Do GM crops help reduce pesticide and herbicide applications? And what about "superweeds"?

GM technology adoption has optimised pesticide use by 37%. The reduction in pesticides for the period 1996 to 2012 was estimated at around 500 million kilograms of active ingredient.

Weeds can become resistant to herbicides – no matter if they are used in conventional agriculture or in combination with GMOs. Weeds have developed resistance to every major herbicide – it is an evolutionary response to external influences. It is highly recommended that farmers follow best management practices for weed control, like diversification of crop and cultivation strategies. Farmers dealing with resistant populations in a field should vary herbicides and, in some cases, combine use of different herbicides with nonchemical weed control options.

Source: ISAAA Brief 49-2014: Executive Summary and GMO Answers