A guide to all the various pests and how to get rid of them.
These small green or brown insects suck the sap of the plant with devastating effects. They deposit a sticky honeydew on which disease spores can stick, so causing further problems. They can also spread virus diseases. Tackle the problem as soon as it is seen and spray with Pirimicarb. As they lay their eggs on the plants and the young can hatch out and cause further problems, continue to spray on a weekly basis.
The larvae feed along the surface of the fruit and then burrow into it. This leaves characteristic marks on the skin of the fruit. Spray with Permethrin a week after the blossom has fallen.
Adult beetles and grubs feed on the shoots of Asparagus. Dust with Derris at the first signs of attack.
BEAN BEETLE (Bruchid Beetle)
This beetle resembles a weevil in appearance and sometimes gets the incorrect name of Bean Beetle. The female lays her eggs on the plant and the grubs then hatch and bore into the seed and eat the inside. Destroy any seeds found to contain the grubs and ensure that you purchase from a reputable dealer.
BEAN SEED FLY
These pests destroy the seeds and seedlings of French Beans and eat the seeds roots and underground stems. Dust with Gamma HCH before sowing or planting out.
BEET CARRION BEETLE
The grub and adult of this black beetle feed on the leaves of Beetroot in the spring. Spray with Derris as soon as seen.
BIG BUD MITE
This pest is prevalent on Blackcurrants and causes the buds to swell up. It also transmits the Reversion Virus, which reduces crops. Spray the bush when dormant with a winter tar wash and then, when the first flowers are open with a fungicide spray. Repeat the fungicide after the flowers have finished opening. If the bush is severely affected, it is best to dig it out and burn it.
This small black Aphid attacks all varieties of beans, in particular the tips of Broad Beans. They usually form in clusters. Spray with Pirimicarb.
CABBAGE ROOT FLY
The maggots of this pest feed on the roots of the plant. Signs of infection are a lack of growth, the plant turning a bluish colour and a general wilting. Sprinkle Chlorophos around the plant base when planting. Special collars can be made or purchased to put around the plant stem. This prevents the adult fly from laying its eggs down the side of the roots.
Not too serious a problem, but can cause marks and blemishes on the fruit. Spray with Permethrin once the petals have fallen.
This pest most commonly attacks Carrots but can also affect Parsnips, Hamburg Parsley, Celeriac, Celery and Parsley. It is not the fly itself that is the real problem, but the grubs of the eggs that it lays. The adult fly is attracted by the smell of the Carrots and lays it's eggs down the side of the roots. The eggs then hatch and burrow down into the Carrot to feed and overwinter. Physical barriers are a very good prevention but if chemicals must be used Chlorophos is effective.
See separate articles on Carrot Root Fly Problems.
CABBAGE WHITE BUTTERFLY
It is the caterpillars that are the problem. They will eat all Brassicas and in severe infestations can completely strip a cabbage until only the skeleton of the leaf is left. Be observant and check regularly for the little clusters of yellow eggs and when found just crush them between your fingers. If you miss some and you find caterpillars, pick them off the plants and dispose of them. Liquid Derris is an effective spray.
CITRUS GALL MOTH
This wasp burrows into new spring growth to lay its eggs. When hatched, the larvae burrow into the shoots and caused swellings or galls to appear. Cut out shoots and leaves infected with galls and burn.
This pest is not seen very often but dead or dying shoots of currants and Gooseberries may indicate the presence of this caterpillar. The moth lays its eggs in June and the caterpillar burrows into the shoots. Cut out infected shoots and dust with Derris.
This pest usually affects Apples. The small maggot like caterpillars tunnel into the apples leaving a small brown mound at the entrance to the tunnel. As there is no cure, prevention is necessary. Spray the fruit with Permethrin 4 weeks after the petals fall and then spray again three weeks later.
CUTWORMS / LEATHERJACKETS / CHAFER GRUBS / WIREWORMS / MILLIPEDES
All of these pests attack the roots of plants below the ground. They are more commonly found in ground that has been covered with grasses and then brought into cultivation. Once the soil is in regular use, they will be brought to the surface by hoeing and the birds will gladly finish them off for you. If they are a severe problem, hoe Chlorophos into the soil.
Earwigs can chew great holes in leaves. Dust the area with Gamma -BHC or Derris.
Bulbs in particular are infected by these worms and there is no cure for them. Dig up and destroy infected bulbs and do not grow bulbs on the site for at least two years. Dressing the soil with Chlorophos may help when replanting a new crop.
This is a small black beetle that attacks most young seedlings and soft leafed plants. It is mostly found on Turnips, Swedes, Radish, and most Brassicas. The symptoms on the plant are small holes in the leaves. Dust with Derris.
It is the caterpillar like larvae that cause the damage and they can strip a plant in days. Attacks usually start in the spring and can persist until autumn. Inspect the plant regularly and pick off any larvae found. Dusting with Derris can help.
These cause yellow spots on the leaves of Geraniums and Primulas. They carry viral diseases, so a systemic spray is advisable.
These pests burrow inside the leaves and feed off them. Spray with a systemic insecticide containing Permethrin.
This black and yellow caterpillar feeds on currants and Gooseberry bushes and can cause severe defoliation. Either pick off and destroy .
MANGOLD FLIES (Beet Leaf Miner)
These damage Beetroot by eating into the leaves and causing brown blisters. Pick off and burn infected leaves and spray with Trichlorophon or a systemic insecticide.
This pest is more usually found on houseplants indoors. It looks like a small tuft of cotton wool and usually leaves a waxy mark on the leaf. A cotton bud dipped in Methelated spirits and then dabbed on the insect will usually cure it but an aerosol of houseplant insecticide can be used.
MEALY CABBAGE APHID
This rarely seen insect gather on the underside of the leaf and sucks the sap. Insecticidal soap will remove them.
These microscopic, soil borne creatures burrow inside the bulb and cause distortion. Treat the soil with Chlorophos when sowing as a prevention.
It is the maggots of this fly that cause the damage, usually on Onions but can also affects Leeks. These are normally seen just below the soil when hoeing. They cause the plant to turn yellow and eventually to die. Regular hoeing will expose the grubs for the birds to eat. A treatment with Derris dust when seedlings first emerge and then again two weeks later will help.
PEA / BEAN WEEVILS
This pest is rarely seen as they are nocturnal, but the damage they cause on the plant is very obvious. They eat notches in the edges of the leaves. Dust the plant and ground with Derris.
This is a common pest of Peas but is only a problem between June and August. The adult lays it's eggs when the Peas come into flower and the grubs then feed inside the forming pods. Spray with Permethrin a week after flowering to control it.
This tiny insect attacks the new fruit lets and turns them black. This is caused by the tiny grubs inside. Spray with Permethrin when the buds are still white. Ensure that you remove and destroy any buds that have fallen to the ground, as these will contain grubs that can hatch and re-infect the tree.
This pest attacks all briar fruit and feeds on the ripening fruit. Spray with Derris when you see the first pink fruits. Blackberries need spraying as the flowers start to open and Loganberries need spraying just after flowering.
RED SPIDER MITES
This is more commonly found in greenhouses but can be found in the open during hot dry weather. They attach Cucumbers, Peppers, Aubergines and Tomatoes in the greenhouse and can affect French beans, Courgettes and Marrows in the open. The mites themselves are very tiny and can only just be seen with the naked eye. They weave web likes spiders on the plants and it is this that can more easily be spotted. They cause speckling and discolouration of the leaves which dry up and die. The best prevention, especially in the greenhouse is to keep the atmosphere damp with a regular misting of water. Chemical control is difficult and most chemicals are ineffective. Regular weekly sprays with Permethrin may help eradicate them.
The adult fly lays its eggs on Rose leaves in spring and injects a chemical into the leaf, which causes it to roll up into a tube to protect the grubs. The most effective insecticide to use is a systemic type that contains Dimethoate or pirimiphos-methyl, as this penetrates into the plant itself. When the grubs feed on the leaf they will be killed.
SLUGS / SNAILS
The dirty white caterpillars of this moth can be very destructive. They live in the soil and feed on the roots of plants. Regular hoeing will kill some and bring others to the surface where birds will find them. If the attack is severe try using Trichlorophon.
Especially destructive in hot weather when they can swarm on flowers and devastate them. Spray with Permethrin.
This moth can be a serious pest in some areas of the UK. It is sometimes found on Strawberries. It joins several leaves together using a silken web. Inside these webs it lays its eggs. Pick off the affected laves and destroy. Try using an insect trap.
These hard, beetle like insects, lay their eggs in plantpots where they attack the roots of the plant. The adults will also chew the edges of the leaf.
This small white fly can be a real problem, especially in the greenhouse. It will basically attack any plant in the greenhouse and is particularly fond of Brassicas in the open. They congregate on the underside of the leaves and deposit a sticky honeydew, on which Sooty Mould can grow. When the leaf is touched they take off in a mass, only to land on another nearby plant. For this reason they can be hard to combat. Permethrin is fairly effective against them, or if in the greenhouse, you could try one of the newer Biological controls that are very effective. As they only have a short life cycle be sure to spray at least three times at a weekly period.
These grey insects are not normally a problem but occasionally they can cause damage to seedlings. They like to hide in moist dark places. Avoid having litter lying about so that they have nowhere to hide.
Woolly Aphids are very similar to Green/Black fly but they coat themselves with a waxy secretion that looks like cotton wool. This waxy coating makes control of them difficult. The spray has to be applied at a higher pressure to penetrate the coating. Pirimicarb is an effective spray.
The caterpillar of this moth is black with red and white markings. It is very hairy and can cause a skin rash if handled. It is sometimes found on Raspberries where it causes skeletonization of the foliage. It is not normally found in great numbers so it is best to just pick it off.
© copyright 1999, P. A. Owen