Plant-parasitic nematodes can be a potential cause of stunted and yellowing corn plants. These nematodes are commonly found in corn fields in various regions, including Iowa. However, it's important to note that the mere presence of these nematodes does not necessarily mean they are causing damage. Careful field sampling is required to accurately assess the situation, identifying which nematode types are present and in what numbers to determine if they are indeed causing harm.
Symptoms of Nematode Damage in Corn:
Fields exhibiting symptoms like swollen roots, dead root tips, lesions on roots, stunted root and shoot growth, and yellowing foliage may be indicative of nematode damage. These symptoms should prompt further investigation.
Sampling Strategies Depending on Corn Growth Stage:
1.Sampling at V6 Growth Stage or Earlier: Gather both soil and root samples by inserting a soil probe beneath corn plants within the root zone. Collect about 20 soil cores, each around 12 inches long, from the symptomatic area. Combine these cores in a labeled plastic bag. Also, carefully collect root masses from 4 to 6 affected plants using a shovel, avoiding damage to smaller roots. Place the roots in a separate sealed bag.
2. Sampling from V6 to R3 Growth Stages: Collect soil samples as previously described, but only soil samples are needed for corn that has advanced beyond V6 but not reached the R4 (dough) stage.
3. Sampling at and After R4 Growth Stage: Beyond the R4 stage, nematode population densities are less consistently linked to yield potential, making sampling less relevant.
Where to Send Samples:
Samples for nematode analysis can be processed by various university plant disease clinics, nematode diagnostic labs, and private soil-test laboratories. The Iowa State University Plant and Insect Diagnostic Clinic offers a complete nematode count test. Follow their guidelines for sample submission, and keep in mind any associated processing fees.
Nematode Damage Thresholds:
Different nematode species have varying population densities that correlate with different risk levels for damage and yield loss. The consensus among experts is that understanding the types and numbers of nematodes present is vital for assessing the potential for yield loss. Managing Nematode Damage:
If damaging nematode populations are detected, immediate season-specific interventions are limited. However, identifying the specific nematode species and their densities helps in planning future pest management strategies. Options for managing nematode damage in subsequent corn crops include using soil-applied nematicides like Counter® 20G and seed treatments such as Avicta®, Lumialza™, Nemasect™, Trunemco™, and Votivo®.
Tips for Managing Nematode Damage to Corn:
• Have your soil tested regularly to monitor nematode populations.
• Plant resistant varieties of corn.
• Rotate corn with non-host crops.
• Use cover crops.
• Apply nematicides as needed.
By following these tips, you can help to protect your corn crop from damage by nematodes
For additional information on Nematode, please visit the following link: https://www.farms.com/field-guide/crop-diseases/root-knot-nematodes.aspx
Categories: Iowa, Crops, Corn