Reduction of viability of soil borne inoculum of common bunt (Tilletia tritici) by collembolans

The aim of the study was to test the effect of collembolans on the viability of soil borne inoculum of Tilletia tritici (syn. T. caries). Teliospores were fed to five species of collembolans: Onychiurus cebennarius, Mesaphorura macrochaeta, Folsomia fimetaria, Proisotoma minuta and Orchesella villosa. Faeces were collected from all species and only faeces from M. macrochaeta did not contain teliospores. Ingestion by the four other collembolan species reduced germination rates of T. tritici teliospores from 76.5% in the uningested control to below 3% after ingestion. There were no significant differences between the germination rates after ingestion by the different collembolan species. The effect of collembolans on the viability of teliospores in the soil was tested in two soil types, a sphagnum based potting medium and a coarse sandy field soil. 5 ml of soil was inoculated with 0.1, 0.2 or 0.3 mg of teliospores and incubated with 15 F. fimetaria or P. minuta for 3 days. In both soil types F. fimetaria significantly reduced the proportion of viable spores in the two lowest inoculation levels, while P. minuta only had a significant effect at the lowest inoculation level. The effect of collembolan density on the infection of wheat was tested by inoculating field soil in 5-l pots with 2.0 mg of teliospores and collembolan densities equivalent to between 0 and 199,200 P. minuta m−2. Incubation with densities of 59,800 P. minuta m−2 or higher for 10 days before sowing, reduced the infection of wheat from 30% in the control to 3.5%.