1. Brazil battles spread of "mad soy disease"
2. Mad soy disease hits Brazil farmers

NOTE: Approximately 50% of the soy fields in the Northern Region of Mato Grosso, Brazil are currently cultivated with GM varieties.

Previously, Asian rust disease has proved a problem in Brazilian soy. Now a second disease, "mad soy disease", is devastating soy crops.

There are two prime suspects in this case.

(i) Glyphosate herbicide: GM soy is sprayed with glyphosate. There is a well-documented link between glyphosate and increased plant diseases. Don Huber, plant pathologist and professor emeritus at Purdue University, said, “There are more than 40 diseases reported with use of glyphosate, and that number keeps growing as people recognize the association [between glyphosate and disease].” This may be in part because the reduced nutrient uptake caused by glyphosate makes plants more susceptible to disease.--"GM Soy: Sustainable? Responsible?" Summary, p. 5,

(ii) No-till farming: GM soy is usually grown in a farming system called no-till, in which farmers avoid ploughing and control weeds through glyphosate herbicide. Studies have found that no-till encourages plant pests and diseases, which thrive in the crop residue left on the soil. The link between no-till and increased pest and disease problems has been well documented in studies in South America and elsewhere.--"GM Soy: Sustainable? Responsible?" Summary, p. 6,
1. Brazil battles spread of 'mad soy disease', 5 October 2010

You will have heard of mad cow disease.

Now "mad soy disease", is troubling farmers and scientists in Brazil, where it causes yield losses of up to 40%, and is expanding out of its stronghold in the north of the country. And, like its bovine namesake, it is incurable.

Indeed, its growing occurrence in Mato Grosso state, which produces nearly 30% of Brazil's soybean crop, has "brought this issue to the forefront", US Department of Agriculture staff said.

"In past years, the anomaly affected soybeans in hot northern growing regions on a sporadic basis, but is now extending to more southern temperate growing regions with increased prevalence overall," they said.

'No treatments'

The disease is "manifested through an endless vegetative cycle" meaning that the maturation of infected plants is retarded. Typically, they produce deformed pods with fewer beans in each.

It is in fact the second mad soy disease to be identified, after a previous ailment which caused similar symptoms, was proven to be insect borne, and is now under control.
However, while scientists believe that that mad soy disease 2, or soja louca 2 as it is known in Brazil, is linked to mites encouraged by low-till farming methods, the link has not been proven.

"There are no known effective treatments," the USDA staff said.
2. Mad Soy Disease Hits Brazil Farmers
Kieran Gartlan
DTN Progressive Farmer
August 19, 2010

While Asian rust disease has been the biggest threat to Brazilian soybean production in recent years, farmers may soon have a new disease to contend with.

The latest anomaly, known as Mad Soy disease, caused losses of up to 40 percent in some areas of the country this season, most notably in the states of Mato Grosso, Tocantins and Goias.

The new disease, whose origin is still unknown, prevents soybeans from maturing with plants remaining green until they eventually rot in the field.

Other symptoms include thinning of the top leaves and thickening and deformation of the stem. Leaves also have a darker color compared to healthy plants as well as deformed pods, with fewer grains.

Researchers have yet to find a cure for the disease, as they are still unsure what causes it. The prime suspects at the moment are black mites found in stubble when soybeans are grown in no-till production systems.

One positive compared to Asian rust, though, is that the disease is not easily transmitted. It is mostly present in warm conditions and requires physical contact from infected plants to spread.

Asian rust, on the other hand, can be carried several hundred miles by infected spores travelling through the air, making it very difficult to contain.