Splash dispersal of Coniothyrium minitans in the glasshouse

Abstract

Summary Coniothyrium minitans, a mycoparasite with biocontrol activity against Sclerotinia sclerotiorum, was found to disperse during glasshouse trials where overhead irrigation was used. Consequently, the role of water splash in dispersal of C. minitans was investigated using soil‐incorporated inoculum and a range of irrigation regimes found to occur in the glasshouse. The resulting inoculum deposition over horizontal distances up to 2 m was measured. Using drops < 6 mm diameter at 680 mm h‐1, C. minitans was splash‐dispersed at least 2.0 m, whereas with drops > 6 mm diameter at 30 mm h‐1 it was dispersed to only 1.75 m. Irrigation with droplets < 1mm diameter at 49 mm h‐1 failed to disperse inoculum beyond 0.5 m. The dispersal gradient produced by drops < 6 mm diameter at 680 mm h‐1 was best described mathematically by the power function, whereas irrigation with drops > 6 mm diameter at 30 mm h‐ resulted in a gradient described well by power or exponential functions. The latter regime produced a significantly steeper gradient than irrigation with drops < 6 mm diameter at 680 mm h‐1. C. minitans was isolated using an Andersen air sampler at concentrations of 2839 cfu m‐3 or 22 cfu m‐3 during irrigation with drops < 6 mm diameter at 680 mm h‐1 or > 6 mm diameter at 30 mm h‐1, respectively. After irrigation, deposition of C. minitans‐canying aerosol particles declined exponentially and distance from source had no effect on the amount of inoculum isolated. Conidia of C. minitans, splash‐dispersed by irrigation with drops < 6 mm diameter at 680 mm h‐1 were able to infect sclerotia of S. sclerotiorum such that almost all sclerotia at 0.5 m from the inoculum source, and c. 50% of those at 2.0 m, became infected with the mycoparasite.

Effect of inoculum type and timing of application of Coniothyrium minitans on Sclerotinia sclerotiorum: control of sclerotinia disease in glasshouse lettuce

“…Coniothyrium minitans infection of sclerotia recovered from the control plots was recorded. Water splash from overhead irrigation, as well as soil mesofauna, have been reported to spread C. minitans from the site of application to other plots in glasshouse trials (Williams et al ., 1998a, 1998b, 1998c). These dispersal mechanisms may again be important for long‐term control of S. sclerotiorum in glasshouse crops.…”

Use of Coniothyrium minitans as a biocontrol agent and some molecular aspects of sclerotial mycoparasitism

“…However, it is dispersed by water splash directly and as aerosols (Williams et al 1998) and by animals including slugs, collembolans, mites and sciarid larvae (Whipps 2001).…”

Potential for biocontrol of sclerotinia rot of carrot with foliar sprays of Contans® WG (Coniothyrium minitans)

“…In this study, C. minitans infected sclerotia were also recovered from control untreated pots and plots. Water splash and mesofauna have been reported to spread C. minitans from the site of application to other plots in previous trials (Williams et al 1998;Whipps et al 2008). Spread of C. minitans from plots sprayed with Contans † WG to neighbouring untreated control plots in the field trial could have been caused by spray drift or by secondary transmission of conidia by insects.…”

“…Washing sclerotia individually eliminated possible cross contamination of sclerotia by a heavily infected sclerotium that could occur during batch washing of sclerotia. Sclerotia were then bisected with each half being placed on a 15-mm diameter PDA disc containing chlortetracycline (20 mg L (1 ) in a Petri dish (Williams, Whipps, and Cooke 1998). The number of sclerotia showing mycelial growth of S. sclerotiorum (viable) and/or infection by C. minitans were assessed after 10Á14 days incubation at 208C.…”