to delay the build-up of resistant strains. At-risk fungicides ought to be used at the manufacturer's counseled rate (full rate) and application interval. Using full rates is anticipated to minimize selection of strains with intermediate fungicide sensitivity when resistance involves many genes (quantitative resistance). At-risk fungicides ought to be employed in alternation with other at-risk fungicides with totally different modes of action or different chemical teams, and that they ought to be combined or alternated with fungicides that have a low resistance risk.
When one crop may function a supply of inoculum for a subsequent crop, the alternation scheme among at-risk fungicides ought to be continued between successive crops such that the first at-risk fungicide applied to a crop belongs to a different cross-resistance group than the last at-risk fungicide applied to the previous crop. Some at-risk fungicides are formulated as premix product with other fungicides to manage resistance. At-risk fungicides ought to be used solely when needed most. the foremost important time to use them for resistance management is early in a virulent disease when the pathogen population is small. Multi-site contact fungicides ought to be used alone late within the growing season, where they have been shown to provide sufficient disease management to shield yield. Another necessary element of resistance management is assessing disease management and reporting any loss of efficacy probably due to resistance.
0 komentar:
Posting Komentar
No SPAM COMMENT Please