Farmers in parts of southern Malawi are facing a new threat to their livelihoods following the outbreak of a highly destructive maize disease that has the potential to wipe out entire fields if left unchecked.
A statement from the Ministry of Agriculture, Irrigation and Water Development has confirmed an outbreak of Downy Mildew Disease (DMD) in maize, with the Blantyre and Machinga Agricultural Development Divisions (ADDs) being the most affected areas so far. However, the ministry has warned that the disease could easily spread to other areas.
According to the Ministry, DMD is a severe foliar disease caused by a water mould, known scientifically as oomycetes in the genera Peronosclerospora, Sclerospora and Screlopthora. Once established, the disease can cause total yield loss. It does not only affect maize, but can also infect other important crops such as sorghum, sugarcane and millet.
The Ministry says early symptoms can appear as soon as nine days after germination, beginning with pale, chlorotic stripes on young leaves. Plants infected at the seedling stage often become stunted and may die within four weeks. In older plants, the disease causes chlorotic streaks starting from the leaf base, with a clear boundary between healthy and infected tissue.
One of the most visible signs of DMD is a mould-like growth on the underside of leaves, usually white in maize, although it can also appear grey or purple depending on the species. As the disease progresses, leaves become narrower and more erect, tassels become malformed, and cob formation fails, resulting in sterile plants. In severe cases, tassels are replaced by twisted, bushy leaf growth commonly referred to as âcrazy topâ.
The Ministry has emphasized that Downy Mildew Disease should not be confused with Maize Streak Virus (MSV). Unlike MSV, DMD streaks originate from the leaf base and are not restricted by veins.
DMD spreads through infected seed, contaminated soil, crop residues and airborne spores. High humidity and mild temperatures ranging between 21 and 26 degrees Celsius create ideal conditions for spore production and rapid disease spread.
To manage the disease, the Ministry is urging farmers to take preventive measures before planting, including deep ploughing, using certified seed from recommended suppliers, treating seed with Metalaxyl at 6 grams per kilogram, avoiding planting maize near sugarcane, and practicing crop rotation with legumes. Maintaining recommended plant spacing is also encouraged to improve air circulation in fields.
During crop growth, farmers are advised to uproot and bury infected plants immediately, minimize movement in infected fields to prevent spore spread, and avoid ratooning sorghum which can increase spore build-up.
After harvest, all crop residues from infected fields should be destroyed through burning to prevent the disease from surviving into the next season.
The Ministry has urged farmers and the general public to remain vigilant and report any suspected cases of Downy Mildew Disease to their nearest agricultural extension officer or a government office.
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