Sustainable Garden Pest Management

We had a wonderful conversation today about how great it is that we seem to be staying ahead of the squash bug infestation on the pumpkins by manually squishing bugs and eggs, rather than having to spray.

In the garden, there are three groups of bugs: pollinators, predators (the bugs that eat other bugs), and herbivores (the bugs that eat the plants). In general, we really want the first two groups in the garden, but don't really want those plant eaters (like the squash and cucumber beetles). But most pesticides affect all or most of the bugs in the garden, so when we spray there is a good chance that we are hurting as many "helpers" as "hurters." By squishing the squash bugs and their eggs, we are able to keep the population of bad-guys to a minimum, while not bothering the good guys.

Another interesting factor with pesticide use is that predatory insects tend to have a much slower rate of population increase than the herbivorous bugs that they eat. What this means is that if we spray something that kills virtually all of the bugs in the garden, the plant-eating bugs are going to come back much faster than the bug-eating bugs. And with fewer bug-eating bugs in the garden, the population of plant-eating bugs is even more likely to get out of control.

This does not mean pesticides have no place in gardening. But we must recognize the full spectrum of consequences of their use, and use them as efficiently and localized as possible.

Other important practices in sustainable pest management include ensuring that crops get rotated. What this means is that we don't plant the same crop (or family of related crops) in the same place in the garden year after year. Many of the bugs that attack our garden plants spend the winter in the ground very near to the plants they were eating. If we plant in the same plants in that spot next year, the bugs can easily find them. If we move the plants some distance away, it is much harder for the bugs to find them.

Additionally, we intercrop. Intercropping means planting various crops together. Often one crop will deter or confuse a pest that is attracted to another crop. Planting the two crops amongst each other can keep the pests away.

Other tricks are planting flowers and plants that the bugs don't like. In our garden we have borage planted amongst the tomatoes to keep the tomato horn worms away, and nasturtiums planted in the pumpkins and cucumbers to keep the squash bugs away (these flowers are still very small–they were planted late–probably part of the reason they are not doing much to keep the squash bugs away right now).

And finally, sometimes we plant a trap crop. This is a crop that a pest likes more than most anything else in the garden. Our garden has both zinnias and sunflowers which are favorites of japanese beetles, and will hopefully keep these hungry bugs busy enough to stay out of our beans and other crops.