The citrus-root nematode—Tylenchulus semipenetrans—appears to affect the growth of young citrus trees in four ways: it may injure the bark of the roots; remove plant nutrients during feeding; impair the normal growth and functioning of the roots; and possibly inject a toxic material into the tree. Recently, investigations were undertaken to determine the effects of the nematode on young lemon and orange trees growing under controlled conditions, and to establish the causal relationship of the nematode to the frequent failure of young citrus trees to grow satisfactorily when planted on old citrus soils.

The above progress report is based on Research Project No. 1377