Effect of inoculum type and timing of application ofConiothyrium minitansonSclerotinia sclerotiorum: control of sclerotinia disease in glasshouse lettuce.

The effects ofConiothyrium minitansinoculum quality and an 8-week interval between inoculum application and crop planting on sclerotinia (Sclerotinia sclerotiorum) disease in three successive lettuce crops were investigated in a glasshouse trial. Spore suspensions of three isolates ofC. minitans(Conio, IVT1 and Contans) applied at 108 CFU m−2 and a standard Conio maizemeal–perlite application (06 L m−2, 1011 CFU m−2) were assessed for their ability to controlS. sclerotiorum. Only the maizemeal–perlite inoculum (isolate Conio) consistently reduced sclerotinia disease. In the third lettuce crop only, isolates IVT1 and Contans formulated by Prophyta and isolate IVT as an oil–water formulation, all applied as spore suspensions, reduced disease at harvest compared with the untreated control. Recovery, viability andC. minitansinfection of sclerotia buried during the 8-week period prior to each of the three lettuce crops, and of sclerotia formed on the crop, were tested. Only the maizemeal–perlite inoculum (isolate Conio) reduced the recovery of sclerotia buried in soil for weeks between inoculum application and crop planting, reducing their viability and increasing infection byC. minitans. Eight weeks was sufficient to enableC. minitansto infect sclerotia ofS. sclerotiorum, and may account for disease control. After harvest of the second and third crops, maizemeal–perlite treatment (isolate Conio) reduced the number and viability of sclerotia recovered on the soil surface and increased infection byC. minitanscompared with spore-suspension treatments. The effect of inoculum concentration and the influence of soil temperature (varying with time of year) on infection of sclerotia byC. minitansare discussed. [ABSTRACT FROM AUTHOR]