Prevent & Control Window Boxes Pests & Diseases

Window boxes become packed with soft stems and leaves during summer, creating succulent feasts for pests. Many of these are common and widely seen outdoors, such as aphids (greenflies), while thrips and white-flies, although also garden problems, are more likely to be noticed on plants displayed in troughs in conservatories. 

Crawling pests such as snails, earwigs and woodlice often reach ground-floor windowboxes, but seldom upper storey ones. Dusting insecticides around the bases of walls helps to control them.

Slugs are sometimes a problem to plants in ground-floor windowboxes during wet, warm summers and can be controlled by baits, placed under tiles or pots to keep them dry and away from animals.

Whatever insecticide or fungicide is used, always adhere to the manufacturer’s instructions. Increasing the concentration of chemicals is wasteful and may damage plants. Regular spraying at ten to fourteen-day intervals is essential to control infestations of greenflies and whiteflies.

APHIDS (greenflies)

Suck sap, causing mottling and distortion. Blackflies also infest some window box plants, especially nasturtiums. Spray plants every ten to fourteen days throughout the summer.


Chew soft leaves and stems. Pick them off and spray at ten-day intervals with an insecticide. At the end of summer, clear away and burn all rubbish to prevent infestations occurring during the following year. 


Are pernicious pests, hiding during the day and eating flowers, soft stems and leaves at night. Pick off and destroy them. Also , trap them in inverted pots filled with straw: empty and destroy each morning.

GREY MOULD (botrytis)

Is a fungal disease that enters plants through cuts and wounds. It is encouraged by damp weather. Remove infected tissue and spray with a general fungicide.


Are tiny, black insects that especially attack begonias and fuchsias. They cause silvery streaks on leaves and spotting and distortion on flowers. Use an insecticide as soon as the damage is noticed.


Infect many plants, causing discolouration and distortion. Leaves may have white streaks. There is no cure: throw away badly infected plants and spray with insecticides to kill pests such as aphids that spread them. 


Are small, white, moth-like insects that spread from plant to plant, sucking sap and exuding honeydew. Check under leaves and spray regularly throughout summer. Plants growing in dry compost are especially badly damaged.


Often climb walls and ravage soft plants in window-boxes. Pick them off and use baits around the bases of the windowboxes.


Sometimes climb walls during warm, damp nights and eat plants in ground floor windowboxes. Pick off and destroy. Also , use baits.


Climb walls and enter windowboxes, hiding in damp places during the day and chewing stems, leaves and roots at night. Dust with gamma-HCH.

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