March 2012. A question about how to control Pythium of Chinese kale (broccoli), Brassica oleracea var. capitata.
First, it was asked whether the problme was caused by Pythioum or Rhizoctonia. What is the evidence? There are two products available in UK that are natural pesticides:
- Bacillus subtilis QST713 (sold as Serenade). Labelled for Botrytis and Rhizoctonia and recently approved for use in certain crops for Phytophthora. Manufactured by Agaquest in USA.
- Gliocladium catenulatum Strain J1445 (sold as Pre-Stop). This has a label recommendation for Pythium. Manufactured by Verdera Oy of Finland.
Growers in UK find these products do work provided you are growing a strong plant and not overwhelming it with infection. Both are best used as preventative not curative. Gliocladium is VERY expensive and probably only justifiable if the cost is restricted to the propagation stage. Check legality of use.
The member went onto say that control is as much an engineering problem as pesticide application. If the plants have infections from Pythium, is there too much inoculum or too much moisture in the soil? Sterilise propagation trays, improve drainage of growing medium or soil, ensure correct application of irrigation and that the water is free from Pythium. When does the problem occur – this may help identify at what growth stage to apply a treatment or where to eliminate the source of inoculum.
Trichoderma was also suggested.
In New Zealand, a Trichoderma hazarium product called Unite is registered for the control of Pythium. As it grows the Trichoderma fungal hyphae parasitize the Pythium strands. Unite is also registered for Rhizoctonia and Cylindrocarpon, meaning less dependence on positive identification of the disease.
Unite has organic approval in New Zealand and does not have a withholding period. This will probably not be available in Cambodia, but probably another product of similar Trichoderma strain may be. The same product is available on a kibbled grain substrate as Trichopel Nursery and Field. See the brochure for photos on Pythium activity on: www.tricho.com/nzproducts.html