AG ON CAMPUS 2016
A monthly supplement to The Delmarva Farmer
VT scientists study Cambodian soils, nematodes
BLACKSBURG, Va — A Virginia Tech researcher working in Cambodia this summer links the presence of sterile soils in one part of the country and the presence of nematodes in another to atrocities committed by a dictatorial government decades ago.
Jon Eisenback, professor of plant nematology in Virginia Tech’s College of Agriculture and Life Sciences, and postdoctoral associate Paulo Vieira, were in the Southeast Asian country to study farms in both the north and south.
The nation of approximately 15 million people is a fourth the size of the Texas.
In the north they found sterile soils in the fields of cucumbers, sweet melons, eggplants, tomatoes and cantaloupes.
There was no life, including nematodes, in these sterile soils. They blamed this on over-use of pesticides.
In an interview in his Virginia Tech office here Oct. 6, Eisenback explained what nematodes, the animals he studies, are and reviewed the history of Cambodia that has left the land without the educators and researchers it needs to help its farmers.
“Nematodes are microscopic worms that cause plant disease,” is Eisenback’s simple explanation of the animals he finds fascinating and beautiful.
He held up pictures of nematodes enlarged to an 8-by-10-inch page to show some of the many different ones.
He said 80 percent of animals or four out of five alive right now are nematodes.
The percentage rises to 90 percent for animals in the ocean, he continued.
He said farms people in Virginia have nematodes as well but they have help. It can be found by contacting a local Virginia Cooperative Extension agent.
Nematode assays are is also available to farmers in Maryland, Delaware and Pennsylvania at a cost of $25 each.
These resources are not available in Cambodia where a large portion of the population is involved in very unsophisticated farming.
They have a severe lack of researchers.
Eisenback pointed out that this lack goes back to the 1970s when the Communist Khmer Rouge regime under the dictator Pol Pot brutally killed approximately one out of every four people in the nation, including most teachers and the educated.
Estimates of the death toll range from 2 to 2.5 million people.
At least 20,000 graves sites, many of them mass graves, have been researched through the years.
Eisenback said the mostly microscopic worms are non-segmented, unlike other worms such as the earthworms which are segmented. It Nematodes can occur on all plants.
A sign of a nematode infestation is plants not performing as they should.
They do occur mostly are most important in monocultures where one kind of plant is dominant and suggested diversification of plants can help reduce the nematodes.
Rice, the main crop in Cambodia, has been thought to be free of nematodes according to the International Rice Institute, he reported.
However, he and Vieira found the rice fields they surveyed showed a significant loss of production caused by the rice root nematode.
He estimated they are cause a loss of 20 to 30 percent of the crop where they occur.
He noted that even in Virginia, nematodes can cause losses of 5, 10 or even 20 percent of a crop.
“Every root we looked at had lesions,” Eisenback said in a Virginia Tech news release. “Rice roots should be creamy white.
“These were speckled with brown and orange lesions.”
He identified this parasitic nematode as Hirschmanniella muscronata.
Eisenback found his research limited by the lack of resources that the Cambodians experience all the time.
He said they had no microscopes for studying nematodes so they had to be innovative in using the insect microscopes that were available.
He noted that they visited a limited number of farms, most of them considered progressive.
Also they had to study the soil in Cambodia and could not bring it back to Tech labs because that is illegal. Soils from there are quarantined.
The vegetables in the North are grown in soils covered with plastic mulch and drip irrigation is used to water them, Eisenback reported.
He said the farmers use pesticides to control insects and the thinking seems to be if a little is good more is better.
When the researchers looked at samples of those soils that could be expected to hold thousands of nematodes they found nothing.
This led to their recommendations for use of less pesticide to help the soils, make farming less expensive and to make the food safer for human consumption.
Eisenback believed that Integrated Pest Management practices are needed in the country to bring about these results.
Lack of researchers to develop these and find answers is a problem, he indicated.
He said there is one person in the country with a master’s degree in nematology who earned his degree in Belgium and returned to Cambodia where he is doing research with insects due to the lack of resources to study nematodes.
Eisenback and Vieira worked with the Royal Agricultural University in Phnom Pinh.
Their work is made possible by the United States Agency for International Development, a group devoted to providing economic, development and humanitarian assistance around the world in support of the foreign policy goals of the United states as well as improving the lives of people; an IPM Grant to help several countries including Nepal and Bangladesh as well as Cambodia; and the government of Cambodia among others.
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