Soybean Cyst Nematode Symptoms Starting!

These microscopic, worm-like nematodes damage the root system and prevent the uptake of water and nutrients. In many cases, SCN symptoms may not be obvious in a field until populations build significantly. At this point, typical above-ground SCN symptoms include yellowing of the leaves, stunting of plants and early maturity, particularly on lighter soils under dry conditions or stressed areas in the field. Damage often occurs in circles and is often confused or misdiagnosed as nutrient deficiency, flooding, herbicide injury, compaction, drought or root rot damage. Yellowing of the leaf margins can resemble potassium deficiency symptoms. However, the addition of potassium will not reduce the damage from SCN or eliminate symptoms.

Never pull up a plant to check for SCN since too much root will be lost, and the nematodes will be stripped off. Instead, use a shovel and dig up the plant along with the soil surrounding the roots.

Below-ground SCN symptoms include dwarfed, stunted and discoloured roots (due to root rot pathogens) with few nitrogen-fixing nodules. However, the most obvious sign of SCN infection is the presence of the adult female "cysts" on the roots - white to yellow-brown cysts less than 1 mm in diameter (size the period at the end of this sentence).

As mentioned nematode injury symptoms (including plant death) are most obvious under stressed growing conditions, especially hot, dry environments. Under good growing conditions, the visual damage from soybean cyst nematode may go unnoticed. In contrast under high-stress conditions, even low SCN numbers cause considerable visual damage and high yield loss. SCN infection symptoms may not be obvious and yield reductions of 25%-30% on susceptible fields can occur without visual (above-ground) symptoms. Areas of the field where above-ground SCN symptoms will most often occur include entrance points for equipment into the field, equipment and vehicle storage areas, tops of knolls, compacted headlands and along the fencerow where wind-blown soil tends to accumulate.