Heterodera cruciferae (Cabbage Cyst Nematode),
H. schachtii (Sugar Beet Cyst Nematode)
Heterodera cruciferae only infects crucifers, while H. schachtii infects crucifers and sugar beets. Foliar symptoms are dependent on plant age, season and temperature. Generally, plants first appear small and nutrient deficient. As the disease progresses, leaves may wilt or curl, especially during hot weather. Invaded roots branch profusely, while the taproot remains small. Plants that survive produce loose, small heads and discolored roots. Invasion of infected roots by fungi is common. A characteristic sign of this pathogen is the appearance of lemon-shaped cysts on the root surface, which are white, tan or reddish in color. Plants often die prematurely.
Conditions for Disease Development
These nematodes overwinter as cysts and hatch soon after transplant, releasing juveniles that penetrate host root tissues. Loamy soils favor disease development, and irrigation water or rainfall allows these nematodes to swim or float to susceptible roots. The nematodes are also spread through contaminated soil, infected seedlings, tools and machinery.
Sow resistant varieties and rotate to non-hosts for a period of three to five years in order to help reduce nematode populations. Fumigate soil, apply nematicides, incorporate crop residues immediately after harvest, and eradicate weeds and volunteers to help control this disease.