Chewing damage to amaryllises this time of the year in southeast Louisiana is often due to insects – such as grasshoppers.
Trim off the yellow and most badly damaged leaves. Apply a couple of inches of mulch around the base of the plants to cover the bulbs and reduce the chances they will get chewed on.
This damage is not life threatening and is well tolerated by the bulbs (this kind of damage happens to amaryllises all over the area every year).
Control is optional, but you could treat weekly through the summer with carbaryl (Sevin) or permethrin (Bonide Eight and other brands). You may still see some damage despite using the insecticide, but regular applications should reduce it.
Consumer Horticulture Specialist
The LSU AgCenter and the LSU College of Agriculture