Look up fall army worm.

I am having the same problem. They quickly adapt to chemical sprays which are bad for all of us. I have tried neem oil, citronella oil with soap, and have got mixed results for short periods of time. I am running low on the supplies so I will also be looking at using garlic and pepper spray. But it also looks like you need to get them before the flower comes out and they damage the top of the plant and before they get into the stem and corn. Many of my corn are blowing over now because the base of the stem has been attacked.

There also seems to be a bacteria that can be used and sprayed. It is called BT i cant remember the full name. But one variety even effects pollinators and good bugs, so we have to do our research very well.

Fall army worm seems to be pretty new in Ghana potentially introduced as late as 2017. Do I guess we are seeing a major wave of that throughout the region. I am also seeing Japaneses Beetle which is getting a lot of crops for me.