Condensation forms when moisture meets a cool surface. You need to reduce moisture contained in the instrument cluster, or equalize the temperate of the cluster with surrounding air.
If it's still under warranty, you can take it back and have them replace the cluster and it should work for a little while. If you want a permanent fix, you'll need to drill a small hole somewhere in the cluster where it won't damage anything. That'll let the air temp equalize and allow the moisture to escape the cluster.
If you store the tractor outside, recommend you cover it with something.