Neophyte
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Posts: 11
Joined: Thu Mar 30, 2017 3:14 pm

Frost after dormant oil spray

I sprayed my fruit trees (in urban yard) with dormant oil but the forecast was uncorrrect and the next day the temp fell to -1. The whole yard was covered with frost; when it melted b 10 am my trees were wet to touch.
i am worried that i have damaged my trees ( 3 of them are two years old) with this premature spraying.
I checked several websites, they all say dormant oil should be applied when there is no danger of frost within 24 hours but before the buds open. However, i could not find the info about what happens if the frost still occurs.
Will the bark be damaged? Or is this recommendation to ensure greater effectiveness of the application?
thank you

JONA
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Joined: Fri Jul 25, 2014 11:11 am
Location: Sussex. England

Re: Frost after dormant oil spray

Hi Neophyte.
There is always a danger of damage from these oils if applied prior to frost I'm afraid.
Frost can cause the oils phototoxicity to penetrate the bark and tissues and cause damage. Hopefully ...especially if your trees are fully dormant still and the frost was fairly light...they will come through ok.
I do question using oils nowadays at all though as they not only remove the eggs and larvae of pests from the tree but also the predators too....and if you start with completely clean trees then the first things that are going to come back will be the. ' baddies ' , after all, there's nothing for the ' goodies ' to eat.
Hope all proves to be ok.
John

Neophyte
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Joined: Thu Mar 30, 2017 3:14 pm

Re: Frost after dormant oil spray

Thank you, John.
Gardening is so tricky, what can i say. I try to go as organic as possible but last year my older apple trees produced fruit that was too bad to eat, too many worms and other blemishes. So, this year I decided to try dormant oil and now this problem happened...
I can see that buds continue to swell but the bark on younger trees looks more pale than it should. Oh, well.

If not dormant oil, do you use any other spray, (maybe something natural home-made) to combat pests?

JONA
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Joined: Fri Jul 25, 2014 11:11 am
Location: Sussex. England

Re: Frost after dormant oil spray

Hi . Neophyte
Let's have a look at the major pests that infect apple trees in the order that they naturally come.
There are a whole host of creatures that can effect apples...but these are the most important ones.

From soon after bud burst to just prior to bloom.....aphids.
Spray with soapy water when seen.
If you put a grease band round each tree you will stop Winter Moth damage at this time too. This is a Moth that hibernates in the soil over winter and drops her wings to do this. So to get into the tree to lay her eggs she has to climb the trunk. The band stops her. Her caterpillars eat the fruit buds as they open at blossom time.

There are two major moths that cause the most damage on apples.
The Totrix Moth and the Codling Moth.
Totrix causes small holes on the surface of your fruit and trailing scars on the fruit.
Codling lays her eggs on the surface of the fruit which hatch and then drive into the fruit and these are the ones that cause
Worms ( maggots). As you can only get at them from the egg being layed and it hatching and eating into the apple the spray period is only 10 days wide with each laying, and in hot summers she may have many laying periods.
Both of these moths can be monitored and partially controlled by useing pheromone traps that you can buy at good garden centres.
The traps catch the males as they seek out the females for mating. Light catches mean you need not worry....very heavy catches mean you may need further control. (These traps only catch the targeted Moth ...no other species are affected.) There are organic chemicals for this... also biological control is possible using Granulosis Virus. The great thing about this control is that only the worms are effected. Even if birds etc eat the worms they will not be harmed.

Hope this helps a bit.
John

Neophyte
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Posts: 11
Joined: Thu Mar 30, 2017 3:14 pm

Re: Frost after dormant oil spray

Wow, John, this is so much useful information for me, thanks a lot. I only need some clarification regarding the grease band, please.

What kind of grease and how much of the trunk should it cover? When is the best time to apply it?

I have natural wax for covering tree cuts after pruning; would that do as 'grease'? It's very sticky and lasts the whole season, no matter the rain (of which we sometimes have plenty in Ontario)

Also, I looked up the info on Granulosis Virus; it sounds promising, would you recommend any specific brand or maybe a place to buy it? I suppose it's only available online. I don't think I've seen it in gardening centers, though i might be wrong.

Thank you.

JONA
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Posts: 803
Joined: Fri Jul 25, 2014 11:11 am
Location: Sussex. England

Re: Frost after dormant oil spray

Hi
The grease bands can be bought at any garden centre. They need to go on as soon as the buds start to break on the trees.
The wax you use on wounds would dry out too quickly. The band is around six inches wide.
I guess the Granulosis would be on line...but as I'm in the UK I'm not sure of your markets.
John

Neophyte
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Joined: Thu Mar 30, 2017 3:14 pm

Re: Frost after dormant oil spray

Thank you again,

You would be surprised but It turned out grease band is not available in gardening centers in Canada. I called three largest places and none of them has heard about it. Now that I looked up the picture I remember seeing those bands on trees in Europe (I am originally from Ukraine) but not in Canada.

I can buy it online but the shipping is from UK, which will take 7-10 days. Meanwhile, since the buds are opening, I think my only option is to put some wax on the trunk until the parcel arrives

I am learning a lot from you. Hopefully other Canadian gardeners will see this post and introduce this simple but apparently effective 'device'. For enthusiasts of organic gardening, if you can eliminate even one type of pest, that's a big victory.
Great exchange of international experience!

JONA
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Posts: 803
Joined: Fri Jul 25, 2014 11:11 am
Location: Sussex. England

Re: Frost after dormant oil spray

That should be fine.
It's even possible that winter Moth is not a problem in Canada.

You can bet your life that something else is there to replace it though!
John

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