A pest is “a plant or animal detrimental to humans or human concerns (as agriculture or livestock production)”; alternative meanings include organisms that cause nuisance and epidemic disease associated with high mortality (specifically: plague). In its broadest sense, a pest is a competitor of humanity. In the past, the term might have been used for detrimental animals only, thus for example, causing confusion where the generic term ‘pesticide’ meant ‘insecticide’ to some people. It is any living organism which is invasive or prolific, detrimental, troublesome, noxious, destructive, a nuisance to either plants or animals, human or human concerns, livestock, human structures, wild ecosystems etc. It is a loosely defined term, often overlapping with the related terms vermin, weed, plant and animal parasites and pathogens. It is possible for an organism to be a pest in one setting but beneficial, domesticated or acceptable in another.
..although it’s often tempting to reach for an insecticide spray at the first sign of an infestation, I prefer encouraging a natural balance in my garden.
An early start to the season with warm weather through April and May has really given growth a boost. I know commercial rose nurseries always have blooms at the RHS Chelsea Flower Show, but in my East Midlands garden I usually have to wait until much later in June for the first flowers.
Not this year. Fat flower buds are bursting open on many bushes, and I’ve just cut some deliciously fragrant flowers to bring indoors from ‘Golden Celebration’ – a fragrant English rose bred by David Austin.
But I’m not the only one enjoying this new growth. The greenfly and other aphids are loving it too! Soft shoots and sappy growth provide the perfect feeding ground for aphids, and in warm weather one aphid soon gives birth to more, until shoots are coated in ever-growing colonies of the pesky things.
I have seen one of two ladybirds around, so I know they’ll soon be breeding, and both adults and their larvae with their insatiable appetite for aphids will help provide natural pest control. Without pests there won’t be anything for these natural predators to eat, so although it’s often tempting to reach for an insecticide spray at the first sign of an infestation I prefer encouraging a natural balance in my garden.
And balance is the operative word, as pest and predator go hand in hand. So much of the wildlife we try and encourage into our gardens feeds on home-grown pests – caterpillars for the nesting bluetits to feed their chicks, slugs for the frogs and toads, snails for the song thrush, and so on. Patience is required as it does take a while for this balance to be reached, and some plant damage has to be tolerated, but in a wildlife garden that’s only to be expected.
Of course, not every pest has a natural predator either. Sawfly can completely defoliate a gooseberry bush or Solomon’s seal in a couple of weeks, lily beetle devour leaves and flower buds, and woolly aphid coat the stems of apple trees. For these pests I’m always vigilant, and take prompt action to remove them.
Hoverflies will soon be seen around the garden too, with adults feeding on pollen and nectar from broad, open flowers. They’ll soon breed and lay eggs on ornamental plants, fruit and crops, and their tiny larvae will then help out by feeding on aphids.
Achieving a natural balance requires slightly more than a ‘live and let live’ mentality. Where large greenfly or blackfly colonies develop with no signs of predators I do sometimes resort to rubbing pests away between finger and thumb. It helps to do this using a flow of water from a hose, washing away pests in the process. And I’ve an assortment of other things to help keep plants healthy including netting and fleece to protect crops, and pheromone traps to hang in my fruit trees to control codling moth and plum moth.
For now I’m just enjoying the moment, and the fragrance from those cut roses. What a wonderful start to summer!
Cabbages and other brassicas can be extensively holed by caterpillar feeding by the end of summer.
What are cabbage caterpillars?
Caterpillars are the larval stage of various butterflies and moths. There are several species of caterpillar that feed on cabbages, other brassicas and other plants including turnip, swede, horseradish and nasturtiums. Large cabbage white butterfly caterpillars are yellow and black with obvious hairs on their bodies. Those of small cabbage white butterfly are pale green and covered in short, velvet-like hairs. Cabbage moth caterpillars are yellowish green or brownish green, with no obvious hairs on their bodies.
Holes are eaten in the outer leaves of all brassicas and damage may also be seen on the inner leaves of cabbages when the heart is cut through. Caterpillars and their excrement are often found on the plants.
There are three common caterpillar culprits:
- Large cabbage white butterfly (Pieris brassicae)
- Small cabbage white butterfly (Pieris rapae)
- Cabbage moth (Mamestra brassicae)
All three may be present at the same time. Caterpillars of cabbage moth and small white butterfly are more damaging as they bore into the hearts of cabbages, whereas the yellow and black caterpillars of the large cabbage white stay mostly on outer leaves.
- Inspect plants regularly and pick off the pale yellow butterfly eggs and caterpillars when seen
- Growing brassicas under fine netting or horticultural fleece can exclude adult butterflies and moths from laying eggs on the crop. Care must be taken to keep the netting off the crop or the adults can lay eggs through it.
- A biological control is available for caterpillars, this is a pathogenic nematode, Steinernema carpocapsae, available from Agralan Ltd., 01285860015, pestfreegardening.co.uk; Just Green Ltd, 01621785088, just-green.com; Organic Gardening Catalogue, 01932253666, organiccatalogue.com; Ladybird Plantcare, 08450945499, ladybirdplantcare.co.uk; Pippa Greenwood, pippagreenwood.com. The longer the treated caterpillars and foliage stay wet, the greater chance of the treatment being effective, so apply during cool dull weather.
- Spray with pyrethrum (e.g. Py Spray Garden Insect Killer, Bug Clear Gun for Fruit and Veg, Defenders Bug Killer, Growing Success Fruit & Veg Bug Killer, Growing Success Shrub & Flower Bug Killer), lambda-cyhalothrin (e.g. Westland Resolva Bug Killer), or deltamethrin (e.g. Bayer Provado Ultimate Fruit & Vegetable Bug Killer). Pyrethrum has a one-day harvest interval and no restrictions on numbers of applications. For lambda-cyhalothrin and deltamethrin, read and follow the label instructions regarding each crop in general there is a seven-day harvest interval and a maximum of two applications can be made during the growing season (up to three applications for deltamethrin on cauliflower, broccoli, kale or Chinese cabbage)
Woodlice, also known as slaters and pillbugs, are abundant animals in most gardens and greenhouses. They cause little damage to plants. Large numbers often occur in compost heaps, where they help break down the plant material and are a useful part of the composting process.
What are woodlice?
Woodlice are terrestrial crustaceans that shelter in dark damp places, especially where there are accumulations of decaying plant material.
Woodlice are not usually plant pests, theya rea however often found in damage caused by other pests. Woodlice occasionally damage soft plant tissues, such as seedlings and sometimes strawberry fruits
Holes in older, tougher plant material will have been caused by something else, such as slugs or caterpillars.
Keep greenhouses tidy to avoid creating too many damp hiding places for woodlice. Remove dead flowers and leaves.
Woodlice have many natural enemies, such as shrews, toads, centipedes, some spiders, ground beetles and parasitic flies.
Woodlice are tolerant of most pesticides and as they are not significant plant pests, it is not worth trying to control them in gardens. Pesticide dusts are available from hardware stores and garden centres for use in buildings and on hard surfaces, but not on plants,. Woodlice come into houses from gardens but are unlikely to survive for long indoors unless they can find a damp place to shelter.
Hedge bindweed or bellbind (Calystegia sepium) with its pure white trumpet flowers is a familiar sight, choking plants in borders and twining around any plant shoot or cane. The smaller field bindweed (Convolvulus arvensis) with white or pink flowers is problematic in long grass and bare soil.
Slugs are familiar slimy pests that cause havoc in the garden, eating and making holes in leaves, stems, flowers, tubers and bulbs. There are several species of slugs that are garden pests. They can cause damage throughout the year on a wide range of plants, but seedlings and new growth on herbaceous plants in spring are most at risk and may need protection.
Snails are familiar pests that can cause a lot of damage in the garden, eating and making and making holes in leaves, stems and flowers.
Capsid bugs spoil the appearance of plants by giving the foliage a tattered and distorted appearance and causing flower buds to abort.