Why does the GM corn variety not effectively target the remaining 10% of corn borers?

The reason the GM corn variety does not effectively target the remaining 10% of corn borers relates to the genetic variability of the corn plants themselves. In genetically modified (GM) corn, the traits intended to control pests, such as the corn borer, rely on the expression of specific genes that produce proteins toxic to certain insect pests. However, the effectiveness of these traits can vary due to genetic diversity among different corn plants.

Some corn borers may have developed resistance to the trait that the GM corn expresses, or the corn itself may not produce sufficient levels of the pest control proteins in certain plants. This can result from variations in the genetic makeup of the corn plants, even within a single variety, leading to incomplete control of the target pest population. The pest's ability to survive and reproduce in the presence of the GM corn indicates that it has adapted, which is a common occurrence in pest management scenarios involving genetically engineered crops.

The other factors mentioned—such as the age of the corn, weather conditions, or soil types—do not inherently address the core issue of genetic variability and resistance mechanisms that play a crucial role in the effectiveness of pest control in GM crops.