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Africa: Disease Attacks Elephant Grass and Cattle Die

29 August 2008

DENMARK - It is a fantastic grass, the fast-growing and lush Elephant grass. Harvested several times a year and chopped to pieces, it is an important fodder source for cattle on many small farms in Uganda and other countries in East Africa - typically farms that are so small they only have one cow.

Billedtekst: The lush elephant grass is used for cattle fodder in Africa. Elephant grass is threatened by a disease that Danish scientists help to control.

According to Aarhus University Faculty of Agricultural Sciences, when the elephant grass fails, the farmer and his cow find themselves ”up the creek without a paddle” – and unfortunately that happens regularly.

The scientific name for elephant grass (also called Napier grass) is Pennisetum purpureum. Despite its everyday name, there is no way that an elephant can hide in the grass once it has been infected with Napier grass stunt disease.

As the name suggests, the disease inhibits grass growth. In some cases the stunted growth leads to the grass dying. Typically, the grass yield is reduced to less than half the normal level. With such a dramatic reduction of the vital fodder, problems arise with regard to meat and milk production from the cow. In the worst cases the cow must be slaughtered and that also means an end to the nutrient-rich manure for the fields.

All told, it is a bad cycle to enter and therefore scientists from the Faculty of Agricultural Sciences at the University of Aarhus are participating in a Danida-financed project aiming at helping Ugandan farmers to control the disease. This is done in close collaboration with local scientists, advisers and farmers.

There are some things the Ugandans manage on their own while there are some things that the Danish scientists assist with.

  • The Ugandan scientists have carried out surveys and investigations to identify the symptoms of the disease, estimate yield decrease and determine the farmers’ knowledge of the disease and advised how to control it. We now have a good picture of how widespread the problem is, explains Head of Research Unit Steen Lykke Nielsen from the Department of Integrated Pest Management at the Faculty of Agricultural Sciences, University of Aarhus.

    The Danish contribution has been to carry out a positive identification of the pest in order to control it as efficiently as possible.
  • What we are doing is going down to the molecular level to study the pest, says Steen Lykke Nielsen.

Phytoplasma and leaf hoppers

The disease is caused by a phytoplasma, which is a specialised kind of bacteria living in plants. Phytoplasmas are difficult to identify with classical plant pathology methods. Instead, a DNA-based method is used, which is available in the Danish laboratory. The Danish scientists also carry out DNA sequence analyses of the phytoplasmas in order to find out if there are just one or several types of them.

There are, however, more villains than the phytoplasmas. In order to move from plant to plant, the phytoplasmas need a mode of transportation – a so-called ”vector”. Phytoplasmas typically use leaf-hoppers as their vector of choice, but which particular type of leaf-hopper does the phytoplasma infecting elephant grass use for getting around? -
  • There are an awful lot of species of leaf-hoppers. We don’t even know for sure if a leaf-hopper actually is the vector. In order to control the disease in elephant grass, we must first find out if the elephant grass phytoplasma is spread by a specific vector. After that we need to study the biology of the vector. Not until then can we find the best programme to control the disease. At the end of the day it’s all about pest control, explains Steen Lykke Nielsen, who hopes to find funds for this important part of the project.
Meanwhile, the Ugandan colleagues are in the process of selecting elephant grass varieties that are resistant to the growth-stunting disease. Once they find potential candidates, the Danish scientists can help to develop a method of detection that can be used locally for screening new varieties of elephant grass.

TheCattleSite News Desk



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