Friday 15 November 2019

Controlling garden pests and diseases

Sometimes it might seem that the garden is some type of war zone, with threatening animals and insects on one side and a host of plant diseases on the other just waiting to wreak havoc on your garden.

In reality, there are very few pests and diseases that kill garden plants.

If you think about it, it is not in the self-interest of either pests or diseases that the plant dies as they depend on living plants for their food.

The secret of a healthy garden is to try to keep conditions unfavourable for the 'bad' pests and diseases.

This is often a lot easier than you might think.

Common pests and what to do

Slugs and snails

Find young, soft plant leaves irresistible. In wet weather they feed 'round the clock'. In dry weather they eat at night, so if you see damage to young leaves but can spot no culprit, he is hiding just below the soil or under a nearby stone.

Defence tactics

a. Traps -- Strategic placement of traps often filled with beer. The offenders die happily.

b. Grab a torch when dark and round up the intruders.

c. Slug and snail pellets -- Immediately effective, but can kill birds and hedgehogs who help greatly to control the problem.

Vine weevil

Curiously it's not the parents of this pest that cause the most damage but the 'kids'. Small, bright, white grubs with an orange head hatch in spring or autumn and begin nibbling at the base of soft fleshy plants with deadly effect. They are most common in containers.

Defence tactics

a. Vine weevils love the softness of peat composts against their skin:

i. If you are potting up containers with plants that are intended to last for a number of years, use a soil-based compost.

ii. Alternatively, empty and replant your containers every year.

b. If you spot the grubs, obtain a biological predator that will naturally attack the grub.

c. Grab the trusty torch and arrest the parents (who are active after dark) on august nights. They look like common black beetles.


Also known as aphids and have cousins that come in white and black. They suck out tasty sap from soft plant stems.

Defence tactics

a. Spray badly infested plants with soapy water or a low-level insecticide (strong insecticides will kill other 'good' insects that eat greenflies).

b. Plant flowers such as French marigolds that attract hover flies and ladybirds. These insects eat the greenfly by the barrow load.

Common diseases and what to do


Cause plants to drop leaves even in the middle of summer. Most common on fruit trees, eg apple. Dark and greenish brown patches appear on the leaves.


Another fungal disease, which particularly affects roses. As the name suggests, black spots appear on the leaves.


This fungus appears on leaves, buds, flowers and young shoots in the form of a pale grey coating on a wide range of plants. Usually occurs during dry summer weather, so regular watering helps.

Defence tactics for three diseases

Only rarely do any of the three fungal diseases mentioned kill, but you can help your plants by:

a. Picking off infected foliage and removing fallen leaves from the base of plants.

b. In severe cases, use a suitable fungicide.

Shopping list:

Slug and snail trap
Soil-based compost
Biological vine weevil control
Bird feeders and food

This article originally appeared in 'It's garden time', in association with Bord Bia

Irish Independent Supplement

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