Since first identified in Ontario in 1988, soybean cyst nematode (SCN) has been detected in a number of counties in southwestern Ontario. SCN continues to move across the province into previously non-infested counties. In 2001, a nematode survey was initiated in eastern Ontario as a cooperative project between county Soil and Crop Improvement associations, Ag Retailers, Agriculture and Agri-Food Canada and OMAF. Approximately two hundred soil samples were collected for analysis. Fortunately, at this point analysis results have proven negative for soybean cyst nematode adults, juveniles, cysts and eggs.
The microscopic, worm-like nematodes damage the root system of soybeans and prevent the uptake of water and nutrients. Typical SCN symptoms include yellowing of the leaves and stunting of plants, particularly on lighter soils under dry conditions. Yellowing of the leaf margins can resemble potassium deficiency symptoms. In the field, damage occurs in a circular pattern ranging from a few metres to over 50 m in diameter.
The disease can be managed effectively, but the key strategy is early detection and awareness. SCN infection symptoms may not be obvious yet yield reductions of 25% to 30% on susceptible fields can occur without visual (above-ground) symptoms. Above-ground SCN symptoms will most often occur at the entrance points for equipment into the field, in equipment and vehicle storage areas, on knolls, in compacted headlands and along the fencerow where wind-blown soil tends to accumulate. When looking for SCN on soybean plants, never try to pull up a plant. Too much root material will be lost and the tiny white nematode cysts will be stripped off as the roots are pulled through the soil. Instead, use a shovel and dig up the plant along with the soil surrounding the roots.
SCN is usually introduced in a field through the movement of contaminated soil. Once a field has SCN, eradication is impossible. To reduce the likelihood of introducing the disease on your farm:
– plant certified or good-quality, clean seed that is free of soil peds
– try to avoid bringing farm equipment from infested areas onto your farm, including used equipment from parts of Ontario where SCN is present
– if farm equipment from infested areas is to be brought onto your farm, ensure that it has been thoroughly wash prior to arrival since nematode eggs can remain viable in the soil for a number of years
Fields showing typical SCN symptoms should be soil sampled and the sample analyzed for both an egg count and a total cyst count.
From the Archives:
OMAF Update 1, May 2004
