Farmers need to “get out of their comfort zone”
Farming is like most other fields of human endeavor – when we find something that works, we stick with it. When selecting pest control options in corn and soybeans, for instance, if the cost is right and the treatment is effective, growers tend to stay with the control programs they know work well. With all the things that can change over the course of a growing season, selecting “tried and true” crop protection programs helps make production agriculture more predictable and manageable. But staying the course with crop protection chemicals can lead to unexpected challenges.
For many years now, we have known that repeatedly using the same herbicide program causes weed species shifts in the field. Plant species that can tolerate the herbicide program become the dominate weeds. Continuous use of herbicide programs selects for species that have an edge to survive. But in addition to species shifts, we can also see a development of pests that are resistant to the pesticide program.
Tolerance is different from resistance. Tolerant species are less responsive to a herbicide program; resistance occurs when a weed species that used to be controlled by a herbicide is suddenly no longer controlled by the chemical. Pesticide resistance can develop by various mechanisms. The most common occurs when a pest evolves the ability to detoxify the pesticide, effectively reducing the amount of the active ingredient that is available for control. The pest may also change the metabolic process that the crop protection chemical attacks, rendering the material harmless to the organism. Pest resistance is not limited to pesticide programs. Even crop rotation, one of the oldest non-chemical tools in the pest management toolbox, can be thwarted. Western corn rootworm beetles changed their behavior to laying eggs in soybean fields in the Corn Belt during the 1990s.
In managing pesticide resistance, field crop producers have been relatively lucky compared with fruit and vegetable growers. In Michigan, herbicides were the only pesticide in field crop production that was routinely used each season. Michigan fruit and vegetable producers make multiple pesticide applications each growing season to control disease and insect pests. They have been battling resistant pests such as fungicide-resistant apple scab, streptomycin-resistant fire blight, and insecticide-resistant coddling moth and Oriental fruit moth for many years in parts of southwestern Michigan. These pests are costly to manage, and now growers have few options for control in many areas where they are prevalent.
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