Warming Climate Marches Pests and Pathogens Polewards

Locust Swarm © Wild Center
Locust Swarm © Wild Center

The distribution of plant pests and pathogens has been observed to be moving away from the equator towards the North and South poles and inhabit areas previously too cold for their existence. This threatens to increase the percentage of crops lost annually to pests and pathogens and subsequently raises major concerns over global food security.

A new study published in Nature Climate Change revealed distributions of plant pests and pathogens are advancing polewards at an average rate of 2.7 km (1.7 miles) per year. The current shift in the range of plant pests and pathogens will increase the percentage of crops lost every year. This is expected to increase as temperatures continue to rise. Dr Dan Bebber and his co-authors from the University of Exeter warned that “If crop pests continue to march polewards as the Earth warms the combined effects of a growing world population and the increased loss of crops to pests will pose a serious threat to global food security”.

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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

Animal and Human Pathogens Can Cross from Manure into Food Crops

Following the recent outbreak of E. coli food poisoning in Germany that claimed at least 39 lives as of 16 June 2011 and still counting, numerous articles have been written, but many fundamental questions still remain unanswered.

As you will remember, contaminated Spanish cucumbers were initially blamed for the outbreak of E. coli infection, which prompted the Spanish government and farmers to vehemently deny this claim (justifiably, as it turned out) and demand compensation.

As soon as “the Spanish cucumber story” was shown to be a false alarm, tomatoes, salad and vegetable sprouts (grown in Germany) were declared as potential culprits. It is unclear why other vegetables, such as peppers and courgettes to list but a few, or even mushrooms, were kept off the list of suspects. However, last week, German investigators finally said that they had determined that vegetable sprouts from a farm in the north of the country were the source of the E. coli. However, identifying the pathway of contamination is still proving difficult.

While looking for potential sources of vegetable contamination with pathogenic microorganisms, I searched CAB Direct database and came across a very interesting review published 20 years ago by German Professor Strauch of the Institute of Animal Medicine and Hygiene, University of Hohenheim, which explains how pathogens may contaminate food crops. He warned about the potential of pathogenic organisms to cross from manure or sewage into food crops and suggested that “the agricultural utilization of hygienically dubious sewage or sludge poses a risk for the whole national economy.”

In his 1991 review “Survival of pathogenic microorganisms and parasites in excreta, manure and sewage sludge” (Rev Sci Tech. 1991 Sep;10(3):813-46), Strauch also reported that two groups of researchers had found that pathogenic organisms can be taken up by crops that are used in human and animal nutrition.

Once pathogenic microorganisms are incorporated into crops (including vegetables), washing the outside of fresh vegetables is of little benefit, because all the pathogens from the sludge (bacteria, viruses and parasites) are inside the plant. Therefore, such crops would be unfit for human or animal consumption.