Pest patrol

GROWING plants is one of the greatest pleasures of gardening. Unfortunately, as all gardeners know, it is very difficult to keep the plants healthy from unwanted pests as they can cause serious damage.

Aphids are a real problem that everybody will have encountered while outside in the garden. Aphids are a nasty pest that can cause lots of damage to plants. They are sap-sucking insects that can cause a lack of plant vigour, distorted growth and they often leave a sticky residue on the plants foliage, which then leads to other problems such as sooty moulds.

Aphids are very easy to identify, ranging in size from 1mm to 7mm long. They are usually seen from spring to late summer on outdoor plants and all year round if kept in a closed environment such as a greenhouse. The most common aphids are known as greenfly and blackfly, but there are many more species.

Aphids cause stunted growth with curled or distorted leaves. You can often see the aphids themselves with the naked eye, they tend to be on the shoot tips, flower buds and on the underside of leaves. Controlling them can be very difficult if you have a large colony. Using a biological control is an effective alternative to pesticides.

Currant blister aphid is very common on red, white and blackcurrants. The aphids again suck the sap that infests the underside of the leaf. The aphids are seen from late spring – early summer. The symptoms are very noticeable. The leaves at the tips start to curl and become blistered, causing the foliage to turn to a reddish or yellowish green discolouration. No control is necessary as the plant will still put on growth and will produce a crop. If not that many leaves have been attacked, they could be removed and burnt.

Newly emerging veg crops are always vulnerable. In the kitchen garden at Harlow Carr we make full use of the materials that we have around. Any branches that have been taken down or blown off the trees are then cut up into little twigs and placed around the plants. This slows the birds down as they do not like to land on the twigs and find it difficult to get through the little gaps between. The twigs are also used as a support to protect the plants from weather damage.

Nets are a good protection from birds. Place the netting over frames, leaving the edges inside making sure the birds cannot enter and get stuck inside. Using a finer gauge net will also mean cabbage white butterflies will also not be able to enter to lay their eggs on the plants.

Carrot root fly is a major pest to some root crops such as carrots, parsnips, parsley, celeriac and celery. This fly is small, black-bodied and up to 5mm long.

The maggots hatch from eggs in late May – June and in August –September. The symptoms are rusty brown scars that ring the tap roots, which makes them inedible and susceptible to secondary roots. Inside the carrots you often see a slender creamy-yellow maggot up to 9mm long.

There are many ways in which carrot root fly can be controlled such as sowing thinly to avoid thinning seedlings. Female carrot flies are attracted by the smell released when plants are removed. Sow between the carrot root fly generations. Barriers can be put up around the crops making sure they are 60cm high or cover the plants with an insect- proof netting such as Enviromesh. Choose carrot cultivars that are less susceptible to carrot fly.

Why not visit RHS Garden Harlow Carr to get more advice for the garden and productive team. We now have a free advisory session every Monday this summer from 1pm to 3.30pm