If you have grown plants for food or aesthetics, you have probably experienced the frustration of losing some of your crops to insects and other pests. That is just a part of gardening, although if you grow crops year-round, you’ve probably realized that the upside of winter gardening is that you don’t have to spend much time fighting herbivores, since the cold weather kills them or drives them into a dormant stage. Animals are a different story, however, and you may find that hungry squirrels, deer, raccoons, or other critters are helping themselves to your plants even through the cold season.
To get rid of insect herbivores, many gardeners resort to using insecticide-pesticides. (Pesticides consist of a number of substances, including weed killers like RoundUp, insect-killing chemicals, and molluscucides, or “snail bait.”) In fact, most commercial (and many non-commercial) plants are grown with the aid of pesticides. While this may seem like a solution to the problem of insect herbivores ruining all your hard work, it has many downsides that have implications for your plants’ health, the health of the environment, and your own as well.
What effects do pesticides have on plants, the environment, and human health?
Regular use of pesticide undermines plant health because insects develop greater resistance to those pesticides, which means that you have to use more pesticide. That increased usage can stunt the plant’s growth, interfering with photosynthesis and killing of beneficial microorganisms in the soil that help the plant to complete the chemical processes involved in delivering nutrients to its roots and leaves. Pesticides also contaminate the soil, water, and air harming wildlife and other, non-target plant species.
Pesticide use has been linked with a number of health problems in humans, directly and indirectly. Most produce you eat is sprayed with pesticides that have been definitively linked with physical and neurocognitive disorders. Numerous studies have demonstrated that acute pesticide exposure often results in neuropsychological disorders like insomnia, depression, and anxiety, as well as increased risk for diseases like diabetes and cardiovascular ailments. Other studies have shown links between low levels of pesticide exposure and diseases like Alzheimer’s and ADHD. The risks to children from organophosphate pesticides are especially high.
Are organic pesticides better?
Some people believe that using organic (i.e. plant- and mineral-based) pesticides is better for human and environmental health than synthetic pesticides. This is a common misconception, and one that the organic food industry is not too eager to correct. In fact, while most people believe that using pesticides that are approved for organic farming are less harmful than using synthetic pesticides, there is not much evidence to support this. However, the main reason for the lack of evidence is that there just haven’t been enough studies done to show the effects of regularly using organic pesticides on the health of plants and animals, the environment, and humans.
The studies that have emerged in recent years suggest some disturbing facts: one such study,[i] published in the journal PloS One in 2010, noted that the natural pesticides 1) mineral oil and 2) beauveria bassiana (a fungus), both USDA-approved for organic farming, were not only less effective in controlling soybean aphids than their synthetic counterparts, they killed off beneficial insects that kept the aphid populations down and thus had a negative environmental impact. Other natural pesticides, including insecticidal soap, pyrethrins, sabadilla, diatomaceous earth, horticultural oil, spinosad, and copper sulfate (a fungicide), are all toxic to bees. Rotenone, also approved for organic farming, is toxic to fish. Bacillus thuringiensis (Bt), a soil-dwelling bacterium and the most widely used pesticide in organic farming, is harmful to butterflies, moths, flies, and beetles.
Finding a solution to the problems that growers face
This is not intended as a dig at the organic food industry (in fact, I often choose organic over conventional when buying produce, or snacks for my kids). Organic farming, in my opinion, deserves more support from consumers as well as state and federal governments. The research also demonstrates that consumers who eat organic most or all of the time tend to be healthier and have fewer negative health outcomes than people who never eat organic. While some of this has to do with overall lifestyle choices, much of it is related to what is already known about how synthetic pesticides negatively affect human health: we know that synthetic pesticides cause health problems in humans, whether exposure to them is acute or not.
However, organic farming is not a panacea for the problems facing agriculture, especially industrial ag, today. What is needed is a new approach to farming that can help mitigate the risks that the use of pesticides, whether synthetic or organic, pose to the health of the environment and humans.
So what can you, as an individual urban peri-urban, or rural grower, do if you have unwanted pests sharing your crops? Here are three suggestions:
Use Integrated Pest Management (IPM) techniques
Simply put, IPM, or Integrated Pest Management (aka Integrated Pest Controls) refers to a broad array of techniques that aims to use ecological controls to reduce pest damage to crops, while causing the least amount of harm to the environment. Some IPM techniques include using netting, screens, or other barriers to keep pests off of your plants, attracting beneficial predatory insects to your garden, using beneficial nematodes (microscopic groundworms that help control pests in your soil), and changing watering practices to prevent disease (which attracts insects).
Work with plants’ own innate immune systems
A strong plant can tolerate many stressors, in part because it has a powerful immune system that enables it to fight pathogens. Did you know that plants with strong immune systems can even fight off garden pests? They use a variety of direct and indirect defense tools to do this, including producing chemicals in “defense mode” to make insects that eat them sick, thereby deterring the pest from causing major damage and encouraging it to leave, or changing their chemical composition to make themselves taste unpleasant to the insect.
Several companies offer fertilizer formulations or soil additives to help your plants develop strong immune systems. The main task involved, as a grower, is making sure your plants have enough vital nutrients so that they can develop a strong immune response to stressors. In my own garden, I have found that using EM1, a microbial inoculant and “probiotic for plants,” gives my crops a much-needed boost.
Spray if you must, but in moderation and infrequently
If all else fails, you can make your own homemade pesticides, but be aware that if a pesticide kills an insect, it will likely cause harm to the environment in some measure. I have found that homemade insecticidal soap, which I make with water, Dr. Bronner’s Peppermint Soap, and a couple of pinches of Drum tobacco (which I let soak in the solution for a few days, then strain) kills aphids, whiteflies, spider mites, and a few other pests.
I also make a (truly foul-smelling) insect deterrent from the mature leaves of tomato plants. Soak the leaves in water overnight, then strain. It smells horrible, but deters grasshoppers, katydids, and kills aphids. With both of these you should use gloves when applying.
Do you have a method of deterring or killing insects in your garden that doesn’t involve using pesticides? I’d love to hear more – use the comment box below.