Genetically modified corn seeds are no longer resistant to devastating tropical bugs in Brazil, a farm group said.

Producers are calling for four major manufacturers of "BT" corn seeds to reimburse them for the cost of spraying up to three coats of pesticides so far in 2014, said Ricardo Tomczyk, president of Aprosoja farm lobby in the Brazilian state of Mato Grosso.

"The caterpillars should die if they eat the corn, but since they didn't die this year, producers had to spend on average 120 reais (US$54) per hectare ... at a time that corn prices are terrible," he said.


The main corn culprit in Brazil is Spodoptera frugiperda, also known as the corn leafworm or southern grassworm. However, seed companies reportedly warned farmers to plant a part of their corn fields with conventional seeds to prevent bugs from developing a resistance to the GMO seeds. 

Dow Agrosciences, a division of Dow Chemical Co., has programs in Brazil to help corn farmers develop "an integrated pest management system that includes, among other things, the cultivation of refuge areas," the report says. Other companies, including DuPont and Monsanto Co., have said they have not yet received any formal notice. 

"There are barely any non-GMO seeds available ... it is very uncomfortable that the companies are blaming the farmers," Tomczyk said. Aprosoja hopes to reach a negotiated agreement with the seed companies, but if all else fails farmers may sue to get reparations for pesticide costs, according to Tomczyk.