Bugs or Fungus

I am as beginner as one can get. For 2 years in a row when my crop start to mature well, something strips the leaves and grapes all off in about 1 week. 75' trellis. I put up deer avoidance but dont see any tracks or scat. I see no sign of racoons. I dont see leaves on the ground as if the died and fell off. Can someone help me?

Only the lower leaves are gone and there are partials of leaves or petioles left. Don't look like it's due to bugs or diseases, more likely some kind of animal.

yep, it’s a vertebrate of some kind.

Most likely deer. Nothing survives here without fencing. I’ve had a buck destroy my deer fencing out of spite no doubt. Last winter they even ate all the rhododendron which is poison to them.

Even though you have not seen any animal might not mean that they are not there.  Stealth mode ...

We did not know the amount of wildlife we had until we put a pan of water on the patio.

Some like foxes come even though they cannot reach the water.  I assume the fox can smell the water and is drawn to it.

I have a spot where I have been feeding the wildlife since 2013 and I have never seen the wildlife, yet the food disappears.

Welcome Dave. Some context for where you are (region, zone, elevation, precipitation) helps get better answers, and that can be put in your profile (upper left of post) or signature (bottom of post).

I would also suspect deer, which eat my grapes off the fenceline they grow on. Deer can jump anything short of 8ft. They will not jump a double fence 4ft tall and 4ft apart, as they do jot have good depth perception. Elk are our biggest herbivore issue here, as they can jump anything short of 14ft and can also knock down most fences. You’d know if it was elk.

At my friend’s Willamette Valley vineyard, heatwaves followed by wind can knock grapes and desiccated leaves off, but yours do not look heat stressed or even that far along into fall color. Young, stressed grapes—particularly grafted rather than self-rooted—will drop fruit and foliage with drought. That doesn’t look like your issue though. On that note however, my friend has had much better  hang time through these stressors than his neighbors, likely because of his  regenerative practices with minimal soil disturbance, interspersed tree plantings, self-rooted vines, and many of his are over 40yrs old.

It looks like something that could not reach the top wire grazed on it. Some regenerative vineyards have started using short legged sheep to do weed management and leaf thinning very similarly to what looks like happened at your place, of course timed to not take all the grapes.

Yes deer browse on a schedule to avoid being seen. They remove leaves below 7 feet.  I took a permaculture approach.  My vines at trained on a wire 8 feet high above a 4 foot  fence. The deer prune the excessive growth for me and don't  jump over. I get good production on vines over 5 years old though many of them  are 50 to 100 years old and 100 feet long.