Daylily leaf streak may be avoided by purchasing disease-free stock plants and propagating only from healthy specimens. To control leaf streak the fungicide thiophanate-methyl may be applied to slow disease development and to protect susceptible new growth from infection. Infected plants slowly deteriorate, grow poorly and become stunted, turn yellow, wilt and often die. The symptoms are very similar to moisture stress. Roots will often have small bumps or nodules where the nematodes feed and inject toxins.
Nematodes are most common in sandy, moist soils.
They are generally more of a problem on former cropland that has been re-utilized for residential use. The best option is to choose plants that are not susceptible to the root-knot nematode. Erwinia carotovora causes bacterial rot at the base of the flowers and in the rhizomes. The bacteria that cause rot are normal soil inhabitants. Disease development is favored by high temp- eratures, poor air circulation, poor soil drainage and improper fertilization.