From the article: “They can test for GMO (genetically modified organisms) … but corn that’s not GMO, you can’t tell whether it’s been sprayed or not sprayed.” "Technically, you can, but you’re not likely to get a positive result unless the inspector hits it just right and collects a plant sample before the residues wash away." Yes. See this Forbes article. By the time it reaches retail, you can't tell.[1] Non-organic…
For example, non-organic oats are often sprayed with roundup at harvest time, so cereals made from them routinely have unsafe levels of carcinogens in them:
https://www.ewg.org/childrenshealth/monsanto-weedkiller-stil...
Organic oats have less than 1/10th as much roundup in them on average:
https://gimmethegoodstuff.org/pesticides-in-organic-oatmeal-...
Also, the more farms go organic, the less contamination there will be in the organic crops.