I'm not pro-chemical, but it's hard to imagine other solutions that are actionable in the timeframe of a weather prediction (this timeframe is critical because these swarms were spawned due to weather anomalies). Indeed, according to TFA it sounds like the UN isn't even trying to curtail the locusts at all but are just preparing for disaster recovery.
Crop insurance seems like a more tractable solution.
I think the problem is rather that they destroy crops than insurance; farmers probably can't grow crops in time before another swarm destroy them.
As for stopping them, I would try covering a wide enough area with a giant electric net (just like those insects killers) also placing additional screening nets on the upper and lower side so that the screens would keep birds away, and the actual electric net would have its holes large enough so that smaller insects would remain mostly untouched. The idea is that if they're stupid enough, they will eat all crops in vicinity then eventually die attempting to attack the only remaining field.
Why it shouldn't? The purpose is to attract and exterminate locusts when it becomes the only field in vicinity with intact crops. Build a strip of nets large enough to cover some area where the locusts will travel during migration, and they'll attempt to feed from the fields underneath. Sure it will be costly, but we're talking about decades old technology and cheap materials.
Crop insurance seems like a more tractable solution.