Aphids

Aphids are a common pest usually not known by their family name, Aphididae. There are some 1,351 species of aphids currently recorded in the US and Canada, of which about 80 species are pests of food crops and ornamental plants. Most get their names from the plant they primarily attack, i.e. the green peach aphid, the cabbage aphid, or the rose aphid.

Aphids are usually less than 1/8 inch long and are slow moving. They come in shades of green, red, brown, black and yellow. Their fat pear-shaped bodies have two small tubes called cornicles projecting from their rear. No other insect has these. Aphids have needlelike mouthparts which they use to suck juices out of plants. They don't chew, so if you have chewing damage on a plant, aphids are not to blame.  

Aphids have a unique lifecycle. The only time they lay eggs is in the fall. These hatch out in the early spring as winged aphids, which fly to find a suitable plant upon which to feed. The winged aphids are all female, and for the rest of the year until fall comes, they give birth to live young females. The young mature in 7 to 10 days, ready to produce live young. Each is capable of producing 40 to 60 offspring. The process is repeated several times, resulting in a rapid population explosion. Less than a dozen aphid "colonizers" can produce hundreds to thousands of aphids on a plant in a few weeks! If the plant cannot support the colony, then winged female aphids are produced instead of wingless, and they go out in search of a new host. In the fall, both male and female offspring are produced, and eggs are laid. For protection, many of these are taken by aphid-farming ant species into their mounds to wait out the winter. The ants return the eggs to near the surface so they can hatch and fly away in the spring.

Each plant will react differently to aphid attacks. Some will show no adverse response to aphids, while others react with twisted, curled or swollen leaves or stems. Plants exhibiting aphid damage can have a variety of symptoms, such as decreased growth rates, mottled leaves, yellowing, stunted growth, browning, wilting, low yields and death. Since aphids can move from one plant to another, it's possible for them to carry plant diseases from plant to plant. The removal of sap creates a weakness in the plant; plus, aphid saliva is toxic to plants. Aphids frequently transmit disease-causing organisms like plant viruses to their hosts. For instance, the green peach aphid (Myzus persicae) is a vector for more than 110 plant viruses.

One of the most common annoyances caused by aphids is their excessive waste production, cleverly called “honeydew”. This sticky substance drips onto plant leaves and stems and can become covered with black sooty mold. Patios, outdoor furniture, walkways and cars under trees with aphids get covered with this sticky fluid. Even though plants may look bad from the growth of sooty molds, these fungi generally won't damage the plant tissues. Once the aphids are eliminated, the sooty mold often dries up and falls off the plant.

Aphid Control

High levels of nitrogen help aphids reproduce. Never use more nitrogen than necessary for your plants. Using organic fertilizer that is slow release can avoid a nitrogen spike. Aphids don’t care for healthy plant juices.

Prevention is an important key. Aphids do not tolerate garlic odors, so be sure to use Crop Guard or Garlic Barrier if aphids have visited your garden before.

Since young plants are more susceptible than older plants, try keeping young ones under cover or inside and transplanting outdoors when older. Use protective covers if you have aphids in one part of your garden.

Monitor your garden plants twice a week for signs of aphids, since they reproduce so quickly. Check upwind first if you have a prevailing wind pattern, and check near where any aphids have been. Of course, you can also use yellow sticky traps to capture flying aphids and monitor their arrival.

At the first sign of an infestation, act fast–aphids can take over quickly! Be sure to use an organic knockdown like SucraShield, Bon-Neem Insecticidal Soap, Safer® Brand Insect Killing Soap with Seaweed Extract, or Bonide Insecticidal Soap. Mycotrol O, an insect parasitic fungus, is additionally useful for those looking for a bio-control spray. Continue applying your selected spray while you wait for your beneficial insect helpers to arrive.

When daytime temperatures are consistently below 90°, ladybugs are a perfect choice; above 90°, green lacewing will do the trick – they are not called “aphid lions” for nothing! Other generalists, such as praying mantids, Minute Pirate Bug Orius, Cryptolaemus and Delphastus will also benefit your control plan.  If you are growing commercially or have other specialized beneficials in your garden, it’s best to order aphid-specific parasites or predators. We recommend the parasitic Aphidius colemani, Aphidius ervi and Aphidius abdominalis or the predator Aphidoletes aphidomyza in these circumstances. 

Click on the aphid control products and beneficial insects below for more info and ordering.