If this area was frost damaged it will turn black as it warms up. If a very high percent of the plants in the field exhibit this characteristic, you will have to decide if you want to manage crazy cotton or do you replant. For cotton that was planted, but had not emerged before the rain and cold front, decisions may not be so easy. There is danger of poor emergence making replanting a must. There is also the possibility that seedlings will emerge but may have suffered sever damage to the root systems from chilling injury.
Cotton can survive without a tap root.
However, a cotton plant with no tap root and only a partially developed secondary root system, will have difficulty producing top yields. This is especially true in non irrigated situations. Recommendations on this web site do not endorse any commercial products or trade names.