Glyphosate linked to damaging fungal disease - fusarium head blight (12/9/2005)

Fusarium head blight (FHB) of wheat has become an increasing problem in North America in recent years, notably in the US Corn Belt and the Canadian Prairies. This damaging disease is considered a major threat as it not only greatly reduces yield and grain quality but causes excessive contamination of the grain with fungal toxins (mycotoxins).

Mycotoxins such as vomitoxin (deoxynivalenol or DON), which are produced by the fungus in grain and straw, are detrimental to both animal and human health. This means FHB represents both a serious food safety concern and an economic threat to farmers.

This new paper by Fernandez et al, just published in Crop Science, looks at what predisposing crop production factors may exist in parts of the Canadian Prairies.

The 4-year study points to the application of glyphosate as a significant predisposing factor for the development of the disease. Glyphosate is the active ingredient in Monsanto's Roundup - the herbicide used with Monsanto's glyphosate-resistant Roundup Ready GM crops, which are heavily grown in the US Corn Belt and the Canadian Prairies.

Fernandez et al note that a statistically significant and consistent association was found between previous glyphosate application and FHB. And the authors note that previous glyphosate application was the only crop production factor that was significantly associated with higher FHB levels every year of the study.

As Fernandez et al also note, this is not the first research to suggest that glyphosate could cause an increase in fungal populations - see the excerpt from their paper (item 2) below the abstract (item 1).

1.Crop Production Factors Associated with Fusarium Head Blight in Spring Wheat in Eastern Saskatchewan
M. R. Fernandez,* F. Selles, D. Gehl, R. M. DePauw, and R. P. Zentner

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ABSTRACT Fusarium head blight (FHB) has been increasing in western regions of the Canadian Prairies. The objective of this 4-yr study was to identify crop production factors (CPF), associated with FHB development in spring wheat (Triticum aestivum L.). From 1999 to 2002, 659 were sampled in eastern Saskatchewan for FHB levels, and information gathered on agronomic practices used on these fields. In 2000 and 2001, percent Fusarium-damaged kernels (FDK) was also determined. Differences in the FHB index among years indicated that was the most important factor affecting disease development. The effects of CPFs on FHB were lower in years with high (2001) and low (1999 and 2002) disease pressure, compared with a year with moderate (2000) disease pressure. Previous application of glyphosate [N-(phos-2003). phonomethyl) glycine] formulations (GF) within tillage system, tillage system, previously grown crop, and cultivar susceptibility were the only CPFs that affected FHB. GF application in the previous 18 months within tillage system was significantly associated with higher FHB levels every year; it was the only CPF in 1999, and one of two CPFs in 2002, that affected FHB, suggesting that its effect was not influenced as much by, environmental conditions as that of other CPFs. Percentage FDK also higher in fields previously treated with GF in 2000 and 2001. Because of the nature of this study, we could not determine if the association between previous GF use and FHB development was a cause–effect relationship. Thus, further research is needed to elucidate the nature of this association and the underlying mechanisms.

2.Other research showing glyphosate could cause an increase in fungal populations

Excerpt from 'Crop Production Factors Associated with Fusarium Head Blight in Spring Wheat in Eastern Saskatchewan'

Kawate et al. (1997) reported that Fusarium populations greater in the rhizosphere soil from glyphosate-treated, than from untreated, henbit (Lamium amplexicaule L.) whereas Lynch and Penn (1980) reported that glyphosate-treated quackgrass (Agropyron repens Beauv.) was rapidly colonized by F. culmorum, which subsequently caused damage to the following barley crop. More recently, it has been shown that glyphosate application to glyphosate-tolerant soybean caused a significant increase in the isolation frequency of the causal agent of sudden death syndrome, F. solani (Mart.) Sacc. f. sp. gly-cines form. nov. (Sanogo et al., 2001), and Fusarium populations on the roots and rhizosphere of the plants (Kremer, 2003).

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