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 label. 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 application. Mike Belco Integrated Pest Management Specialist Ruth Mott Foundation/Applewood 1400 E. Kearsley Street Flint, Mi 48503 (810) 396-3111 www.applewood.org<http://www.ruthmottfoundation.org/applewood/> [Ruth Mott Foundation Applewood] [facebook]<https://www.facebook.com/ApplewoodEstate> [flickr]<http://www.flickr.com/photos/applewoodrmf/sets/72157629286276410/> [YouTube]<http://www.youtube.com/user/ApplewoodRMF?feature=mhee> From: apple-crop [mailto:apple-crop-boun...@virtualorchard.com] On Behalf Of Jon Clements Sent: Thursday, March 29, 2018 3:02 PM To: Apple-Crop discussion list <apple-crop@virtualorchard.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) 413.478.7219 Verizon 413.378.3068 Project Fi UMass Cold Spring Orchard 393 Sabin Street Belchertown, MA 01007 http://umassfruit.com
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