Pest Control

BOX TREE CATERPILLAR

Box caterpillar has, unfortunately, moved into the London area over the last few years. The leaves of the box plant (Buxus) are eaten and the plant is covered in webbing, mainly from April to October. The green caterpillars are the larvae of a moth that feeds on box; the adult moth has white wings with a brown border.

Treat as follows:

• Remove caterpillars by hand as much as possible.

• Use a pheromone trap, a biological control, from April to October in order to control the moths.

• Use Provado, Bug Clear Ultra or Pyrol Bug & Larvae Killer to kill the caterpillars – don’t mix any two pesticides together.

When spraying, wear rubber gloves and do not spray in windy or very hot conditions – early morning, late afternoon or evening is best. Make sure that no children or pets are nearby and take care not to spray any flowers as this will affect pollinators such as bees.

Spray thoroughly including stems, buds and the undersides of leaves but without excessive run-off or drift. Rake your hands through the plant as much as possible so that the chemical is spread throughout the plant.

Repeat this procedure every 10-14 days in order to break the cycle of the pest. 

Wash your hands after use and keep the spray container only for pesticide use. 

CABBAGE WHITE BUTTERFLY CATERPILLARS

Cabbage whites lay their eggs on brassicas (broccoli, cabbage, cauliflower) from May onwards. The best form of prevention is to enclose the brassicas with a cage with protective crop netting and canes to keep the butterflies out. If the caterpillars are already present, spray with a pyrethrum based insecticide such as Neudorff Pyrol. As always with insecticides, make sure you spray during calm conditions, and when beneficial insects such as bees and hoverflies are absent.

APHIDS

There are many different types of aphid affecting a wide variety of plants. Small green or black insects with or without wings, often present on the young growing tips of plants, aphids such sap causing distorted curled leaves and stunted growth. They also excrete honeydew which can attract moulds.

Aphids have many natural predators including ladybirds and lacewing and hoverfly larvae. Try adding a bug hotel to your garden to encourage these beneficial insects. Aphids can also be dislodged from plants they are feeding on with a strong jet of water from a hose. Chemical controls include spraying with a pyrethrum based insecticide such as Neudorff Pyrol or a Fatty acid spray such as Doff Universal. As always with insecticides, make sure you spray during calm conditions, and when beneficial insects such as bees and hoverflies are absent.

GLASSHOUSE WHITEFLY

Small white flies which feed on the sap of plants, weakening the plant. They also excrete sticky honeydew which can attract moulds. Small white scale like nymphs may also be seen on the underside of leaves. These are often present in greenhouses or on houseplants as they like warm conditions. Chemical controls are often ineffective for Glasshouse whitefly as they can rapidly develop resistance; instead try attracting beneficial insects which predate on whitefly such as ladybirds, lacewings and hoverflies to your garden by adding a bug hotel. Fly sticky paper in greenhouses can also provide some control if put in place before their numbers increase rapidly.

SLUGS AND SNAILS

Slugs can cause immense damage to young plants and seedlings, often devouring them entirely. Fortunately there is a wide variety of methods for controlling them.

• Cover young plants and seedlings with plastic cloches
• Install beer traps – slugs are attracted to beer and will fall in and drown
• Attract beneficial wildlife such as birds, hedgehogs and frogs. Try hanging a bird feeder in your garden.
• Doff Slugs be gone – This forms an absorbent barrier around plants that slugs will not cross. Non-toxic and safe for use around children and pets. Needs reapplying after rain.
• Wool pellets (Slug gone) – These pellets are sprinkles around plants and then water. They then expand to form an impenetrable mat around the plants that the slugs will not cross.
• Copper tape – Surround pots with copper tape to deter slugs and snails.
• Desiccant spray such as Grazers Slug and Snail
• Slug pellets: These should be used very sparingly. The only type of pellet now available is based on ferric phosphate (Bayer slug killer)

As slugs are so prolific, a certain level of slugs in your garden must be tolerated. Focus controls on young and particularly susceptible plants.

VINE WEEVIL

Adult vine weevils cause irregular shape notches in leaf margins during summer (round holes will be leaf cutter bees); however the main damage is done by their larvae eating plant roots especially in pot plants.

Attract predators to your garden such as birds, frogs, hedgehogs and predatory beetles by adding bird feeders and bug hotels to your garden. If chemical controls are needed, an acetemaprid based liquid compost drench (Bug Clear Ultra) can be used in mid to late Summer to destroy the eggs and larvae.

OTHER INSECTS IN YOUR GARDEN

Not all insect life in your garden should be considered a pest, and are often a sign of a healthy and balanced eco system. Tolerance of a low level of pests such as aphids and slugs will ensure the success of beneficial predators

Ants - While ants can be a nuisance they rarely cause damage to ornamental plants and vegetables; however some ants are known to farm aphids which do cause a lot of damage in the garden. If this is the case, you will have more success focusing your efforts on controlling the aphids. While ant controls are available, tolerance of a few will be necessary in the garden.

Woodlice - Woodlice eat dead and decaying plant material. If you see them on dying plants, they won’t be responsible for the plants’ death, they will be simply taking advantage of the dead material. Look elsewhere for the culprit.

Hoverflies - Useful pollinators, their larvae also feed on aphids. Often resembling bees or wasps with yellow and black markings, they are in fact harmless with no sting. You can tell the difference as they do not buzz and often stop stationary in mid-air.

Lacewings - Flying insects with bright green bodies and green veined translucent wings. Adults and larvae eat aphids and other pests.

Ladybirds – Adults and larvae are some of the best aphid predators. Attract them to your garden with a bug hotel.