I would suspect rats. They have a habit of chewing seedling, especiall corn, melons, sunflowers, peas, beans. This happened to me last year. I was suspecting rabbits. So I make a rebbit trap. But what I catching were rats. I let them loose in the beginning; I was saying to myself "I don't want to catch rats but rabbits" haha. I kep sprinkling my garden with rabbit repelents, salt/pepper but something didn't give a damn and kept on chewing off my seedlings.This was not definitly a squirrel habit. Squirrel dig up the seeds(corn, peanut..) but do not eat or chew greens. After some internet search, I found out that it was the rat not the rabbit. From then on I went after the rats. Rabbits generally eat the top of the plants, if they can reach it. But rats chew off stems. leaving the top behind. I know this, because I almost eradicated the rats last yar and this year I have some rabbits eating the top of carrots. With the peas on trelis, since they cannot reach the tops, they eat those laying on the ground and the lower part of the rest. So I think, If your father lives in a rural area, with wooded area nearby, then it is most likly that rats are the culprits. Best thing is to get a Mouser cat that can go after rats. It has to be a big cat, rats are much bigger than mouse. The other options are placing all kinds of traps and baits. But be aware of the birds and cats not to eat the poison baits and get caught in the traps. For further information, google rats in the garden. I am sure you will find a lot of information. Good luck!

Fencing is the best option according to all the previous discussions here on this question. They also sell several different repellents that some report work to varying degrees. Dave Here is a link that might be useful: rabbits in the garden discussions

Yuck!! That picture gives a great visual, LOL. I will look for that saliva-like substance, but I don't think there is any. I am going to take the chewed off leaves, along with the spotty leaves from Elvis Lives, and another issue I am seeing with fuzzy white stuff over to the lab at NCSU later today. Should get some quick answers that way. Thanks for the info, Hostanista, and the suggestion to contact the plant disease lab :)

Oh no, that's awful. Have never seen that so don't know what would have done that. It does look like a lot of damage. You could try wrapping it with grafting tape, but with that much damage you might have to cut it off. I have attached a link to a GW discussion on this subject. JM's are pretty resilient and you might get new growth below the damage next spring if you do have to cut the top off. If the plant has been grafted, it might not grow back. The new growth will come out in a wagon wheel pattern around the trunk and take several years to look natural again. You can root JM cuttings in wet perlite and covered with plastic. I usually do this in the spring, but this is an emergency. Cut as many different size twigs and branches as you can then dip in rooting hormone. It takes a long time to get a nice JM this way though. Here is a link that might be useful: Using grafting tape on Maple