Radishes (Raphanus sativus) are a cool weather crop that are rapid growers, easily sown for successive crops every ten days. Because it is easy to grow (and delicious), radish is a common choice for the home gardener. Even so, it has its share of radish growing problems and radish diseases. What types of radish disease problems are there and how can they be treated? Keep reading to learn more.
Diseases of Radishes
Radish is a member of the family Brassicaceae, and is grown for its slightly spicy, crunchy taproot. This herbaceous annual or biennial should be grown in full sun in loose, compost amended, well-draining soil. Seeds can be sown as early as 5 weeks prior to the last average frost date for your region and then for a continual supply, sown every 10 days. Quit sowing when temps reach over 80 degrees F. (26 C.). Keep the plants consistently moist. Harvest the radishes when they are under an inch (2.5 cm.) across by lifting them out gently. Seems fairly straightforward, and it usually is, but even the undemanding radish can fall victim to radish disease problems. While the majority of radish growing problems are primarily fungal, here are the most common issues you may come across.
- Damping off – Damping off (wirestem) is a common fungus found in the soil in areas of high humidity. Radishes are prone to seed rot or the collapse of seedlings when afflicted with damping off. Don’t plant seeds in cold, moist soil, and be sure the soil is well-draining.
- Septoria leaf spot – Septoria leaf spot is a fungal disease that often affects tomatoes but can afflict radishes too. This radish disease is appears as pale yellow, gray spots on foliage that look like water spots. The spots get a gray center and become more circular as the disease progresses. Again, make sure the radish area has well-draining soil. Remove and destroy and infected parts or plants, rotate crops and keep the garden free of other plant debris.
- Fusarium rot and Downy mildew – Fusarium rot and wilt is a fungal disease that thrives in warm soil. Downy mildew is also a disease of radishes caused by a fungus. Keep the garden free of detritus, destroy infected plants, avoid overhead watering and improve upon air circulation and practice crop rotation.
- Black root – Black root is another possible radish growing problem. This fungal disease causes yellowing of leaves with brown, curled leaf margins. The stem’s base darkens to a dark brown/black color and becomes slimy, along with black, slimy roots. Be sure to amend the bedding area with plenty of organic matter to improve drainage and practice crop rotation.
- Alternaria blight – Alternaria blight causes dark yellow to black spots with concentric rings on foliage. The center of the ring often dries out and drops, leaving the leaves with a shot-hole appearance. Complete leaf drop may occur. Be sure to buy plant certified, disease-free seed. Rotate crops. Irrigate in the morning to allow the foliage to dry and apply fungicide.
- White rust – White rust appears as white pustules on foliage and flowers. The leaves may curl and thicken. This particular fungal disease thrives in dry conditions and is spread by the wind. Rotate crops and plant disease free seed. Use a fungicide if the disease progresses.
- Clubroot – Clubroot is another fungal disease that mimics damage done by nematodes. It leaves stunted plants with yellow leaves that wilt during the day. Roots become distorted and swollen with galls. This pathogen can survive for many years in the soil. The addition of lime in the soil may reduce fungal spores but, in general, this disease is difficult to control.
- Scab – Scab is a disease that is also found in potatoes, turnips and rutabagas that causes brownish-yellow lesions on roots and irregular blotching on foliage. This bacterial disease is difficult to control since it remains in the soil for lengthy periods. Don’t plant the area for four years.
Some insects act as vectors to disease. Leafhoppers are one such insect. They spread Aster Yellows, a mycoplasma disease, which as its name suggests, causes leaves to yellow and curl and stunts plant growth. Destroy infected plants. Control leafhoppers and keep the garden free of weeds and plant detritus. Aphids also act as vectors spreading leafroll virus. Treat the same as for Aster Yellows. Lastly, to avoid the incidence of fungal disease, harvest the radishes before they reach maximum size. They taste better and you can avoid potential cracking, which can open a window to fungal disease.
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FAQs
Black root rot, Aphanomyces raphani. Radish roots infected with this fungus disease show sunken dark streaks and blotches. As the disease progresses, the blotches may develop into a dry rot which tends to distort the shape of the growing root. The fungus lives in the soil.
What's wrong with my radish? ›
Problem: Cracked Radishes
cracking Cracking is often the result of uneven watering. Trying to make up for a period of drought with a lot of water all at once will cause the radish to grow too rapidly on the inside and split open. Make sure your radishes are consistently getting at least 1 inch of water per week.
What is the secret to growing radishes? ›
Plant 2-3 weeks before the last frost in spring and again in early September for fall production. Radishes taste best when grown in cool weather. Avoid water or fertilizer stress during growth. Irrigation should be frequent and uniform to ensure good growth.
Why are my radishes hard and woody? ›
Drought stress can cause the roots to develop poor flavor and a tough texture. If the planting does not get one inch of rain each week, soak the soil thoroughly at least once a week.
What are the symptoms of Fusarium wilt of radishes? ›
Damage symptoms
Fusarium oxysporum is the species causing vascular wilt. First the leaves turn yellow and wilt, mostly on one side of the plant. Finally, the whole plant wilts. Other symptoms are brown discolouration of the xylem vessels which can be seen when the stems are cut.
What are the symptoms of radish virus? ›
Main affected crops are different cruciferous plants such as rape, mustards, cabbage, arugula (Eruca sativa), and false flax or gold-of-pleasure (Camelina sativa). Symptoms include mosaic, ringspots, leaf distortion, veinal necrosis and systemic necrosis.
How do you bring radishes back to life? ›
To revive root vegetables such as beets, carrots, potatoes, and radishes, or limp celery, asparagus or broccoli, simply trim the ends and soak the veggies in a glass bowl or mason jar of ice cold water for a few hours or overnight and the veggies will rehydrate and be crisp again.
What fertilizer is good for radishes? ›
Some common mixed fertilizers are 5-10-5, 5-10-10, 8-16-16, and 12-12-12. Apply these fertilizers at rates of 1 - 2 pounds per 100 feet of row. After plants are 3 to 4 inches tall, sidedress nitrogen in narrow bands or furrows and water thoroughly after application, or apply through the drip system.
What are the symptoms of boron deficiency in radish? ›
The leaves of boron deficient radishes are deformed, brittle, and chlorotic. In cases of severe boron deficiency, the leaf tip dies. The roots crack and are pale in color. The water-soaked flesh may show brown flecks.
What not to plant with radishes? ›
They could have a difficult time germinating and growing near other brassicas, so avoid planting radishes near broccoli, cabbage, cauliflower, turnip, and mustard. Avoid hyssop, a flowering plant that attracts many pollinators and beneficial insects, as it inhibits the growth of radishes.
The fast growth of radishes comes with conditions, including an uncompromising need for space. Seedlings that grow too close together will not plump up, so you must either sow the seeds at uniform spacing or thin them soon after they sprout.
Why is it so hard to grow radishes? ›
In new beds, it is often because you didn't loosen soil deeply enough. As a root crop, radishes depend upon loose soil to expand and develop thick roots into bulbs. Excess nitrogen in soil and neutral acidity will also slow the forming of radishes. A common cause of radishes not growing bulbs is overcrowding.
Is Epsom salt good for radishes? ›
When planting root crops like radishes, turnips and onions, sprinkle Epsom salts over the area to be planted, and you won't be bothered with bugs, says Wallace Shelby. Don't make these 5 common mistakes in the vegetable garden.
What is radish disease? ›
Root Rot of Radish(Erwinia rhapontici)
It is a bacterial disease, which spreads through implements and irrigation water. Symptoms appear as rotting of pith tissues resulting in cavity formation and wilting of plants. The disease spreads when the roots are transplanted for seed production.
When should radishes be thinned? ›
To give French Breakfast Radishes enough room to grow, they require 'thinning' 10 days after planting when the seedlings are about an inch tall. These seedlings can be eaten, or planted in another area of fresh soil.
What are the post harvest diseases of radish? ›
Bacterial Black Spot.
(Xanthom*onas campestris pv. vesicatoria) is a problem in some production locations and will develop in postharvest storage at warmer than optimum temperatures. Refrigeration is the primary control but washing roots in chlorinated water is reported to significantly control this disease.
What attacks radishes? ›
A fairly wide range of soil-dwelling insect larvae can cause damage to the below-ground portion of radishes. The primary villain is the root maggot, the larva of a small fly. To prevent root maggots, use Lightweight Floating Row Cover, to prevent the adult from laying eggs on the newly seeded bed.
