Cannabis Aphids

General

In a nutshell: A recently introduced insect to North America; pest exclusive to hemp and cannabis; sap suckers—cause leaves to wilt and yellow, excrete sticky “honeydew”; winged form appears in late summer; viral disease vector.

What are cannabis aphids?

Although it was first described in 1860, the cannabis aphid (Phorodon cannabis; a.k.a. bhang aphid or hemp aphid) is a very new pest to North America. It was first seen on cuttings originating from Colorado in 2016 and is now widespread throughout that state and Oregon. Its range also includes several other states and parts of Canada.

What kinds of plants do they attack?

These aphids feed only on cannabis and hemp plants.

What do they look like?

Cannabis aphids are between 1.8–2.7 mm long. The adults are normally wingless, but the winged form will appear in late summer. Early in the season, they’re nearly colourless to pale yellow. Later, as days become shorter, they change to light green or brown with dark green stripes running the length of the body. The winged forms have a dark head and thorax. Cannabis aphids have long antennae (1.1–2.2 mm) and between these are two short knobs (antennal tubercles). Their cornicles (the pair of small, upright, backward-pointing tubes on the aphid's rear end) are white and almost ⅓ the insect’s body length.

How do I know if my plants are under attack?

The cannabis aphid is a sap sucker, like all aphids. Affected plants are damaged by the loss of this vital fluid. Heavy infestations slow plant growth and cause leaves to wilt and turn yellow. The insect is especially harmful to female buds because it will settle in to feed inside the flowers.

Excess sugar from the sap is excreted on leaves and flowers as a sticky “honeydew”. Black fungal moulds will often grow on this substance, reducing photosynthesis.

White skin moults appear on the leaves, and aphids may be present in visible colonies if the population is large enough.

These aphids can also transmit several viruses between plants, specifically: hemp streak virus, hemp mosaic virus, hemp leaf chlorosis virus, cucumber mosaic virus, hemp mottle virus and alfalfa mosaic virus.