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Whiteflies Under the Leaves

Shake a plant and a cloud of tiny white insects is the tell. They suck sap, spread viruses, and breed fastest in hot rooms.

pests ipm temperature
Whiteflies Under the Leaves — Marijuana Grower's Handbook, page 788
Full book

ID and damage

Look

about 0.04 inch (1 mm), powdery wax, more like a tiny moth than a true fly

Kin

relatives of aphids and scale, with the same sap-sucking habit

Flight

disturb the plant and they lift, then settle back on the undersides

Plant

spotted, drooping leaves, honeydew, extra mold risk, and virus spread

Breeding window

Eggs

about 100 per female on leaf undersides, hatching in roughly 7 to 10 days

Adults

live another 4 to 6 weeks after a 2 to 4 week larval period

Heat

most species do best around 80 to 90 F (27 to 33 C)

Slowdown

keep the garden under 80 F (27 C) to cut the reproductive rate

Prevention

Debris

clear plant waste quickly

Filter

a fine dust filter on intake blocks flying adults

Cards

yellow sticky traps catch some and show whether numbers are rising

Shake test

if you suspect them, shake the plant and watch for the white cloud

Control options

Vacuum

shake them off, then suck them from the air with a hose attachment

Remove

take heavily loaded plants out of the room before you treat the rest

Encarsia

tiny wasps that lay eggs in immature whiteflies; one indoor release can build on its own

Helpers

lacewing larvae, pirate bugs, Beauveria, soap, neem, pyrethrum, sesame oil, and herbal oils

Note

the book also lists carbon dioxide among whitefly controls