Weeds, Pests and Diseases

The strawberry crop is relatively shallow rooted and a poor competitor against deeper rooted weeds. In annual hill culture systems, complete weed control prior to planting and the use of mulches may suffice. Under matted-row systems, cultivation and chemical weed control is also important in the spring.

There is a wide range of pests and diseases that affect the strawberry crop.

Nematodes damage roots making them more susceptible to disease. Slugs and snails also graze leaves. Aphids primarily attack new leaves, transmitting viruses within the crop. Mites are also a worldwide problem and are particularly damaging in already stressed plants. Sucking insects such as thrips focus on flowers and developing fruit causing fruit shape to deform.

Drosophila suzukii, an Asian fruit fly has become a major pest, spreading rapidly through the USA and many parts of Europe. Unlike common fruit flies which only lay eggs in rotten fruit, D. suzukii is able to use its powerful saw-like ovipositor to break through the skins of ripe fruit and deposit its young inside. When these maggots hatch, they eat through the fruit, causing it to rot. In the first year that D. suzukii was detected in the state of California, producers lost $300 million worth of strawberry crops.

Weevils that affect roots can cause severe damage particularly under tunnels.

The key to pest control is vigilance and a programmed approach utilizing Integrated Pest Management methods. Chemical pesticides are available, and natural predators can help within the glasshouse environment.

Disease is a particular issue: Phytophthora and Rhizoctonia species cause root rots. Crown rots are caused by a range of organisms; Colletotrichum, Fusarium, Phytophthora and Verticillium species.

Powdery mildew (Podosphaera aphanis), leaf spot (Mycosphaerella fragariae) and leaf scorch (Diplocarpon earliana) commonly affect the plant foliage.

Gray mould (Botrytis cinerea) – where the fruit is covered by a velvety grey growth – and anthracnose (Colletotrichum spp), causing dark brown lesions, are probably the most common fruit diseases. The removal of plant debris and mulch plus the use of resistant cultivars are key control measures. Systemic and protectant fungicides are also commonly utilized. Balanced crop nutrition will also help. Avoiding high rates of nitrogen after mid fruit development and ensuring a high calcium and potassium status in the fruit, will help minimize berry diseases.