A general recipe for plant extracts is 100 to 3,600 grams of plant parts (leaves) cooked for 20 minutes in 1 liter of water, let it soak a day, sieve and add some mild soap. Dilute for use 1:4.

Some well-known examples of the many extracts

field horsetail (horsetail, Equisetum avensis) - against fungi.
absinthe - against caterpillars and aphids, leaf roller and gall mites on blackberry
nettle - against lice and fertilizes the earth
citrus peel – against scab
marigold - plant strengthener
chamomile - against lice
garlic - against fungi, especially powdery mildew and rust
rhubarb leaf against aphids, caterpillars and cabbage fly
comfrey - brings potassium
elderberry extract - aphids, caterpillars and other insects

Extract of tobacco leaf contains nicotine. It is active (toxic) against aphids, thrips, caterpillars and larvae.

By (leaf) lice: infusion, decoction or tea of wormwood or tansy, or male fern (Dryopteris filixmas) or bracken (Pteridium acquilium), or tobacco.