Bayoudh disease is the date palm equivalent of plague. In Morocco, which has suffered major epidemics of the disease, it has had a devastating effect. In the last one hundred years it has destroyed more than two-thirds of the Moroccan palm groves (12 million trees), and it continues to cause the death of 4.5% to 12% of date palms per year. The result has turned Morocco - once an exporter - into an importer of dates. Now scientists may have found a way of tackling Bayoudh disease.
The cause of Bayoudh disease is a fungus, Fusarium oxysporum f.sp. albedini, which produces chlamydospores in the dead roots of diseased palms. As the tree wilts and dies the rotting plant matter releases the chlamydospores into the soil where they can remain dormant for as long as eight years or be carried by irrigation water. These chlamydospores do not need to be present in high concentrations and even small amounts are enough to infect a tree and cause its subsequent death. The transplanting of diseased trees has also assisted in spreading the problem. It is believed that very few palm groves in Morocco are free from the problem.
|an infected palm|
The first external symptom of the disease, noticeable to experienced observers, appears on one or more leaves of the middle crown. The affected leaf takes on a leaden or ash-grey colour and then withers in a characteristic way: some pinnae or spines situated on one side of the leaf become white; then, the disease progresses from the base to the apex. After one side has been affected, the withering begins on the other side, progressing this time from the top of the leaf to the base, until the whole leaf dies.
The Possible Cure
An Algerian research team have turned to traditional medicine in their search for a cure to what the UN Food and Agriculture Organization describes as "plague to Saharan agriculture". The team, from Béchar University, tested extracts from four poisonous plants, which grow in the Algerian Sahara desert. People of south-west Algeria use the extracts as an antifungal traditional medicine. The team, led by Abdelkrim Cheriti, director of the university's Phytochemistry and Organic Synthesis Laboratory (POSL), announced its results at a press conference in November last year.
Cheriti pointed out that most desert plants produce substances that help them adapt to their environments and fend off diseases. "We had the idea of using such metabolites, found in plants that grow in the same environment as the date palms and are able to resist Bayoud, to create an effective treatment for date palms," he said. A field trial of the treatment began in October in south-west Algeria and results are expected within three years.