Root diseases of cotton can occur during all phases of the growing season.Once a seed begins to germinate,fungi and nematodes will move to infect the roots.During the first two weeks after planting,most plant pathogens are already colonizing roots.Seedling disease, which can include root discoloration (necrosis) and sunken lesions on the root and hypocotyl, is usually the first root disease problem observed.Later in the season other symptoms can be found such as galling from root-knot nematodes or complete root death from the fungus causing Texas root rot.Once the plant is dead,it is difficult to determine what caused the root problem.However,if roots are examined when plants first begin to show above ground symptoms of stress,it is often possible to diagnose a root disease problem.

Root-knot Nematode
Meloidogyne incognita
The root-knot nematode of cotton is Meloidogyne incognita, or the southern root- knot nematode. The nematode eggs survive in roots or soil during the winter and hatch in the spring to produce second-stage juveniles. These nematodes can move to cotton roots and infect them.They cause the root to swell and form galls around the nematodes as they mature. A mature nematode can produce hundreds of eggs that hatch and go through another life-cycle.The galls can reduce plant performance if formed in high numbers on young cotton plants.Generally, root-knot nematodes do not build up to high numbers until mid-season or later,when the plant can tolerate more galling. The galls make it more difficult for the plant to transport water and nutrients from the soil to the above ground plant parts. Since the plant has to expend more energy to remove water from the soil,it may be less productive. Management of root-knot nematode involves crop rotation (primarily with peanuts) and chemical control with Temik ® 15G (Aventis) at planting or Telone II ® (Dow AgroSciences) before planting as a fumigant.

Root-knot nematode


Root-knot nematode