August 11 ‘Tackling Pests and Diseases’

PESTS and diseases are always lurking in the background ready to munch on your hostas or wipe out your tomatoes. At this time of year, it is particularly important to keep vigilant and take swift action before it’s too late.

 Slugs and snails are our number one pests especially when it’s been warm and wet so pick any off your plants when you see them and dispose of them. They are particularly active at night so get your torch out. Other pests to look out for are green fly or black fly (aphids) which are sap sucking insects which also spread viruses and white fly which can be a problem on tomatoes.

 As for diseases the top priority to look out for is blight on tomatoes and potatoes, especially towards the end of the month. This fungus can be devastating and turn your crops into mush within days. Luckily there forecasting system for blight called a ‘Smith Period’. This is defined as 2 consecutive days starting at 9am in the morning where temperatures are over 10 degrees C for at least 11 hours and the relative humidity is over 90%, in other words blight will spread when it is warm and wet. You will start to see brown patches on the leaves (potatoes and tomatoes) and tomato stems may develop black patches. Prevention is better than cure, avoid growing potatoes and tomatoes in the same spot, try not to water with sprinklers as spores can develop on wet leaves. Grow resistant varieties and grow early potatoes so you can harvest before blight takes hold. On potatoes it is a good idea to remove the haulm or foliage if blight arrives late in the season so that the tubers do not get infected as blight will spread from the leaves down to the tubers by rain splash. The only sure fire way to keep tomatoes and potatoes free from blight is to spray the leaves with a protectant fungicide before blight appears and then spray regularly to keep it away

 Good garden husbandry will minimise a lot of these pest and disease problems. Regularly remove dead, damaged or weak wood or leaf material. Clear infected leaves in the autumn and pick up any old fruit and get rid of it. Don’t leave discarded vegetable matter lying around as they can harbour problems and keep the weeds down as again they can harbour diseases that can spread onto your plants. If you can when you are choosing new plants keep a look out for varieties that are more disease resistant than others. There are a lot of other good organic methods for protecting your plants, from simple techniques such as soaking your Cotoneasters with the hose pipe to deter red spider mites to more sophisticated biological control methods using natural predators.

 You could try some companion planting, which is a method of growing another plant alongside your main plants to help protect them from pests and diseases. For example, growing something quite aromatic like chives or thyme will help to keep aphids off your roses as they don’t like the smell and growing marigolds will attract slugs and snails, they love them. Whilst they are eating your marigolds they aren’t feasting on your lettuces!

 Although we do try to garden organically, if you do have a particularly bad infestation sometimes you might have to use chemical control. Particularly effective for insect pests and vine weevil is a product called ‘Provardo’ which is widely available in all the garden centres. But do read the label and always use pesticides responsibly.

 As a last general point It is very important to keep your plants in top condition; they need to be keep well fed, watered, spaced out, and have plenty of light.  Healthy plants just like healthy people are more likely to resist pests and diseases.