Production of PG Suspension

 

A biological control agent for Heterobasidion annosum (formerly known as Fomes annosus)

PG Suspension is manufactured in Forest Research’s Tree Health Division at Alice Holt Lodge in Surrey. On average three batches are produced each year to supply Santon Downham Forest District in East Anglia.

The product is a suspension concentrate composed of live spores (oidia) and mycelium of P. gigantea. The formulation contains:

• Spores: 0.5%
• Water: < 33%
• Sugar and honey: < 67%
• Cellulose polymer: 0.06%
• Hexacol Supra Blue: 0.02%

The PG Suspension mixture is pumped into sterile plastic tubing and sealed at intervals to produce small sachets which contain 7-10ml of product. If kept refrigerated the product will retain its viability for six months as the low water activity (aw) of the formulation ensures that the growth of most bacteria and yeasts is prevented.

P. gigantea mycelium is scraped off Malt agar plates

Spores are mixed with sugar water and honey

The solution is pumped through plastic tubing

Completed sachets

Each sachet must contain at least 3.5 x 106 viable spores per ml of concentrated product. The concentration of viable spores is monitored before the product is dispatched to the field, and another mid-term test on viability is carried out in the laboratory to ensure the product has not deteriorated over time.