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How to identify it
- A soft, pear-shaped aphid with fairly long antennae and a pair of cornicles, the 'tailpipes' at the rear of the body.[2][3]
- Color shifts with the season: cream to pale yellow early in the year, then light green, pale pink or light brown as days shorten.[1][2]
- Winged adults may have dark spots, and wingless ones may show a pale yellow stripe split by a thin green line down the back. Colonies leave white cast skins behind.[2]
- Color alone is unreliable. Under a microscope, the cannabis aphid has horn-like projections at the base of the antennae and bulb-tipped hairs on the head, thorax and antennal bases.[3][1]
- Eggs start yellow-green and turn black.[1][3]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Hop aphid | The hop aphid (Phorodon humuli) looks almost the same and can be separated only by examining the front of the head under a microscope.[1] |
| Green peach aphid | Green peach aphids on hemp are pale or dark green, and under magnification the bumps at the antennal bases converge instead of forming horns.[3] |
| Potato aphid | Potato aphids are pink and green, with antennal bumps that slope upward rather than horn-like projections.[3] |
Where it lives
Newly recognized in North America, it has been found in several U.S. states, including North Carolina, Utah and the Pacific Northwest, and in parts of Canada. In Utah it is usually found in low numbers outdoors and higher numbers indoors.[1][2][3]
Biology and life cycle
It lives on leaves, stems and flower buds and feeds on plant sap from the phloem with piercing-sucking mouthparts.[3][1][2]
Through the growing season females give birth to live young without mating; all are female, winged or wingless, and winged ones appear more often when colonies get crowded. Nymphs can mature within a couple of weeks, so numbers can climb quickly.[3][1][2]
Winged forms become common in late summer. After mating, females lay overwintering eggs, which NC State reports typically on seed capsules, the Pacific Northwest handbook on leaves around the bud, and Utah State on the plant or in nearby crop debris. The eggs hatch in spring.[1][3][2]
A dormant egg needs a hemp seedling nearby when it hatches, and overwintering eggs survive better indoors.[1][2]
How it reaches outdoor fields isn't clear, but it most likely arrives on greenhouse transplants or volunteer hemp plants. Outdoor populations peak in summer and fall, with high numbers seen in late August and early September in Utah.[3][2]
Damage and signs
- At high, sustained numbers, feeding reduces plant vigor, slows or stunts growth, and causes wilting and yellowing leaves. Damage tends to worsen in late summer and early fall as colonies build.[1][2]
- Shiny, sticky honeydew and white cast skins are telltale signs. The honeydew grows black sooty mold and draws ants.[2][1]
- It has been reported to spread at least two viruses to hemp, cucumber mosaic virus and alfalfa mosaic virus.[1]
- Along with the rice root aphid, it is the most damaging aphid on hemp, mainly in indoor production; outdoors, aphids are generally held down by natural enemies, and Utah State says it will not cause severe economic damage unless populations are high.[3][2]
Health risk
It feeds only on hemp plants; the three extension sources discuss it as a crop pest and mention no risk to people.[3][1][2]
Control
Prevention
Start with clean plants: transplant healthy seedlings from reliable sources, and inspect or pretreat indoor-grown transplants before they go out.[3][1]
Sanitation
Remove plants in the fall, keep crop areas free of weeds, and rotate and till fields to destroy volunteer seedlings that overwintering eggs need at hatch. Avoid excess nitrogen.[2][1]
Traps and physical control
Scout at least weekly from shortly after emergence: shake plants over a beating sheet, tray or white bucket, check leaf undersides and stems, and use yellow sticky traps at field edges or near greenhouse plants. No treatment thresholds have been set.[3][2]
Biological control
Minute pirate bugs, big-eyed bugs, damsel bugs, lady beetles, lacewings, syrphid fly larvae and parasitoid wasps attack aphids on hemp. Outdoors these often occur naturally; indoors, the commercially available parasitoid Aphidius matricariae can be used against cannabis aphid.[3][1]
Pesticides
Insecticides registered for hemp are limited, and products must contact the aphids to work. Some azadirachtin (neem) formulations have been reported as potential controls; ask your local extension agent about current labels, and treat only when populations are high and causing economic damage.[1][2]
Common questions
- Does the cannabis aphid feed on other plants?
- The Pacific Northwest handbook describes it as a specialist that feeds only on hemp, unlike green peach and potato aphids, which have broad host ranges.[3]
- Why is it worse indoors?
- Overwintering eggs survive better in indoor cultivation, while outdoors, natural enemies generally keep aphids in check.[2][3]
- Is there an action threshold for cannabis aphid?
- Not yet. The Pacific Northwest handbook and NC State both say no treatment thresholds have been established, so regular monitoring is the starting point.[3][1]
Sources
- NC State Extension, “Cannabis Aphid in Industrial Hemp (M. Pulkoski).” content.ces.ncsu.edu/cannabis-aphid-in-industrial-hemp (accessed 2026-11-09)
- Utah State University Extension, “Cannabis Aphid (Hemp IPM pest notes).” extension.usu.edu/planthealth/ipm/notes_ag/hemp-cannabis-aphid (accessed 2026-11-09)
- Pacific Northwest Pest Management Handbooks (Oregon State University, Washington State University and University of Idaho Extension), “Hemp-Aphids (Pacific Northwest Insect Management Handbook).” pnwhandbooks.org/insect/agronomic/hemp/hemp-aphids (accessed 2026-11-09)
- iNaturalist, “Phorodon cannabis taxon page (order and family).” www.inaturalist.org/taxa/1089022 (accessed 2026-11-09)