Pest Control: Aphids

There are many species of Aphids including green peach aphid, cotton aphid, potato aphid, cannabis aphid, rice root aphid, and foxglove aphid. Some are host specific (monophagous), while others feed on many plant species (polyphagous).

There are different traits which help identify aphids including the head shape, siphunculi size and angle (protrusions at the posterior side of body) and the size and length of the cauda (tail at the posterior of the body).

Aphids can vary considerably within the species. 

Identification:

     

The green peach aphid (Myzus persicae) can be yellowish-green, red, or brown in color because of morphological differences influenced primarily by the host plants, nutrition and temperature. In colder conditions they are often darker. Myzus persicae have long antennae and their siphunculi are slightly swollen towards the tips and have a rather pointed cauda.

The cotton aphid (Aphis gossypii) is found on more than 700 plant species making it one of the most biologically diverse and widely distributed aphid species. A distinguishing mark is that the siphunculis are always black no matter the color of the aphid which can vary from light yellow to light green and even very dark green (almost black).

Potato aphids (Macrosiphum euphorbiae) prefer feeding on plants in the Chenopodiaceae family. They can appear green or reddish-pink; may be winged or wingless and have a preference for Solanaceae plants (potatoes in particular) yet have been identified in many vegetable and ornamental crops; therefore, scouting and identification are key. 

The cannabis aphid (Phorodon cannabis) is pale yellow and later turn light green or pink with darker green stripes running the length of the body. The siphunculis are white and short, almost a third of the insect’s body length. Phorodon cannabis aphids reproduce asexually; females are essentially born pregnant and give birth to live, genetically identical offspring.                               

Rice root aphids (Rhopalosiphum rufiabdominalis) also known as the red rice root aphid, prefer soil and media surroundings, making it difficult to detect. They can appear dark green to brown with yellow or red tinges and like most aphids, may be winged or wingless. The winged rice root aphid will emerge to colonize new plants. Female rice root aphids give live birth to genetically identical daughter offspring that mature quickly. Nymphs and adults feed on all plant development stages.   

The foxglove aphid (Aulacorthum solani) is also known as the glasshouse-potato aphid; pear shaped and shiny yellow to pale green, it is capable of infesting a wide variety of ornamental and vegetable plants. The antennae have darkened joints and are slightly longer than the body while their siphunculi are pale with dark tips and are characterized by a darker green or rust colored patch at their base.                                                  

Damage:

Aphids can inflict various kinds of damage on a crop including retarded plant growth, black sooty mold, and malformations.

Retarded Plant Growth

Adults and nymphs feed on plant sap disturbing the growth hormone balance. As a result, plants who are infested with aphids can develop deformed leaves, and fruit. Infestations that occur early in the season, may result in the death of young plants.

Black Sooty Mold

Aphids secrete a sticky honeydew on which black fungal mold develops. Plant sap has a low protein content but is rich in sugars. Therefore, aphids need to extract large quantities of sap to obtain sufficient proteins. Excess sugar is secreted in the form of honeydew, making the crop and its fruit, sticky. Black fungal molds grow on the excreted honeydew, contaminating the crops and rendering them unsuitable. Photosynthesis in the leaves is also reduced, which affects production.

Malformations 

Saliva from aphids can induce strong “allergic” reactions such as malformations of the growing tips. Aphid vector plant viruses (pathogenic organisms) can be transmitted to the plants. An example of this is Cucumber mosaic virus (CMV). An aphid colony has a clear effect on a plant. A growing plant will translocate more resources to an affected part to maintain growth, which of course further advantages the aphid colony.

Natural Enemies

There are specific natural enemies for different species of aphids.

The primary beneficial insects that are natural enemies of aphids are as follows. Click the name of the beneficial insect for additional information.

BioAphidius (Aphidius colemani) is a parasitic wasp. This polyphagous parasitoid attacks over 40 species of aphids. The adults are small slender wasps with black, brown, and yellow coloration, brown legs, and long antennae. Aphidius colemani’s size depends on the size of the parasitized aphid but is usually about 2 mm long.

BioErvi - (Aphidius ervi) is an effective parasitic wasp for larger aphid species that are not effectively controlled by Aphidius colemani such as potato aphids (Macrosiphum euphorbiae), foxglove aphids (Aulacorthum solani) as well as pea aphids (Acyrthosiphon pisum) and can also parasitize cannabis aphids (Phorodon cannabis).

BioLacewing(Chrysoperla rufilabris) also known as the red-lipped green lacewing, is an insect of the Chrysopidae family. The delicate looking adult feeds on nectar and pollen while the larvae of BioLacewing is the active predator. The three larval instars are the voracious ones.

In addition to these insects, the following insects also target aphids along with their primary enemies:

BioCryptolaemus(Cryptolaemus montrouzieri) is a predatory beetle, also known as the “Mealybug destroyer” because it is a voracious predator of multiple species of mealybugs in both greenhouses and open fields.

BioOrius(Orius insidiosus) also known as the insidiosus flower bug, is a predatory minute pirate bug equipped with piercing-sucking rostrum and two pairs of wings, the front pair being partially rigid. Omnivorous, it feeds on plant pollen, sap, and a large variety of insect prey. The adult BioOrius female can lay between 150-200 eggs during her lifetime. The availability of quality feed, such as BioArtFeed (premium Artemia cysts) improves its establishment in the crop as well as its development and reproduction.

Aphids Banker Plants - plants that can be used in greenhouses or other environments where aphid control is needed. The plants work very well with the introductions of beneficial insects such as the BioAphidius.