Sorry, but it's true. A big part of that is due to synthetic pesticides tending to be much more effective than their organic counterparts, allowing farmers to use less of it per acre. According to Scientific American:

> Canadian scientists pitted 'reduced-risk' organic and synthetic pesticides against each other in controlling a problematic pest, the soybean aphid. They found that not only were the synthetic pesticides more effective means of control, the organic pesticides were more ecologically damaging, including causing higher mortality in other, non-target species like the aphid's predators.

As for glyphosate (the active ingredient in RoundUp), it's both highly potent while also having a low toxicity. Additionally, glyphosate isn't used with all GM maize and soy – there is a small but significant segment of those crops which contain only Bt traits.