Effect of tebuconazole (Folicur R) and prochloraz (Sportak R) treatments on Fusarium head scab development, yield and deoxynivalenol (DON) content in grains of wheat following artificial inoculation with Fusarium culmorum.

摘要

The effectiveness of the fungicides Folicur R (a. i. tebuconazole) and Sportak R (a. i. prochloraz) applied either separately or in combination against Fusarium head scab of wheat (cv. Grief), caused by F. culmorum, was tested in field experiments conducted at the research station of the University of Hohenheim, Karlshof and at Neuhausen, Germany in 1995 and 1996. Wheat plants were inoculated artificially with a conidial suspension (5X105 spores/ml) of F. culmorum mid-flowering (GS 65). Besides thedevelopment of Fusarium head scab, grain yield, thousand-grain weight (TGW) and deoxynivalenol [vomitoxin] (DON) content in the grain were determined. In 1995, head scab diseases in infected control plants of the cv. 'Greif' continuously increased until26 days after inoculation (dpi) and reached a disease index of 7.9. All Folicur R and Sportak R treatments reduced disease severity compared to the infected control. The early postinfectional applications (2 dpi; GS 65) proved to be most effective. Folicur R diminished disease severity by 56% and Sportak R by 41%. The fungicide treatments resulted in higher grain yields as compared to the inoculated control. The early postinfectional (2 dpi; GS 65) application affected yield more than the late postinfectional (9 dpi; GS 69) and the early preinfectional fungicide treatments. The TGWs showed similar tendencies as the grain yields. The severe Fusarium head scab symptoms in cv. 'Greif' of the inoculated control variant were associated with a high DON content (27 mg.kg-1) in the grain. The DON contents in the grain of the fungicide-treated variants were reduced in comparison with the inoculated control; the most distinct reduction of 71% was obtained by the combined treatment 2 dpi. In 1996, field experiments were conducted with the two winter wheat cvs. 'Kontrast' and 'Pegassos'. Both fungicides were applied exclusively 2 dpi. At Karlshof, the more sensitive cv. 'Kontrast' exhibited 31 dpi a disease incidence of 91% and a disease index of 6.1; the lesssensitive cv. 'Pegassos' showed a disease incidence of 67% and a disease index of 4.4. Of the fungicide treatments, the combined application suppressed disease development most effectively; the disease incidence of the cvs. 'Kontrast' and 'Pegassos' wasdiminished by 52 and 64%, respectively; the disease index in both cultivars was 2.8. Fusarium head scab reduced the grain yield by 29% in both cultivars. Folicur R treatments increased grain yields in the cvs. 'Kontrast' and 'Pegassos' by 21 and 22%, respectively, and Sportak R applications by 17 and 18%. The combined treatment resulted in the highest yield increases: 31% in cv. 'Kontrast' and 29% in cv. 'Pegassos'. DON contents in the grain of the cvs. 'Kontrast' and 'Pegassos' were 11.77 and 8.11 mg.kg-1, respectively. Single Folicur R treatments diminished DON content in the grain as compared to the infected control in the cvs. 'Kontrast' and 'Pegassos' by 55 and 49%, respectively; Sportak R treatments by 43 and 42% and the combined applications by61 and 62%. Similar results were obtained with both cultivars on the field site at Neuhausen. The studies indicate that fungicide treatments may not always be sufficient to reduce both Fusarium head scab and trichothecene contaminations in the grain of wheat.