was it wrapped and is now ripped? if so most farm shops sell black baler tape ( we use if for hoses absesses) and it will patch it up, tho you may still get a mould spot, its better than leaving it open.
if its not wrapped - just netted - then im suprised it didnt unravell! i sure the wrap has to be tight to keep the air out. maybe you could clamp it - im not sure exactly how that is done, but i think its covered and sprinkled with something.