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Giant knotweed

Scientific name: Reynoutria sachalinensis
Family: Buckwheat Family (Polygonaceae)

Plant parts used


Mode of action

Induced resistance, plant strengthener


Materials Methods of preparation How to use Target pests
Giant knotweed leaf extract
Giant knotweed leaves

Collect the upper ground parts
of the plant especially the leaves.
Dry the leaves. Grind them.
Add 10 grams of the grounded
leaves into 1 liter of water.
nLet it stand for 1 hour or
a little bit longer.
Strain to get a clear extract.

Use the plant extract immediately,
never set it aside for the future use.

Generally, the extract is sprayed
as a plant strengthener at 1 week interval.

For example;
on tomato, 2 weeks;
on cucumber, 1 week;
and on grape, 10 days interval.

Spray the plants at the latest
immediately when you see the first spot
or lesion on the leaves, otherwise the
extract is no longer effective when
the infection has widely spread.

Powdery mildew on tomato,
pepper, cucumber, grape, begonia
Botrytis on young tomato,
pepper, and ornamentals

Standard procedures for the preparation and application of the plant extracts

  1. Select plant parts that are free from diseases.
  2. When storing the plant parts for future usage, make sure that they are properly dried and are stored in an airy container (never use plastic container), away from direct sunlight and moisture. Make sure that they are free from molds before using them.
  3. Use utensils for the extract preparation that are not use for your food preparation and for drinking and cooking water containers. Clean properly all the utensils every time after using them.
  4. Make sure that you do not have direct contact with the crude extract while in the process of the preparation and during the application.
  5. Make sure that you place the plant extract out of reach of children and house pets while leaving it overnight.
  6. Harvest all the mature and ripe fruits before plant extract application.
  7. Always test the plant extract formulation on a few infested plants first before going into large scale spraying. When adding soap as an emulsifier, use a potash-based one.
  8. Wear protective clothing while applying the extract.
  9. Wash your hands after handling the plant extract.

Effect on humans

None known during the write-up, however take extra caution as extract maybe harmful to people with very sensitive skin.

Effect on non-target organisms


External links


 to the top        PAN Germany, OISAT; Email oisat@pan-germany.org