Potential for Integrated Control of Sclerotinia sclerotiorum in Glasshouse Lettuce Using Coniothyrium minitans and Reduced Fungicide Application

Abstract

All pesticides used in United Kingdom glasshouse lettuce production (six fungicides, four insecticides, and one herbicide) were evaluated for their effects on Coniothyrium minitans mycelial growth and spore germination in vitro agar plate tests. Only the fungicides had a significant effect with all three strains of C. minitans tested, being highly sensitive to iprodione (50% effective concentration [EC50] 7 to 18 μg a.i. ml-1), moderately sensitive to thiram (EC50 52 to 106 μg a.i. ml-1), but less sensitive to the remaining fungicides (EC50 over 200 μg a.i. ml-1). Subsequently, all pesticides were assessed for their effect on the ability of C. minitans applied as a solid substrate inoculum to infect sclerotia of Sclerotinia sclerotiorum in soil tray tests. Despite weekly applications of pesticides at twice their recommended concentrations, C. minitans survived in the soil and infected sclerotia equally in all pesticide-treated and untreated control soil trays. This demonstrated the importance of assessing pesticide compatibility in environmentally relevant tests. Based on these results, solid substrate inoculum of a standard and an iprodione-tolerant strain of C. minitans were applied individually to S. sclerotiorum-infested soil in a glasshouse before planting lettuce crops. The effect of a single spray application of iprodione on disease control in the C. minitans treatments was assessed. Disease caused by S. sclerotiorum was significantly reduced by C. minitans and was enhanced by a single application of iprodione, regardless of whether the biocontrol agent was iprodione-tolerant. In a second experiment, disease control achieved by a combination of C. minitans and a single application of iprodione was shown to be equivalent to that of prophylactic sprays with iprodione every 2 weeks. The fungicide did not affect the ability of C. minitans to spread into plots where only the fungicide was applied and to infect sclerotia. These results indicate that integrated control of S. sclerotiorum with soil applications of C. minitans and reduced foliar iprodione applications was feasible, did not require a fungicide tolerant isolate, and that suppression of Sclerotinia disease by C. minitans under existing chemical control regimes has credence.

Use of Coniothyrium minitans transformed with the hygromycin B resistance gene to study survival and infection of Sclerotinia sclerotiorum sclerotia in soil

“…This was followed by rinsing individual sclerotia twice for 1 min in 2 ml SDW in separate wells of a 25 well Petri dish (Bibby Sterilin, Stone). Washing the sclerotia individually eliminated possible cross contamination of sclerotia by a heavily infected sclerotium that could occur during batch washing of sclerotia (Budge & Whipps 2001). The sclerotia were bisected and placed on pairs of agar discs (15 mm diam) in a Petri dish.…”

Effectiveness of the chemical stabilizers of Talaromyces flavus in biological control of tomato and greenhouse cucumber vascular wilt disease

“…There have been abundant reports during the last decade about biological fungicides by solid substrates and optimizing production procedures (Pascual et al 1999;Budge and Whipps 2001;Schuster and Schmoll 2010;Damaso et al 2012;Sargin et al 2013). For instance, Pascual et al (1999) showed the solid biological fungicide containing the fungus Epicoccum nigrum on wheat.…”

Antifungal activities of β-thujaplicin originated in Chamaecyparis obtusa

“…To resolve these problems, it is necessary to develop eco-friendly agricultural materials. For biological control, Budge and Whipps (2001) and Whipps and Gerlagh (1992) reported control of sclerotium disease with an antagonistic microbe, but there has been little progress in control with plant originated extracts.…”