General gardening topics

Cornus (Dogwood) pests and diseases

Last updated on April 28th, 2022

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Dogwood is a very popular ornamental tree that is known for its elegant foliage and bright red fruit. You also get the Cornus varieties such as Cornus alba and Cornus sanguinea that are grown for their brightly coloured winter stems and need to be pruned back hard in spring.

Cornus is very strong but one downside to this shrub is the host of diseases that can infest a Dogwood tree and cause some serious problems, no matter how healthy your tree was otherwise. For most people, serious problems are not very common, however, they can experience these issues, and it’s worth keeping them in mind.

The best way to prevent some diseases is to provide them with the ideal growing conditions. Dogwoods require moist, fertile soil with optimum drainage, this means not too wet, keeping the soil moist but not allowing it to become waterlogged.

They also require dappled lighting and a lot of protection against the hottest sun of the day, this means trying to avoid planting them in open sunny positions to start with. Even if you have all the right growing conditions, providing them with fertilisers and adequate water, you can still come across problems that can have a significant impact on the health of your plant.

Dogwood Diseases

Dogwood anthracnose

Dogwood anthracnose is one of the most common fungal diseases and it only affects the flowering cornus, which include the Cornus florida and Pacific Dogwoods (C. nuttallii), Kousa Dogwood (C. kousa). It does not seem to affect the Tatarian Dogwoods (Cornus. alba) and redosier Dogwood (C. sericea).

For those it does affect, you will initially see the blighted leaves, these eventually manifest in the form of purple margins and brown colours along the perimeter of the leaves. After that, you might notice cankers on the small branches too. Eventually, the problem will make its way to the trunk and result in necrotic weeping areas along the trunk.

Spot anthracnose, powdery mildew and septoria leaf spot

Spot anthracnose

Spot anthracnose mostly affects the Cornus florida. Powdery mildew affects most Cornus varieties (as well as many other plants) and finally, septoria leaf spot, also known as Septoria blight, are all conditions that can negatively impact the leaves.

These diseases are best treated by removing the affected leaves and spraying them with a fungicide. Ideally, if you have been affected by these diseases before, we recommend spraying your Cornus just as the buds begin to open in spring to help prevent it again. Ensuring good air circulation can also help prevent these and many other diseases.

Root rot and Canker disease

Root rot

Root rot and canker disease can take place if you have moist conditions, this means not overwatering your Cornus and making sure the soil is free-draining. This may mean digging in some horticultural grit into the soil to help drainage, ideally before planting.

To combat all of these it’s best that you use listed fungicides in spring and spray every 7-8 weeks, or to the specifications that the manufacturers recommend on the packaging.

FungusClear 18986 Ultra, 3 in 1 Action, Plant Protection Disease Control, 225 ml
  • Systemic protection and control of blackspot, powdery mildew and rust
  • Use on roses and other flowering or ornamental plants
  • Protects new growth and protects plants for over 3 months, when used at intervals recommended in usage instructions
  • Use between March to September
  • Apply using a garden pressure sprayer washed before and after use

Dogwood Pests

There is no ornamental tree that doesn’t have its downside. Dogwood trees are no exception and there are several insects that can make your Cornus their home, so it’s important to treat affected trees quickly to reduce damage.

Dogwood borer

The Dogwood borer is one of the worst pests you will find. The larvae lay inside of the tree and then eat their way out of the tree, taking nutrients and water from it. The result is that the leaves and branches die.

Scale insects

Brown scale insects on Pyracantha
Brown scale insects

There are a lot of scale insects that can cause problems for your tree too but they are usually not too damaging.

Dogwood sawfly larvae

Dogwood sawfly larvae

The Dogwood sawfly larvae love to feed on the foliage, causing a great deal of damage and they can strip almost an entire tree of its foliage very quickly.

Treating these pests

If you have a large infestation of any of these pests, the only treatment is to use a pesticide spray as soon as you notice a problem. Always follow directions on the pesticide.

Bug Clear Ultra for Flowering Plants,Liquid Concentrate Insecticide and Acaricide, 200 ml
  • A contact and systemic insecticide that offers protection against a wide range of pests for flowering plants
  • Kills all major ornamental insect pests including whitefly, greenfly, blackfly and other aphids, scale insects, mealy bugs, red spider mites, caterpillars and lily beetles
  • Also offers a useful level of control of thrips
  • Its systemic action protects treated plants from such pests for up to three weeks
  • For use outdoors and in greenhouses and conservatories

Other potential problems

Dogwoods can show signs of distress if there is flooding or drought, again this means water during dry spells and making sure the soil is well-drained before planting, maybe even adding some grit to the soil to help with drainage.

They require fertile soil, so if the soil conditions change, the health of the tree will eventually decline, again before plating add plenty of compost to the soil. You might notice the foliage turning red or burning in the summer if you haven’t watered it enough.

You can help conserve moisture by adding 10cm-15cm of mulch spread out one metre around the base of the plant. Just make sure the mulch doesn’t directly touch the trunk.

Last update on 2024-04-15 / Affiliate links / Images from Amazon Product Advertising API

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