Avoid splashing water from leaf to leaf. The nematodes can live as saprophytes in soil or potting mix for a short time so replanting the plant into fresh soil mix at the time the leaves are picked off can increase the control. When basil is grown indoors, irregular or ring-like pale tan spots appear on the upper side of the leaves. These may vary greatly in size and severity since some cultivars are more sensitive than others. Injury occurs when water which is colder than the surface of the leaf is used for watering.
Symptoms are often more pronounced during the winter months.
This problem can be avoided by watering with tepid or room-temperature water and by not wetting the foliage during watering. Soluble salt injury, excessive fertilization and accumulation of high levels of soluble salts in potting medium. When herbs are grown indoors, they can develop root injury from excessive levels of fertilizer in the potting medium. Symptoms are similar to those caused by root rot so analysis of the soil is required for correct diagnosis. An indication of high soluble salts is the presence of white crystalline deposits on the rim of the outer surface of the pot or on the surface of the potting medium.