A handful of acorns makes the pesticides go down
Last month we discussed photosynthesis and took a close-up look at leaves. This month we’re going to zoom way out and take a look at how the Earth’s vegetation cycles affect pest pressure.
If we look at the Earth from space, paying attention to the vegetation and using a little imagination, we observe a fascinating phenomenon. The earth’s surface in the tropics is green throughout the year, for the most part, with a few seasonal changes in color between dry season and rainy season. As the seasonal growing conditions change in temperate zones, however, there is a dramatic color change. As spring unfolds in the north, the green color of the tropics flows northward like a green army advancing northward. The flush of green flows northward to the edge of the Arctic Ocean, then retreats to the tropics in the fall. The pulse of green then goes to the south as the southern hemisphere enters spring while the north experiences fall and winter.
As long as there have been green plants, this heartbeat of green has been happening. The pulse of green is a massive accumulation of energy and nutrients that maintains the ecological economy. Each spring across the temperate zones there is an explosion of fresh, tender foliage that is closely followed by an explosion of the insects that eat that foliage. This population eruption of insects is a resource bonanza for insectivorous creatures: amphibians, reptiles and especially birds; this is part of why so many birds migrate seasonally. Our crops, whether annual or perennial, are part of the pulse of green that feeds insects, and that population boom can reduce crop yields, spread disease in our crops, introduce premature decay, and cause cosmetic flaws on crops. As the season progresses, plant growth slows down, pest populations decline, predator populations follow suit, decomposer populations increase, and soon we are back into a season of dormancy.
As ecological farmers and ranchers, understanding these dynamics is key to our food-producing and financial success. Here’s an example to show how this is possible.
Springtime rolls around, and chemical farmer A plants their crop. The crop grows in the warming weather, as fast as fertility and water limits will allow. This pulse of green is now food for plant-eating insects. If Farmer A is a “fighting-against farmer” and sprays a pest control product (whether chemical or organic) the pest population crashes because of the poison. The insects’ original food resource (the crop) is again available for consumption by insects. The pest populations boom again as the remnant population recolonizes the available territory, so Farmer A sprays again to “control” that population.
Farmer A has short-circuited the development of a complete ecological balance — natural pest-predator population control. This may work economically for Farmer A, but it requires additional equipment, time in the field, and knowledge of what and when to spray, and it exposes the farmer and their family to toxic chemicals or not-as-toxic organic poisons.
Stopping pest-control sprays “cold turkey” doesn’t solve the pest problem. Nothing does. Nothing ever has. The only pest “control” there has ever been is the natural balance of ecosystems — which always includes plant-eating insects and the diseases they spread!
In order to improve our baseline pest control, we need to increase the ecological functioning of our system. This may include planting “habitat islands,” “prairie strips,” and other such things, But probably the biggest bang for the buck can come from something as simple as planting oak trees as field perimeter trees or in agroforestry systems. Why oaks, you ask?
There are over 400 species of oak trees native to North and Central America. They grow in every agricultural region of the continent, including deserts and so-called true grasslands. Oaks happen to be, in one sense, the “tree of life,” in that there are more species of creatures that are dependent on oaks than on any other plant. More than 800 species of insects alone depend on oak for their survival.
But wait a minute … I thought we were talking about insect control — not growing more insects! Well, we are talking about insect control. Of all the insect species that depend on oaks for their livelihood, the majority are specialist insects that eat and reproduce exclusively in various parts of the oak tree. Ninety-nine percent of oak-living pests will not touch your crops. The predators of those oak pests, however, are not specialists! They will happily eat corn borers and armyworms after lunching on the oak-dependent red-banded hairstreaks (Calycopis cecrops). The champion insect-eaters are, of course, birds, which will not only eat the insects produced in your oaks — they will nest there and raise their young as well.
As the pulse of green moves north in the springtime, the insect populations begin to boom. Birds, both migratory and resident, shift their diets from seed eating to egg, caterpillar and adult-insect eating. Most baby birds are raised in the springtime alongside the biggest boom in insect populations. When the chicks have fledged, they still require food — they require insects throughout the entire summer and fall.
Yet agricultural pesticides destroy the food source (insects) of our insect-eating birds. Bird populations are stressed worldwide in part because of the loss of habitat caused by the clearing of land for agriculture and the spraying of insecticides, which wipe out their food source. Declining bird populations should bring to mind the old saying, “the canary in the coal mine.” Declining bird populations should be a warning to us to change and to change fast.
So, plant oak trees! At least plant oak trees around the perimeter of your property! Oak trees are the food source for oodles of insects, the majority of which do not affect your crops. These insects have different life cycles, eat different parts of the oak trees, and are available for birds all season long, even when your crops’ pests are not. Insect-eating birds aren’t specialists! They don’t care where that caterpillar was grown, whether in an oak tree or in your fields.
More oak trees means more birds. More birds mean fewer pests and increased nutrient cycling — especially nitrogen and phosphorus. Fewer pests means fewer sprays, which means lower cost of production.
Free insect control, free fertilizer, the color and beauty of vibrant bird life all around, the symphony of birdsong every morning, the peaceful cooing of mourning doves or booming of nighthawks in the evening — all can come from the planting of a handful of acorns.
Mark Shepard is a land designer and consultant and is the author of Restoration Agriculture, Water for Any Farm and the Water for Any Farm Technical Manual.
