Recognizing and Managing Insect Pests in your Garden
One of the more frustrating aspects of gardening can be watching the plants you tended and cared for all spring start to have inexplicable nibbles and bites taken out of them. It can be difficult figuring which of the many insects in your garden is the culprit as well as knowing the tell-tale signs of specific pest damage on your plants. While this is not intended to be a conclusive insect guide, it should cover some of the more common types of pests you’ll come across during your garden season.
Aphids 
This common pest attacks a wide range of plants and suck the sap from the plant, causing leaves to characteristically curl and turn yellow. Though minor numbers of aphids may not present a problem, they survive in inclement weather better than other insects and can start to overtake a garden early in the season.
How to Recognize: Aphids often appear as small whitish-green dots that range from barely visible to somewhat larger than a pinhead. In bad cases of infestation they can overwhelm and completely cover a plant.
Management: Ladybugs are well known in this regard as predators of aphids, as are lacewings and aphid destroyers. Another method is to spray down the plant with a vegetable oil/natural soap mixture and then use a hose to knock off the remaining insects.
Colorado Potato Beetle 
A common insect found in our community gardens, the potato beetle damages plants by feeding on leaves and stems and can often strip entire plant’s foliage bare. Though known for the damage they can wreak on potatoes, they will also feed upon tomatoes, eggplants and peppers.
How to Recognize: Adults have a yellow-orange color and many black stripes over wing covers. Larvae are orange, humpbacked grubs with black spots along the sides. Eggs of the potato beetle are yellow ovals laid in upright clusters.
Management: Plant an early-maturing variety of potato so the adult beetles don’t overtake them in the heat of the summer. Mulching with straw often deters egg-laying, as well as companion planting of the mint family or tansy. Floating row covers can prevent beetles from reaching plants but can be hard to maintain as the fabric can sustain damage over the season.
Cutworms 
A general term for the larval stage of several varieties of moths, cutworms are ravenous and will eat almost any type of plant in your garden. A tell-tale sign of a cutworm is that plants will often appear is if they have been “sawed-off” with the untouched top laying next to the chewed stem.
How to Recognize: The grubs are often grayish green or brown with black striping. They are rarely seen during the day and tend to be most active at night when they come out of the soil.
Management: If you come across any while digging in your bed, promptly throw them out or kill them. Predatory nematodes can also control the larval population. Some people have placed foil or cardboard cutouts around their transplants to great success.
Flea Beetles 
This small insect leaves a distinctive small irregular holes in leaves. Flea beetles attack a wide variety of crops in different life stages, making them difficult to control.
How to Recognize: small blackish insects that can seem to cover plant leaves. The beetles will jump like fleas as you go to grab them.
Management: Companion planting of radishes and catnip is believed by some to help. Placing coffee grounds around the stem of the plant is another method thought to prevent flea beetles. Organic fertilizers have also been found to reduce numbers.
Tomato Hornworm 
The caterpillar stage of the sphinx or “hummingbird” moths, these caterpillars are most often found on tomato plants and eat the upper leaves and in their larger stage, young fruit. They easily blend in with the plant and often aren’t spotted until most of the damage has been done.
How to Recognize: These have a large green body with black and white markings, often in the shape of a “V”.
Management: Handpicking of caterpillars is often enough, but many are also parasitized by braconid wasps, which will lay their eggs either inside of alongside the caterpillar. If you’ve ever seen a caterpillar with dozens of white cocoons around its body, it’s likely now a host to wasp larvae and will soon perish.
Japanese Beetle 
An invasive beetle that is widespread over large swaths of the United States, Japanese beetles are notorious for their ability to swarm and decimate a wide variety of plants.
How to Recognize: These beetles have shiny metallic-green bodies.
Management: Pheromone traps have been utilized to some success, though in some cases they seem to draw more beetles to the site. Removing diseased plants and produce early on can prevent Japanese beetles from collecting at a site en masse. Companion planting of resistant plants such as nasturtiums and Sweet William can reduce the number of beetles that collect in your garden.
Squash Beetles 
These beetles can often be found in squash beds and as adults they suck the sap from the underside of the squash leaf, but late in the season they may also feed upon the fruit.
How to Recognize: Often yellow and black, other varieties often called stinkbugs have a flattened body and are grayish. Eggs are yellowish and are often laid in clusters on the underside of leaves in a “V” pattern.
Management: Getting an early start on removing the nymphs from your garden is often the best way of preventing a later infestation. Hand-picking is a useful, if tedious, way of reducing numbers, while others have suggested that placing bark on the ground near plant will cause the bugs to collect there overnight allowing for their removal the next day.
Some General Tips
Get an Early Start: One of the best methods of reducing the number of pests in your garden is to do some pre-emptive control by tilling or hand-removal of larval pests.
Companion planting: This method can be a convenient way of adding some color to your garden as well as a season-long method to protect it. Flowers such as marigolds, and nasturtiums deter a large number of pest insects while bringing important pollinators and predatory insects.
Maintain healthy soil: A soil that has a healthy ecosystem and is well-balanced in nutrients will often offer enough protection against pests by promoting healthy plants and maintaining a variety of predatory insects.
Some Useful Resources
Purdue University Pest Information Page
http://extension.entm.purdue.edu/eseries3/view.php?article=articles/home.txt&id=1§ion=Home
University of Minnesota’s VegEdge
http://www.vegedge.umn.edu/
Organic Pest Control from No Dig Organics
http://www.no-dig-vegetablegarden.com/organic-garden-pest-control.html
