Those things are grubworms and they eat the roots of plants. They will weaken a tree but the damage I see isn't from grubs. The damage I see is from sucking insects and one leaf with leaf miner damage. In another picture I see sooty mold caused by those sucking insects. It also appears that many of the leaves are yellowing. I don't know if this is a lack of nitrogen or iron but it is one of the two. I would spray with spinosad and fertilize.
It takes at least 1 year, but probably 2 years for Milky Spore to take effect. Epsom salts does nothing about Iron or Nitrogen deficiency. It affects calcium in the soil and adds magnesium. The Monterey Insect spray is what you need. Fertilize with a good organic fertilizer at the rate of about 3 lbs per inch of the trunks diameter out to the dripline.
