NC State Extension Publications

Problem

Nutritional disorder – boron toxicity

Symptoms

Lower leaves with necrotic spotting, followed by the development of a marginal necrotic band. Under severe conditions, symptoms can spread over the entire leaf and also develop further up the plant. Plant growth can be stunted.

Initial symptoms of boron toxicity

Initial symptoms of boron toxicity.

Brian E. Whipker  CC BY - 4.0

Moderate symptoms of boron toxicity

Moderate symptoms of boron toxicity.

Brian E. Whipker  CC BY - 4.0

Moderate symptoms of boron toxicity

Moderate symptoms of boron toxicity.

Brian E. Whipker  CC BY - 4.0

Severe symptoms of boron toxicity

Severe symptoms of boron toxicity.

Brian E. Whipker  CC BY - 4.0

Severe symptoms of boron toxicity

Severe symptoms of boron toxicity.

Brian E. Whipker  CC BY - 4.0

Root formation less with excessive B (plant at right).

Root formation less with excessive B (plant at right).

Brian E. Whipker  CC BY - 4.0

Similar Problems

Leaf necrosis symptoms also occur with sodium (Na) toxicities.

Additional Information

Typically excess boron levels are the result of over applications.

Diagnostic Tips

Submit a leaf sample for nutrient analysis. The sufficiency range for boron in strawberries is 25 to 50 ppm. Values above 50 ppm would be considered excessive.

Corrective Measures

In the short term, it is difficult to correct excess levels. Damage to the plants cannot be reversed. Overhead irrigations my help leach some of the boron out of the root zone (but irrigations need to be managed to avoid gray mold).

Avoid boron applications the following season. Ensure that your calcium levels are adequate, which may help moderate the effects of the excess boron.

Management

B can be leached, especially in sandy soils. Strawberries are a moderate feeder for B. Test soil for B level prior to planting and follow local crop production guidelines for boron application in your area. Typical recommendations, based on if the soil test values indicate less than 1 ppm B, is an application of 1 pound of actual boron per acre prior to planting. Over application of boron can lead to toxicities.

Funding Sources

Funding was provided in part by the National Sustainable Agriculture Program: Sustainable Strawberry Initiative and the following sources.

A thank you is also expressed to Kube Pak of Allentown, New Jersey for donating strawberry plants.

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Author

Professor
Horticultural Science

Publication date: April 10, 2014

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