Survival of the Nematode-Antagonistic Fungus Verticillium Lecanii in Alginate Prills1,2)

Strains of the fungus Verticillium lecanii have been incorporated into alginate prills and studied as potential management agents for plant-parasitic nematodes. Since long-term storage is essential in material intended for field applications, the viabilities of two V. lecanii strains in prill formulations were recorded after storage in the freezer (-15°C), refrigerator (4°C), ambient room conditions (ca. 25°C), and glasshouse (15-43°C). In a wheat bran formulation, both strains generally grew from 90%-100% of prills storcd in the refrigerator for up to 43-45 months (although one batch of the mutant strain lost viability by 12 months). Viability at -15°C did not always remain as high as when prills were stored at 4°C. Viability of both strains was 0% within 2 years at ambient room conditions and within 7 months in the glasshouse. Similar results were obtained with the mutant strain in a pyrophyllite formulation. One batch of wheat bran prills made with the mutant strain plus soybean cyst nematode sex pheromone (vanillic acid) was also tested. Fungus viability was 0% after 25 months (freezer, refrigerator), 4 months (ambient room conditions), and 1 month (glasshouse). Fungus in prills made with the pheromone analogue syringic acid had a similar longevity to fungus in prills without added pheromone.