Regional Gardening Reports :: National Gardening Association

In the Garden:
Lower South
July, 2009
Regional Report

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This syrphid fly larvae has a yellow aphid in its mouth (small end) while nearby other aphids have turned brown indicating they have been parasitized by a tiny wasp species.

Beneficial Insect Allies

A landscape or garden filled with a variety of plant species is a highly complex ecological system inhabited by multitudes of insects and other small creatures. Each affects many other species in various ways whether they are predators and prey, or competitors for shelter and food supplies.

There is also a fascinating interaction to the balance of nature in our gardens. By working to maintain this balance we can create landscapes and gardens where pest problems are minimized.

Most of the pest control in our gardens does not come out the end of a spray wand. Pests are kept in check by weather conditions, diseases (yes pests get diseases), and other insects. It is only when these factors break down that we gardeners may need to step in and take action to manage an outbreak.

Natural enemies of garden pests are at work 24/7 keeping pest populations suppressed. Take aphids for example. A single aphid can be born pregnant and within days it is popping out babies like a Pez dispenser! When you do the math, one solitary aphid in the spring could multiply geometrically so that by summer a garden would be knee deep in aphids if weather and naturally enemies were not at work.

Alas but these poor little aphids (note the feigned concern!) are running for their lives from the moment they are born. Lady beetle adults and larvae are chasing them down as are lacewing larvae with giant "ice hook" type mouthparts. Parasitoid wasps are flying overhead about to land and inject an egg to hatch and grow inside the aphid's body, eating it from the inside out -- an entomological version of the movie Alien! Syrphid fly larvae are laying eggs nearby that will hatch out into "Jabba the Hut" type maggots who'll begin to grab aphids to suck the contents out of them. Life ain't easy when you're an aphid!

There are many other beneficial insects in our gardens working silently behind the scenes to keep pest populations in check. These include true bugs such as predatory stink bugs, bigeyed bugs, assassin bugs, ambush bugs, damsel bugs, threadlegged bugs, minute pirate bugs, and flower bugs. Predatory beetles include the ground-dwelling rove beetles and the most famous beneficial of all, the lady beetle, which can consume several thousand aphids during its lifetime. Hurray!

Lacewings, praying mantids, predatory mites, and spiders are among the other insect-feeding beneficials in our gardens. Then there are the beneficial flies which include robber flies, long-legged flies, and hover or syrphid flies which often look like tiny shiny bees darting about. Their larvae are effective predators of aphids and certain other insect pests.

Wasps are one of our best groups of predators. The next time you see a webworm nest in that old pecan tree try breaking the web up with a pole and then check it out 20 minute or so later. You'll likely see wasps moving in to haul off the bounty. A large paper wasp colony can consume up to 2,000 caterpillars in a single season.

Parasitoids feed on and inside insects. Some lay eggs inside caterpillar eggs, their larvae consuming the contents. Others lay eggs inside insects such as aphids or caterpillars. Way cool! There are even parasitoid species of flies.

Take time to learn about the beneficial insects in your garden. A Web search will provide helpful photos for identifying them. As you go about your gardening activities avoid broad-spectrum sprays, include plants that provide pollen and nectar, and remember that a few pests are okay as they attract the beneficial that feed on them.

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