Soyabean is one of the major crops widely grown worldwide due its high protein content and its exceptional nutritive value to human and animal nutrition. Diseases has been identified as a major cause production shortfall every planting season.
Therefore, the following soyabean disease and the best management practises will be our main focus:
- Phytophthora Root and Stem Rot (PRRS): The causative organism is Phytophthora sojae and characterized by visible and dark brown lesions on the outer stem tissue that extends from the roots and up the lower stem. It usually occurs when soyabean is planted in a waterlogged and soil with high clay content or compacted soils.
- Stem Canker: The causative organism is Diaporthe spp. and characterized by brown to black, slightly sunken lesions which starts start from the nodes and grow completely around the stem. It occurs when there is excessive rainfall during the planting season.
- White Mold: The causative organism is Infected plants will have growth of white fluffy mould have on the stems and development of lesions on the nodes which spread up to the stems .The disease is associated with the rainy season and affects the plants at the flowering stage.
- Sudden Death Syndrome: The causative organism is Fusarium virguliforme. Symptoms noticed on affected plants are necrosis of the leaflets, leaves will be turning yellow while the veins remain green, leaflets will later curl and drop off.
- Pod and Stem Blight- The causative organisms are Diaporthe spp and Phomopsis spp when soyabean plants are maturing which results in the formation of small and black specks on the stems, petioles, pods and seeds.
- Soybean Cyst Nematode: The causative organism is Heterodera glycines and infected plants will have white cysts on the roots. Symptoms include uneven plant height, a delay in canopy closure, or early maturity and stunted growth with yellow foliage.
- Saprophytic Fungi: The infected plants infected have microsclerotia in the inner stem and root tissue. Stems will be dark and microsclerotia will be seen in the roots.
- Charcoal Rot: It is a fungal disease and infectedwill have reduced vigor, wilt and yellowish. It can infect seeds, seedlings, or mature plants. Infected seedlings may become discolored and die. Symptoms of patches are evident in the field.
Farming is a complex venture that requires proactive management to control diseases that are capable of hindering the farmers from having sustainably high yields and good quality crops. Therefore, use fungicide for seed treatment, use of resistant varieties and adoption of some proven cultural practises has been effective.
The following management practises will be helpful in controlling soyabean diseases efficiently:
- Seeding Rate
Reduction of seeding rate will reduce stress that predisposes the crops to fungal infection and the standard seeding rate should be used.
- Crop Rotation Rotation with any other crop is effective in the control of diseases. Soyabean can be rotated with maize, sorghum, millet ,wheat , experience has shown that some fungi have host preferences and this helps in breaking disease cycles.
Cultivation of resistant varieties of soyabean has been very successful especially when combined with other management practises.
Irrigated soyabean reduce damage caused by fungi and control of disease in this system is very effective in soyabean cultivation. Irrigation can reduce the damage caused by charcoal rot when soil moisture is predominantly low.