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November 26, 2013

How Potentially Damaging is the Corn Earworm in Brazil?

The question on everyone's mind is what is the potential for damage from this new pest. At the present time this early in the growing season, I would say the corn earworm is more of a financial problem than a yield problem, but that could change later in the growing season.

During the last growing season it was estimated that the pest costs farmers in Bahia about one billion dollars through additional control costs and lost production. The worm impacted the three major crops in the state - soybeans, cotton, and corn. On an individual field basis, some yields were reduced by as much as 50%, but no one expects that to happen this growing season. Last year, the caterpillar came as a complete surprise and it took a while for scientists to even identify the type of caterpillar it was and then to recommend control measures. This year everybody is on high alert for the presence of the insect and there has been time to formulate a plan of attack. Even with time to prepare, controlling this insect is going to be a "work in progress" this entire growing season.

The real problem may come later in the growing season, especially if there is a period of wet weather that would hinder the application of insecticides. During the peak of the rainy season in December or January, there may a period of 10-20 days when it might rain nearly constantly in central Brazil. In 2009 for example, it rained 34 inches during the month of January in Rondonopolis, Mato Grosso.

Under those types of conditions, farmers can't get into the fields with sprayers and you can't fly on aerial applications either. Even if there is a small window for spraying, the frequency of the rain could reduce the efficacy of the insecticide. It is under these types of conditions that pest such as the corn earworm and diseases such as soybean rust can get ahead of control measures and result in yield losses.

There is no history of this insect in Brazil, so judging how bad it could be is a real guess. Under a worst case scenario, I think it could be entirely possible that the infestation could result in a loss of as much as 5 million tons of soybeans (5% of the total), but let me emphasize, that is only a guess. As is the case most of the time, the weather during the growing season is going to be more important to the overall soybean production than the corn earworm.