Soil containing nematodes threatens global food production

May 23, 2014

A Murdoch University academic has warned that all crops worldwide are facing an increasing risk of nematode damage which could lead to billions of dollars loss and an increased inability to feed our growing population.

Speaking at the International Nematology Congress in Cape Town, Chair in Biosecurity and Food Security, Professor Shashi Sharma, said that soil dwelling microscopic worms or nematodes are causing over $100 billion worth of crop losses per year.

“Soil appears to be one of the major culprits for introduction and spread of plant parasitic nematodes with inadequate attention being given to the consequences of soil dissemination,” Professor Sharma said.

“International reports indicate that dust and dirt samples taken from shipping container surfaces contain live nematodes. This is a worrying statistic when you know that small quantities of soil can slip through visual inspections as they cross borders.

“For example, even clean looking shipping container surfaces may have about 20gm of dust on them, which even if a country has restrictions on the importations of soil, is unlikely to be noticed when performing visual inspections. But when you consider that hundreds of thousands of containers could be imported, that would equate to tonnes of undetected soil potentially infested with nematodes.”

Professor Sharma pointed out that not only has the movement of goods around the world increased but people movement has increased exponentially.

“The need to prevent inadvertent nematode dispersal and spread is paramount when you consider the impact of losing a multitude of crops,” he said.

“We have seven billion people in this world yet we are able to feed only five billion.  The other two billion are either not getting enough nutritious food or are starving.

“We can’t afford to suffer food losses noting that our population will be over nine billion in less than 40 years. To feed nine billion we will need to produce more food than we did in the last 10,000 years.”

Professor Sharma said nematode quarantine and biosecurity capabilities are generally lacking in many countries particularly in the food insecure developing countries. These countries are at a high risk of incursions of plant-parasitic nematodes and consequent crop damage.

“All countries need pest risk management plans that not only contain strategies to prevent nematodes entering their borders, but plans to eradicate the nematodes that do make it through,” Professor Sharma said.

“Nematode quarantines and stringent regulatory measures play a role in preventing, containing and slowing the spread of some highly damaging nematode species but now a border approach alone is inadequate to safeguard our crops,” he said.

Professor Sharma said we must maintain world soil restrictions and stop nematode infested soil transfer where possible.

“If soil infested with nematodes is detected at a border then countries need to employ one of three strategies, export the commodity or equipment containing the soil back to the country of origin, destroy it or treat it,” he said.

“Australia has one of the best biosecurity systems in the world. Developing countries can learn from Australia’s biosecurity system.”

Professor Sharma was awarded a gold medal of appreciation for his outstanding contributions and commendable service by the President of International Federation of Nematology Societies at the meeting of the Afro-Asian Society of Nematologists at the Congress which was held in May.  He was also nominated as the Vice President of the Afro-Asian Society of Nematologists.

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Comments (2 responses)

Rodney Wells May 28, 2014

I am a student currently studying towards a Diploma in Project Management through AIPE and the Murdoch University. I found Professor Sharma's speech warning us about the potential failure of crops worldwide to be of great importance. I myself have no academic qualifications but I do have some knowledge on the life of the common earthworm and its behavioural patterns beneath the surface.

I am intrigued by the Professors findings and would like to know if this microscopic parasite still had the same crop degradation capabilities in soil enriched in castings produced by earthworm secretion. There is a well known pesticide made from soaking castings in water for a nominated amount of time. You then drain, the solution, dilute further and the mixture is sprayed upon your plants thus acting as a natural insect repellant. Whether or not this mixture would repel these nematodes is something I am unable to confirm.

This is in no way put forth as a challenge towards Professor Sharma's report, but a mere inquiry into the effect one may have on the other. I am unaware of any research which may have been conducted in this area and if so I would love to read the outcome of any reports.

The use of earthworms and their byproducts as a natural fertiliser is still a long way from becoming common practice but I believe in the potential increase of crop yields associated with the use of one of our, often overlooked and forgotten hard-working animals.

If these nematodes have the ability to ruin our crops, could the common earthworm have the ability to restructure the soil composition and repair the damage caused by the nematodes after all they both belong to the worm family!! Maybe it isn't that simple?

What the professor did fail to mention is how do we treat nematode infested soil, or are we still looking for a way to eradicate these worms other than returning the infested equipment back to its country of origin, as this would not solve anything. Again, I am not aiming this question towards the professor but merely asking out of curiosity.

I am highly fascinated in the Geology of our Earth and with each new day I learn something new. So when someone such as Professor Sharma comes along I tend to sit up and listen to what it is they have to say. I look forward to reading more reports posted by this Professor in the future as the topic here today is of great interest to me.

Shashi Sharma May 29, 2014

I thank Rodney for these thoughtful questions. My response to these questions is given here:

1. First, let me clarify that plant parasitic nematodes are known as roundworms but they are totally different from earthworms. The two belong to very different classes of invertebrate animals. To the best of my knowledge, earthworm castings are not known to cause nematode kill. In fact some reports indicate that earthworms feed on organic matter and roots, and they consume plant-parasitic nematodes in the process. The nematodes pass through the earthworm’s gut and emerge in the castings alive and active.

2.Effect of castings on nematodes: This is perhaps unexplored area of research as there are very limited reports on earthworm castings and nematode management.Plant parasitic nematodes are harmful to crop production and earthworms are beneficial. The two may have limited direct impact on each other however it is possible that any adverse impact of nematodes on plant growth may be compensated by positive impact on plant growth by earthworms.

3. Treatment of nematode infested soil: Soils can be fumigated to eradicate nematodes; however, a practical approach would be to not allow introduction of imported commodity that has contaminant soil to go to crop production regions without proper cleaning.

You may like to google search ‘Shashi Sharma+food security’ for my other reports.

You are very welcome to meet with me if required to clear any other doubts and seek additional information.

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