Tiny Game Hunting

Environmentally Healthy Ways to Trap and Kill the Pests in Your House and Garden

Hilary Dole Klein and Adrian M. Wenner

Aphids are probably the commonest pest in your garden, and they may be the most prolific of all insects.
Thomas Huxley claimed that the descendants of a single aphid might at the end of one summer equal the population of China. Moreover, pesticides kill o¤ the beneficial insects that prey on aphids. For instance, aerial sprayings of malathion in California to kill the medfly have led to tremendous and discouraging aphid proliferations.

Small--less than a tenth of an inch long--pear-shaped, and soft-bodied, aphids come in many colors: white, green, pink, gray, red, brown, and black. Woolly aphids have a ßuffy coating. Aphids love the tips, buds, and tender stems of plants, and the 4,000 or so species infest a wide variety of plants. They are often called plant lice (or green ßy), and there are few plants that are not attacked by one kind of aphid or another. Hundreds of aphids may be found on a single plant, but with a little diligence--and an eye out for ants--they are really not that hard to control.

When aphids go to work on a plant, they insert their piercing mouth into the stem or onto the underside of a leaf. The sap starts to flow, and they just suck the day away. The leaves curl up or turn yellow, growth stops, and the plant may die. But the worst thing aphids do to your plants is transmit diseases through their salivary secretions.

To extract the nutrition they need--namely, nitrogen--aphids have to draw out huge amounts of the plant's juices. (Using a high-nitrogen fertilizer to induce quick growth is often an open invitation to aphids.) They excrete the excess in the form of a sticky-sweet liquid called honeydew, often producing many times their own weight of the stuff in one day. Honeydew coats the leaves of the plants, making them look slightly silvery in the light. Sometimes the honeydew nourishes a black, sooty-looking fungus.

Ants milk aphids for this sweet honeydew, stroking the aphids' abdomen to get them to release it. Some ants move aphid nymphs to new plants, and into their own nests during bad weather, and they assiduously guard their aphid cows from their natural enemies. If you see aphids or signs of aphids, look for ants traveling up and down the stem of the plant, and then keep the ants away, using sticky barriers, diatomaceous earth spread around the base of the plant, or a boric acid bait (see Ants).

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Control
If you have an aphid infestation, the first thing to do is direct a strong stream of water at the insects. Once knocked off the plant, aphids usually can't get back on. You can also simply brush them off, crush them with your hands (wearing gloves), or use a little rubbing alcohol to kill them.

Other methods of aphid control include spraying with soap spray, garlic/hot pepper spray, or limonene or linalool sprays; but try the water first. Spray fruit trees in early spring with dormant oil spray.

Sticky yellow traps can be used, but they only work for flying aphids; if aphids are on the wing, they will likely alight on these traps. Or place bright yellow bowls filled with soapy water around plants so that the aphids will fly into them.

Plant nasturtiums around plants that tend to get aphid infestations. Garlic plants work as an aphid repellent.

Another deterrent is to place strips of aluminum foil underneath plants particularly susceptible to aphids. Light reflecting off of the foil confuses them and prevents them from landing on the plant.

Too many aphids is a sign of something amiss--too much fertilizer, or an imbalance in the soil. Have your soil tested.

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Natural Enemies
When ants aren't keeping them away, the best natural predators for aphids include ladybugs, ladybug larvae (which look like little alligators), birds, lacewings, lacewing larvae (called aphid lions), earwigs, hover (flower or syrphid) ßy larvae, soldier beetles, and parasitic wasps. If you order predators, lacewings are best.

If you observe an aphid that is swollen and metallic, dull brown or blackened, it is a mummy, an aphid that has been parasitized by a wasp. Leave it alone so that the wasp larva can develop. Remember: if you don't have any aphids at all, there won't be anything for their predators to eat, and they will go elsewhere. The FDA considers forty to sixty aphids in a serving of brussels sprouts to be perfectly acceptable.

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