Delayed Dormant Sprays
March 23, 2012
Delayed Dormant Sprays
Wow, this spring is the polar opposite of last spring, when at this time of year, we were bundled in our down coats shoveling sidewalks. Now, apricots are blooming and it’s shorts and flip flops. Are you ready?
The first pest management action to perform in the next few weeks is your delayed-dormant spray. “Delayed-dormant” is when the trees are between dormancy (tightly closed buds) and partial leaf expansion. We recommend spraying at this time because
Keep in mind that dormant sprays are not required every year. If you had an aphid problem last season (they were plentiful in many locations), then apply your delayed-dormant spray this spring. If you have had very little damage from aphids, then you could consider skipping the spray. The table below shows which pests a delayed dormant spray will treat, and what materials to use.
When to spray
The ideal time to apply a dormant spray is after the buds of fruit trees have started to swell, and up to the point where leaves have begun to emerge.
What to use
Usually horticultural oil alone is sufficient for delayed dormant sprays, particularly for backyard and hobby growers. Most oils are simply sold as "dormant oil" and the ingredients will be "98% (or higher) petroleum oil". This type of oil is suitable for sprays in the delayed-dormant time (2% rate in water) as well as sprays during the growing season (0.5-1% rate).
Commercial growers may consider mixing oil with an insecticide such as Asana, Sevin, or Esteem, depending on the target pest(s).
When applying the delayed dormant spray, make sure you thoroughly cover all bark cracks and crevices. Also, oils should be used when the air temperature is above 40 F and when there is no threat of freezing temperature for the following 36 hours. Applying between 50 and 70 F on clear days is ideal.
What you are treating
The 2012 edition of the Utah-Colorado Commercial Tree Fruit Production Guide is available for distribution. New information includes a chapter on weeds and thinning, as well as information on mating disruption and new products added to the spray tables.
If you are a commercial grower in the state and have not received a copy, please notify Marion Murray
Precautionary Statement: Utah State University Extension and its employees are not responsible for the use, misuse, or damage caused by application or misapplication of products or information mentioned in this document. All pesticides are labeled with ingredients, instructions, and risks. The pesticide applicator is legally responsible for proper use. USU makes no endorsement of the products listed herein.