Thanks for asking these questions about which I'm now wondering. I'd never heard of applying the HOil as a pre-emergent until your recent thrip thread. Anything to help with pests. (At least you know how to prune. : ) )

If you're going to use any oil, now is a better time to use it than when the sun is higher, more directly over head; water stresses are higher and temperatures are higher. Take a cue from the fruit growers. You apply oils before the foliage emerges to suffocate insect eggs and disease spores.

Thanks roseseek... sorry I'm feeling dense right now and need it broken down a little further... so I need to prune and defoliate and disbud in order to apply the horticultural oil properly?

No you don't NEED to prune and defoliate but if you are going to do it anyway, it's more convenient and effective to do it before spraying. Spray either very early in the morning or better at dusk when you are not expecting temps higher than about 83F and when humidity is not too high. You should also not spray when you're expecting freezing temperatures. It would be better to keep the spray away from any seedlings or very young bands. I suppose you will be using a light summer oil not a heavier winter one. You can use a winter one which is more effective but that can easily affect leaf and tender tissue on plants which are not dormant (and I suppose you have many such plants in your warm climate garden..).

No problem, Cori Ann. Oils, ANY oils, can easily burn the foliage and soft, new growth when the plant is water stressed; the sun intensity is high and/or temps are high. You don't HAVE to defoliate before spraying. Heavier oil sprays have been used to defoliate the roses in the rose fields prior to harvesting the plants. If you don't want the dropped foliage all over the place, defoliate then spray. If you don't care, just spray and most are going to fall, whether they are just old and the plant is finished with them; they are diseased and the plant sheds them; or they are fried from the oil and the plant sheds them. You also don't have to dis bud, but buds formed right now are likely not to be "perfect" anyway due to temps and the amount of water diluting and flushing away nitrogen. If you intend to disbud to encourage faster growth on newer, younger plants, do it. If you want to "clean up" the garden by removing the old foliage for whatever reason, do it now. Of course, whatever you intend to do, do it before spraying. Finish all of your intended tasks, THEN spray. Even if the material is relatively innocuous, why expose yourself to any unnecessary chemical? And, oils ARE messy. They don't rinse off easily, which is why they are as effective (and potentially damaging) as they are. Personally, I HATE being greasy/oily, so if I intend to use any oil, it is THE last thing I do so I can avoid the area as long as possible so I don't get tangled up in the oily mess. Have fun!

Got it. Disbud. Prune. Defoliate. Keep it away from the babies. Do it at dusk. Then go wrestle with my husband while I'm oily. Ummm I mean shower. ;)

Ok, well I'm half way done with my roses. I disbudded (is that a word?) and defoliated. They're naked! Most of them anyway.

I'm leaving a few with some foliage. It's a lot more work than I usually do for pruning!

Tomorrow they will be naked and oily! Hopefully they're into it.

That would be nice! LOL! Congratulations!

I am going to wait to oil up the front yard later since I applied elemental sulfur near my azaleas and I read there needs to be 30 days between that and horticultural oil.

I figure when I do my front yard I could do the second application for the backyard too... in about 2-4 weeks.

My oil (Bonide all season) also says not to apply if rain is expected in 24 hours. Oil can harm fish (I'm assuming it would actually be damaging to all aquatic life, much like an oil spill). Which is why I'm doing it now.... we have a break from the rain for a few days.

Hopefully this helps some other oil newbies too. :)

On the Bonide site it also says its safe and PLEASANT to use... I wonder what they mean..

Roseseek, I wonder what kind of oils you've been using or in what dilution you've been using them as such mess is not part of my experience of using modern thin summer oils and I've used them a lot. Both the ones looking like very thin vegetable oil and those that look like mayonesse. In fact most of it evaporates soon hence the advice to not spray when the humidity is high, in order not to hinder evaporation. There's a thin residue left that also mostly goes away after a few days or after a good shower. In my experience if you're going to have any leaf tissue damage that will manifest itself within a few hours not in a few days if things get hot.. And I've seen damaged leaves on roses (meaning having burnt spots on them) but I have never had real defoliation on them... If I want to defoliate a rose in purpose I would use limesulphur. You make it sound like you've been spraying with gearbox oil (or with the kind of horticultural oil my grandad would spray his dormant fruit trees 50 years ago..).

Pleasant? Ask my husband.... ;)

Ultra Fine, Sun Oil, Jojoba, Neem, pretty much anything out there in the market. I ALWAYS follow the directions. Always have. I could get away with spraying them at the beach for perhaps six to seven months of the year, as long as it remained cool, wet, foggy, but when "summer" temps hit there, no dice. Fried foliage. I have never been able to safely use any of them in the San Fernando nor Santa Clarita Valleys (inland, hotter valleys north of Los Angeles). Either it was too hot; the plants experienced too great sun (winter or summer) or they experienced sufficient water stress that the foliage fried. I know others have used them in other climates and that's fine. Location, location, location. But everywhere I have gardened since 1968, except for the beach, they were sure-fire fried foliage.

Just had a thought. I am also using predatory nematodes for pest control here.

Horticultural oil will kill those just like pests. Unless I time this right. I did a quick search to confirm and found this good read on oils: https://puyallup.wsu.edu/wp-content/uploads/sites/403/2015/03/horticultural-oils.pdf

Huh.

Ok so 2 weeks to a month of separation between applications should be ok right?

Which should I apply first? Meaning this weekend? The nematodes or the oil?

Maybe try a home experiment in my yard and do horticultural oil in the back yard only and predatory nematodes in the front yard only?

or should I just forget the oil after all?

I imagine the nematodes wouldn't be as active in colder soil. The oils would be safer to use in colder temperatures. Would that not then suggest spraying first then after the suitable period, release the nematodes? Perhaps at this time of year, if you already have the nematodes and the package says you may release any time of the year, go ahead, release them then wait and hope it remains cool and damp?

That makes sense about the temps. I will also call the nematode vendor to see what they recommend.

Naked roses!

I'd be sure to wear a respirator. Oil is not a poison but it is not good for your lungs.

http://www.ladybug.uconn.edu/FactSheets/hort-oil.php

Thank you to all for helping me along. Here's an update for any other newbies to oil! :)

I used Bonide all seasons spray oil. For roses, the directions said 2-5 TBSP per gallon for summer and 5-7.5 TBSP per gallon for "dormant" oil. January in my area of CA is so mild... I used just 4 TBSP per gallon-ish.

I just got a hand held flo-master sprayer. Didn't want to shell out big bucks my first time doing it. It held 56 oz (half a gallon).

Since my roses are mostly new (so they're small) and I pruned & defoliated them first, I could get through about 15 roses before needing to refill.

It was really easy. Wasn't messy at all. It was a consistency like neutrogenia bath oil, but a little thinner. If any of you use Moroccan oil in your hair/skin... this does not even feel remotely close to that. Way thinner.

Defoliating helped A LOT!!! I think that probabaly got most of the bugs without even needing to oil. It was a lot of work, but I can see the benefit. Roses I thought looked healthy, I could see black dots (thrip poo?) under the leaves once I got in there and started taking off the leaves.

The avocado and citrus trees I didn't defoliate and they were messier and harder to spray since you kind of need to spray it upwards in order to get under the leaves. I read later that it may not have been the right time to do avocado and citrus in my area of CA. Oops.

It was hard not to get the seedlings near my roses. I could adjust the spray, but I'm sure I still got some.

I didn't spray my herb garden, strawberries or veggie garden. The directions say I could. I might end up doing it. I didn't spray any other trees or flowers either.

I didn't use the protective gear recommended. I don't have a good reason. I just didn't. But, i didn't really feel like I needed it after I was done. No wind. I did NOT set the sprayer to the misty setting because that was messy. I set it to a manageable spray setting. It went right where I wanted it to go and didn't really get anywhere else. Disposable gloves are a good idea so you can spray while you turn over leaves without getting your hand a little oily.

That's about it! :)

Oh! I did spray my blueberries and raspberries though. And didn't defoliate them either. I think it seemed to help to get underneath the leaves if I kind of gently pulled them to the side from different angles so I didn't have to try to spray the oil upwards.

Ok. Now that's it. :)

New tech paraffin oils are not messy at all and, used properly, the probability of plant tissue damage is really small. I told you they are very thin. Most of the oil should evaporate soon leaving behind a very thin residue which will too go away after a couple of showers.

As far as I know, any time is good for spraying oil on citrus as long as there's no mature fruit on them, there are no flower buds and temps are what they should be for spraying oils. Citrus leaves can take heavy concentrations of summer oils with no apparent damage. I have sprayed fivefold the recommended dose by mistake with no issue. Good for controlling mites and scale insects.

My lemons seem to always have at least a couple flower buds. Oh well. Gardening is like life. Life is an experiment and mistakes will be made.

I really like how the leaves and canes look once they're sprayed with this light oil. It's all an optical illusion, but they look greener and luscious. Kind of like what our winter ashy skin looks like when we put on a little lotion. :)

I got some really good advice about applying horticultural oil in my area of CA from a local nursery and thought I would share it! They even have it published online to make it easy! http://www.aldenlane.com/dormant-winter

Basically, the roses in our area don't go dormant, so we can help force them into dormancy in January by removing their leaves. January is the time to prune them, strip them of leaves, and spray them with the higher dormant season rate. The roses will thank you soon by pushing out new growth. And since most roses bloom on new growth... they will give you a bunch more blooms!

For all season oil, like the one I used, you can use the stronger dormant rate when spraying leafless, dormant roses. But use a lighter rate when roses are pushing out new leaves.

In this area, a January dormant spray application is considered optional if pests have not been a huge problem in the past (it's a good preventative measure). Most fruit trees and roses benefit from 2 sprayings to control insects (smothering overwintering eggs).

I will be doing my second application of horticultural oil this weekend, which is a little less than 2 weeks from my first application. 2-4 weeks apart is recommend. My schedule just works out best this way.

Thank you for this info. I've started doing this with all the leaves that are dead, but still on the canes as I clean up the beds and add compost, paper and leaves. Remaining leaves may persist til spring, but I plan to next apply the oil. I've seen oil with a fungicide....is that what one should use? My main issue besides those pesky sawfly and cucumber beetles is Blackspot. We are rarely below 70%humidity with temps in the 90s all summer and usually have higher humidity with heavy thunderstorms in a river valley. Lots of BS, but only in the Fall so far for me. I guess I should call my county extension or rose society, but they once told me (the rose society), that it was impossible to avoid BS here without the chemicals.

I would call the Master Gardeners instead of the rose society. (no offense to anyone in a local rose society... I don't mean that how it sounds).

It's just that the Master Gardeners in your areas will have access to university professors, labs, research, experts ... and they will be more focused on cultural and biological controls first.

I chose to use just the oil without the fungicide (or copper). I like to just try one thing at a time so I can see what type of a difference each change makes on it's own and evaluate.

I can always choose to try an oil with a fungicide (with copper) next year. Since oil is new to me, I wanted to just add it alone.

This way, I will be able to tell what the oil did in my yard... and compare it to what the oil with fungicide does. That's just me though.

I've used lime sulfur with oil as a dormant spray in the past but did it with only a bandana over my nose and afterwards I could feel the irritation in my lungs. Lime sulfur is strong stuff, probably caustic, and not good to breathe. I think any spray is bad to breathe, but you are probably right , Cori Ann, that if you don't spray a fine mist it is less apt to be in the air to breathe. I just think that it's better safe than sorry with your lungs. I use a respirator for things like spray paint , or for scraping old paint. The respirators at Lowe's cost about $30 and while they might not be ultimate protection I think they help and they're very easy to breathe through. I have done without my respirator at times and it is tiresome to worry about it but I think it's a good idea. From what I hear the dormant spray can help with insects but also with bs and downy mildew. I have a lot of weed seeds sprouting right now , having had Jan. temps into the 70's, so I'm thinking that I will spray those baby weeds too hoping it'll get rid of them.

I don't know erasmus... the oil may protect the weeds from insects and help them grow! I would just pull the weeds. That's just me though. Good points about a respirator. Especially if you have asthma or anything else that makes breathing hard. Always good to take care of lungs. :)

Hey vaporvac do you have to defoliate in cooler areas to force dormancy --- or don't the roses defoliate on their own and go dormant on their own? That may just be a warmer climate thing. Not sure... but definitely something to ask the experts.

Thanks for the respirator suggestion. I have one I used frequently, so it's not an issue. BTW, they make them in small sizes, as well which may help will fit and efficacy. You may have to go to a paint store to find one, though.

They do go dormant and defoliate on their own in cold climates.

The purpose of spraying summer oil is to smother insects and their eggs. You'll get better coverage if the plants are defoliated. I rarely do use oil but that is because I don't at this time have a serious insect problem. I did spray a plant that was suffering quite a bit from rose sawfly last year, and it seemed to help. I observed very little damage after that. Insecticidal soap can also be used for sawfly.

Fungicides and oils have a possibility of causing leaf burn when used together, or even within 3 weeks of each other. Removing leaves would certainly reduce that, and I'm sure that not all fungicides have that problem. Sulfur is notorious for this. It is my second choice fungicide, which is why I am aware of it. Copper is my first choice. I just happen to have never tried to use these two at the same time so I don't know if they have that problem,

It's about 2 weeks from when I first sprayed horticultural oil, so I did my second application today. I didn't see any sun damage on the plants, so I tried going up to the "winter" ratio of 7.5 TB per gallon for my defoliated roses. I still used the lower ratio for citrus, berries and anything else that still has leaves.

Since it's been 2 weeks since I defoliated, I have a lot of brand new growth. Some bright green aphids have found it. It was fun to spray them off with the oil!

Actually, I find the pump up sprayer very similar to a pump up "super soaker" water gun. :) A water gun would be a much more fun way to apply hort oil. If I still had young kids I would probably make it a family affair and get a bunch of super soaker water guns for us all to apply hort oil instead of just me doing it with a boring old sprayer.

What is that sprayer?

It's a little pump up flowmaster ... you can see it in a photo if you scroll up a little. I think it cost between $5 and $10

I thought I would give a little update and share my experience for those like me who are new to horticultural oil and defoliating. I defoliated all my roses on Jan 13ish and now, about 6 weeks later, the roses are all leafing out nicely. Some even have buds. None of my old garden roses have buds yet, but that's probabaly because they were all brand new babies. Here's some that do have buds now, 6 weeks later...

Don Juan

Barbra Streisand

The weaker solution of oil didn't seem to damage anything, but when I mixed and sprayed the stronger "dormant" oil solution, some of the roses didn't seem to like it. No real damage, but some canes have a little tan, or maybe even a little sunburn.

Even though I was trying to be careful, some of my newer bands got oil on them. The weaker "summer" solution didn't seem to bother them, but they didn't like it when they got some of the stronger "dormant" solution on them. Again, no catastrophic damage, but just not happy, killed some of their new growth, and they are a little set back. I'm going to imagine that it only got rid of the weaker growth, allowing for a stronger plant in the long run, so I don't feel guilty. ;)

All in all, I think I will stick with the weaker "summer" solution in the future if I have little bands or other sensitive plants nearby where I'm spraying.

That's about it for the update! :)

Use dormant / winter oils or 'dormant dilutions' only on dormant plants with no young foliage or active bud-eyes.

Thanks Nik. Good advice.

This is all just my own personal thought process, and based on hardly any experience since I just sprayed oils for the first time this season, but I would imagine that 'dormant dilutions' may be best used where temperatures get into the freezing ranges.

Since we don't get that here (except a few rare early morning frosts)... not a lot of plants really go dormant. Just from these two experiences, I'm gonna stick with the summer dilutions in the future. Even in the winter. :)

Oils, 'dormant' or not, should not be applied when temps are close to or below freezing because the oil's efficacy is diminished as its chemical structure can be affected. I only use 'dormant' oils on my pear and almond trees and on just pruned HTs only when no bud-eyes have woken up (some years there's no such time..) and only when I have a scale insect problem (which I often do). On smaller heavily pruned roses I prefer to apply oils with a brush rather than spray. It is easy to apply on a naked pruned HT and is easier to make sure all problem areas are covered.