They represent four out of every five animals on earth. They comprise 90% of all life on the earth’s seafloor, but they aren’t aquatic. They’ve caused as much as $81M worth of damage annually to crops in a single state, however they are rarely more than one eighth of an inch long. But there may be billions of hungry nematodes in your field. 

Four of every five animals on earth are nematodes.

Nematodes. Small. Inconspicuous. Invisible to the naked eye, but more damaging than you can imagine. These tiny parasites can rob growers of profitable yields without growers ever even realizing it. As nematode awareness grows and more is learned about the interaction between plants and nematodes, it is obvious that crop yields are negatively affected.

Listing of nematodes by crop with photo:

Corn

  Common Name Damage Rating Soil Type Threshold*
(per 100 cc soil)
Additional Information
Needle Needle High Sandy 5 to 25 Most damaging. Prefers cool, wet conditions. Can kill corn plants. Causes stubby roots. Found near rivers and streams and continuous corn.
Root-Lesion Root-Lesion Moderate All Types 5 to 100
Pre-Plant Soil
Most significant impact in Midwest corn. Smaller root systems that are dark and discolored. Moderate stunting.
Lance
Lance Moderate Sand and Others 40 to 150 Reduces root system. Darked and discolored roots. Moderate stunting and chlorosis.
Dagger
Dagger Moderate All Types: Worse with coarse soils 40 to 150 Kills root tips. Sensitive to tillage. Severe stunging and chlorosis. Fewer fine roots remaining.
Stubby-Root
Stubby-Root High Sandy 50 to 100 Severe stunting and chlorosis. Stubby lateral roots. Excessive upper roots.
Spiral
Spiral Damage with High Populations Heavier Soils 300+ Mild stunting. Smaller-than-normal root system. Root Decay.
Root-Knot Root-Knot Damage with High Populations Sandy 100 Corn damaged by root-knot nematodes is often stunned and has the appearance of moisture and nutrient deficiencies.
Stunt Stunt Damage with High Populations Heavier Soils 150 to 300 Moderate stunting and chlorosis. Smaller-than-normal root system.

 

Soybean

  Common Name Damage Rating Soil Type Threshold*
(per 100 cc soil)
Additional Information
Cyst
Cyst High All Types 1 Cyst Consider management practices at 1 to 3 cysts per 100 cm3 of soil
Root-Knot
Root-Knot Damage with High Populations Coarse or Sandy 50 to 100
spring sampling
100 to 250
fall sampling
Nematode-induced galls are global, irregular shapped and can be easily distinguished from nitrogen-fixing nodules that are spherical in shape.
Reniform
Reniform High Loam, Sandy Loam, Clay Loam 100
spring sampling
1000
fall sampling
The most destructive nematode in the South can cause as much as 50% reduction in yield in severe cases.

 

Cotton

  Common Name Damage Rating* Soil Type* Threshold*
(per 100 cc soil)
Additional Information*
Root-Knot Root-Knot High Coarse or Sandy 50 to 500 Throughout the Cotton Belt. Root galling, stunting, wilting and premature death with Fusarium wilt pathogen interactions. Spotty within a field.
Lance Columbia Lance Moderate; Severe with Limited Geographical Distribution Sandy Loam, Sandy 250 to 500 Primarily in the coastal plains of NC, SC, and GA. Seen in LA and AL. Taproot stunting, increased secondary branching, above ground stunting and mild chlorosis.
Reniform Reniform High All Types;
worse with coarse soils
1,000 to 5,000 NC to West TX. Stunting, delayed maturity and reduced yields. Potassium difficiency in severe cases. Can interact with soil diseases such as Rhizoctonia, Pythium and Thielaviopsis.
Sting Sting High Sandy Loam, Sandy 10 to 25 Sting can be found in most southeastern states, but is restricted primarily to old river bottoms or other very sandy areas. Can be extremely damaging to cotton. Generally restricted to small areas of a field.

 

The cultural practice of planting the same crop year-after-year increases nematode populations. Some other reasons for spikes in nematode populations include:

  • The reduced use of carbamate and organophosphate insecticides, due to the introduction of insect control in or on the seed.
  • The increase in no-till and reduced tillage practices (less soil disturbance).

The genetic traits in corn do little or nothing to control nematodes and nematode resistance in soybeans is not complete. Fortunately, our tools to diagnose nematodes have improved, making it easier to identify types and levels of nematodes in a field.

Spikes in nematode populations can be traced to the reduced use of carbamate and organophosphate insecticides.

Perhaps the most troubling aspect of the nematode issue is that the symptoms of nematode attacks either can’t be seen or are often credited to other problems. Because the symptoms are common to a number of crop stresses, it is sometimes difficult to distinguish nematode damage from insect or herbicide injury, nutritional deficiencies or soil problems.

Symptoms in corn, soybeans, and cotton can include:

  • Thin stands
  • Uneven plant height
  • Stunted plants and roots
  • Leaf yellowing
  • Chlorosis or other discoloration
  • Wilting of the plant
  • Uneven tasseling
  • Cysts or galls on roots

The question should never be whether to test, but when to test.

Populations grow throughout the season. University nematologists recommend the following timing for nematode sampling:

  • Corn – 60 days post emergence
  • Soybeans – fall to planting time
  • Cotton – fall to planting time
  • Sorghum – as soon as summer crop has been harvested

Contact your local Extension agent or Crop Science representative about how to sample and analyze site locations. For more tips on nematode testing, see the Nematode Sampling Guidelines.

Nematodes are parasitic, and their life cycle is fairly common across types. Although nematodes progress through the stages of egg, juveniles, and adult, it is the juvenile stages that represent a threat. Here’s how they cause damage to your plants.

  1. Juvenile nematodes travel toward identifiable food sources – the roots and the exudates. When they encounter a root system, the juveniles of some nematodes penetrate the root and move into the cell in search of nutrients.
  2. In some species of nematodes, females swell so large they break through the root surface and become visible to the naked eye. Impregnated by male nematodes, they fill with eggs and eventually die, their body cavities forming cysts that incubate hundreds of nematode eggs.
  3. Other nematodes feed from outside the root surface using needle-like structures, or stylets, to pierce the root, creating an opening that allows them to remove nutrients. Most nematode species complete several life cycles during a plant’s life, while a few species take a year to finish the cycle.

Because VOTiVO is living bacteria, it protects against the multiple life cycles of nematodes.

Some nematode species can produce six generations in a single year.


Some nematode species produce 6 generations in a year
*Image from Iowa State University

While nematodes may be too small to see, they’re causing problems too large to ignore. Many nematode species are known to focus their attention on three of the leading agricultural crops—corn, cotton and soybeans. Losses are staggering. The Society of Nematologists estimates that plant parasitic nematodes cause more than $3 billion worth of crop losses annually.

  • Nematodes cost soybean growers over $1.5 billion annually.
  • It is estimated that soybean growers lose 1 to 2.5 bushels per acre for every 1,000 Soybean Cyst Nematode (SCN) eggs at planting. See the Nematode Sampling Guidelines for help determining SCN presence in your fields.
  • Reniform nematodes are the most destructive type in the south in cotton and can cause yield losses of upward of 50% in severe cases, and currently account for $130M in annual losses to the U.S. cotton industry.
  • Columbia lance nematodes commonly generate losses from 10% to 25% per field in cotton and soybeans, but can exceed 50% in sandier fields under drought stress.
  • Needle nematodes—among the most decimating to corn yields—consistently produce between 10 and 75% reduction in grain yields.
  • Root-knot nematodes can cause losses in many crops, including corn, soybean, and cotton.

Plant parasitic nematodes cause more than $3 billion worth of crop losses annually.

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