How To Deal With Red spider mite in Your Irish Garden
What is Red spider mite?
Red spider mite, more accurately called two-spotted spider mite, is a tiny arachnid pest that causes significant damage in greenhouses and on indoor plants throughout Ireland. Despite its name, the mites are usually yellowish-green with two dark spots on their backs, only turning red-orange in autumn when they enter dormancy. Adults are barely 0.5mm long and virtually invisible to the naked eye. They feed by piercing leaf cells and sucking out the contents, leaving characteristic fine pale stippling on the upper surface of leaves. In severe infestations, fine silky webbing appears on shoot tips and between leaves. Red spider mites thrive in hot, dry conditions, making them primarily a greenhouse and conservatory pest in Ireland's humid climate.
Damage Caused by Red spider mite
Red spider mite causes a fine pale mottling or stippling on the upper surface of leaves as the mites feed on the cell contents from the undersides. Heavily infested leaves turn bronze, dry up and fall prematurely. Plant vigour, flowering and fruiting are all reduced. In severe infestations, fine silky webbing appears across shoot tips, giving plants a neglected, dusty appearance. Greenhouse crops including tomatoes, cucumbers, peppers, aubergines and strawberries can be seriously affected. Ornamental plants such as roses, fuchsias, and houseplants are also vulnerable.
How to Prevent Red spider mite
Maintain high humidity in greenhouses by damping down floors, benches and pathways regularly — red spider mites dislike humid conditions. Mist plants frequently with water, paying particular attention to the undersides of leaves. Avoid growing plants in hot, dry, stagnant conditions. Inspect new plants carefully before bringing them into the greenhouse. Remove and destroy heavily infested leaves promptly. Good air circulation without excessive dryness helps prevent outbreaks. Avoid over-feeding with nitrogen which produces the soft growth mites prefer.
How to Treat Red spider mite
Introduce the predatory mite Phytoseiulus persimilis as a biological control from April onwards — it is highly effective in warm, humid greenhouse conditions and will eliminate red spider mite populations within a few weeks. Spray with organic insecticidal soap or neem oil, ensuring thorough coverage of leaf undersides. Repeat applications every seven days. Increase humidity by regular misting and damping down. Chemical miticides are available for severe infestations but destroy biological controls and predatory insects.
Red spider mite in Ireland
Red spider mite is primarily a greenhouse and indoor pest in Ireland, as the outdoor climate is generally too cool and humid for large populations to establish in the open garden. However, warm dry summers can occasionally lead to outbreaks on outdoor strawberries, beans and ornamental plants. Irish polytunnel and greenhouse growers should be particularly vigilant from June through September when internal temperatures peak. The predatory mite Phytoseiulus persimilis works excellently in Irish greenhouse conditions where the humidity is naturally higher than in more continental climates. Conservatory plants and houseplants are vulnerable year-round due to the dry atmosphere of centrally heated Irish homes.
Plants Affected by Red spider mite
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