Symptoms of Nutrient Toxicity1. Mature Foliage Affected First

• Older leaves drop rapidly with necrotic leaf margins. – Spray Injury
• Older leaves do not drop at first, main vein remains green as the leaf first turns yellow then brown, then leaves drop after drooping. Young shoots become stunted, buds may be distorted. – Zinc Toxicity
• Browning of mature leaves at the leaf edge, separated from the green tissue with a distinctive pink margin, brown, irregular spots, then eventual leaf drop. – Boron Toxicity
• Small black spots on older leaves. May also cause iron deficiency symptoms to appear. – Manganese Excess
• Similar to high salt concentrations, followed by rapid falling off of older leaves. – Sulfur Toxicity

2.   Younger Plant Parts Affected First

• Younger plant parts are affected first with chlorosis of terminal growth. Buds fail to develop after cutting. Too much urea may cause plant hardening. Often the foliage is increased in size and blooms smaller than normal. -Nitrogen Excess
• Symptoms of copper, iron and zinc deficiencies will occur with excessive use of phosphorus as it makes these elements unavailable to the plant. This is especially true with a low pH. – Phosphorus Toxicity
• Chlorosis, root loss and wilting of young shoots. – Potassium Toxicity