Stubby root nematodes are showing up all over the place. Their symptoms are tricky to identify because they mimic nutrient deficiency symptoms. However, these symptoms appear randomly around the field rather than uniformly like a true nutrient deficiency. This photo show the random pattern of stunted plants.
So the stubby root nematode actually is causing a nutrient deficiency. By feeding on the roots, the nematodes weaken the root system and decrease its ability to take up water and nutrients. Below is a photo of an infected plant and a healthy one from a field of V3 corn. you can see how stunted the one on the right is. The lower leaves are showing N deficiency as well.
The photo below shows the difference in a healthy and infected plant from a field of V7 corn. Again, the infected plant on the left is stunted and showing N deficiency in the lower leaves.
The stubby root nematode gets its name from the symptoms it causes on the roots. The photo below show the roots towards the tip are short and stubby while higher up the root looks more normal.
Stubby root nematodes are the most damaging nematodes to corn and populations can build up rapidly as the soil warms. They have a wide host range that includes other grass crops, cotton, and soybeans. Therefore, proper rotation may not be effective. Chemical control is an effective approach, but must be done preplant or at planting. Telone II can be applied preplant and Counter can be applied in furrow. Seed treatments like AVICTA and PONCHO VOTiVO can also be used. So far, Telone has shown the most consistent results in research plots.
At this point in the game, since it is too late for chemicals, good nutrient and water management is a must. Growers with the ability to irrigate should be very careful do so in a timely manner to reduce further stress. Dryland growers will be at the mercy of the weather. Fertility should be watched closely and additional nutrients may be necessary. The plants are weakened but not doomed in most cases. Under proper management, a decent yield can still be salvaged.