Stalk borers attack ‘insect-resistant’ cultivars

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Grain producers in the eastern and north-western Free State are concerned about stalk borer infestations in Bt maize cultivars with the MON 810 gene, as the cultivars are supposed to be resistant to the insects.


Wesselsbron farmer Thabo van Zyl said seed companies should take responsibility for the failure of MON 810 and must return the technology fee paid for the Bt cultivars.

“We paid a R300 technology fee on every bag of seed we purchased but didn’t receive the Bt technology as specified,” he explained. Van Zyl added that although Monsanto, as the MON 810 technology provider, had agreed to provide the insecticide to combat the stalk borers, he as the farmer was responsible for the application cost. “Up to six weeks it can be applied by tractor but from then on the maize grows too high and it must be applied aerially, which is very expensive,” he explained.

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Van Zyl said he had used Monsanto’s DKC 78/45 BR and Pannar’s 5Q433 Bt cultivars this season and wanted to use them again, but emphasised that he did not want to pay a fee “for non-existent technology”. Bothaville maize producer Llewellyn Niksch said that all of his maize had to be treated for stalk borer.

“We should have been warned by the seed companies about the possibility of stalk borer infestations. We bought technology that we didn’t get. It costs between R90/ha and R100/ha to apply the insecticides by air. A bag containing 60 000 Bt seeds costs between R1 100 and R1 600, so it’s a very expensive exercise.”

Pieter Rademeyer, product manager at Pannar, said the main cause of the stalk borer problem had been farmers’ reluctance to plant the recommended non-GMO refuge areas adjacent to Bt gene maize lands. The problem had started in the Christiana area of North West and Vaalharts in Northern Cape and had since spread to the Orange River region and Free State.

Bt cultivars comprised 75% of maize plantings in SA, according to Monsanto’s business manager, Kobus Steenekamp. “Stalk borers’ dynamics change. The insect resistance management procedures as set out for Bt genes were not followed correctly over the years,” he said. “All farmers using the Bt gene cultivars are contractually obliged to plant refuge areas according to our requirements.”