Area of impact: Stem
Description: Emerging seedlings may sport brown lesions. New leaves may be small and eventually wilt. The taproot and lower stem will be light gray with small black dots embedded under the surface of the stem and taproot making them look as if they’ve been sprinkled with charcoal. The inner stem and root tissue will take on a reddish-brown color.
Pathogen involved: Macrophomina phaseolina (a fungus)
Timing/Conditions: Symptoms appear during or after flowering in dry hot conditions. Seedlings may also be infected in hot dry soils.
Contributing factors: Most common in the southern Midwest. Plant stress or injury increases risk. Overwinters in dry soil and residue and is spread by seed.
Management practices: Plant resistant varieties and reduce drought stress. Minimal tillage is also reported to help.