You will know your trailer tires have dry rot when you see many little cracks appearing on the circumference and/or surface of the tire. This can be very dangerous, as this makes tires more susceptible to leaks and tread separation. Trailer tires, especially seasonally-used boat trailer tires, tend to sit for long periods of time without any use. Made essentially of nylon, these tires can develop flat spots. These flat spots then become a huge risk for separating. And if they separate, water can seep in. This is a very dangerous condition, especially if you are traveling at high speeds.
Ultraviolet light from the sun can also cause your trailer tires to crack. Covering them with UV light resistant tire covers will allow the damaging rays of the sun to be reflected away, protecting the tires and making them last longer. This cover will also protect tires from high temperatures. Tires are very vulnerable to the changes in seasons and temperature.
If you notice dry rot on your tires, they need to be replaced immediately or you could be putting yourself, anyone else in the car with you or anyone traveling on the road at serious risk.