Spring is finally here and it’s time for us to stop hibernating and start seeding! Unfortunately, as we come out of our holes to embrace the warmth of spring, so do the pests. There are all kinds of pests ready to try and damage crop production, but thankfully farmers have pesticides to fight back. But wait, before you spray your pesticide have you checked to see how it will interact the beneficial microbes in your soil? Is it safe to use with your inoculants? What other effects could it be having? In this week’s edition of Growing Possibilities, we will discuss the effects of pesticides and their environmental safety and interactions with microbes in the soil.
To start let’s define what is a pesticide. A pesticide is a substance or mixture that is used to control or kill a pest. In agriculture this includes herbicides, insecticides, fungicides, nematocides and so on. Pesticides are great at killing their intended targets, but sometimes they are good at killing and/or harming things outside their intended target as well. A large issue with pesticides is that they can move outside their intended area and end up in various water sources, such as ponds, streams lakes and wells. Once water sources are polluted with pesticides it can start to have harmful effects on the life that depend on them including fishes, animals, plants and even humans. These effects include various living things being killed or harmed, which can lead to an entire ecosystem being disrupted. There are various ways that pesticides move from your crops and end up in water sources, such as spray drifts, leaching, runoff and volatilization (1). Humans can also be greatly affected by pesticides not only by contaminated water sources, but also by breathing in pesticide fumes and by consuming them unintentionally. Research has shown that pesticide exposure has been linked to certain cancers, Alzheimer’s Disease, ADHD and birth defects (2). To determine how harmful the pesticide you are using, one thing to look for is the signal words, which are CAUTION, WARNING and DANGER. A pesticide that only has labels that say CAUTION will have the lowest toxicity, WARNING will have a medium toxicity and those labelled DANGER will be most toxic (3). Though just because a pesticide says DANGER and is considered most toxic does not mean that it cannot be used, it simply means that you must take precautions when using it. This includes being aware of what the upcoming weather will be to avoid runoff if it is going to rain and accurately measuring the amount of pesticide needed to treat your field and maintaining a buffer zone around your crops.
Every pesticide has it’s intended target, however sometimes there are other things, like the microbes in your soil, that get caught in the cross hairs. Many studies have shown that pesticides can have harmful impacts on soil microbes (4), which can be detrimental to your crop’s yield. Though not every pesticide will be detrimental to every type of microbe in your soil. This means that one pesticide may kill one type of bacteria in your soil, but not the other bacteria; or that one pesticide may kill a specific bacterium, but a different pesticide may not. There are some bacteria that we worry more about being killed off by pesticides than others, particularly those that we know directly benefit the plants. These are often the microbes that we annually add to the soil like crop inoculants (e.g., nitrogen fixing bacteria or phosphorus solubilizing bacteria). To determine if a pesticide is detrimental to the bacteria (active ingredient) in a specific inoculant, inoculant manufactures/developers generally go through a series of experiments to see if they are compatible, called compatibility testing. Compatibility testing involves mixing the pesticide and inoculant together and then to determine if and how much of the bacteria survived and how long they survived. An important part of compatibility testing is time, as studies (2) have shown that some pesticides may affect microbes gradually and reduce the number of bacteria over a longer period of time than what might be immediately obvious. Therefore, compatibility tests are done over hours or days or weeks or even months depending on the products being used, so that they can be accurately monitored to see if the products are compatible for use.
If you are curious about any of XiteBio®’s product compatibility, please check out the following links to our compatibility charts: XiteBio® SoyRhizo® for soybeans; XiteBio® PulseRhizo® peas, lentils & faba beans; XiteBio® Yield+ for oilseeds, cereals, legumes & tuber crops and XiteBio® OptiPlus® for soybeans. If you are interested about a product that is not listed on our compatibility chart, contact your local XiteBio sales representative and we would be happy to do a compatibility test for you!
References:
(4) https://iopscience.iop.org/article/10.1088/1742-6596/1294/7/072007/pdf