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RRDI_RiceDiseases_Diagnose_PlantSymptoms

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RICE IN SRI LANKA - Rice Diseases

Plant symptoms

Symptoms of affected plants hold the key to an accurate diagnosis of the field problem in question. Symptoms and signs of already recorded rice diseases have been very well described and recorded, and therefore, one should use such available literature in relation to the field problem in question. 

Careful examination

Plants should be carefully dug up from the field (with roots intact) and soil attached to the roots should be removed carefully in a way that will not damage root system.
Examine affected plants carefully for discolorations, abnormal growth, wilting of the leaves, injuries caused by heavy winds and insects, lesions, galls, any abnormality on the plant that may result in a disruption in the flow of water or nutrients and or any softened tissues.

Holistic approach for investigations

Yellowing, or spots/ lesions of a different colours on leaves or leaf sheaths might be an indication of a disease. Therefore, observations on the pattern, colours and sizes and the characters of the leading margin of such spots might provide clues for the diagnosis.
Browning of leaves or seedling death might be a result of root rot. Careful observations on root system might support to distinguish root rot from herbicide injury (as roots appear off-white with elongated, fibrous, lateral rootlets), which also show similar symptoms on leaves.
Nematode feeding and herbicide injury may also cause confusions and a soil analysis is required to determine the cause of a stunted or stubby root system (e.g. di nitro aniline carryover and nematode injury in corn)
Root diseases may be observed either as a brown discoloration of the root. A rotted root system may be caused directly by a root rotting pathogen or indirectly as secondary rot of dead tissue initially killed by excessive moisture or phytotoxicity effects of residual herbicides.
Therefore, in plant disease diagnosis and recognition, it is best to take a holistic approach in investigations.

Careful examination

Plants should be carefully dug up from the field (with roots intact) and soil attached to the roots should be removed carefully in a way that will not damage root system.
Examine affected plants carefully for discolorations, abnormal growth, wilting of the leaves, injuries caused by heavy winds and insects, lesions, galls, any abnormality on the plant that may result in a disruption in the flow of water or nutrients and or any softened tissues.

Holistic approach for investigations

Yellowing, or spots/ lesions of a different colours on leaves or leaf sheaths might be an indication of a disease. Therefore, observations on the pattern, colours and sizes and the characters of the leading margin of such spots might provide clues for the diagnosis.
Browning of leaves or seedling death might be a result of root rot. Careful observations on root system might support to distinguish root rot from herbicide injury (as roots appear off-white with elongated, fibrous, lateral rootlets), which also show similar symptoms on leaves.
Nematode feeding and herbicide injury may also cause confusions and a soil analysis is required to determine the cause of a stunted or stubby root system (e.g. di nitro aniline carryover and nematode injury in corn)
Root diseases may be observed either as a brown discoloration of the root. A rotted root system may be caused directly by a root rotting pathogen or indirectly as secondary rot of dead tissue initially killed by excessive moisture or phytotoxicity effects of residual herbicides.
Therefore, in plant disease diagnosis and recognition, it is best to take a holistic approach in investigations.

After all evidence are gathered,  past experience, available reliable literature, and the opinions of experts or a well experienced personal could be utilized in final identification or diagnosis.

The crop growth stage may also provide possible causes of the present problem as some pest and diseases are crop growth stage specific.