There are many species of Aphids (green peach aphid, cotton aphid, potato aphid, cannabis aphid, rice root aphid, foxglove aphid), while some are host specific (monophagous), others feed on many plant species (polyphagous). There are different traits which help identify aphids: head shape, siphunculi (a pair of tube like protrusions at the posterior side of the body) size and angle and cauda (a sort of “tail” at the posterior of the body through which honeydew is secreted) size and length. Aphids come in many colors (white, black, brown, gray, yellow, light green, or even pink) and can also vary considerably within the species. Aphids possess siphunculi, used to secrete a waxy substance in order to repel or deter potential natural enemies. The siphunculi, which vary in length, position and angle are also used to identify aphid species. The morphology of aphids helps, in most cases, identify the aphid species or genus, thus scouting and identification are key to using appropriate control strategies.
Aphids can inflict various kinds of damage on a crop.
Retarded plant growth
Adults and nymphs feed on plant sap disturbing the growth hormone balance. As a result, the plant’s growth is retarded giving rise to deformed leaves, meristems or fruit. If the infestation occurs early in the season, it 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. Aphids therefore need to extract large quantities of sap in order to obtain sufficient proteins. The excess sugar is secreted in the form of honeydew, making the crop and its fruit, sticky. Black fungal molds grow on the honeydew, contaminating fruit and ornamental crops and rendering them unsuitable for the market. Additionally, photosynthesis in the leaves is reduced, affecting production.
Malformations of growing tips
The aphid’s saliva can induce strong “allergic” reactions such as malformations of the growing tips. Aphid vector plant viruses (pathogenic organisms) can be transmitted to the plant. Cucumber mosaic virus (CMV) is an example. An aphid colony has a clear effect on a plant. A growing plant will translocate more resources to an affected part in order to maintain growth, which of course further advantages the aphid colony.
There are specific natural enemies for different species of aphids.
For more information contact your local BioBee field agent.