Here is the third and fourth (and hopefully the last) of my peach tree troubles. The gash on the peach is the only one like it that I’ve seen (but obviously I don’t want to see anymore). The stream of peach juice (I’m assuming that’s what it is) which has oozed and hardened, however, can be spotted on a good number of the peaches. Does anyone recognize this or know how to treat it (assuming it’s not too late) organically?
revelgardener 
Many years ago back in Bklyn we had a peach tree in the yard. I remember that sap, but offhand have no idea what it is or what causes it. It was a long time ago, but about all I can remember attacking the peaches were worms that ate into the fruit.
As far as I know ants themselves are not a problem to plants, but if there’s a lot of them you may have aphids. They produce a sweet substance that attracts the ants, and if memory serves (check out SSG insect episodes) they bite into leaves and suck out the juice. The small spots on the leaves make aphids or a similar leaf biting insect prime suspects.
I’ve never used copper based insecticide, but a very effective natural pesticide is pyrethrum. It comes from a certain type of daisy. I managed to grow a couple from seeds last year and they flowered. Pyrethrum is all natural, very effective against bugs, and very quickly breaks down in natural surroundings. You can buy it commercially prepared, since I doubt you want to wait long enough to grow the plants now. Possibly one ‘catch’ is that it is best if you can get it onto the little buggers. I got my seeds from http://www.seedman.com and they have a very large variety of unusual seeds. They also had a section on making your own natural medicinal teas, natural bug sprays, and other info of interest.
If I run across any info on peach bugs I’ll post it.
Check out these links about peaches, it’s too long to post the text here:
oriental fruit moths:
http://forums2.gardenweb.com/forums/load/fruit/msg0518093429871.html?478808631bf317fc705f91e87413220a5cV3n
more bugs and sprays:
http://patwelsh.com/wpmu/blog/trees/preventing-sap-from-oozing-from-peach-and-nectarine-fruit/
from botanical garden, scroll down page for peaches, copper sprays:
http://www.botanicalgarden.ubc.ca/forums/showthread.php?t=3646
http://web.extension.illinois.edu/askextension/thisQuestion.cfm?ThreadID=9881&catID=35&AskSiteID=34
Clear sap can suggest the presence of cankers. This is a conditions caused by some type of stress to the tree such as cold temperatures, hot dry conditions or other things not allowing the best growth. Best thing to do is make sure the plant has proper water, good fertility and is in good vigorous growth. It can usually grow past this condition then.
Google search on “peaches+sap” (no spaces, include plus) for the above and more.