Urea sprays may be used on apple trees to supplement soil applications of nitrogen. They are not effective on stone fruits or pear and can cause leaf burn.
To reduce the hazard of leaf burn on apples do not use rates over 3-5 pounds of urea per 100 gallons of water, or more than 10 to 20 pounds per acre.
Caution: On apple use only formulations that contain less than 2% biuret because of potential injury. Urea also is a very good leaf penetrant and spreader stickers may actually reduce the efficiacy of urea sprays. Applications of urea with some pesticides can reduce their effectiveness. On the other hand, applications with growth regulators can increase their absorption, resulting in an over effect. Consult the product label.