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Nutrients Pests and Diseases Soil

Posted By: Plant Magic

Pests and Diseases That Affect Carrots

Alongside aphid infestations, a common pest that affects most plants, carrots are also susceptible to a wide range of pests and diseases. Hydroponic nutrients provide everything plants need to be healthy and to provide bigger yields.

Knowing how to grow carrots is essential so that any issues that arise are addressed as soon as possible and any pest or disease symptom easily recognised.


Carrot Rust and Carrot Rust Flies

Carrot rust flies cause carrot rust, as they lay eggs in the surrounding soil where the top of carrot plants is. The eggs become larvae, which will burrow into the soil and affect carrot roots by eating through carrots. They cause rust-coloured tunnels that tend to span through the lower two thirds of the vegetable.



Cool and wet weather is often conducive of damping-off, providing the ideal conditions for fungi in the soil to be active. Damping-off can be caused by fungi such as Pythium, Rhizoctonia, Alternaria, and Fusarium. Should carrot seedlings fail, one of these fungi is usually to blame.

Fungi attack roots and stems by producing spores that quickly spread to newly planted areas. Products like Pyth Tabz sterilise the water on contact and continue to work for 7-10 days to ensure that any spores are instantly killed.

Pyth Tabz

Black Root Rot

The fungus Thielaviopsis basicola causes black root rot in carrots, mainly during storage when the humidity and the temperature are too high. Symptoms are limited to the skin at first, with dark brown masses appearing in random patterns.

Wounded tissue can be rapidly invaded, so it’s advised that carrots are harvested carefully, cooled and stored immediately to decrease the impact of this disease.


Bacterial Leaf Blight

Caused by the Xanthomonas campestris pv. carotae bacteria, this is a common disease that affects carrots. Symptoms tend to appear on leaf edges first with yellow and small, angular spots that keep expanding. These spots become brown and black with a yellow halo before turning dry and brittle.

This disease can be transmitted through irrigation water, rain, insects, infected seeds, and infected tools, remaining in the soil for around a year. Avoid watering carrots overhead and keep an eye on new seeds to ensure they aren’t infected.

Man Watering Garden

Alternaria Leaf Blight

Alternaria leaf blight is caused by the plant pathogens Alternaria dauci and Alternaria radicina. The former causes symptoms such as green-brown, water-soaked lesion types on the leaves’ edges. These become bigger and turn black with a yellow halo often developing.

The more susceptible leaves to this infection are the older growth and, when the disease spreads to almost half of the leaf, it becomes yellow and it dies. Alternaria radicina has similar symptoms but it typically causes an additional dry, black decay called black rot on stored carrots.


White Mould

Caused by the fungus Sclerotinia sclerotiorum, white mould affects carrots late in the growing season and when they are in storage. The symptoms consist of white mycelial growth in addition to black, hard sclerotia on the crown of affected carrots.

When carrots are affected during storage, they present symptoms such as watery and soft rot composed of fluffy and white mycelial growth and black sclerotia. Sclerotia in particular can be difficult to manage due to remaining in the soil for many years and having a wide number of hosts.

Pile of Carrots


These insects are the larvae of click beetles, and they can be active all year around. Wireworms are usually a concern when grassy areas have been converted into vegetable beds. They can grow up to 22mm long, having a yellow-brown, thin body with three pairs of very small legs near the head end.

Wireworms tend to feed on roots, seedlings, and stem bases, with carrots and potatoes often being tunnelled by these insects. The damage they caused shouldn’t be confused with carrot flies or slugs; wireworms tend to tunnel straight through vegetables and don’t leave a cavity, while slugs leave small openings that lead to cavities.


Flea Beetle

This insect affects younger plants more than older ones, as older plants can often tolerate an infestation. Flea beetles cause pits or small holes in plant leaves and may affect plant growth. Should the damage be too severe, carrot plants can die.

Flea beetles are more active during spring and summer, with adults feeding on plant leaves and larvae feeding on the roots. Although they are only about 2-3 mm in length, their enlarged hind legs allow them to leap off plants whenever they’re disturbed.

Flea Beetle


These gastropods are soft-bodied, single-shelled animals belonging to the mollusc animal group. They’re active all year around, with several species being present in gardens. The most common slugs tend to be the Milacidae, the Arion spp., and the Deroceras.

Symptoms include slime trails that appear as silvery deposits on surfaces, irregular holes in carrots, and tunnel-like damage similar to wireworm damage. Young seedlings can die off completely when slugs eat them.

Ensuring that all plants are monitored and treated with products such as a Bugicide will help to prevent carrot plants from being affected. At Plant Magic we always ensure that our products provide plants with the best possible chance, so that they grow healthy and strong.

Get in touch with our team on 01695 554 080 to know more about our hydroponic nutrients.

Our Blog: Hydroponic Tips & Tricks

Whether you are an expert who already has a thriving crop of healthy plants, or you are trying to grow your very first hydroponic yield, we can help you to grow the strong and healthy crops you have always wanted.

Here at Plant Magic Plus, our team of gardening experts work very hard behind the scenes to provide you with the high quality nutrients, additives and growing media that will help you to get the most out of your growing plants.

But we understand that successful horticulture is about more than just having good quality chemicals, nutrients or fetilisers, that's why we have written this blog to provide you with the insights, tips and techniques you will need to give your garden that extra magic touch.

From helpful advice about watering your plants in soil and a guide to magnesium nutrients, to top tips about growing hydroponic vegetables and a comprehensive overview of microbes, we’ve got everything covered.


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