Worldwide distribution. On papaya and celery, but boron deficiency also occurs in many other plants, for instance, brassicas (e.g., broccoli, cauliflower, turnip), sweetpotato, and palms. An important deficiency.
On papaya - deformed fruits, sometimes with cracks oozing latex, and stunted, brittle claw-like leaves.
On celery - splits across leaf bases, and wet rots on inner leaves.
Normal boron level in leaves is >25 ppm.
Cultural control: add composts, if this fails, have soil analysis done to compare boron with K, N and Ca, and check pH. Add borax as follows: (i) for papaya - spray/drench with 0.3% borax or 0.5g/tree, or spray root area (may need to increase up to 5g per tree); (ii) for celery - 2 g borax per m2 at 2 and 6 weeks.