Little Leaf on Loropetalum – A Deficiency of Copper

Summary

Little leaf disorder on Loropetalum grown in containers is caused by a deficiency of copper. Our research shows that repeated foliar applications of copper or substrate incorporation of copper sulfate and/or copper oxide can help eliminate the problem for production nurseries.

Situation

Loropetalum chinense var. rubrum, Chinese fringe-flower, was introduced into the United States in 1989 and quickly became on of the most popular plants in the nursery trade. Growth abnormalities (little leaf disorder) started to become a problem on container-grown plants in pine bark substrates during the late 90's. Symptoms are as follows: darkening of older growth, shortening of internodes, upward cupping of leaves, crinkling of new growth, particularly the distal part of the leaf, decrease in leaf size. In severe cases leaf necrosis occurs along with stem elongation, thus branches appear to be elongating without new leaves. Petioles become very short. Branchlets may also be reflexed or drooping. The cultivar 'Ruby' consistently has the problem, while it has also been noted on 'Sizzling Pink' and 'Suzanne'. Plants in the ground do not express the problem. This leads me to believe there is an element present in the native soil that we are not supplying in sufficient quantity in our organic substrates.

Response

Foliage from a commercial nursery was sampled for micronutrients concentrations. Initial data indicated that copper, zinc, and nickel were low and could be causing the problem. In May, 2005, a study was initiated at a commercial nursery in Grady County, GA. Copper and zinc sulfate, along with nickel lignonsulfonate, was applied as foliar sprays to symptomatic plants of 'Suzanne' growing in #5 containers. Within two weeks after treatment, plants sprayed with copper sulfate resumed normal growth. Control plants, or plants treated with zinc or nickel did not resume normal growth. A second study was initiated in June to evaluate different rates of copper sulfate and Kocide, a copper fungicide. Medium to high rates of copper sulfate and the high label rate of Kocide were effective. The plants in this study had severe symptoms and required repeated applications of copper. A new study was initiated in fall of 2005 to evaluate incorporation of copper sulfate and copper oxide into the substrate before planting. Results to date indicate that a two to three X rate of copper is required to prevent the problem.

Impact

Growers have successfully saved their crops based on this research. One grower in North Georgia has had great success with just one application of foliar copper. A grower in Florida saved six acres of plants, worth an estimated $250,000. This research finding, applied across the southeastern United States, could easily have an annual economic impact of several million dollars. Research findings are being utilized by nurseries across the country and in Australia.

State Issue

Agricultural Profitability and Sustainability

Details

  • Year: 2006
  • Geographic Scope: International
  • County: Tift
  • Program Areas:
    • Agriculture & Natural Resources

Author

    Ruter, John M.

Collaborator(s)

Non-CAES Collaborator(s)

  • Stewart Chandler, Monrovia Growers
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Research Impact