Soybean plants can show yellowing (chlorosis) as a symptom of various issues, including nutrient deficiencies, diseases, or pest infestations. Based on the provided reference, one significant cause for soybean plants turning yellow is infestation by the Soybean Cyst Nematode (SCN).
Yellowing as a Symptom: Soybean Cyst Nematode (SCN)
According to the reference "Soybean Cyst Nematode":
Serious infestations of soybean cyst nematodes (SCN) can cause yellowing in soybeans, often in circular patches in the infested areas (Figure 7). SCN attacks the root system, making the plant more susceptible to soil borne diseases such as SDS and BSR.
This indicates that yellowing in soybean plants, particularly in specific field patches, is a common symptom associated with serious SCN pressure.
How SCN Causes Yellowing
- SCN are microscopic worms that infect soybean roots.
- They disrupt the plant's ability to absorb water and nutrients efficiently.
- This damage to the root system leads to nutrient deficiencies, which manifest as yellowing of the leaves (chlorosis).
- The patchy, circular pattern of yellowing in fields is characteristic because nematodes spread outwards from infestation points.
Furthermore, the weakened root system makes the plant more vulnerable to other soil-borne diseases, which can exacerbate stress and yellowing.
Practical Insight
Observing yellowing in soybean fields, especially in patches, should prompt investigation for potential SCN infestation. While other factors can cause yellowing, SCN is a significant concern for soybean health and yield.
