If we crossed the locusts with vampire bats we could control the entire problem.
Doesn't that only work if you're the Alpha vampire? So you would have to become a vampire first, then infect the vampire bats, cross them with locusts and send them out to infect the population.
You would then have the biggest coven of vampires under your control ever.
As a side effect, you would solve the locust problem as your nation of vampires wouldn’t need vegetation.