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Dormant Oil - Did I mess Up?

Posted by iowajer 4a/4b (My Page) on
Wed, Mar 20, 13 at 11:46

I guess I didn't watch the weather forecast close enough. Yesterday it got maybe 40 here, and so at about 10ish (or mid-morning sometime) I sprayed my two peach trees, my North Star, Early Richmond, and Carmine Jewel cherries with a tank mix of Dormant Oil/Liqui-Cop.

I woke up this morning and it showed 11 degrees outside.

I think I'd read that you're not to spray dormant oil when there's a hard freeze expected. I guess I don't know if high single digit/low double digit temps overnight means I messed up.

it's 10:45 and up to 20 outside now, so it's not staying cold long.




Follow-Up Postings:

RE: Dormant Oil - Did I mess Up?

It is important that there is 24 hours of above freezing temperatures or else the night time cold will break down the oil making it ineffective so then you will need second application

RE: Dormant Oil - Did I mess Up?

Thanks for the reply Bluesky204.

Whew!!! I was thinking maybe the oil freezing on the li'l buds might have done harm to them. If it's just a matter of a re-app that's a HUGE weight off my shoulders!

Thanks again!!!

RE: Dormant Oil - Did I mess Up?

  • Posted by olpea zone 6 KS (My Page) on
    Wed, Mar 20, 13 at 21:46

"Whew!!! I was thinking maybe the oil freezing on the li'l buds might have done harm to them."

I hate to worry you, but your concern above is exactly why it's not recommended to spray oil before freezing weather. Supposedly, oil "de-hardens" buds and tender bark, making them more susceptible to winter kill.

I've never personally sprayed oil and had a significant freeze within 24 hrs. of the application. Hopefully it won't damage your trees, but I'd appreciate any observations you could report.

By the way, it will probably make a difference what concentration of oil you mixed. Did you mix it at 2%?

RE: Dormant Oil - Did I mess Up?

You did not do any damage to your trees just what you sprayed is useless. I have a lousy weather too and my solution for that I spray every weekand use 5% oil concentration.. Who can fight mother nature?

RE: Dormant Oil - Did I mess Up?

Well, the brand of oil I used was Hi-Yield and the label said to mix 3 oz per gal, so I mixed 3 oz of the oil along with 4 tsp of Liqui-Cop. And it was probably on there a good 12 to 14 hrs before the temps started to drop until they eventually just took a nose-dive!

I'm going to be so stinking mad at me if this has a bad outcome.

Kinda feel like the guy who knows just enough to be dangerous! Here I am thinking I'm doing right by my trees, and oops, there ya go....

But I'm gonna keep my fingers crossed, and pray that everything works out.

I'll keep ya posted.

Thanks for all the replies.


P.S. I'm tired of winter dragging out...

This post was edited by iowajer on Thu, Mar 21, 13 at 2:33

RE: Dormant Oil - Did I mess Up?

  • Posted by olpea zone 6 KS (My Page) on
    Thu, Mar 21, 13 at 12:23

You folks implying oil can be applied in the face of 11 degree weather without risk of damage to trees/buds, I'm curious how you've come to this assessment? Has it been experience or did you read it somewhere?

I've read many times that applying oil before freezing weather puts buds at risk but I've wondered just how common damage occurs in real life and the details (i.e. rate of application of oil, hours from oil application to a freeze event, minimum temperature of freeze event)?

I'm also wondering where you've read oil is ineffective when applied before a freeze event. Supposedly oil applied during freezing weather can cause the emulsifiers to break down, giving uneven coverage, but once it's already applied on the tree (in non-freezing weather) how does subsequent freezing weather render it ineffective?

RE: Dormant Oil - Did I mess Up?

I was looking around to see if there were any studies on this same kind of situation and ran across this tidbit from Penn State Extension. The quote is from a Cornell University Professor. I'm starting to feel a little bummed again... :(

"Finally, we have heard of some growers who have recently expressed unfounded concern that oil has a negative impact on the health of their trees. To this I can only re-assert that petroleum oil has been used for well over a century as a delayed-dormant treatment to control mites, scales, and even some aphids, with no ill effects on the health of the tree or the current season's crop. The primary cautions we advise when using oils at this time of year stem from their use a) in association with or too close in time to applications of sulfur-containing fungicides, or b) just before or too soon after sub-freezing temperatures; both of these practices risk the occurrence of phytotoxicity, as oil's penetrant activity is capable of damaging the bark, wood, or bud tissues in these situations. Application of oil under any circumstances that do not allow for normal drying to occur can also result in some tissue damage. Also, oil sprays during pink bud can cause burning of the sepals or petals, which may affect normal pollination and fruit set. (Arthur M. Agnello, Cornell University Professor of Entomology)

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