Aphids and the Ants That Farm Them

How to spot aphids

Shape

soft, pear-shaped, about 1 to 3 mm, with a pair of tailpipe-like cornicles

Color

green, yellow, black, or brown; some blend into young leaves

Site

stems and leaf undersides; heavy numbers curl leaves, wilt plants, and stall growth

Honeydew

leftover sugar feeds sooty mold and draws ants that guard the colony

Why ants make it worse

Herding: many ant species move aphids, mealybugs, and whiteflies to new grazing.

Nests: colonies in the mix can also damage roots.

Replacement: most workers stay in the nest, so killing a few foragers does not end the colony.

Order: if ants are present, Rosenthal says clear them or aphid control stays hard.

Stop ants at the pot

Moats

Aromaants do not swim

Scent line

Example strains

cinnamon cloves or bay leaves as a dry perimeter they often will not cross

Stem wrap

Example strains

put paper around the stem then sticky trap or Tanglefoot on the paper not on the bark

Baits

Aromacommercial ant baits and stakes send a small dose back to the nest

Aphid prevention and control

Filter

winged aphids ride air, so a fine intake filter helps

Weather

worst damage often lands between about 65 and 80 F (18 to 26 C)

Outdoors

a hard water spray, plus lady beetles, lacewings, and syrphid larvae, often keeps numbers down

Indoors

parasitic wasps (Aphidius) and gall midges (Aphidoletes) work best before the outbreak is huge

Contact

insecticidal soap, neem, pyrethrum, Beauveria bassiana, and commercial herbal oils are listed

Note

do not pair Aphidoletes with beneficial nematodes; the nematodes eat the midge pupae