You can identify powdery mildew by noting the white, powdery patches of the fungus that form on upper and lower leaf surfaces, flowers and fruit. With most polytunnel plants, this fungus will be obvious, and affected plant tissue can be quickly removed. However, it can be helpful to have a better understanding of this disease, in case it does take hold in your polytunnel. Below you will find information which will help you determine what has caused the problem, how to treat an outbreak, and how to reduce the chances of getting it again in the future.
What Causes Powdery Mildew?
Inadequate or patchy watering can often lead to an outbreak of this fungal infection in a polytunnel, most notably on courgettes and other cucurbits such as squash and pumpkins. The mildew is caused by the fungal spores which are present in the environment, though plants which are under stress due to watering problems will be more likely to succumb to the disease.
How To Treat Powdery Mildew In Your Polytunnel
If you encounter powdery mildew on the leaves of crops in your polytunnel, the first thing to do is to promptly remove all affected plant material, and dispose of it well away from your growing areas. Do not put any leaves that show signs of powdery mildew into your compost heap.
If you have seen a problem with powdery mildew in your polytunnel, after removing all leaves and vegetation which shows signs of infection, spray other leaves on affected plants, and the leaves of any other susceptible plants in your polytunnel with the bicarbonate of soda solution, or with a diluted milk solution (one part milk to ten parts water) to slow down its spread.
Reducing the Chances of Getting Powdery Mildew
As with any disease, removing affected material quickly is the best way to reduce the chances of spreading or recurrence. Making sure that you remove and destroy all affected leaves will reduce the chances that there will be infectious spores about to spread to other plants or to resurface the following year.
Since water stress is often one of the main reasons why powdery mildew has taken hold, you can also reduce the chances of getting powdery mildew in the future by:
Watering well and consistently.
Watering early in the morning.
Mulching crops to reduce water loss from the soil around your plants.
If you are having difficulties keeping up with watering in your polytunnel, or are finding it a challenge to water consistently by hand, you could consider investing in an automated watering system for your polytunnel. There are a range of different watering and irrigation systems available which could help you to meet the water needs of your plants more effectively and efficiently.
If you want to know more about maintaining good health in your polytunnel, there are plenty of other articles for you to read on this website. Check out our articles to learn more about effective watering systems and other issues of plant care.
Elizabeth Waddington is a writer and green living consultant living in Scotland. Permaculture and sustainability are at the heart of everything she does, from designing gardens and farms around the world, to inspiring and facilitating positive change for small companies and individuals.
She also works on her own property, where she grows fruit and vegetables, keeps chickens and is working on the eco-renovation of an old stone barn.