The Threat to Corn.

Nematodes can decrease yields by 10-75%.

Corn nematodes are plentiful, but two in particular produce the most damage to corn crops. Root lesion nematodes are the most populous plant-parasitic nematode in Midwest corn production. At least five species of lesion nematodes exist in corn. The lesion nematodes, no more than 0.75 mm in length, attack corn roots to produce severe pruning, stunting, reductions in stalk diameter and chlorosis, among other symptoms. In a one-month period, females lay up to 68 eggs in the soil and on the roots.

Needle nematodes are larger than the lesion nematode, yet their transparency makes them only visible under a microscope. Prevalent on sandy or coarse soils, needle nematodes feed on root tips, stunting lateral roots and effectively damaging the fibrous root system. Females lay an egg a day for one or two months, producing a rapidly renewing population. Swollen roots, stunted plants and small barren ears at harvest are symptoms that can produce a 10-75% decrease in yields.

The Threat to Cotton.

Common symptoms include slight to severe stunted plants with reduced yields.

Reniform nematodes are the leading cause of nematode damage to cotton crops. Within a month, eggs hatch, reach an infective stage and penetrate root systems, and female reniforms reach maturity. Most common in heavier soils, reniform nematodes can survive in any soil in the southern U.S. Sorghum and corn are common crops used in rotation in an attempt to reduce nematode populations. Common symptoms include slight to severe stunted plants with reduced yields.

Cotton crops are frequently plagued by southern root-knot nematodes. The southern root-knot nematode, given the right environmental conditions, can produce devastating yield losses to cotton crops from between 10-80%. Second-stage juveniles enter the root systems and migrate to the root cap, which is full of nutrients. Females migrate to the surface to lay 500-1500 eggs in a gelatinous mass. Common in light, sandy soils, symptoms include galling of the roots and subsequent stunting, reductions in stem diameter, root weights, as well as discoloration.

The Threat to Soybeans.

SCN cost producers nearly 100 million bushels a year.

More than 100 different species of nematodes feed on soybeans, but one clearly produces the most damage—the soybean cyst nematode (SCN). SCN cost producers nearly 100 million bushels a year. SCN reproduce at prolific rates, have long-term survival, and protect their eggs in a hardened cyst in which eggs can survive for a decade. Six generations of SCN can be produced annually. In their juvenile stage, SCNs invade root systems, seek vascular tissue, and create specialized feeding sites. Females produce egg sacs and later fill their own body cavities with eggs. Once dead, the female cavities form cysts that incubate and protect up to 400 eggs. Many hatch and renew the life cycle within a year, but more survive in the cyst for years. Yield reductions range anywhere from 15% to 30% depending on a variety of factors including soil type, temperature, moisture, nutrient levels and most importantly, crop resistance.