YEMEN: Ministry issues warning on maize smut

The Ministry of Agriculture and Irrigation (MAI) has warned farmers about a fungus known as "maize smut" and asked them to use seeds that do not contain the fungus.  The warning comes as the maize cultivation season gets under way. 

Mansour al-Aqel, director-general of the MAI’s agricultural information department, said maize smut appeared in Yemen many years ago due to farmers not selecting improved, clean seeds. The fungus only attacks maize [see http://www.inra.fr/hyp3/pathogene/6ustmay.htm]. 

“The spread of the disease depends on the farmers themselves. It is caused by selecting unclean spikes,” he told IRIN on 12 August, adding “there are improved seeds that are treated in a way that can fight the fungus.” 

Al-Aqel said if farmers do not select improved and clean spikes, the losses caused by maize smut could be big. “Losses differ from one farmer to another. The lazy farmer would lose the most. On some farms, losses could run to 60 percent. If the fungus is left untreated, then it causes higher losses,” he said. 

“Maize production has begun to increase. It is cultivated on 600,000 hectares and this year the area [of cultivation] has increased,” al-Aqel said.  Yemen imports about 75 percent of its food needs, including 2.1 million tonnes of cereals each year.  

More about the disease  
According to al-Aqel, when the maize crop is infected, black spores replace the kernels, making the plants useless. 

Maize smut is a kind of fungus caused by the pathogenic plant fungus Ustilago maydis. It often enters plants through wounds made by cultivating equipment. The fungus grows down the silks to the kernels and causes galls on the ears. [see http://www.ext.vt.edu/pubs/plantdiseasefs/450-706/450-706.html] 

According to a factsheet by Cornell University’s Plant Disease Diagnostic Clinic [http://plantclinic.cornell.edu/FactSheets/corn%20smut/smut.htm], maize smut is now present in nearly all countries where maize is grown. “Any part of the plant above the ground can be invaded, although it is more common on the ears, the tassels and the nodes than it is on the leaves, the internodes and aerial roots. After the spores mature, the covering becomes dry and brittle, breaks open, and permits the black powdery contents to fall out,” the factsheet says.  Maize grown on heavily manured soil often develops severe smut, especially in hot and humid conditions. 

[R]Description  
Symptoms of the disease can show on all the young growing parts of the plant but mostly affected are the male and female inflorescences.

On seedlings large whitish then purplish-grey swellings occur which, if the collar is attacked, can lead to the death of the plant. 

On leaves, stems, panicles (male inflorescences) and cobs (female inflorescences) masses of white vesicles occur which turn grey and release a black smut at maturity.

The smut balls on the cobs grow instead of the seeds giving the cob a grapelike appearance. The yield of these cobs is very low. Smut might be toxic to livestock. 

[R]Biology  
The fungus is viable in the soil as spores generated on the lesions at maturity.
The spores are rain and wind-borne. They can be carried over very long distances.

The first contamination in the year is caused by the spores. Several contamination cycles will follow caused by the spores forming on the first lesions. 

[R]Epidemiology  
Hail may cause wounds and also helps the rapid release of the spores by hitting their envelope allowing an outbreak of the epidemics. High nitrogen fertilization and damage (Oscinella frit.) also favour the spread of the disease. 
[R]Treatement  
Use resistant cultivars. Deep plough the infected crop debris. [R]Possible misleading  Sphacelotheca smut but in this case there is only one envelope of the cob.

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