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CHEMICAL FROST PROTECTION FOR FRUIT BLOSSOMS 



B.R. Boyce 

 Department of Plant and Soil Science 



University o£ Vermont 



Frost injury on fruit blossoms amounts to millions of dollars 

 worth of crop losses annually. Methods of reducing these losses 

 fall into four general categories: 1) variety selection; 2) site 

 selection; 3) adding heat during a frost; and 4) reducing heat lo..^ 

 during a frost. A fifth method would be through the application of 

 substances to lower the killing temperature of the blossoms. Sev- 

 eral chemicals are currently being tested for this purpose. One of 

 these materials is Chem-Frost*, a commercial product marketed by 

 Chemical Frost Control Corporation of Meridian, Idaho. 



Chem-Frost* was sprayed at a dilution of 1 to 100 on Catskill 

 strawberry plants under both greenhouse and field conditions and 

 on Mcintosh apple, Delicious apple and Bartlett pear trees in the 

 field. Three applications were applied to the point of run-off. 

 The first application went on the strawberries as growth started 

 but before flower buds were visible, the second application as the 

 buds were first noticeable, and the third just prior to the first 

 bud opening. The first application on the apples and pears occur- 

 red at silver tip, the second at green tip, and the third at half- 

 inch green. 



Blossoms were collected at full bloom from the treated plants 

 and from untreated checks and frozen at several temperatures. Af- 

 ter two hours at each temperature they were floated on water for 

 24 hours and evaluated for injury. 



Table 1 summarizes the number of blossoms killed at each tem- 

 perature. The temperatures ranged from 31°F, which did not kill 

 any blossoms to 23°F which killed all blossoms. Under the condi- 

 tions of this experiment, Chem-Frost* did not significantly reduce 

 the amount of low temperature injury to the blossoms of any of the 

 fruits tested at any of the temperatures used. In some cases, in 

 fact, there appeared to be a trend towards more injury where the 

 material was used than on the unsprayed checks. 



The manufacturer of Chem-Frost* is now marketing a new formu- 

 lation of the frost-protection agent. We have not tested the new 

 formulation. However, the results of our tests showed that under 

 the old formulation, Chem-Frost* applied under Vermont conditions 

 had no effect on lowering the killing temperature of strawberry, 

 apple, or pear blossoms. 



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