Corn stunt disease catches Argentina by surprise

The Buenos Aires Grain Exchange lowered the Argentina corn estimate last week by 2.5 million tons to 49.5 million and the Rosario Exchange lowered the corn estimate to 50.5 million. These estimates are 6-7 million tons below the initial estimates at the start of the growing season. The reason cited by both exchanges for the lower estimates was damage caused by corn stunt disease.

The Buenos Aires Grain Exchange stated that 150,000 hectares of late-planted corn in the center-north of Santa Fe and north of Cordoba that was destined for grain production was instead harvested for forage after being infected by corn stunt disease. Additionally, corn yields in far northern Argentina have declined 30% in the last three weeks due to the disease and moisture stress.

Corn stunt is a bacterial/viral disease transmitted by corn leafhoppers or similar insects. The earlier the plant is infected, the greater the potential yield loss which could be up to 100%. Once the plant is infected, there is nothing more the farmer can do to rejuvenate the plant. His best hope is to control the corn leafhoppers as best as possible to keep them from infecting additional fields. An additional way to control the disease is to plant as early as possible and in as tight of a window as possible. The disease is not transported by the wind or transmitted by seed; it is solely transmitted by insects like corn leafhoppers.

This pest first became a problem in Brazil about 4-5 years ago and it has now spread to most of the corn producing areas of Brazil. This is the first growing season that corn leafhoppers have become a significant problem in Argentina. It has probably caught a lot of producers by surprise and they are in a "learning curve" on how to control the pest.

The insect moves from more mature corn to later developing corn, so the latest planted corn is more at risk for corn stunt disease. In Brazil, scientist recommend that farmers plant their corn in as tight of a window as possible to minimize the spread of the insect. This insect is probably going to be an ongoing problem in Argentina because the early corn is planted in September and October and the later planted corn is planted in December and January, so there is ample time to spread the disease to the later planted corn.

Controlling the disease is difficult because you must control corn leafhoppers or similar insects and sometimes that is not easy or cheap. There does not appear to be corn hybrids resistant to the insect, so multiple insecticide applications are generally necessary to maintain control of the insect.