http://www.barc.usda.gov/anri/sasl/vinegar.html

"Environmental fate of acetic acid: Acetic acid readily degrades in
water and shows little potential for bioaccumulation. It is
biodegradable (MITI Report 1984, Ministry of International Trade and
Industry, Tokyo). In an experiment conducted at Swedish Agricultural
University it was found that addition of 24 % vinegar to a peat soil
decreased the pH of the soil from 7.3 to 5.6. However, after 48 hours
the pH values of the soil returned to 7.0-7.5. "


"Nature, left alone, is in perfect balance.
Harmful insects and plant diseases are always present,
but do not occur in nature to an extent which requires the use of poisonous chemicals.
The sensible approach to disease and insect control is to grow sturdy crops in a healthy environment."

Masanobu Fukuoka, One Straw Revolution--1978