Here’s what I’ve heard over the years. This isn’t from the official oil label:
Precautions on using oils:
Oils are highly refined petroleum products and, as such, will have some
compatibility problems. Generally speaking, oils should not be used within 14
days of a pesticide containing sulfur (such as Captan, Sulfur, or Morestan). If
applied closer than 14 days, phytotoxicity can occur with symptoms such as leaf
tip burn showing up on trees. Many fungicides are compatible with oil – be sure
to check the compatibility chart in the Fruit Management Guide or the pesticide
Temperature also plays a role in the safety of oil sprays to the tree.
Generally speaking, oil sprays will make plant tissue more susceptible to cold
injury and should be applied when temperatures are going to be above 40 degrees
F. This makes it difficult to apply oils under typical Michigan conditions.
Leaf tip burn and blossom damage can occur when there are sub-freezing
temperatures after oils sprayed at half-inch or later.
Overall, an oil spray that is properly timed is one of the most important
insecticide applications you will make all year. Often, insect and mite
populations are controlled well enough with this spray so that later aphid,
scale, and mite control can be reduced or eliminated.
My fruit extension agent says you pretty much have the whole month of April –
just do it before the flower buds spread apart.
Per my extension agent – freezing temperatures within 24 hours after applying
oil can damage flower buds. Generally to smaller, part-time and backyard fruit
growers the recommendation is don’t use if temperatures below 40. However, as
you dig further into the topic recommendations for commercial fruit growers
talk about temperatures in the range of 35 or so. Another commonly asked
question at this point of the year is “When is it too late to apply dormant oil
in the season?” Over the years I have used a rule of thumb which is that once
flower clusters have separated then it is too late to apply dormant oil sprays.
Lastly, most of the killing effect on mite and scale insects of dormant oil
occurs in the first 24 hours after application. This is important to know in
that you would hope not to have any rain event during that first 24 hours after
Integrated Pest Management Specialist
Ruth Mott Foundation/Applewood
1400 E. Kearsley Street
Flint, Mi 48503
[Ruth Mott Foundation Applewood]
From: apple-crop [mailto:apple-crop-boun...@virtualorchard.com] On Behalf Of
Sent: Thursday, March 29, 2018 3:02 PM
To: Apple-Crop discussion list <email@example.com>
Subject: [Apple-Crop] Oil application myth busting...???
True or false?
1.) When dormant, or late dormant, it's OK to put oil on when the night time
temperatures drop below 32 F.? (Note the Damoil label simply says do not apply
when the temperature is below 32 F.)
2.) As buds break, and green tissues shows, tissue damage is more likely if oil
is applied during the day and night time temperature drops below freezing?
3.) Pears and apples different when it comes to oil application(s)?
4.) 2 to 3% oil is magical because that is in all the recommendations and it's
been that way forever? (But the damoil label says "For concentrate spray, use
no more than 4 gallons of this product per acre in minimum 20 gallons of
spray." Huh, isn't that like 20%?)
JMCEXTMAN (aka Jon Clements)
413.378.3068 Project Fi
UMass Cold Spring Orchard
393 Sabin Street
Belchertown, MA 01007
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