How To Control Aphids Organically

Aphids, family name Aphididae, are a common pest to gardeners, commercial growers and greenhouses due to their wide species diversity and rapid reproductive cycle. 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.

Identification & Appearance:

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 do not chew, so if you have chewing damage on a plant, look to Identify a different culprit.

Life Cycle of an Aphid:

Aphids have a unique lifecycle. The only time they lay eggs is in the fall, which then overwinter until spring. The eggs 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. These mature in 7 to 10 days, ready to produce live young with an individual adult capable of producing 40 to 60 offspring. This process is repeated several times, resulting in a rapid population explosion. If the plant cannot support the colony, winged female aphids are produced to go out in search of a new host. Once fall arrives, 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 near the surface during spring so they can hatch and fly away to repeat the cycle the following year.

Aphid Damage:

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. Due to the way they feed, aphids can vector Bacterial and Viral diseases, which can be much more difficult to control than the aphid population. 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, called "honeydew". This sticky substance drips onto plant leaves and stems and can become covered with Black Sooty Mold. 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.

How to Get Rid of Aphids:

Prevention is an important key. Aphids do not tolerate garlic odors, so Repellents like Garlic Barrier can keep aphids away before they visit your garden. Also, high levels of nitrogen help aphids reproduce, so proper Soil Amending and Soil Medium selection is imperative. Using slow release Organic Fertilizers can avoid a nitrogen spike while providing long-lasting nutrition for your plants. Constant monitoring should be done, particularly of new plantings, as aphids prefer plants under stress. Yellow Sticky Traps can be used to give you early indication of aphids moving in and help you monitor the growth of an aphid population.

Act quickly at the first sign of an infestation. An organic knockdown spray like Bonide Insecticidal Soap or Neem Oil will serve to reduce aphid numbers to more manageable levels. Botanigard and Mycotrol contain Beauveria bassiana, an insect parasitic fungus, and are useful as a biological control spray for aphid control. B. bassiana is most effective controlling aphids in the juvenile life stages when molting occurs less frequently.

Beneficial Insects That Target Aphids:

  • When daytime temperatures are between 55°F & 90°F, Ladybugs are a perfect choice.
  • When temperatures are above 90°F, Green Lacewing will do the trick.

Other Generalists for aphid control:

We offer several Aphid Parasites that work under the following, specific conditions:

  • Aphidius colemani are most effective between 70° - 77°F. They require two weeks for development and up to 200-300 aphids are attacked by each female. Fertilized eggs develop into females and non-fertilized eggs develop into males. The female has a pointed abdomen, while the male's abdomen is round-shaped.
  • Aphelinus abdominalis like temperatures beginning at 68°F. They are very versatile because they parasitize a wide range of aphid species and work effectively in fields and greenhouses.
  • Aphidius ervi consume larger aphids and prefer temperatures between 65° to 77°F with relative humidity of 60-80%. They work at higher temperatures but show a decline in activity at temperatures above 86°F.
  • Aphidoletes aphidimyza controls aphids including the green peach aphid as well as the hemlock wooly adelgid. A. aphidimyza prefers greenhouse and indoor environments with temperatures 60-77° with relative humidity of 70%.

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