Pests and diseases

Open PLAYLIST on the video below, for mini guides on how to recognise and treat common fruit tree pests and diseases

These days, apples and other top fruit grown conventionally are sprayed on a regular basis to prevent fungal disease scab and invertebrate pests. Even organic orchards spray with copper sulphite sprays that can be toxic when they build up in soils, and can damage the very soil food web that is essential to tree vitality.  We believe in agricultural systems that nourish ecosystems, not deplete them, and so we strongly advocate an ecological approach, and one that is not dependent on damaging pesticides, fungicides and herbicides.

Growing tree fruit organically has been described as the ‘final frontier’ of organic growing as preventing the build-up of pest and disease cannot be countered by crop rotation – trees being long-lived perennials. As orchards tend to be a monoculture, they will inevitably attract a build-up of both (although community orchards do tend to be a more diverse assemblage of trees and are usually on a much smaller scale).

So the key to preventing pest and disease is good management of the whole system starting with the soil. Healthy soils, developed so that they are heavily fungal, not bacterial, will give the best chance of healthy trees as fruit trees prefer a fungally dominated ‘forest’ soil. The more diverse a system we can create, the more resilient it will be. Building a healthy soil with a diverse food web is the starting point, as these subterranean organisms break down matter and convert it into forms that the tree can utilize. Nurturing organisms at the microbial level extends to the phyllosphere, the above ground portion of the tree, where benign fungi can be encouraged outcompete damaging fungi such as scab.

Creating beneficial guilds of plants by under-planting the trees with plants which attract beneficial insects and deter pest ones will also help to keep things in balance and may provide additional sources of nutrition for the host tree through nutrient mining and nitrogen fixing plants.

So, keeping trees healthy in the long term largely depends on a holistic approach; developing and maintaining a healthy orchard ecosystem, from the soil upwards, and working with nature to achieve balance.

By building a thriving soil food web, attracting beneficial predators, ensuring there are sufficient nutrients in the system and correct pruning (to prevent the humid microclimates favoured by unhelpful microorganisms), we can give the trees the best chance of remaining healthy and fruitful for the long term.

Read a light hearted blog entry about ladybirds and aphids on fruit trees

Variety and rootstock selection

You can make things easy for yourself by selecting varieties that are suited to organic culture. Varieties described by ‘easy to grow’, or ‘trouble-free’ etc have usually had disease resistance bred into them, and tend to be newer varieties, although some of the heritage varieties also have good resistance. It’s also worth finding out what other people are growing successfully locally, and have done historically in the area. Modern rootstocks also have some pest and disease resistance bred into them, for example MM106 is meant to be woolly aphid resistant, so research your local conditions and find out which stock are appropriate.

This does not seek to be a comprehensive guide to fruit tree pest and disease, but an overview of some of those we’ve come across in our community orchards throughout London and urban areas. It is worth noting that climate change brings with it the ever increasing threat of new pest and diseases for our trees, the rate of arrival far exceeding the trees’ ability to adapt. Recent cases of ash die back, leaf mining moth in horse chestnuts and oak processionary moth all serve to highlight the increasing risk of new dangers, in the threat of spores and invertebrates, which makes the idea of creating health and resilient systems all the more important.

Integrated Pest Management

Seeks to learn about the life cycles of pest and disease organisms so that vulnerable stages can be identified and exploited. This is where ecology comes in and it pays to learn about the creepy crawlies on and around your trees, both friends and foe!

We’ll be developing individual fact sheets on the most common pests and diseases soon, so watch this space…