That looks pretty severe so your plant may be lost. Go ahead and
remove all the leaves that show the larvae trail and see if the plant
survives. But you really need new plants.
If you don't mind pesticides, then sevin dust applied periodically
will stop a lot of fly and many other insects from bothering your
plants. Also pyrethins are good for this type of insect, but you have
to apply these BEFORE you see any damage.
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