The radish has yellow leaves: why do radish leaves turn yellow?

Radishes are vegetables grown for their edible underground root. However, we should not forget the part of the plant that is on the surface. This part of the radish produces food for growth and also stores additional nutrients needed for the growing phase. It is therefore not surprising that the leaves of the yellow radish are a sign of a radish growth problem. Why do radish leaves turn yellow and how can a radish plant with yellow leaves be treated? Read on.

Why do radish leaves turn yellow?

Radish growth problems can result from anything: overcrowding, lack of adequate sunlight, competing weeds, lack of water, nutrient deficiencies, pests and diseases. Yellowing radish leaves can also be the result of any of the above factors.
There are a number of diseases that cause leaves to yellow as a minimum sign of infection. This can include Septoria leaf spot, which is a fungal disease. The diseased foliage appears as yellow spots on radish leaves that almost look like water spots with a gray center. Avoid Septoria leaf spot by modifying it with organic materials and planting it in a well-drained area of the garden. Also practice crop rotation. To control the disease when plants are already affected, remove and destroy infected leaves and plants and keep the garden free of debris.
Blackleg is another fungal disease. This infection occurs when radish leaves turn yellow between the veins. The edges of the leaves turn brown and curl, while the stem turns dark brown to black and gooey. The roots also become slimy and black-brown towards the end of the stem. Before planting, the soil should be amended with a lot of organic matter and make sure that the site has good drainage and practice crop rotation.
If your radish plants wilt and appear weak with yellow leaves combined with oval and red spots at the base of the stem and roots with red stripes, you probably have a case of Rhizoctonia or Fusarium root (stem rot). This fungal disease develops in warm soils. Rotate crops and plants to avoid the disease. Remove infected plants and waste. Solarize the soil in late spring or summer to kill winter spores.
Stick root is another fungal disease ( Plasmodiophora brassicae ) which not only causes yellowing of the leaves but also swelling of the roots with tumor-like gills. This disease is common in moist, low pH soils. The microorganism can live in the soil for 18 years or more after an infected crop! It is spread by soil movement, water and wind. Practice long-term crop rotation and remove and destroy all crop debris and weeds.
Common in cool weather, mildew causes angular yellow spots on the leaves that eventually turn cinnamon, areas of paper texture surrounded by a yellow border. A diffuse gray to white mold develops on the underside of the leaves and brown to black sunken areas appear at the root with a rough, cracked exterior.
Black rot is another disease of radish that causes yellowing of the leaves. In this case, the yellow areas are distinctive V-shaped lesions on the edges of the leaves, with the tip of the «V» following a vein towards the base of the leaf. The leaves wilt, turn yellow and rapidly turn brown and die as the disease progresses. The veins become black throughout the plant from the leaves, stems and petioles. Warm and humid conditions favour black rot, which can be confused with Yellow Fusarium. Unlike Fusarium, black rot diseased foliage coincides with bacterial silt.

Additional reasons why a radish plant has yellow leaves

The yellow leaves of radishes can also be due to insect infestation. A virus called Aster Yellow is a mycoplasma disease that is spread by grasshoppers, which act as a vector. To control Aster Yellow, the grasshopper population must be controlled. Remove infected plants and keep the weeds in the garden free of the disease as they harbour the disease, thus protecting the grasshoppers.
Brilliantly marked harlequins suck fluids from plant tissues, resulting in wilted plants with deformed leaves splashed with whitish or yellow spots. Pick these insects by hand and destroy their egg masses. Keep the garden free of weeds and plant debris that harbour insects and their eggs.
Finally, yellowing of radish leaves can also be the result of nitrogen deficiency. This is quite rare, as radishes are not heavy, but if necessary, feeding the plant with a high nitrogen fertilizer will restore its bright green colour.
Start your radishes correctly and you can avoid many of these problems with radishes. Plant in a place with at least six hours of sunshine per day. Prepare the area by raking to keep it free of weeds and debris. Work with lots of compost or old manure and gently rake the area. Then sow the seeds in furrows spaced one inch apart and ½ deep with the seeds spaced one inch apart.
Cover lightly with soil and water until moist. Keep the bed moist, not soggy, constantly. Thin out the radishes, leaving 2 to 3 cm between plants. Keep the bed free of weeds. Pick one or two radishes from time to time as they grow to check for insects below the surface. Discard any infected plants immediately.