Birds (key predators of insect pests), he notes, "generally do not fly across wide expanses, preferring to move from greenway to greenway." He continues:
And indeed, the traditional farm was edged by woods and broken up with hedgerows. There is clear evidence that such a structure gives greatly improved natural protection against pests. Even in the case of large farming operations, preserving small amounts of natural habitat in the form of woods and copses and providing hedgerows can lead to thriving populations of wildlife. Because they act as both pollinators and as predators of many common pests, this can be a cost effective approach to pest control and pollination. It may also lead to crops with higher market value, as consumers are often willing to pay more for food grown without pesticides.
Reading this made me think about something interesting that happened in my own organic garden recently - in which we plant tomatoes, various types of hot peppers, chives, corn, beans, peas, zucchini squash, eggplant, lettuce, spinach, strawberries, and a bunch of culinary herbs. To attract pollinators, we maintain strips of native California grasses and wildflowers at each end of the garden, and in an island in the middle (it also looks very nice, and is a nice backdrop for our solar fountain).
A couple of weeks ago, our landlord told me he was going to have gardeners come by the house. I emphatically told him to please make sure they don't touch the garden. We were surprised to come home the night the gardeners had come and find that all of our grasses and wildflowers had been pulled. The garden had been left completely bare except for our food and herb plants - a few of which were actually missing (they pulled 2 productive bean plants, our dill weed, and a bunch of mint and oregano). When I called and yelled at the landlord about the demolition of our garden, he told me that it had looked "messy", so he had the gardeners cut all the native grasses and wildflowers. (he's not the brightest bulb, to be sure)
Suddenly this week when I went to harvest tomatoes for a fresh batch of salsa, I noticed something interesting. There were snails eating our tomatoes. We'd had no problem with snails until the gardeners had removed all the native grasses and wildflowers. It seems that the grasses and wildflowers not only helped to attract pollinators, but also to control pests! They must have kept the snails well enough fed that they didn't need to eat our fruits and vegetables. Either that, or some type of snail predator had lived in the grasses and wildflowers.
This observation of the pest control benefits of maintaining strips of native grassland plants in our garden seemed to be a mini-example of what Heal was talking about concerning the benefits of maintaining hedge rows in large agricultural fields.
Have any of you experienced anything similar to this in your garden?