A couple of weeks ago I read a good newspaper article on a potential new herbicide for farmers that might help with some Roundup resistant weeds.
Technology has allowed for the development of corn and soybean seeds that are resistant to the herbicide Roundup (e.g. glyphosate). The benefit is that farmers can spray the weeds in the field without killing the crop. This technology has saved farmers a lot of money and time and has decreased the need to cover fields several times with weed control products that don’t work.
This technology is also controversial. Some critics fear that “super weeds” will eventually develop. This occurs when the same spray is time and time again, and a few strains of the weeds become genetically resistant to the herbicide. Eventually, as these multiply, we would have a field of resistant weeds.
I don’t want to get into the controversial side of this. There are strong feelings on both sides. I do, however, want to bring this down to your backyard garden and warn you about the same thing happening.
When applying pesticides, it is important that you alternate the class of pesticide that you are using. The class means the mode of action or how the pesticide works.
For instance, some pesticides are considered stomach poisons, while some are contact pesticides. Some of the newer chemistries prevent an insect from developing into its next stage in life, while others confuse the adult male with pheromones so that they can’t find the females to mate.
Pesticide resistance occurs when you use a pesticide regularly on the same insect. For instance, carbaryl is found in a lot of products that can be used to kill Colorado potato beetle. If a gardener uses it every time in the garden, sooner or later one or two of these beetles start to resist the chemical.
Then these mate and their offspring are resistant and so on until eventually the entire population becomes resistant.
Unfortunately, this has already occurred ,as carbaryl is no longer very effective on Colorado potato beetles.
In this case, carbaryl carbaryl falls into the group of carbamates. These work by inhibiting an enzyme that leads to interrupting the transmission of nerve impulses. Permetrhins, which are also labeled to kill beetles, are sodium channel modulators and eventually lead to paralysis.
So each time you decide to use a pesticide, switch up the products so that you are confusing the pests.
There are also other methods for preventing resistance, including using pesticides only when necessary, using tolerant or resistant varieties, and considering cultural and biological controls as opposed to chemicals.