Tools To Prevent Build-Up Of Pest Tolerance In Bt Maize

While Bt technology in genetically modified maize helps farmers to control certain crop pests more effectively, measures should be taken to prevent the development of resistance to the technology. Seed industry representatives Grant Pringle and Magda du Toit shared their opinions on this important issue with Lloyd Phillips.

- Lloyd Phillips

Certain varieties of maize are genetically engineered to express proteins from the soil bacterium Bacillus thuringiensis (Bt). These are toxic to a number of important maize pests, enabling farmers to reduce the use of chemical pesticides.

However, a potential concern for South Africa’s farmers of Bt maize hybrids is the resistance of maize stalk borer (Busseola fusca) to the proteins expressed by a particular Bt technology incorporated into these maize hybrids.

The owner of this technology, Bayer Crop Science (Bayer), has admitted that although a small degree of feeding on the leaves of MON89034 Bt maize hybrids was expected under high insect pressure, the level of damage seen recently in southern KwaZuluNatal’s Himeville and Kokstad areas came as a surprise.

According to Magda du Toit, spokesperson for Bayer Southern Africa, mitigating action was taken as soon as the maize stalk borer damage was discovered. Efforts were also made to understand the causes of the problem.

“Larvae from the affected area were collected and sent to the Agricultural Research Council in Potchefstroom for evaluation. The results from the feeding studies indicated a potential localised population of B. fusca showing resistance to the proteins expressed by MON89034.

“Bayer consulted with customers in the impacted areas to discuss a mitigation plan and moth traps were installed in the lands to monitor moth flight patterns. Bayer is also monitoring all maize lands in the area, as well as the planting of refuge areas in the region.”

BT-RESISTANT STALK BORER LIMITED IN SA