Steve:
The only source IK kknow for fish oil is Integrated Ferti;lity Management. This is from thier web site

Crocker`s Fish Oil

When mixed with pesticides, Fish Oil is an excellent Sticker-Spreader. It provides greater coverage and penetration, thus allowing reduced pesticide dosages. Mixed with foliar herbicides to control weed grasses in wheat, Fish Oil can reduce by half the amount of herbicide needed. Fish Oil mixes well with most spray materials applied during dormancy and is readily absorbed through the bark carrying nutrients with it. Unlike petroleum oils, Fish Oil is a natural material having beneficial nutritional properties of its own. Used as a spreader-sticker, Fish Oil appears to improve the effectiveness of Bt`s due to its UV screening properties. Fish Oil will provide a more even application of wettable powders. It stays put once applied thereby avoiding concentration spots even after repeated applications. Upon drying, Fish Oil forms a tough varnish-like coating that resists weathering and will not wash off.

Special Note: Do not use with sulfur after dormancy. Clean your equipment before the oil dries.

The give recommented rates in 100 gallon doses. See Spring pome News for home orchardist small mixes as per 1 gallon.
For winter dormant spray us 4T per gallon, Summer spray, 2T per; gallon.
This works.

Ted