Ah Facebook. You’re a sputtering font of knowledge. A murky, shallow pool of occasional wisdom. Especially this time of year, in mid-June, when gardens really start to look like gardens and life busts out all over the place.
I’m an admin for the Master Gardeners of Ontario Facebook group and also a fairly regular visitor to the Hamilton Plant Sharing group. The barrage of questions and panic about “bugs” is coming on strong now, as the leaf-chewing insects are becoming apparent. The constant advice to spray with dish soap or neem or vinegar, or to douse a plant with salt or baking soda or any number of DIY concoctions makes me shake my head. I would love it if others would jump in and help with education on these fronts.
The topic of garden DIY remedies deserves a nuanced and researched article. Right now, though, I need to get this off my chest. Why do so many gardeners want to “get rid” of stuff? To kill things.
These wasps are beneficial insects in the garden. The caterpillar has stopped feeding by this point.
What would be the point of killing this caterpillar?
Years ago I thought that pesticides were bad simply because they were toxic to humans. One person, an Organic Master Gardener, tried to lead me to higher ground. He failed because he did not explain the way things are connected–the big picture.
With the benefit of fifteen additional years of experience and a diploma in Organic Land Care I now have a better, more ecologically sound, understanding of the problem with trying to kill the creatures we don’t like. It’s a human-centric mindset that is pernicious and often invisible. It makes people want to spray the creatures in their gardens.
Let’s start with neem. Neem is extracted from a plant native to India and South China. The neem plant has been used for centuries for all kinds of products and cures, from toothpaste, to acne salve, to food flavourings.
Benign to humans, neem is a systemic insecticide– not registered as such so there’s not a lot of knowledge about it when it’s used this way. “Systemic” means that it enters the tissue and cells of the plant, turning the whole thing into a toxic meal for chewing insects. If you’re an ecologically conscious gardener, this is bad news. You are killing everything–good, bad, indifferent. It remains in the plant for a long time. When used on trees to fight Emerald Ash Borer, it’s active for two years.
Another often-recommended spray involves dish soap, often blue Dawn. There’s actually a reason why the blue kind is specified but I won’t go into that here. It is a contact pesticide. This means that it actually must TOUCH the bug for the bug to die. Spraying the leaves has no residual or prophylactic effect and will likely damage your plant.
Insecticidal soap is also a contact pesticide. With a different molecular composition than dish detergent, it is especially made to do minimal damage to plant leaves. There is so much information from trusted internet sources (dot edu sites) that explain how to use it. These sources explain why a commercial soap such as ‘Safers’ is far better than a DIY concoction of any colour.
Now, here’s the big picture and big message about killing stuff in the garden.
All creatures must eat. If we try to kill off the ones we don’t like, we are depriving predators of a meal and we are allowing the predated to grow unchecked. It’s a complex food web and all the parts are interdependent. Gardens are much healthier if we encourage diversity, keep the soil fauna happy, stop killing stuff, and accept some damage as the cost of having a healthy garden.
Encourage diversity: grow lots of plants, different species, a lot of native ones. Remove invasives. Have something blooming all the time, from spring to fall. Have a variety of flower shapes and colours.
Keep the soil fauna happy: Irrigate your soil, not just your plants. Relieve and minimize soil compaction. Add organic matter (but don’t bury it) and leave the trimmings/duff.
Otherwise, lay off the spray.
Accept some damage. Most insect activity is not going to kill your plant. Caterpillars are bird food–allow them to feed and enjoy the birds they attract. Holes in your plant leaves are not signs of imperfection. They’re signs of an ecosystem working.