John, I was raised in Topanga Canyon. Maybe you've heard of my father who died a couple of years ago. He was dubbed by the Topanga Messenger as "the birdman of Topanga" and he wrote a nature column for that paper. His real name was Gerry Haigh. His wife (not my mother, but good friend) still lives in the house I was raised in on W. Hillside Dr. Here's some info on oil from my experience over the years managing quite a number of orchards in the southern NY area. When trees are dormant to tight green cluster a 2% rate is usually recommended to compensate for less insect vulnerability- as the trees get to tight cluster (speaking of apple maturation) you reduce the concentration to 1% although to control psyla on pears you might want to hit them both times at 2% because psyla are so persistent. I believe I've read from Cornell that scale are more vulnerable with the earlier ap and mites with the later but I've managed both problems with either application. I don't believe that heavier oils were more affective in any meaningful way (although I totally respect Scott's opinion) or I assume they would still be manufactured for commercial growers. That's not information- just a strong hunch. The beauty of the refined oils is that they can be effectively used throughout the spray season and I've been able to knock down mites and scale without even doing an oil spray before petal fall. This has allowed me to control scale and the most harmful insects we face here with only 2 sprays all season, starting at petal fall and following 10 to 14 days later. These sprays have 1% oil (on either the first or second spray) mixed with an appropriate insecticide and fungicide. Of course what is necessary and affective here doesn't always apply elsewhere but the oil part should be fairly universal. You have to be careful with Captan if you do this, however, as it is strongly incompatible with oil. I've even suffered some phytotoxic reaction with Captan residue on leaves that had been applied 10 days prior to an oil ap. Just make sure you follow the label for oil and don't spray when it's too cold or too warm. This stuff can be extremely destructive when used incorrectly and I've seen terrible damage when put down during frost on trees at half inch green. The more refined the oil the less chance for damage, so I go with Purespray.

Are there any fruit trees that are intolerant of the copper in these recommended sprays. I just bought a three pound bag of CuPro 2005 containing 53.8% copper hydroxide, but the directions on the packet were exclusively for ornamentals. My yard and orchard is highly varied with apples, pears, peaches, blueberries, pomegranates, persimmons, goji, cherries, mulberries, apricots, paw paws, figs, pecans, heartnuts, lemons, satsumas, and oranges(potted for winter removal). ..Would any of these be harmed by a late dormant spraying of dormant oil and the copper hydroxide mix? ...Could anyone reccomend a good mix rate for the copper? I only have a total of fifty or so trees that are fairly young and plan to hand spray them for now. I am very sensitive to the comment on copper buildup harming the worm population, and would like to limit copper applications as much as possible. I predominately use organic techniques in my gardens, but early problems with the orchard plantings are forcing me to turn toward spraying my young trees. They all receive generous doses of compost, worm compost, and compost teas in the Spring and Fall. Thanks for your input, Ed

Kquat: Generally, the terms "dormant oil" and "horticultural oil" are interchangeable, but there are some distinctions that can be inferred. There are several grades of paraffin-based oils sold, as well as a number of vegetable-based oils, as Scott has noted. Heavier, paraffin-based oils are more useful as dormant sprays on fruit trees because the oil must act to smother overwintering larvae of such pests as aphids, mites, and scale insects. True dormant oils are often used at the rate of 4-6 ounces per gallon of water. Lightweight oils (i.e. Sunspray etc.),properly diluted, can usually be used during the growing season on both outdoor and indoor plants. Increasing the dilution rate of these oils makes them even safer to use without leaf burn caused by phytotoxicity. The lighter oils, even when highly diluted, can still be moderately effective on growing season insects like aphids and whitefly. However, these lighter oils will not be as persistent or effective against overwintering eggs on fruit trees, or tough scale insects. When you buy an oil spray, make sure you understand its intended use, then read the label to see exactly what you have. Dilute and apply it roughly in accordance with the directions on the insert; heavier for dormant use and much lighter for growing season use. I usually apply paraffin-based dormant oil at a somewhat higher rate than indicated on the insert. I want a good coating of oil on the trees, and there is no danger of damage when application is made during the dormant season. Whether or not dormant oil is considered "organic" is an issue for the organic commissars to determine. Most of them would agree that it is. I know it is safe and non-toxic, and that's what matters to me. Don Yellman, Great Falls, VA

JaG, unless dormant oils are combined with other products - sulphur or copper/lime solutions are common - they DO NOT address disease issues. The link you provided contradicts what you are saying ;) It plainly says horticultural oils have been found effective against some fungal pathogens. It also didn't address dormant oils, just horticultural oils (unless my skim reading missed it). Applying a dormant oil is different than using a lighter weight oil during the growing season. The purpose of a dormant oil is that it is heavier and denies oxygen entry through itself. Anything overwintering on/in the tree that requires oxygen will likely die. Such an application can't be made during the growing season without major damage to the tree because the tree needs oxygen during the growing season, but can survive for awhile without it when fully dormant. The article did address the use of horticultural oils on dormant trees very briefly in that it mentioned it can delay bud break/blooming. This would be very desirable in areas where the springs can go from warm to sub freezing overnight. It's not relevant to the OP, but it does point to the value of using dormant oil sprays as part of a routine program rather than waiting to ID a specific pathogen. Every source I have ever read finds dormant oils applied during the dormant stage to be effective against many insects, their eggs, larvae as well as many fungal pathogens overwintering even as spores in the bark/buds. I don't really see a down side to routine applications during the dormant season. The link you provided didn't address any.