Imagine a scenario where a disease has infected many species of grass in the savanna. How would this situation affect the animals that live there?

The effect that a situation like this:

Imagine a scenario where a disease has infected many species of grass in the savanna.

Would have in is A disbalance in the ecosystem because the infected plants would die and they won't be able to feed the animals that eat them and they would have to migrate to look for plants to eat. That would also lead to predators that eat the animals that feed on plants to follow them and both types of animals would be reduced in the trip.

Explanation:

To understand this answer we need to analyze the full context. First of all the plants are used as food by the herbivores, therefore they would see themselves in the need to look for healthy plants that could be used as food. Predators would follow them and this trip will reduce the number of both because they would require energy and food to keep traveling. The herbivores would take the worse part because they are bigger in number and their food would scarce, while they would be used as easy food for the carnivores.