PRIMROSE AND COWSLIP PESTS AND DISEASES

Primrose and cowslip pests and diseases

Like many soft herbaceous plant, primulas can be effected by a range of pests and disease. It's important to be able to identify them due to the differences in their control. Below is a list of the more common problems you are likely to meet.

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APHIDS

Cause: Aphids are a well known pest insect that can quickly colonize the soft tissue parts of your plant. They damage and weaken the plant by sucking the sap out of pressurized parenchymal cells just below the leaf cuticle.
Symptoms: Clusters of these small insects are readily identifiable, normally at the plants tips or on the underside of their leaves. In severe cases, the infected parts can begin to wither due to the quantity of sap being removed from that area.
Treatment: There are many chemical treatments available including a number of organic, but all of these must be applied at the first signs of infection to achieve the best effect. For further information click onto:

How to Make a Natural and Organic Insecticide for Aphids
Sacrificial Planting

MOSAIC VIRUS

Primrose and cowslip pests and diseases

Cause: Primulas can be cross infected by the cucumber mosaic virus which is transported from plant to plant by aphids.
Symptoms: This can be identified by a mosaic, yellow leaf mottling, often appearing on severely stunted growth. You may also see browning of the veins.
Treatment: Although its not a serious problem in the garden, the plant should still be lifted and destroyed to prevent further spread of the virus.

FOOT ROT, CROWN ROT, ROOT ROT AND BROWN CORE
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Cause: These rots are caused by a wide range of fungal attacks making exact identification almost impossible. However their action and treatment are all very much the same.
Symptoms: The earliest signs of this fast acting rot are indicated by the production of smaller leaves which turn yellow before wilting. Flowering will be reduced and the plant will be loose in the pot or ground due to its decaying root system.
Treatment: Any infected plants should be removed and destroyed. Sometimes, improvements in drainage, nutrient availability and changes in the soil pH can indirectly improve the situation but there are no effective chemical cures.

GREY MOULD and DOWNY MILDEW

Cause: This group of fungi can affects many plants and unfortunately they are not host specific. This means that they are able to cross infect plants from a variety of different host plant families.
Symptoms: These moulds can easily be identified by a white or grey powdery coating that can appears on the leaves, stems or flowers of your plant. As the infection progresses this coating will spread to envelope the rest of the plant, eventually killing it.
Treatment: There are a number of effective chemical treatments that can be applied here, but infected plants will need fortnightly applications during the Summer - particularly during prolonged dry periods. Sulphur is a popular choice, particularly with organic gardeners although it can damage sensitive plants. A more reliable alternative is to use a general systemic fungicide.

PRIMULA RUST or LEAF SPOT- Puccinia primulae

Cause: More commonly found on Primula vulgaris, rust isn't often seen in the south of the country, but it can be encountered on plants growing in the north of England and further into Scotland.
Symptoms: It can be identified by checking on the underside of the leaves, looking for groups of yellow spots which later turn a dark brown in color.
Treatments: It is a difficult fungus to treat involving rotating applications of different fungicides. Fortunately, the disease isn't particularly invasive and so can be dealt with by either removing the infected leaves or just to leave it as it is.

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In text image Attribution: Bob Danylec https://creativecommons.org/licenses/by-sa/2.0/deed.en

For related articles click onto the following links:
HOW TO GROW AURICULAS FROM SEED
HOW TO GROW NATIVE WILD PRIMROSES AND POLYANTHUS FROM SEED
HOW TO PROPAGATE COWSLIPS AND PRIMROSES
OLD ENGLISH PLANTS - Polyanthus ‘Gold Lace’
TULIP DISEASES