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Carrot Diseases and Pests, Symptoms, Control Methods

Carrot Diseases and Pests, Symptoms, Control Methods

Introduction to Carrot Diseases and Pests:

Today let us go through the common Carrot Diseases and Pests and thier Symptoms as well control methods

Diseases in Carrots:

Alternaria leaf blight: the infected leaves have green-brown water-soaked lesions which enlarge and turn dark brown or black; infected leaves will turn yellow and die. Wet foliage, rain, fog and warm weather will encourage the development of disease.


  • Wet, warm conditions will keep plants away from diseases.
  • Apply organic fungicides when the first symptoms appear.
  • Treat seeds with organic fungicide or hot water before sowing.
  • Application of gibberellic acid will prevent diseases and promote air circulation.

Black rot:

The disease causes damping-off of seedlings; necrosis in root and crown; foliage blights; this disease will turn lower portion of petioles black; you can observe black ring around petiole and sunken lesions on the taproot. This Disease is spread through infected seed.


  • Black rot is very tough to control and survive in the soil for the long term.
  • Implement long crop rotations.
  • Plow crop residue after every harvest.
  • Use plant resistant varieties.
  • Treat the seeds with hot water before sowing.

Cercospora leaf blight:

The main symptoms of the diseases are small, necrotic flecks on leaves later turn to chlorotic halo and expand into tan brown spots. The lesions cause leaves to wither, curl and die. Infected seed can be  a root cause of the diseases and it is spread through wind or water splashes. Young seedlings or foliage is mainly affected with this disease.

Read: Frequently Asked Questions About Plant Diseases.


  • Used only pathogen-free seed.
  • Implement crop rotation.
  • Plow the crop after every harvest.
  • Use organic fungicide sprays.

Cottony rot:

Small, water-soaked, soft lesions on the crown and roots are the main symptoms of this disease. You can observe white fluffy fungal growth in affected tissues. This fungus can survive up to 10 years.


  • There are seed varieties that are resistant to this disease.
  • Using drip irrigation is a good control.
  • Deep plowing of soil and trimming back foliage to promote air circulation, which can control disease to some extent.

Downy mildew:

The main symptoms of the disease are yellow spots on the upper surface of leaves, white fluffy growth on underside of leaves. You can also observe lesions which turn darker when they mature. This disease mainly affects the young and tender leaves. Foliage wetness will encourage the growth the development of disease.


  • Use pathogen-free seed.
  • Maintain spacing and avoid crowding.
  • Implement plant rotate with non-umbelliferous varieties.

Powdery mildew:

You can observe powdery growth on leaves, petioles flowers stalks and bracts. The infected leaves arechlorophylldeficient and severe infections will make the flowers distorted. This disease is spread mainly through the winds. High humidity and moderate temperature will encourage growth of fungus. This infection more in shade areas.


  • Plant disease tolerant varieties.
  • Avoid excess fertilization.
  • Use protective organic fungicides.
  • Application of sulfur in the early season can control disease to some extent.

Bacterial leaf blight:

The symptoms are small, angular, yellow spots on leaves which turns into irregularly shaped, brown, water-soaked lesions with a yellow halo. The centers of lesions will become and brittle. The infected leaves will become curled, the infected flower stalks have lesions with bacterial ooze. Water splashes and poor sanitation are root causes of this disease.


  • Use pathogen-free seed.
  • Avoid using sprinkler irrigation.
  • Use bactericides if necessary.

Soft rot: The main symptoms of the disease are sunken dull orange lesions on taproot. Bacteria will deplete plant tissue. Water saturated soil will increase disease emergence. This bacterium enters into the plant through wounded roots.


  • Use only well-drained soils to plant carrots.
  • Make soil completely dry before every irrigating.
  • Skip the wounding plants during harvest to control the post-harvest development of disease.
  • Good sanitation.

Cavity spot:

The main symptoms of the diseases are sunken, elliptical, gray lesions across the root. The outer layer of the root will turn dark with elongated lesions. The cavities will have small vertical cracks. This fungus sustains for many years in the soil. Wet and soggy soil will increase the chances of the disease.


Avoid the fields that suffered with the carrot spot disease in previous crops. Over-fertilization of plants can also increase the chances of this disease. The Application of organic fungicide can control the disease efficiently.


The symptoms are soft, rotting of seeds, sometimes the seeds won’t germinate. Damping-off diseases leads to low seed germination, this fungus spreads in the water, penetrates in the soil or on equipment.


Avoid poorly draining soil for planting, cool, wet soil. Planting in the raised beds will promote the soil drainage. Use high quality seeds that germinate quickly. Treat seeds with organic fungicide before planting to control fungal pathogens.

Pests in Carrots:

Aphids: Aphids are small soft bodied insects stay underside of leaves and stems of plants. These insects are usually green or yellow in color.  A severe aphid infestation will turn leaves yellow and distorted, necrotic spots on leaves and stunted shoots. Aphids encourage the growth of sooty mold on the leaves.


Prune the infected plants and leaves. Transplants should be aphids free. Use pests’ free varieties. Use reflective mulches made of silver colored plastic which control pests. Use organic insecticidal soaps or oils such as neem or canola oil that are best to control aphids.

Carrot rust fly:

This pest creates tunnels on the taproot. And these tunnels are filled with a rust. The adult flies are small, dark colored flies.


Use of row covers which protect plants from damage, use row covers before adult fly lays eggs on plants. It is recommended to harvest carrots in blocks.

Carrot weevil: This pest forms Irregular dark grooves on the roots. The infected cleaves of plant turn yellow. The  adult insect will be in a dark colored beetle and the larvae will be in a white to pinkish white C-shaped grubs.

Prevention: Clean up all the debris of the previous crops. Implement the crop rotation without umbelliferous crops.

Flea beetle:

Beetle forms small holes or pits on the leaves. Young plants and seedlings are mainly susceptible to this disease. If the infestation is severe plant may be killed. Older plants can tolerate these pests.


Use floating row to protect the young plants prior to the attack of pests. Early planting can also protect the plants from common pests. A Thick layer of mulch will prevent beetles. Use some organic pesticides like neem oil or garlic oil, which effectively controlsbeetles.

Root-knot nematodes:

Forked, distorted or stunted taproots are major symptoms of pest attack. This infection reduces the yields.


Solarizing the soil can reduce nematode populations to some extent. There are new carrot varieties that are resistant to nematodes.

Read about: Growing Radish.

Last Updated: October 26, 2018
Author: Jagdish

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