Compost tea (or manure tea) greatly boosts growth and suppresses plant disease.
Contested
Compost tea is a weak liquid feed at best — no better than using the compost itself, which also improves the soil the tea can't. The "cures disease" claims don't hold up in trials, and a badly brewed or manure-based tea can grow harmful bacteria you don't want on food crops. Put your compost on the beds; skip the tea as a disease cure.
What is actually known
Steeping compost in water extracts a little soluble nutrient, so a mild fertiliser effect is real — but no larger than just using the compost itself, which also builds the soil structure the tea does not. The bigger claim, that spraying compost tea protects plants from disease, is not reliably supported: trials are inconsistent and the effect, where seen at all, is small. There is a real downside, too: a poorly-aerated (anaerobic) brew, or one made with manure, can multiply human pathogens like E. coli and Salmonella, which is why food-safety guidance warns against spraying it on edible parts. Compost tea is a minor supplement at best, not a tonic or a fungicide.
Evidence: not yet confirmed against its 1 source.
what this rests on - one pointer
University of Connecticut, 'Compost, Compost Tea, and Manure: Food Safety Implications in the Vegetable Garden' (soiltesting.cahnr.uconn.edu/compost_compost_tea_and_manure, read 2026-07-14): 'ingredients commonly added to compost tea may promote growth of bacteria that can cause illness in humans, including Salmonella and E. coli'; unless methods minimize pathogens, 'it would be wise to save them ... for nonedible plants.' Backs the food-safety caveat; the disease-suppression benefit is inconsistent in trials.
When would that grow at your place? →