Soluble salt injury on geranium

The symptoms on this geranium suggested wilt disease or micronutrient toxicity due to the spotting and foliage edge burn. An electrical conductivity (EC) test revealed high soluble salts. High growing medium EC can injure or inhibit the growth of plants. Common causes of high EC include: excess fertilizer (too high level or too frequent application), subirrigation, root disease, or restricted drainage. A soil test is almost always needed to confirm a soluble salts problem.

Fact Sheets
Basic Fertilizer Programs for Containerized Greenhouse Crops
pH and Fertility Review for Vegetatively-propagated Annuals
Root Diseases of Greenhouse Crops