Edible Landscaping

How to: Control Insects in Your Garden

Select vegetables that are more resistant to insect attacks, such as butternut squash, to reduce the need for spraying.

Summer time means lots of delicious fruits and vegetables in the garden, but it's also a time of insects. Insect populations are increasing as the days warm and as migratory bugs move into northern areas after overwintering in the South. All this means more pressure on your plants with the potential for damage.

The idea behind edible landscaping is to work with nature to create a balance in the garden. Planting a diversity of plants creates an ecosystem that will not let any one pest get out of hand. This method also means your plants will suffer some inevitable damage. The questions are how much damage is acceptable and what to do about it.

The first steps are to decide what's causing the problem and whether it should be controlled. Damage to plant parts can be caused by a host of factors other than insects, such as disease, weather, animals, and even the gardener. Determining what or who's causing the damage is critical. Once you've decided it's an insect, then you need to properly identify it. Although there are many bugs in the garden, few are causing damage to your plants. Properly identify the bug that's causing the damage and you're well on your way to controlling it.

Floating row covers can be used to protect young plants from insect attacks.

Then you need to decide how much damage is critical and if the problem warrants control measures. For example, potatoes can lose up to 1/3rd of their foliage to Colorado potato beetle feeding and still yield a good crop. A few holes in a broccoli leaf usually aren’t cause for concern. A completely skeletonized broccoli plant is. Knowing which insect is causing damage will allow you to control it at the right stage before it causes so much damage it's pointless to spray.

Speaking of spraying, that should always be a last resort. There are many steps to take to create a healthy garden before considering spraying. If you do everything right, there will be fewer instances when you have to use organic or chemical sprays in your home vegetable garden. So, let's take a look at five ways to control insects in your garden.

Cultural

Cultural controls revolve around the planning of the garden. Select insect resistant varieties to grow. For example, plant butternut squash instead of acorn squash because the squash vine borer is less likely to attack it. Planting varieties adapted to your growing area and keeping them healthy will also reduce insect attacks. Insects can sense when a plant is struggling and, like animals in the wild, are more likely to attack a weakened prey.

Rotate crops by not planting the same family of vegetables in the same location for at least 3 years. This will reduce the number of harmful overwintering insects in the soil.

Keep fruits, such as melons, off the ground to reduce problems from slugs and other critters.

Growing a trap crop to lure insects away from favored plants is another cultural method of control. For example, plant radishes on the edge of the garden to lure flea beetles and root maggots away from cabbages. Plant trap crops early so the invading insect finds them first. The temptation may be to spray and kill all the insects on the trap crop, but often these pests attract beneficial insects to your garden to control the infestation.

Mechanical

This sounds fancy, but what it really means is hand picking adults, squishing eggs, and creating barriers to keep pests away. Once you've identify the insect, look for its egg stage. If you can crush the eggs before they hatch, you'll reduce the population and potential problem. Picking off and squishing adults, such as Japanese beetles, every morning will also reduce the pest pressure.

There are many types of barriers you can use to keep bugs out. Floating row covers let light, air, water, and sunshine in, but keep insects out. Cardboard or newspaper can be rolled up into a cylinder and wrapped around stems or transplants as a cutworm collar. Aluminum foil can be wrapped around squash vines near the base of the plant to prevent the vine borer from laying eggs.

There are also traps that work well in the vegetable garden. Yellow sticky traps attract aphids and white flies away from plants and kill them. Of course, there is always the slug beer trap used to kill slugs and snails and use up some (spare) beer.

Sanitary

Keeping the garden clean and healthy can help reduce insect problems. Remove rotting fruit or heavily infested plants where insects are breeding. Use mulch to keep fruits off the wet ground and trellis plants vertically to help avoid some pest problems.

Encourage beneficial insects, such as ladybugs, by not spraying pesticides, growing a diversity of herbs, flowers, and vegetables and having water and shelter nearby.

Biological

Nature has a way of taking care of plants. I've always noticed that an aphid infestation is quickly followed by a plethora of ladybugs in the garden. If you plant a diversity of vegetables, herbs, fruits, and flowers, you'll create a habitat that attracts beneficial insects to your yard. To make them really feel at home, have grassy areas, shrubs for shelter, and a water source nearby. While beneficials won't kill every pest, they will keep the numbers down so you can harvest most of the produce.

Sprays

As I mentioned this should always be your last resort. If everything else fails, you can use sprays to control a nuisance pest. It's best to use targeted pesticides that only kill certain pests and avoid harming other insects, wildlife, and people. For example, Bacillus thuriengensis (B.t.) spray for cabbageworms is safe, effective, and relatively harmless to the environment.

Spraying at the most vulnerable stage of the pest is also important. For example, spraying B.t .'San Diego' for the Colorado potato beetle is most effective if you target the larvae right after the eggs hatch. It doesn't control the adult beetles.

Some sprays, such as Neem oil, don't necessarily kill, but repel, insects. Other sprays are relatively non-toxic, such as insecticidal soap. However, these "weaker" sprays may need to reapplied many times to gain control of an insect.

I'm an organic gardener, but just because a spray is listed as organic doesn't mean it's not toxic to some of the good guys. For example, pyrethrum is an effective broad spectrum, botanic spray for beetles such as the cucumber beetle. However, it also is quite toxic to honey bees. So when using a spray, start with a targeted organic spray first and only use broad spectrum sprays that kill indiscriminately if absolutely necessary.

Check out the Pest Control Library for more ideas on controlling vegetable pests.

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