The only papers I've seen that indicate GMO has reduced pesticide use were published by various industry groups with unclear ties to pesticide manufacturers. Academic papers seem to indicate pesticide use is higher, especially as the pests develop a resistance to the pesticide. E.g. https://enveurope.springeropen.com/articles/10.1186/2190-471...
> Contrary to often-repeated claims that today’s genetically-engineered crops have, and are reducing pesticide use, the spread of glyphosate-resistant weeds in herbicide-resistant weed management systems has brought about substantial increases in the number and volume of herbicides applied.