Naturally Bug-Free (10 page)

Row covers

Flea beetles aren't a major problem on most vegetables, but they tend to kill eggplants in our area.

Of course, if you don't plant cucurbits, you won't have to deal with squash vine borers, cucumber beetles, and squash bugs at all. While that's generally not my preferred approach to insect control, I have been known to avoid planting a vegetable species entirely due to insect pressure. For example, eggplants aren't our favorite vegetables, and in our area the plants are defoliated by flea beetles in short order. Rather than hunting for a solution to the beetle problem, we just skip growing eggplants and focus our energy on vegetables we think taste better and that are easier to handle.

What would I have done if eggplants were our favorite food? In that case, I would have mimicked the effects of planting a resistant variety by growing the vegetables under row covers. When using row covers to exclude pest insects, it's essential that you find a way to weigh down all of the edges of the fabric, and that you cover the plants at the seedling stage so no pest insects will find their way inside the protected tent. If you're growing vegetables like squash that require pollination, you'll either have to remove the row covers once the plants begin to bloom, or you'll need to hand-pollinate. As you can tell, row covers add another level of complexity to vegetable gardening, but they can provide a chemical-free pest solution if all else fails.

Companion planting

Companion planting is a bit like choosing resistant vegetable varieties, but you instead plant the varieties you want and then cozy up a more toxic (from an insect's point of view) plant beside them. For example, some gardeners believe that interplanting basil with tomatoes will keep hornworms at bay. My experience with companion planting has been largely negative since I find that the plants need to be very close together to get any effect, and then you see competition between the vegetable you're trying to grow and its companion.

Hoverflies like this one are attracted to nectar sources in the garden, and their larvae stick around to eat aphids and caterpillars.

Agricultural scientists agree that most companion-planting lists aren't going to provide much pest-control help to the backyard gardener. However, a few interplanting mixtures seem to work. Trap crops (as I'll discuss in chapter 8) can be used to draw insect pests away from your main crop, and flowers near your vegetables can attract beneficial insects. (See chapter 2 for suggestions on which flowers to plant.) The roots of African and French marigolds have been shown to emit a chemical that repels nematodes (a type of microorganism that can harm roots), although you'll get the most bang for your buck by planting marigolds as a cover crop that is killed shortly before planting your nematode-sensitive crop. Finally, at least one source suggests that corn planted amid your squash may confuse squash vine borers looking for a spot to lay their eggs.

A diverse garden attracts pollinators and confuses pests.

Although I poo-poo most kinds of companion planting, I do feel that a diverse garden will fare much better than a monoculture when treated organically. On my own homestead, I break the ground up into permanent beds about three feet wide and anywhere from five to twenty feet long. Except for corn (which has to be grown in large blocks for wind-pollination purposes), I plant each type of vegetable in several different places around the garden, so a bed of cucumbers might be surrounded by beans, tomatoes, and Swiss chard rather than by the other cucumbers I'm growing that year. This patchwork-quilt garden gives me many of the benefits of companion planting without requiring the extra work of dealing with species mixtures all in the same bed. (On the downside, my technique does make planning the garden rotation more complicated, but they say puzzles are good for fending off Alzheimer's, right?)

The last facet of outwitting insects is to make your garden less susceptible to insect infestations by keeping your plants healthy. I already touched on this issue briefly in chapter 1 when I mentioned that many aphid problems can be traced back to over-fertilization of the plants being consumed. A related problem occurs with green beans—bean beetles can't digest the form of nitrogen created by bacteria in nitrogen-fixing nodules in the plants' roots, but the beetles love the form of nitrogen that the plants suck up directly from compost (or from other fertilizers in the soil). So one way to keep bean beetles in check is to skip topdressing any garden area where you plan to grow beans that year, forcing the plants to create all of their own nitrogen from scratch.
On a related note, many organic gardeners will tell you that every insect infestation is linked to a nutritional deficiency in the plant. While this idea has intuitive appeal, I've yet to find any solid data to back the hypothesis up. On the other hand, a well-nourished plant is likely to provide more nutrient-dense food for the table, so there's no reason not to provide the best possible nutrition for your vegetables. Applying organic amendments like compost and mulch will probably do the job for you, especially if you mix things up and draw your organic matter from different sources each year. If you want to be scientific, a soil test is a good way to get a handle on any potential deficiencies, at which point you can apply rock dusts or other amendments to boost levels into the recommended range.
Keeping the soil balanced and plants healthy is something I do as a matter of course, but there are times when I put more energy into the campaign than usual. If a new insect problem pops up and doesn't respond to any of my usual control techniques, that's a good time to start researching nutrient deficiencies. I was tipped off to the bean problem mentioned earlier because many of my bean beds were overrun with beetles, but the beans I'd planted into not-very-decomposed rye stubble were virtually untouched. The rye stubble was locking up nitrogen from the compost I'd applied to the soil, which in turn required the bean plants to kick their rhizobial bacteria into gear to create homegrown nitrogen for the plant. If you keep your eyes open for similar scenarios in which one bed of a vegetable is untouched while its neighbors are overrun, you'll soon discover which deficiencies or excesses may be at work in your own garden.

Japanese beetles are one of the insects I control by hand-picking.
Digger wasps are supposed to prey on Japanese beetles, but I see few digger wasps and lots of beetles in my garden.

I hope the previous chapters didn't make you think that keeping bad bugs in check is as simple as sitting on the porch and watching the good bugs and other wildlife eat them up. Sure, some of that happens, but there are times when the gardener needs to step in and keep things in line. When that time comes, my first line of defense is hand-picking.

How to hand-pick

If you catch them early, tent caterpillars are easy to hand-pick. You can greatly reduce tent-caterpillar populations by removing egg cases (top photo) while pruning your fruit trees over the winter. Once the eggs hatch, the cobwebby homes of the caterpillars are also easy to pull out of low branches.