Citrus greening threatens Floridian groves

Symptoms of citrus greening on citrus leaf
Symptoms of citrus greening on citrus leaf © CABI

Mabel Smith is an Oxfordshire school student, studying both the arts and the sciences. She is interning at CABI for Plantwise and the marketing department.

The disease, citrus greening, which is also known as huanglongbing and caused by the fastidious bacteria Candidatus Liberibacter, continues to cause problems for Floridian growers this week. The psyllids that spread this pathogen are now running rampage throughout more than half of Florida’s citrus producing counties, causing an expected 20% decline in  harvest. Over the last 20 years around 60 million citrus trees have been abandoned across half a million acres of land due to this rapidly spreading and, so far, incurable disease. Citrus greening has already caused irreversible damage in Asia and South America and many growers in Florida are giving up on the citrus market altogether to turn to more reliable alternatives like peach growing. Despite this, many growers are still optimistic and millions of dollars are currently being invested in further agricultural research into a cure.

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Yellow Rust Adds to Famine Worries


In terms of food security the big story recently is that two regions of southern Somalia are in the midst of a famine. More than 10 million people are currently at risk of starvation with 1.8 million people displaced in East Africa’s worst drought for 60 years. Ethiopia and Kenya are neighbouring food insecure populations according to the UN food security classification.

However East Africa may soon experience more food shortages in the future due to yellow rust. Yellow rust (Puccinia striiformis) is a fungal disease which reduces wheat yields and can be found in many countries (Where is yellow rust found?). It causes the formation of necrotic areas and yellow pustules which together form stripes on the leaves. In the past it has not been found to destroy entire crops and was managed by the introduction of yellow rust resistant varieties in the 1970s. Recently a more aggressive strain of yellow rust has appeared and has already affected parts of Europe, Australia and the US. It is able to generate more spores than previous strains and spread more rapidly.

The international community had largely ignored this new strain in its fight against another wheat disease. Ug99 is a strain of stem rust (Puccinia graminis) which was first detected in 1998 and is traditionally regarded as more of a threat than yellow rust in the areas that it exists in (Where is stem rust found?). However this new strain of yellow rust is now considered more of a threat to wheat yields.

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