Punch Out Powdery Mildew On Cannabis

Powdery mildew (PM) is made up of many fungal pathogen species that attack and thrive off healthy, living plant tissue. Golovinomyces sp. (aka Erysiphe sp.) is the most common PM species that growers find on cannabis today. We recognize PM as producing a distinctive white sporulation on the foliage that looks like powdered sugar. Without proper management through chemical and cultural practices, this pathogen can quickly spread throughout your operation and decrease crop quality.

Powdery mildew forms white spores on the surface of the foliage.

Conditions ideal for PM proliferation include moderate temperatures, dry leaf surfaces, and high humidity. Unfortunately, the optimal temperatures for PM go hand-in-hand with the ideal temperatures for cannabis production and keeping a dry leaf surface is needed to prevent other diseases such as Botrytis from developing. Thus, growers should prioritize the management of their relative humidity levels to prevent PM. A constant humidity level of 55-60% in the canopy (65-75% if using predatory mites) is preferable to excessively high humidity (>85%). Growers can maintain adequate humidity within the plant canopy with appropriate HVAC equipment in conjunction with horizontal airflow fans (HAF) or vertical airflow fans (VAF).

Powdery mildew should not be mistaken for trichome production

As for all diseases, sanitation is key to prevention, and it is important to sanitize your production
areas between crops. Following physical removal of debris, the first step is to clean all hard surfaces using a cleaning product such as Strip-It (for greenhouses) or Horti-Klor (for warehouses)*. Once surfaces have been cleaned, use a sanitizing agent such as KleenGrow (rinse direct crop contact surfaces with potable water), ZeroTol 2.0 or SaniDate 5.0 for disinfection purposes*. It is critical to ensure that all cuttings and clones coming into a new production area are free of disease. Immediately remove any infected foliage and dispose of it properly. Replace gloves and other protective equipment after handling infected material. Work in infected areas late in the day and avoid staff moving back into clean areas from infected areas.

EPA registered and 25(b) products need to be approved for use on cannabis by the regulatory agency in the state in which the product would be used. When using biofungicides, best practices call for application of ZeroTol 2.0 before Cease or Triathlon BA to destroy surface spores of the pathogen on contact while the biofungicide protects uninfected tissue. Contact your Griffin sales person or GGSPro for product rates and application intervals.

Product Name		Item Number
25(b) Products
Procidic 2		71-2742
EPA Registered Products
Cease		71-13301
Companion		71-1375
Horti-Klor		74-2105
KleenGrow		74-21101
MilStop		71-2879B
Regalia CG		70-2841
SaniDate 5.0		71-35001
Sil-Matrix		71-2940
Strip-It Pro		74-2125
Triathlon BA		71-3040
ZeroTol 2.0		71-35501

*Check state approval status for these products.

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