Fruit trees are interesting plants to grow. Humans have been selecting for better fruit for centuries, and in the process, some of the natural resistance to pests and diseases have been lost. A further challenge is our mild rainy climate, which is perfect for fungal and bacterial diseases that affect fruit trees.
Customers often ask me, ‘when should I do a dormant spray?’ Old school was to spray oil while your fruit trees were fully dormant. Today, we’ve found that it is more effective to spray oil combined with a bactericide or fungicide at specific stages of bud development, also called bud stages. By using bud stages to time our sprays, we end up spraying less- always a goal in the orchard.
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- Japanese plum buds, at stage 3
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- Cherry buds at stage 2, almost to stage 3
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- Apple bud stage 4
In February, we posted about timing sprays for Peach Leaf Curl. Recently, plum and cherry buds are starting to swell, so now’s the time to look at your trees for timing. Stage 3 flower buds is a perfect time to spray an oil plus copper for cherries and plums. What do these sprays do?
- Oil in delayed dormant sprays smothers overwintering aphid and mite eggs
- Copper helps prevent bacterial canker infections, blossom blight and brown rot in stone fruit trees.
Some years, our stone fruit trees can be at stage 3 (just before bloom) in February. This year the bloom has been delayed by the extended cold weather we had January through early March.
How about your apples and pears? We’re not quite there yet on those, but here are the signs you should be looking for: apples and pears should get a spray of oil plus sulfur between stages 4 and 6.
- Again, the oil in the delayed dormant spray will smother overwintering aphid, scale and mite eggs
- Sulfur helps prevent powdery mildew at this stage.
Once pears and apples hit stage 4, the flowers can open pretty fast. If you grow varieties that are susceptible to apple or pear scab, you will need to be ready to spray a sulfur spray (with no oil) once your blossoms swell just to the point of showing color (pre-pink, or stage 6). Add Bacillius thurengenisis (Bt) to this spray to get the first hatch of leaf rollers. A second sulfur spray at petal fall will keep your trees healthy and mostly scab free.
Thanks so much for staying open online. I needed some advice and the gal who answered the phone was able to answer my question. Please clarify. On the 2nd spray of Sulfur after petal fall, do I add the Bt to the sulfur spray?
Yes, if you didn’t add to an earlier spray, or if you’ve had significant leaf roller in the past, I would add to both pre-pink and petal fall sprays.
Hello, I have a large productive cherry tree that I need sprayed. Is this a service you offer
Hello, I have a large productive cherry tree that I need sprayed. We had one great crop then two subsequent season they turned brownish purple with tiny perforations within a week of ripening. I would like to try your spray. Is this a service you offer ?
We do not do any spraying. What you need is control for brown rot, so if contacting a spray company that is what needs control.
Hello! We purchased a Maxie Hybrid and a Shinseiki Asian pear from Cloud Mountain in the fall of 2020. Based upon the Cloud Mountain chart, Shinseiki buds are currently at Stage 2 and the Maxie buds are at Stage 1. We are signed up for the fruit tree workshop on March 13. Based upon the current bud stage, will we be able to wait to apply dormant oil spray after the class on March 13, or do we need to spray those Asian pear trees now?
Timing for pears is oil plus sulfur between stage 4 and 6.
This may be obvious but do you mix together in one spray container both the horticultural/dormant spray oil and powdered sulfur? Or do you apply them separately for apples between stages 4-6? Thanks!
We mix them in the same solution. And, a note, the caution on mixing sulfur with oil applies if the daytime temps are going to be above 70. That is pretty rare in April, but definitely happened yesterday. Not really a concern if the trees’ flowers are not showing color, but if blooms are out, try to pick a cooler time to spray, evening after the heat of the day is ideal.