The Brazilian Soybean Miracle That Almost Didn’t Happen

Spraying For Soybean Rust

Spraying For Soybean Rust

Soybean production in Brazil grew rapidly since 1960 with area expanding from 400,000 hectares to 22 million hectares. Brazil is a major soybean producer-62 million tons per year. In 2001, soybean rust was first detected in Brazil and by 2003 the pathogen had spread to the entire country with yield losses up to 75% in individual fields. If fungicides are not used, Brazil would lose about 50% of its soybean production annually.

“More than 50 different fungicidal products are currently labeled for managing soybean rust in Brazil, and many of these have been evaluated annually since 2003/2004 in a nationwide network of standardized, uniform field trials (UFTs) coordinated by Embrapa Soja, a research unit of the Brazilian Agricultural Research Corporation.

We present a meta-analytical synthesis of the results of 71 uniform fungicide trials containing 930 entries (specific fungicidal treatments) conducted in Brazil from 2003/2004 to 2006/2007. …on average, fungicide treatments… increased yield by 43.9%.

The results of this analysis showed that fungicidal control of soybean rust in Brazil is highly effective… (indicating a relative disease reduction of between 90 and 100% in response to treatment). …these comparisons show that, despite favorable environmental conditions for soybean rust epidemics in Brazil, the disease can be managed very effectively with modern fungicides.”

Authors: Scherm, H, et al.
Affiliation: Department of Plant Pathology, University of Georgia.
Title: Quantitative review of fungicide efficacy trials for managing soybean rust in Brazil.
Source: Crop Protection. 2009. 28:774-782.

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Fungicides Keep Lettuce from Turning Slimy

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Lettuce Drop

The fungus causing lettuce drop causes a rot that usually begins on the stem near the soil surface and a water-soaked area appears; it can spread downward until roots decay and can spread upward.  The pathogen rapidly ascends the stalk, killing the leaves in succession until it reaches the heart of the lettuce plant. Layers of collapsed leaves lie flat on the soil surface after infection. Inner leaves are invaded completely by the fungus, which reduces the head to a wet, slimy mass. The entire plant may collapse in less than two days.

“Lettuce drop is one of the most destructive diseases of lettuce and has been reported in all lettuce-growing regions of the world. In the USA, the disease regularly occurs in the two primary lettuce-producing states of Arizona and California. Yield losses vary from 1% to nearly 75% depending on conditions, but under ideal disease conditions an entire field may be lost. The disease is caused by two closely related soilborne fungi, Sclerotinia sclerotiorum (Lib.) de Bary and S. minor Jagger.

Sclerotia of S. sclerotiorum can survive up to seven years and their longevity is affected by location of sclerotia within the soil profile, duration of burial and soil temperature and moisture.

Commercially acceptable cultivars with adequate levels of resistance are not currently available. Thus, current management strategies for lettuce drop rely primarily on fungicides such as iprodione and boscalid.”

Authors: Chitrampalam, P., and B. M. Pryor.
Affiliation: Department of Plant Sciences, University of Arizona, Tucson
Title: Population density and spatial pattern of sclerotia of Sclerotinia sclerotiorum in desert lettuce production fields.
Source: Canadian Journal of Plant Pathology. 2013. 35[4]:494-502 Available: http://www.tandfonline.com/doi/abs/10.1080/07060661.2013.841758#.U35Ck_ldV1Y