you can definitely use nematodes since they are a parasite to any host(even humans so don't walk barefoot or spray uncovered) but idk how much time bud worms spend on the ground...if i remember correctly they get blown around in the wind and find a good plant to munch and then nests there. I don't think they have any need to be on the ground so it might be ineffective since nematodes can't jump. I would do more research on the natural predators of bud worms, i think certain types of wasps eat budworm but i cant remember the name. its a parasitic wasp though so like i said do more research on their natural predators. You usually can order the live predators and release them right away but check the temp/humidity to assure it is desirable for the predators natural habitat.