Help me out guys, because I am confused about dormant oil.
Dormant to me implies that you spray it on citrus during the winter or fall, but it seems that it is not good to spray citrus in the winter because of frost damage.
Seems like one contradicts the other.

This is a quote from another thread that never got answerred, but to add to the question that karpes asked:

Are there differences in the oils used for spraying? I have heard of and used Volck oil for years as a dormant season spray on fruit trees and roses. The oil I am currently using is from Garden Safe and it list the oil as neem oil. I have seem some on this forum refer to ultrafine oil. Are these all interchangable?


Skeet

I've tried both, worked equally good or equally bad. They are most effective when mixed 1:1 with canola oil, that's the only time I got rid of nasty scales.

Never heard of the canola oil trick Joe. Thanks. I have a few questions:

- Do you use it with the ultra fine oil and the dormant oil, or both?

- When mixing with water, do you use the same concentration of the combined material (if you combine it)?

- Is there any problem getting the canola to mix with water, or does it act like the product that it is mixed with?

- Are there any other particulars we should be aware of?

I use the ultra fine oil pretty often for certain insects. (I don't use dormant oil any longer.) Most importantly, it works for mites. On occasion I combine it with certain other insecticides, but would caution that there are combos that will damage the plant. I have had no problems when following labeled directions. I have also used neem oil, which works well, but is more expensive.

For those that may not know, virtually any insecticide, herbicide or fungicide label can be downloaded from the web by searching for the product, plus the words "specimen label". You can download the MSDS the same way.

Ned, I looked at the ingredients of ultrafine and dormant oil, they seem to be the same petroleum type, but the exact chain of carbons are not disclosed, so can't really know for sure if they are one and the same. I will check that again.

What I do is I first measure how much ultrafine oil I would need, then use half of it and fill the other half with canola, mixed together in the bottom of the container. I then spray jet them in the tank to mix together and use the same day. This way my oil spray are nearly half as cheap. So if the formulation calls for 2 tbsp of ultrafine oil per gallon, I would use 1 tbsp of ultrafine and 1 tbsp of canola.

Sometimes I add a little bit of malathion depending upon how stubborn the insects are.

For spray oils on Florida citrus, we use materials much more highly refined than "dormant" oils, but less so than "Volck" oils (which are more used in California).

A couple things affect the workings and safety of an oil. One is the middle boiling point. With a pure substance like water, if you boil it, it will boil at the same temperature until it's all evaporated. But with a mixture of substances, it will start boiling at a relatively low temp, then the boiling temp will rise as the more volatile components are evaporated off. So one of the things measured in spray oils (which are mixtures of hundreds of petroleum components) is the "middle boiling point" -- the temperature reached when 50% of the original volume has boiled away. We tend to use 418, 435 (most popular), and 455°F mbp materials. Of course, the range of bp also matters, and you want it to be fairly narrow around the mbp; that is to say, it should start boiling at almost the mbp, and finish not-too-much over the mbp. Generally, the lower the mbp, the safer the material will be for your tree (less phytotoxic), but the less effective it will also be as a pesticide. Of course, our primary use of oil is greasy spot fungus disease control; not insect/mite control, but it does both.

The other major factor in spray oils is their UR rating. A volume of the oil is mixed with concentrated sulfuric acid, and they are shaken together. They never really mix -- the oil floats over the acid, but you shake them like salad dressing. The H2SO4 reacts with unsaturated hydrocarbons (one or more double bonds) as well as aromatic hydrocarbons (a benzine ring or other aromatic group present), and those materials get dissolved in the acid fraction. They then divide the volume of the remaining, unreacted oil fraction by the original oil volume, for the "unsulfonated residue." Under Florida conditions, that number should be higher than 0.85, for the oil to be safe to use on citrus. California needs an even higher number, because of their drier air and (at least in some locations) higher temperatures.

Sunspray or "ultrapure" and other "very highly refined horticultural" oils tend to have very narrow bp ranges, and very high UR ratings, as well as fairly low mbp. This makes them very safe to use.

Thanks Joe. Sometimes I use Malathion with the oil too, especially with mites and whiteflies.

Thanks to you too Dr. Manners. I think I might have to read your post a few times to even begin understanding it, but I do think I read somewhere that one of the differences it the oils was the amount of time it takes them to evaporate form the leaf. The longer the oil stays on the leaf, the more effective, but also the more stressful to the plant. This becomes more of a problem when it is warm, and the plant is actively growing. The ultra fines evaporate faster and are less stressful to the plant, but are also somewhat less effective. I guess I am trying to state this in layman's terms, am I close?


Ned

Since oils are pretty much the same except for viscosity then when would you not spray it to avoid frost damage? I mean say zone 9, the last oil spraying should not occur later than or earlier than? Sorry guys, but I am persistent.
Thanks Karl

I don't spray during the entire winter. I spray only when max temp is below 80 deg F.

JoeReal, did you mean-- max temp "above" 80?

--and one more question, perhaps a little esoteric, but-- how does oil spray inhibit cold conditioning?

Thanks to all for the expert information!

-- Skeet

We don't use mbp 435 or higher oils after about the first of August, and the 418 oil is stopped by the end of August. We would not normally get frost before the second week in December.

Ned, rate of evaporation from the leaf undoubtedly has something to do with phytotoxicity, but I don't believe it is the full story.

skeeter, I meant if air temp do not exceed 80 deg F, then I can safely apply that morning. Otherwise I'll get a lot of leaf drop should i insist on spraying.

How many hours at or below 85 degrees is required? If I spray around 8:00 o’clock PM, this would give me approximately 12 hours before the temps go back to the 90 plus degrees the next day
Directions on the ultra fine oil state to not spray above 85 degrees, but this would eliminate the whole summer if a 24 hour period of less than 85 degrees is necessary. Or does this only mean that you should spray early mornings or late evenings when the actual temps are below 85 degrees?

It basically means spray in early morning or in the evening. - Millet

I wonder if mixing spinsosad with ultra fine oil would be a better combination to fight leaf miner. Or maybe spraying oil after the spinsosad had time to dry on the leaf.
By the way I would like to reserve a copy of the citrus book when you write it, or didn’t you guys think of that yet?