Greenhouse pests to watch for in summer
PESTS seek refuge in the greenhouse in winter because it offers a warmth and security. This is followed in spring by an all-you-can-eat buffet of cuttings and tender seedlings.
Their assault doesn’t stop in summer, when they feast on your welltended tender vegetables and summer cuttings.
The main pests to be alert for are snails, tomato moth caterpillars, greenhouse whitefly and glasshouse red spider mite.
Look for snails in nooks and crannies, under pots and between module cells, then pick them off and dispose of them as you see fit. Tomato moth caterpillars advertise their presence with trails of droppings, and are easy to pick off and add to the bird table.
Whitefly and glasshouse red spider mites are quick to infest plants and will suck their sap, spreading disease and causing the plants to wilt and fail to grow strongly and crop well.
Because these pests breed so quickly and are so prolific, many have built up resistance to sprays, so biological controls are the way forward. A tiny parasitic wasp called Encarsia formosa will tackle whitefly by laying eggs inside the pest, and they are widely available online and from garden centres. Glasshouse red spider mites love warm, dry conditions and can be deterred by raising humidity, keeping plants well-watered and standing bowls of water around the greenhouse. A predatory mite that feeds on red spider mite can also be bought to solve the problem. Avoid using sticky fly papers as they destroy everything they catch and will kill beneficial pollinators a much as they do pests. Leave a few spiders in place too, as they are great gardening allies.
■ Encarsia formosa and predatory mites are available from greenfli.co. uk, greengardener.co.uk and
ladybirdplantcare.co.uk