Crazy top of maize

Crazy top is a systemic disease of maize caused by the oomycete Sclerophthora macrospora. It is a distinctive phytopathological condition that severely disrupts the normal development of the plant, primarily affecting its reproductive capabilities and overall growth structure.

The disease primarily impacts maize, although it can also infect various other graminaceous species, including wheat, sorghum, and several wild grasses. The pathogen acts as an obligate parasite, infecting young seedlings in the early stages of development when the soil is saturated with water.

The most recognizable symptoms appear during the reproductive stage. Instead of a normal tassel, infected plants develop a leafy, proliferated, and distorted structure often referred to as a "witches' broom." Affected plants also exhibit shortened internodes, thickened and curled leaves, and a general stunted appearance, often failing to produce ears entirely.

Environmental conditions play a critical role in the development of the disease. The mobility of the pathogen's zoospores relies entirely on the presence of free water in the soil. Therefore, poor field drainage, waterlogged soil, and heavy rainfall during the early growing season are the primary drivers for the spread of this infection.

The impact on crop yields can be significant, as infected plants are typically barren. Because there are no effective curative fungicides, management relies on preventative agronomic practices. Essential strategies include improving soil drainage to prevent standing water, implementing crop rotation, and managing grassy weeds that can serve as secondary hosts for the fungus.