Cabbage disease mystery in Ghana

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Cabbage © iStock images

Cabbage is an important crop in Ghana where it grows all year round, right across the country. It is mainly grown for commercial production in Southern Ghana, in Akwapim and Kwahu areas and in the moist high elevations around Tarkwa.

Growing cabbage in Ghana is challenging since it can be attacked by a variety of pests, such as cabbage aphids, caterpillars, cabbage webworm, diamondback moth, mole cricket, snails and rodents. Worldwide, aphids are a major concern because they commonly spread plant-infecting viruses. These are often diagnosed as turnip mosaic virus and cauliflower mosaic virus, particularly in Europe and the US, according to Dr John Carr, University of Cambridge, UK (Phys.org, 2017).

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Keeping an eye on banana disease

The bacterial disease Xanthomonas wilt causes banana fruit to rot.
The bacterial disease Xanthomonas wilt causes banana fruit to rot © Pascale Lepoint / Bioversity International

Dr. Fen Beed is an experienced plant pathologist based at the International Institute of Tropical Agriculture (IITA), Dar es Salaam, Tanzania. He leads research for development activities to mitigate the impact of diseases of maize, soybean, cowpea, cassava, banana and vegetables and promotes plant diseases on problematic weeds.

The first and critical step to manage a disease is to diagnose the causal agent(s). Once this is done, appropriate control methods can be deployed, based on available knowledge or on results generated from targeted research. IITA led an initiative to define the factors required to create a functioning disease surveillance network across a region.

The initiative targeted the two most serious threats to banana in the Great Lakes region of sub-Saharan Africa (SSA); namely banana Xanthomonas wilt (BXW), caused by the bacterium Xanthomonas campestris pv. musacearum (Xcm), and banana bunchy top disease (BBTD), caused by the banana bunchy top virus (BBTV). BXW and BBTD are established in several countries in SSA where banana production is of critical importance. Countries included were Burundi, Democratic Republic of Congo (DRC), Kenya, Rwanda, Tanzania, Uganda and Zambia. In order, to strengthen both national and regional communication pathways, representatives from both national research organisations and national plant protection organisations agreed to form a network for regional surveillance of BXW and BBTD. The specific objectives were to share information on the diagnosis and management of these diseases and to map their distribution across locations that were of strategic importance to the region. Continue reading

Cassava virus resistance breakthrough for Africa

Cassava roots
Cassava is a staple food for millions but is susceptible to viruses that make it unpalatable © Seth Anderson (CC BY SA license)

One of the worst diseases of the tuber crop, cassava, in sub-Saharan Africa is Cassava brown streak disease (CBSD). Since its resurgence in East Africa in recent years, it is now spreading to Central and Western Africa. The other major disease of cassava in this region, Cassava mosaic disease (CMD), can also cause widespread damage to the crop, however there already CMD-resistant varieties of cassava available. Until now, very little natural resistance to CBSD has been found. Plant scientists at the Swiss Federal Institute of Technology (ETH) Zurich have combined natural resistance to CMD with modifications of the cassava genome to develop a variety of cassava resistant to both CBSD and CMD that can be grown in Africa. As cassava is a staple food to millions of people, this new variety has the potential to halt the spread of the disease and prevent famine from crop losses. Continue reading

Maize disease in Kenya no longer a mystery and being controlled

Maize showing symptoms of Maize chlorotic mottle virus © CIMMYT (CC BY-NC-SA license, via Flickr)

Update [March 2013]: More information about the pests and viruses associated with Maize Lethal Necrosis disease can be found on the Plantwise Knowledge Bank.

In January this year, ProMed-mail reported an undiagnosed disease of maize that had been destroying farmers’ crops in the Rift Valley of Kenya since the previous September. The Ministry of Agriculture in Kenya swiftly took action to investigate the problem, and at the end of May, the Minister of Agriculture Hon. Dr Sally Kosgei announced their conclusions. Continue reading

Where did black sigatoka come from?

Effects of black sigatoka on plantain leaves in Colombia © Neil Palmer (CIAT)

Black sigatoka, or black leaf streak disease, a disease of bananas and plantains caused by the fungus Mycosphaerella fijiensis, has caused widespread losses to banana crops over the past 50 years. A new study of the phylogeography of black sigatoka on banana leaves from around the world has helped to elucidate the recent origins of this fungal disease. Continue reading