Formulation of an Endoparasitic Nematode, Subanguina picridis Brzeski, a Biological Control Agent for Russian Knapweed, Acroptilon repens (L.)DC

Subanguina (Paranguina) picridis is the only plant pathogen, along with the fungus Puccinia acroptili, known to be effective as a biological control agent against Russian knapweed, Acroptilon repens (L.)DC. The nematode causes galls on stems and leaves of knapweed which considerably weaken and stunt the plants. A formulation technique for long-term storage of the nematode has been developed for nematodes extracted from galls and for those in galls. The nematodes were encapsulated in calcium alginate granules, coated with a unique inverting oil followed by an oil absorbent, and then dried. Survival of the nematodes in whole galls from infected Russian knapweed plants was assessed at two temperatures (4 and −20°C) after drying at room temperature, with or without a coating of inverting oil plus adsorbent. Less than 50% of the nematodes survived for 1 month when coated or uncoated whole galls were stored at 4 or −20°C, with viability declining rapidly thereafter. Nematodes extracted from galls and formulated in calcium alginate survived in dry granules for up to 9 months at −20°C with no significant loss of infectivity.