How To Deal With Scale insect in Your Irish Garden
What is Scale insect?
Scale insects are small sap-sucking pests that attach themselves to the stems, branches and leaves of plants, forming hard or soft protective covers over their bodies. They are among the most difficult garden pests to identify because they look like small brown or grey bumps on plant surfaces rather than insects. Several species affect plants in Ireland, including soft scale on greenhouse and houseplants, and hard (armoured) scale on outdoor trees and shrubs. Once settled, most scale insects become immobile, feeding through a permanently inserted stylet that draws sap from the plant's vascular tissue. Female scale insects produce large numbers of tiny mobile crawlers that spread to colonise new parts of the plant.
Damage Caused by Scale insect
Scale insects weaken plants by extracting large quantities of sap, causing yellowing leaves, poor growth, reduced flowering and eventual dieback of heavily infested branches. Soft scale species excrete copious amounts of sticky honeydew that coats leaves and surfaces below, developing into black sooty mould. Hard scale species do not produce honeydew but can cause severe bark damage and branch dieback on trees and shrubs. Bay trees, camellias, hollies, citrus, orchids and many houseplants are commonly affected in Irish gardens.
How to Prevent Scale insect
Inspect plants regularly, particularly along stems, around leaf nodes and on the undersides of leaves. Check new plants thoroughly before purchasing. Prune out and destroy heavily infested stems. Encourage natural predators including ladybirds, parasitic wasps and lacewing larvae. Keep plants healthy with appropriate watering and feeding, as stressed plants are more susceptible to scale attack. Ensure good air circulation around plants.
How to Treat Scale insect
For light infestations, scrape scale insects off with a thumbnail or old toothbrush. Wipe affected stems with a cloth soaked in methylated spirit or soapy water. Spray with organic insecticidal soap or horticultural oil during the crawler stage in early summer when the young scale insects are most vulnerable. For indoor plants, neem oil sprays provide good control. The parasitic wasp Metaphycus helvolus is available for biological control of soft scale in greenhouses.
Scale insect in Ireland
Scale insects affect both indoor and outdoor plants in Ireland. Soft brown scale is the most common species on greenhouse and houseplants, while mussel scale and horse chestnut scale are found on outdoor trees and shrubs. Bay trees grown in containers, increasingly popular in Irish gardens, are frequently infested with soft scale. The mild Irish climate allows some scale insect species to complete their life cycle faster than in colder regions. Hard frosts can reduce outdoor scale populations, but sheltered gardens in mild coastal areas of Cork, Kerry and Dublin may harbour persistent infestations.
Plants Affected by Scale insect
Treatment Products at MCDS.ie
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