Aphids, family name Aphididae, are a common pest to gardeners, commercial growers and greenhouses due to their wide species diversity and rapid reproductive cycle.
Aphids are slow moving and come in shades of green, red, brown, black and yellow. Their oblong bodies have two small tubes, called cornicles, projecting from their rear that are unique to them. These allow aphids to get rid of excess sugar in the form of honeydew. They have needlelike mouthparts which they use to suck juices out of plants. Aphids do not chew. If you notice chewing damage on a plant, look to identify a different culprit.
Nymphs and adults feed on plant juices, attacking leaves, stems, buds, flowers, fruit, and/or roots, depending on the species. Most aphids especially like succulent new growth. Some, such as the green peach aphid, feed on a variety of plants, while others, such as the rosy apple aphid, focus on one or just a few plant hosts.
- Look for misshapen, curling, stunted, or yellowing leaves. Be sure to check the undersides of leaves; aphids love to hide there.
- If the leaves or stems are covered with a sticky substance, that is a sign that aphids may have been sipping sap. This “honeydew,” a sugary liquid produced by the insects as waste, can attract other insects, such as ants, which gather the substance for food. When aphids feed on trees, their honeydew can drop onto cars, outdoor furniture, driveways, and so on.
- The honeydew can sometimes encourage a fungal growth called sooty mold, causing branches and leaves to appear black.
- Flowers or fruit can become distorted or deformed due to feeding aphids.
- Some aphid species cause galls to form on roots or leaves.
- Aphids may transmit viruses between plants, and also attract other insects that prey on them, such as ladybugs.
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