...a preparation of the beneficial fungus Trichoderma virens.
Trichoderma may work in this situation because beets are chenopods and don't form mycorrhizal relationships. Trich is used to wipe out other fungi in an out of control situation, but then you need to rebuild the soil biology including beneficial fungi. If you don't, you're on the chem fertilizer merry-go-round. There are some EM ("good bacteria") concentrates for the bacterial portion of the soil biology that'll do for chenopods (beets, spinach, amaranth), but "good" aged compost is the best source for inoculating the beneficial fungi back in. Elaine Ingham pretty much built her rep on balancing all that; if you can find a soil tech locally, it's worth checking your compost (soilfoodweb.com) .