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Plant Louse

COMMON NAMES: Aphid, Plant Louse, Greenbug, Ant Cow

SCIENTIFIC NAME: Order Homoptera, family Aphididae, many species

SIZE: Adult--approximately 1/10"

IDENTIFICATION: Small soft-bodied insects of all colors, pear-shaped, with long legs and antennae. The most common color is green, but many species are black, red, yellow, or bluish. Adults are winged and wingless; they usually have a pair of tubes (cornicles) sticking out of the upper end of the abdomen. These tubes spray an oil or waxy fluid on enemies. Aphids also produce a sticky honeydew excretion that ants love; whitish skin casts are left after molts. Some species like the woolly aphids are covered with a waxy white coating.

BIOLOGY AND LIFECYCLE: In general, eggs are laid in fall and hatch in spring. Nymphs feed in masses by sucking plant sap. These aphids are mostly females that give birth to live young. Sometimes a generation of winged aphids appears and migrates to a new host plant where they feed and produce more wingless females. A generation of true males and females appears in late summer or early fall when temperatures start to drop. These aphids mate, and the females lay eggs that overwinter and hatch the following spring to start the process all over. During warm weather, aphids may go through a complete generation in less than two weeks. They have an incomplete metamorphosis.

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HABITAT: You name it. Most ornamental and fruit crops. Foliage of plants, especially the underside of leaves and stems on tender new growth.

FEEDING HABITS: Aphids normally feed in groups on leaves or stems. They pierce foliage or tender stems and suck plant juices, causing leaf curling and stunted growth. The digested sap is excreted as the honeydew commonly seen shining on foliage. Some feed on roots.

ECONOMIC IMPORTANCE: Aphids reduce the health of stressed plants even further, roll or turn foliage yellow (reducing photosynthesis), and ultimately kill plants. On the positive side, they help to eliminate unfit plants. Some aphids are vectors of disease organisms like viruses.

NATURAL CONTROL: Plant adapted varieties and encourage natural biodiversity, healthy plants, and beneficial insects such as ladybugs, green lacewings, hover flies, praying mantids, and braconid wasps. Avoid feeding plants heavy amounts of nitrogen.

ORGANIC CONTROL: Strong blasts of water, garlic-pepper tea, liquid seaweed, and the release of ladybugs and green lacewings. Citrus oil spray can be used for heavy infestations. Biological sprays are also now available. Plant oil products will also work.

To control aphids, plant adapted varieties, encourage biodiversity especially beneficial insects such as ladybugs, lacewings, hover flies, and predatory wasps. Avoid heavy amounts of fertilizers. Spray infested plants with strong blasts of sugar water and release ladybugs. Garlic-pepper tea, Garrett Juice with garlic, neem, and citrus oil based sprays will also help. 

INSIGHT: Aphids, one of the most prolific insects, are considered one of our biggest pests. There are over 200 species. They may produce up to fifty generations per year. Some species produce several generations without mating. The females can lay eggs or give live birth, and those already have within them developing embryos for the next generation. The young can be born with or without wings. It all depends on whether they need to migrate away from a natural enemy or to a better food supply. The life cycle varies widely between different species and may even vary within the same species in different geographical locations.

Photo by Nadine Haefs

With all of their life-sustaining abilities, you would think that aphids would soon destroy all vegetation. But they don't. They have lots of natural enemies in the insect world; more important, healthy, well-grown, and adapted plants have immunity to them. Heavy applications of nitrogen fertilizer will actually attract aphids.

For more information about this and other insects, get Howard Garrett and Malcolm Beck’s book – Texas Bug Book – the Good, the Bad and the Ugly.

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