One nematode research is not the other

A lot of nematodes can occur in soil, some of which can cause major yield losses. There are several surveys that can detect the presence of nematodes. Although they are all marketed under the heading “nematode research”, one nematode research is not the other. Nematode expert Leon Swinkels explains how best to avoid risks to your crops.

"Good nematode testing starts with professional sampling. This is always step 1 in good nematode research," says Leon Swinkels. Although any farmer can take samples from his plot himself, the nematode expert recommends using an experienced, trained sampler. "There is more to it than you think,"he says.

Method of sampling

Soil survey forms the basis for determination at a later stage. "This has to be done accurately. Starting with spotless material to avoid cross-contamination with nematodes from another plot. Furthermore, the maxim is a maximum of 2 hectares per sample and a minimum of 60 stitches per sample bag." Harmful nematodes are not only in the soil, but also in the roots of crops. Stabbing deep enough, therefore, is a must. ‘A professional sampler takes samples to a depth of at least 25 to 30 centimetres,’ he says.

Incubation time

Step 2 constitutes the incubation of the soil sample. Nematodes still in root residues and eggs in the soil (and in the roots) also come into view this way. "With harmful nematodes (especially Meloidogyne and Pratylenchus), it is very important to have a complete picture of the numbers present. For this reason, organic material from a soil sample should always be incubated for at least two and sometimes up to four weeks. If this does not happen, you immediately run the risk of an incomplete analysis."

DNA or microscope

At step 3, Swinkels distinguishes two types of nematode testing: DNA testing and microscopic determination. ‘Microscopic nematode testing is the most accurate,’ states the nematode expert. He explains.

"There is no DNA test available for every nematode. Molecular analysis (DNA) can analyse about 25 nematode species. DNA analysis does not always show low numbers of harmful nematodes. It is also difficult to use DNA analysis to correctly estimate the actual number of nematodes in a sample. You thus run the risk of overlooking the presence of a harmful nematode. The consequences can be disastrous. Especially if crops turn out to be affected by the harmful nematode, but are not treated as such."

Microscopically, each nematode is imaged, counted and identified. "This step has to be done in duplicate and sometimes even three counts are made. A labour-intensive process that only a professional laboratory can perform, but necessary if you really want certainty about the species of nematode in your soil."

100% certainty

According to Swinkels, the fact that microscopic testing gives 100% certainty is also evidenced by feedback from the field. You cannot have better control than the experiences of cultivation supervisors, growers and samplers who are among the crops every day. Swinkels: "Microscopic research is -other than DNA research- not standardised and is done manually. As a result, all nematodes from a sample are analysed in image. The quality is therefore guaranteed."

Price comparison

The prices of microscopic and DNA testing are almost comparable. However, the nematode tests are so different in approach and accuracy that Swinkels calls a price comparison of the two “comparing apples and oranges”. "Just picture the damage cost of a crop or cultivation failure due to harmful nematodes. I think it will then quickly become clear why most farmers opt for 100% certainty of microscopic testing."

Our specialists will help you

Need support in carrying out nematode testing? Our specialists will be happy to support you in this regard. They will help you protect crops. Read more on our nematode testing page or get in touch.

Author: Normec Foodcare Knowledge partner in food safety, product quality and taste