There is nothing more frustrating than watching helplessly as a vegetable crop is destroyed by a pest or disease. One year, 80% of my tomato crop was wiped out by bacterial wilt disease. What is a home gardener to do about managing pests and disease? I have come to learn that prevention and developing healthy plants is the best approach. Instead of treating the symptoms that we see in plants, we need to understand what is causing these symptoms. If we understand the environmental cause, then we correct the problem as opposed to treating the symptom, thus managing pests in the garden.
There is a worldwide standard for managing garden pests (including disease) called Integrated Pest Management (IPM). I like the framework because it guides you through a thoughtful process to understand the underlying cause. Whether you are an organic gardener or not, I believe there is something that each of us can learn from this approach.
Before I describe the approach, I want you to think about yourself. If you are under stress, your natural immune system can be weakened. When your immune system is weakened, disease and sickness can develop. The same is true of plants, when plants are stressed (too much/too little water, sun, nutrients) they become much more susceptible to pests and disease. By taking an integrated approach to understanding the stress your plant is experiencing, there is a higher probability that you will be better equipped to managing pests in your garden.
My green thumb came only as a result of the mistakes I made while learning to see things from the plant’s point of view.
H. Fred Dale
Wasp (beneficial)
WHAT IS INTEGRATED PEST MANAGEMENT?
IPM is a common sense and holistic approach that involves understanding all the factors that influence the growth of a plant: soil, water, air, nutrients, weeds, animals, beneficial organisms, weather and cultural practices. The goal is not to eliminate all pests, but rather to manage pests at an acceptable level. To better understand what it means to ‘manage at an acceptable level’, let me give you two examples from growing cucumbers:
- One year, when my cucumber seedlings were beginning to mature and enter their rapid growth stage, I noticed that beetles were feeding on the leaves. I continued to monitor the situation and hand-picked (and removed) any beetle that I saw. I also noticed that the fruit was not impacted by the leaves being chewed. Eventually, the pace of growth of the cucumber outpaced the ability of the beetles to keep up. I know that I have not eliminated the beetles all together, but the plants are healthy and co-existing with the beetles.
- I met a farmer who talked about the inevitability of downy mildew on cucumbers. As opposed to fighting the disease, his solution was to succession plant his cucumbers. If one succession was showing signs of the disease, he knew he had another succession right behind that would continue to produce.
Cabbage Moth (not a beneficial)
WHY IS PREVENTION IMPORTANT?
Prevention is the underlying tenet of the IPM approach. Here is what needs to be considered with this approach:
- Understand your environment and your plant – putting the right cultural controls in place from the start. For example, planting in the right place, at the right time, with the right spacing, sun, water, soil and nutrients. Strong plants resist pests and disease. Of all the cultural controls, having good soil that is amended with organic matter (like compost) will give your plants the best possible start and opportunity to grow.
- Identify the pest – sometimes this is not easy, but you will have better success if you understand the problem. Knowing the pest will guide you to the treatment options (e.g. like hand-picking beetles).
- Be observant – Make a habit to routinely walk around your garden so that you can spot problems early. It is especially important to look at the leaves of plants and turn them over. Many pests will live on the underside of leaves.
- Evaluate – did your control work what could you have done differently.
WHAT ARE YOUR OPTIONS?
Consider your options – in the IPM approach, chemical (organic or synthetic) should always be your last option.
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- Physical control involves preventing access to your plant or physically removing. For example, one method for ‘catching’ slugs is beer traps that are placed in the soil. Slugs are drawn to the scent of the beer and will climb into the trap and drown. Hand removal of insects is another physical control. Laying down black plastic for weed suppression is another physical control.
- Genetic control – there are now more varieties of plants that are bred to be resistant to certain diseases. For example, cucumbers or basil that are resistant to downy mildew. These seeds are referred to as F1 Hybrid seeds. Hybrids are created by cross-pollinating two different but related species. Hybrids are not to be confused with Genetically Modified seeds (GMO). GMO seeds are created in a lab by using sophisticated gene-splicing technology.
- Biological control – sometimes you will hear about attracting ‘beneficial’ insects to your garden. A few examples include ladybugs (feed on aphids and spider mites), dragonflies (feed on mosquitoes and flies), praying mantis (feed on flies and grasshoppers) and wasps (feed on aphids, flies, caterpillars).
- Chemical control – this should be your last option. There are both organic and synthetic chemical controls to consider once you have identified the pest and the extent of the pest damage.
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