Plant-parasitic nematodes have been negatively impacting our corn and soybean crops for many years; however, most growers are not aware of the problem because it is very easy to misdiagnose nematode injury due to similar above-ground symptomology such as general yellowing or stunting caused by other stressors. For this reason, it is critical to have a solid understanding of nematode biology and management strategies so practices can be put into place to take back the yield nematodes may be stealing from our fields.
The life cycle of nematodes can be separated into three main stages: egg, juvenile and adult. It is during the second juvenile stage (out of four) that juveniles begin feeding on plant roots, and this feeding continues through the adult stages. Timing of reproduction differs greatly among species, but many life cycles are completed within three to four weeks, allowing for several generations to occur per year. This can lead to season-long feeding on plant roots.
The most common symptoms that can be seen above ground include generalized yellowing, stunting and wilting of plant tissue; however, above-ground symptoms tend to only occur when nematode pressure is high. These general symptoms can easily be confused with drought and other stresses; therefore, it is important to look below ground for symptoms. Below-ground symptoms include lack of fine roots, swollen roots, necrotic lesions and minimal root branching. In the case of soybean cyst nematode (SCN), swollen cream-and yellow-colored female cysts can be seen on the roots with the naked eye. Rarely is nematode damage uniform across a field, so look for sporadic symptomology.
Fertilize - Plants without adequate nutrients are more susceptible to nematode injury.
Control weeds - Actively managing weeds can help reduce nematode populations because many weeds act as a host for nematodes.
Crop rotation - Rotating to a non-host crop can keep certain nematode populations in check. Genetic tolerance - Many soybean products have SCN tolerance built in, but this tolerance has been losing efficacy in recent years.
Chemical control - Nematicides, such as products with NemaStrike™ Technology, have shown extremely high efficacy across a range of nematode pressure.