Identification and population monitoring
Aphids are 1 to 3mm, soft-bodied, and range from pale green to yellow or black depending on species. They feed in clusters on growing tips and the underside of young leaves. Visible signs include:
Honeydew: A sticky, glossy coating on leaves and stems below feeding colonies. Ants are attracted to honeydew and their presence near the canopy is often the first indicator of aphid pressure in veg.
Sooty mold: A black, powdery fungal growth on honeydew deposits. Sooty mold does not directly infect the plant but colonizes the deposited sugar and is visible on leaf and stem surfaces near feeding sites.
Distorted growth: Heavy feeding on growing tips causes curling, stunting, and distorted new growth. This symptom appears after populations have been established for at least a week.
Yellow sticky traps placed at canopy level are useful for detecting winged aphid dispersal. Regular visual inspection of growing tips, including leaf undersides, is the standard monitoring practice.
Honeydew, sooty mold, and the TYM connection
The direct plant damage from aphid feeding is the most visible problem, but the secondary contamination risk from honeydew deposits is the compliance-relevant concern for commercial cannabis operations.
Aphid honeydew is an ideal growth substrate for sooty mold fungi — predominantly Cladosporium, Alternaria, and related species. These fungi colonize honeydew deposits within days of deposition and remain on the plant surface. At harvest, flower tissue carrying sooty mold growth will have an elevated TYM count that reflects the fungal load from the mold colonization rather than from facility sanitation failures. This distinction does not matter to the testing laboratory or the state program.
Aphid exuviae (molted skins) also accumulate on flower tissue during heavy infestations. These shed skins are organic material that contributes to the organic particulate load on harvested flower, further elevating TYM.
Controlling the aphid population during flower is not sufficient if honeydew deposits are already present on the canopy; the mold colonizing those deposits continues to develop until harvest.
Entry and spread mechanisms
Aphids enter cannabis facilities through incoming plant material, personnel carrying winged forms on clothing, and air intake. Incoming cuttings or mother plants are the most common introduction vector; aphid colonies on the underside of leaves in a mother room are easy to miss during a quick inspection.
Once established, populations spread through winged dispersal. When a colony becomes crowded or the host plant is stressed, the colony produces winged adults that fly or are carried by air movement to uninfested plants. This mechanism means aphid pressure in one room can appear in adjacent rooms within days, without any physical movement of plant material.