Wednesday, April 10, 2013

Spring 2013 Has Arrived!

The apple trees have silver tipped in the orchard here at Royal Oak Farm orchard in northern Illinois and that is a sure sign that spring has arrived!! It also indicates that just as soon as the nights stay above freezing, it will be time to do our dormant oil and copper spray. The oil (mineral oil) is sprayed for mites, scale and aphids because spring is the time to cover those eggs at the base of the buds. Below you can see aphid eggs that were laid fall.

aphid_eggs

Copper is also sprayed at this time for control of fire blight and to aid in the suppression of apple scab pathogens, both being severe diseases that can destroy a crop as well as the trees. We also have to be aware of the spring critical temperatures as the buds progress in development. Each spring I post the spring critical temperatures chart from Utah State to help you determine at what stage your fruit trees may be at as spring progresses.

Critical_Temperatures_Frost_Damage_Fruit_Trees_Utah_Page_1

Critical_Temperatures_Frost_Damage_Fruit_Trees_Utah_Page_2

As I mentioned earlier, now is the time to do our fire blight copper spray and our horticultural oil spray.  We want to get the copper on the trees before they reach full 1/4” green and the horticultural oil can be sprayed at the same time in a tank mix or done as a dormant,silver tip,green tip, or 1/4” green spray.  In other words, your oil can be sprayed at any time from silver tip through 1/4” green providing you are using a mineral oil based product such as Superior Oil 70sec or an off the shelf Horticultural Oil such as Bonide’s All Seasons Horticultural Spray Oil.  Your copper spray should be done before the trees reach 1/4” green to avoid any phytotoxicity issues.  For your copper spray you can also use an off the shelf brand such as Bonide Copper Fungicide RTU (Ready to Use).  Both of these products should be available at your local hardware store or garden center of from Amazon.com.

A dormant oil and copper spray should not be done until we get at least a 24 hour period that is above freezing at night. The oil cannot freeze on the trees, but it pretty much dries within about 24 hours. We usually get at least one 24 hour period above freezing at night before the trees get to 1/4" green. 

 

This “window of opportunity” for dormant sprays for fruit trees depends on the bud stage of your target fruit tree. You can follow these guidelines:


Apples: swollen bud - 1/2” green
Pears: swollen bud - cluster bud
Peaches/Nectarines: swollen bud - pre-bloom
Apricot: before bloom


When applying, spray trees just until they are dripping to get good application on all the stems and crevices at the buds. If you are using horticultural oil alone, use a rate of 2% (mixed in water) for best resultsor your chosen product’s label rate.  For situations where aphids have been real problems in the past, consider adding an insecticide (such as acetamiprid, etc.) to 1.5-2% oil or use one of the Bonide RTU (ready to use) pre-mixes for insect pests.