Farmers make money from the farm produce that they deliver to the market. This is the source of their income and they would not want any of their farm produce to be lost. They will try to protect every last bit of it. However, when aliens came to town and began feasting on their farm produce, they have no choice, but to drive the tractor as fast as possible till they get to the market. They say that there is strength in number and the market is a crowded place. No aliens would dare to go there if they know what is good for them.
Drive your tractor as fast as you can till you reach the market. But, before you can that, you need to wait till the cargoes are loaded at the trailer. As soon as the farm produce are loaded, you can drive your tractor. Aliens would arrive soon and you need to use your booster to outrun those aliens. You should know when to use the booster since those space ships are really fast. There are here to get the farm produce, but you can't give them anything. You'll make money based on the farm produce that you delivered. You can use the money to upgrade your truck.