Naturally Bug-Free (3 page)

Japanese beetles
(
Popillia japonica
) are iridescent insects that come out for a couple of months in the summer, during which time they can completely defoliate their favorite plants (especially roses, grapes, and cherries). During the rest of the year, Japanese beetles live as white grubs in the soil, where they do some damage feeding on plant roots.

My primary control method is hand-picking the adult insects, along with choosing plant species that are less attractive (which I'll explain in more depth in chapter 6).
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gardeners add the use of trap crops, chickens, guinea fowl, ducks, robins, and bluebirds. In particular, they recommend letting birds work over the ground in late spring when beetle larvae are close to the surface and can be easily scratched up.

The spotted garden slug eats decaying leaves and fungi, other slugs, and young garden plants. Photo credit: Phil Nixon, University of Illinois Extension.

Slugs
(and their shelled relatives, snails) tend to top the list of problematic pests in areas that stay cool and damp during the summer, especially among gardeners who use heavy mulches. However, you shouldn't jump to the conclusion that any mollusc you find in the garden is bad news. Unlike many of the pests mentioned in this chapter, the term "slug" is a very general one, and saying "slugs are bad for gardens" is a lot like saying "birds are bad for gardens." Although many slugs chew on leaves, others are decomposers, breaking down the dead plant matter on the soil surface (like your straw mulch), while a few even eat other slugs.

How can you tell the difference between the good slugs and the bad slugs? I generally consider any invertebrate in the garden good until I'm proven wrong, which in a slug's case consists of catching them in the act of eating my lettuce or strawberries. If you want to learn slug identification, the worst slugs include the milky garden slug (
Deroceras reticulatum
), midget milky garden slug (
Deroceras agreste
), marsh slug (
Deroceras laeve
), great gray garden slug (
Limax maximus
), and tawny garden slug (
Limax flavus
). Those of you living in the Pacific Northwest will be relieved to hear that the banana slug (
Ariolimax
spp.) is not a garden pest.

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readers report good luck with slug-control methods including hand-picking, iron-phosphate baits, diatomaceous earth, beer traps, chickens, garter snakes, and ducks. (More on ducks in chapter 3—they aren't always as well-behaved in the garden as some books suggest.) I've found that promoting habitat for natural predators like toads works wonders at keeping slug populations under control, so you'll read more about that technique later in this book.

Squash bug adults look a bit like stink bugs. Their eggs are found in V-shaped clusters between plant veins and hatch into greenish larvae that later turn pale gray. Photo credit: Ria Malloy, University of Maryland Extension

Squash bugs
(
Anasa tristis
) suck the juices out of the leaves of cucurbits (especially pumpkins and squashes), causing them to wilt. Hand-picking is particularly effective for squash bugs, especially if you catch the insects at the egg stage. Boards on the ground beside your squash plants provide a night-time hiding place for adult squash bugs, which are easy to crush the next morning.
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readers also recommend cleaning up infested plants, applying neem oil to egg clusters and juvenile bugs, protecting plants with row covers, and utilizing late planting. In my own garden, I simply plant resistant varieties, especially butternuts.

Squash vine borers can be hard to see, but their results are evident when your squash plants collapse overnight.

Squash vine borers
(
Melitta cucurbitae
) are often identified by their symptoms rather than by seeing the insects themselves. A happy squash plant will suddenly wilt and then perish even though water is abundant, proving that vine borers have eaten their way through the stem. I'll discuss my methods for controlling this pesky insect in chapters 5 and 6, so here I'll just list
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gardeners' treatments: crop rotation, resistant varieties, mounding dirt over stems to promote rooting at nodes, and late planting.

White cocoons on this hornworm are a sign that the caterpillar has been eaten alive from the inside by parasitoid wasps.

Tomato hornworms
(
Manduca quinquemaculata
) and
tobacco hornworms
(
Manduca sexta
) are large, green caterpillars that eat the leaves of tomato plants before transforming into hummingbird-like sphinx moths. As you can see from the white sacs in the photo above, our hornworm problem is always controlled instantly by braconid wasps, which lay their eggs just under the skin of a caterpillar. The baby wasps feed on the insides of the caterpillar, then they push their way to the outside of the host to spin cocoons. The wasps transform into adults within the cocoons, then chew their way free so they can mate and lay eggs on more caterpillars. If you see hornworms similarly parasitized, leave them alone and the tiny wasps will soon spread throughout your garden. Along with encouraging braconid wasps,
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gardeners use hand-picking and Bt to control tomato and tobacco hornworms.

Whiteflies are usually found on houseplants and in greenhouses. Photo credit: Scott Bauer.

Whiteflies
(
Trialeurodes vaporariorum
and related species) are tiny, winged insects that suck the juices out of plants, much like aphids do. Like aphids, I never have problems with whiteflies unless I've blocked out their natural predators, such as when I grow fall greens under quick hoops or take houseplants inside over the winter.
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gardeners treat whiteflies with insecticidal soaps. I generally just wait the infestation out until I'm able to put the houseplants outside, allowing natural predators to demolish pest populations. Since whiteflies can't stand freezing temperatures, you can also uncover moderately-hardy garden plants during light freezes to kill off whitefly infestations.

Soldier beetle larvae act a bit like bad bugs in our garden since they like to suck sugar water out of fruits. But these insects are generally beneficial since they also suck the juices out of cucumber beetles, caterpillars, grasshopper eggs, and aphids.

In addition to this dirty dozen of problematic insects, runners-up include: Mexican bean beetles (
Epilachna varivestis
), Colorado potato beetles (
Leptinotarsa decemlineata
), flea beetles (several species in subfamily Alticinae), and asparagus beetles (
Crioceris asparagi
). And then there are the insects that many gardeners consider pests, but that don't actually prey on your plants. For example, yellow jackets may sting you, but these wasps are actually beneficial insects in the garden since they eat large quantities of caterpillars and other pests. I'm not going to cover "pests" that are only bad because they bother humans, but I will touch on some of the other problematic insects later in this book. In addition, you'll also want to keep your eyes open and to watch who chews on your leaves and who visits your flowers since each garden has its own array of problematic insects and beneficials.

Chapter 2: How to promote the good bugs

After figuring out who the bad bugs are, your next goal in the garden should be to promote beneficial insects. But how can you tell which invertebrates are doing good work? I'm tempted to say that any bug who isn't obviously bad is a garden ally, but you should work especially hard to protect invertebrates who improve your soil, pollinate your crops, and control problematic insects. The sections below will give you a quick introduction to beneficials in each of these categories.

Soil workers