Charcoal Rot (fungus - Macrophomina phaseolina): Grain sorghum plants affected by the charcoal rot fungus fail to fill grain properly and may lodge in the latter part of the season. Infected stalks show an internal shredding at and above the ground line. This can be observed by splitting the stalk and noting the deteriorated soft pith tissue leaving the tougher vascular strands. Fungal structures (sclerotia) can be observed in the affected tissue which appears as though it has been dusted with black pepper. Another type of stalk rot (Pythium sp. and Fusarium sp.) may show the shredded condition but the black specks (sclerotia) will be lacking. Conditions under which charcoal rot is favored include stressful hot soil tempertures and low soil moisture during the postflowering period. Host plants are usually in the early-milk to late-dough stage when infection occurs. The fungus is common and widely distributed in nature. Avoiding moisture stress, proper management of crop residue, crop rotation, avoiding excessive plant populations, balancing nitrogen and potassium fertility levels, and growing drought-tolerant, lodging-resistant hybrids represent the best means of control.
