Alternative to fungicides for the control of Pecan scab

Symptoms of pecan scab on pecan fruit © Charles J. Graham
Symptoms of pecan scab on pecan fruit © Charles J. Graham

Pecan scab, caused by the fungus Fusicladium effusum, is a major yield-limiting disease of pecan (Carya illinoinensis). Planting varieties with some resistance to the disease is the most practical way to avoid losses from pecan scab, but the scab fungus can change over time to overcome host resistance. The use of chemical fungicides is another widely used method of prevention and control. However, increasing resistance of the scab fungus to fungicides, coupled with greater awareness of the environmental impact of chemicals, is prompting farmers to consider other management options.

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Black Sigatoka Ravages Caribbean

Symptoms of the devastating disease Black Sigatoka on banana leaves. Image by CIAT International Center for Tropical Agriculture (CC-BY-SA 2.0)
Symptoms of the devastating disease Black Sigatoka on banana leaves. Image by CIAT International Center for Tropical Agriculture (CC-BY-SA 2.0)

Caribbean banana farmers are abandoning fields where crops have been badly affected by Black Sigatoka disease. Black Sigatoka has badly affected several countries in the region, including Dominica, St. Lucia, Grenada and Guyana. Black Sigatoka is considered the most destructive disease of bananas and plantains and is caused by the fungus Mycosphaerella fijiensis. It first arrived in the Caribbean in 1991, and has since established and spread throughout the region.   Severely infected leaves die, significantly reducing fruit yield and causing mixed and premature ripening of banana bunches.  As part of the response to Black Sigatoka outbreaks in the Caribbean the Food and Agriculture Organisation of the United Nations (FAO) provided an intensive training programme in management of the disease in Dominica back in June this year. The workshop trained technicians from Dominica, St. Lucia, Grenada, Guyana and St. Vincent and the Grenadines. The Caribbean’s tropical climate with high rainfall and high humidity is conducive to the spread of Black Sigatoka, hence the training program focused on the management of the disease, including the strategic and careful use of fungicides in order to manage the disease while aiming to prevent fungicide resistance developing. Last year, FAO provided an expert from Cuba to assess the management efforts of each country in the Caribbean affected by the disease, and identify areas for improvement. For each country, a management and action plan was created in conjunction with the CARICOM Secretariat, the OECS Secretariat, the Caribbean Agricultural Research & Development Institute (CARDI), Inter-American Institute for Cooperation in Agriculture (IICA), CIRAD, the Ministry of Food Production in Trinidad & Tobago and the Banana Board of Jamaica.

There are factsheets available on Black Sigatoka and it’s management on the Plantwise Knowledge Bank, with factsheets in French, Spanish and English. Click here to see them. 


‘FAO supporting battle against dreaded banana disease’, Dominica News Online, June 2013

‘FAO supporting battle against Black Sigatoka’, St Lucia Mirror Online, June 2013

‘St Vincent and the Grenadines: Banana farmers ‘abandoning fields’’, BBC News, August 2013

Which is the most important plant-pathogenic fungus?

Stem rust on wheat - one of the Top 10 plant-pathogenic fungi © Yue Jin (USDA ARS)

A survey by the journal, Molecular Plant Pathology, had 495 responses from international fungal pathologists on what they thought the most scientifically and economically important fungal plant pathogens were. Several of the ‘top 10’ fungi from these results are those that infect cereal crops, which isn’t surprising as cereals such as wheat and rice are some of the most highly produced crops worldwide. Continue reading

The future might be bright, but it’s not looking so orange

Oranges – from Flickr by Rosino

I start this week’s blog with a challenge for you:

You are a smallholder farmer living in a remote village in Brazil. You have decided to grow oranges, a crop that has done well in neighbouring farms and provided a good income. It’s November and your crop is growing well, but you begin to notice symptoms of a disease on some of your oranges. You correctly identify this as black spot, and decide to look into how you’re going to treat it. You need to know:

  1. What fungicides can you use to treat ‘black spot’ in oranges?
  2. What fungicides can be legally used on citrus fruits in Brazil and in the countries that will be importing your produce, such as the US?
  3. At what levels or concentrations is the use of these fungicides acceptable in Brazil and importing countries?

You only have ten minutes before your access to the internet gets cut off, and as it is November you can only use information published before December 2011. You need to decide what fungicide to use and how much to apply.

Got your final answer?

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Bad date?

Date palm with Bayoud disease,
Image from J. Louvet,

A bad date usually involves awkward conversation or an unfortunate incident with a hot cup of coffee, but for Algerian and Moroccan farmers there is a much fruitier issue at hand. Date palms (Phoenix dactylifera) have long-suffered the effects of the Fusarium oxysporum f.sp. albedinis fungus, which causes Bayoud (or Bayoudh) disease, but a new natural fungicide could now provide the answer.

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