Aphids

Marijuana Horticulture

by Jorge Cervantes

Identify

Aphids, also called plant lice, are about the size of a pinhead. They are easy to spot with the naked eye, but use a 10X magnifying glass for positive identification. Aphids are found in all climates. Normally grayish to black, aphids can be green to pink – in any color, aphids attack plants. Most aphids have no wings, but those that do, have wings that are about four times the size of their bodies. Aphids give birth to mainly live female larvae, without mating, and can pump out 3 to 100 hungry larvae every day. Each female reproduces between 40 and 100 offspring that start reproducing soon after birth. Aphids are most common indoors when they are plentiful outdoors. Install yellow sticky traps near base of several plants and near the tops of other plants to monitor invasions of winged aphids, often the first to enter the garden. As they feed, aphids exude sticky honeydew that attracts ants that feed on it. Ants like honeydew so much that they take aphids hostage and make them produce honeydew. Look for columns of ants marching around plants, and you will find aphids.

Damage

Aphids suck the life-giving sap from foliage causing leaves to wilt and yellow. When infestation mounts, you may notice sticky honeydew excreted by aphids. They prefer to attack weak, stressed plants. Some species prefer succulent, new growth, and other aphids like older foliage or even flower buds. Look for them under leaves, huddled around branch nodes, and growing tips. This pest transports (vectors) bacterium, fungi, and viruses. Aphids vector more viruses than any other source. Destructive sooty mold also grows on honeydew. Any aphid control must also control ants, if they are present.

Controls

Manually remove small numbers. Spot-spray small infestations, and control ants. Introduce predators if problem is persistent.

Cultural and physical control

Manual removal is easy and works well to kill them. When affixed to foliage – sucking out fluid – aphids are unable to move and easy to crush with fingers or sponges dipped in an insecticidal solution.

Biological

Lacewings, Chrysoperla species, are the most effective and available predators for aphids. Release one to 20 lacewings per plant, depending on infestation level, as soon as aphids appear. Repeat every month. Eggs take a few days to hatch into larvae that exterminate aphids. Gal-midge, Aphidoletes aphidimyz, is available under the trade name Aphidend; parasitic wasp, Aphidius matricaria, is available commercially as Aphidpar.

Ladybugs also work well to exterminate aphids. Adults are easily obtained at many retail nurseries during the summer months. The only drawback to ladybugs is their attraction to the HID lamp – release about 50 ladybugs per plant, at least half of them will fly directly into the HID, hit the hot bulb, and buzz top their death. Within one or two weeks all the ladybugs will fall victim to the lamp, requiring frequent replenishment.

Verticillium lecanii (fungus) – available under the trade name of Vertalec – is very aphid specific and effective.

Control ants by mixing borax hand soap or borax powder with powdered sugar. Ants eat the sweet mix and borax kills them. They excrete sweet borax mix in the nest where other ants eat the feces and die.

Sprays

Homemade and insecticidal soap sprays are very effective. Apply two to three times at five to ten day intervals. Pyrethrum (aerosol) applied two to three times at five to ten day intervals.