At the very early stages of growth, symptoms of boron (B) toxicity are indistinguishable from phosphorus toxicity. In time the chlorosis associated with B toxicity is less yellow. The mottled appearance of the chlorosis and necrotic tipping of the oldest leaf are similar for both toxicities; however, in the case of B toxicity, these mottled chlorotic areas have a dehydrated appearance and the necrosis of the tip leads down the margins in a fine necrotic edging. As these symptoms increase in severity, individual chlorotic spots appear in from the margins and well down the leaf. Necrotic areas soon form within the chlorotic spots and finally join together, giving much of the leaf a shrivelled and dead appearance.

Wheat appears to be more tolerant to B toxicity than barley. Symptoms of B toxicity can sometimes be confused with fungal infections.