Drought typically causes Missouri cattlemen to be concerned about their pastures. These concerns can turn to thoughts of replanting, but such plans may be premature.
The major pasture grass in Missouri is tall fescue. Most of it is common Kentucky 31 infected with "endophyte," a symbiotic fungus that protects tall fescue from environmental stress. Infected tall fescue can easily withstand a drought, assuming it is not threatened with a compounding stress such as an insect invasion or severe disease pressure. Even after the prolonged drought of the early 1990s, many tall fescue pastures recovered during the next rainy season. The exceptions were pastures with fall armyworm infestations in combination with dry weather, which caused tall fescue pastures to disappear.
For most years, a drought does not have a long-term affect on a tall fescue stand. If you are worried about losing a stand of tall fescue because of severe drought, it may be premature to replant and thicken up the stand. It is best to wait for a rain before spending any money and time on reseeding. If a rain does not come soon, the seeding effort will have been wasted anyway. And if a good rain does come, it will likely cause the field to green up, rendering the seeding effort unnecessary and the time and money wasted.
It may be frustrating to "hurry up and wait," but it is probably the best approach. If the next big rain reveals a patchy stand that will not likely recover, the thin canopy can be exploited by thickening up the field with red clover, annual lespedeza or another summer forage. These crops can be drilled into a thin stand and thrive especially well in absence of a thick grass canopy, assuming it rains.