Summer’s prolonged droughts and extreme heat have made plants more susceptible to problems such as fungi and insects this coming autumn, the Royal Horticultural Society has warned.
Plants stressed or damaged by the heat are most at risk of disease, but the charity’s experts say gardeners should also look out for specific plants that are typically more vulnerable such as tomatoes.
Tomato growers may be noticing more blight than other years and the RHS advises those worried to “pick off green tomatoes and leave them to ripen on a windowsill”.
The changing seasons are also expected to lead to more mildew. “Mildew can look bad but it’s nothing to panic about for gardeners,” said the RHS. “Gardeners can pick off the worst affected leaves and ensure plants are watered but not saturated.”
The RHS also warned gardeners to look out for an increase in honey fungi and glasshouse thrips – a type of garden pest – in the coming months.
Honey fungus (Armillaria mellea) is described by the RHS as the “most destructive fungal disease in the UK” and is expected to cause greater devastation than usual this autumn after summer’s exceptionally hot weather left plants more vulnerable. It can be deadly to plants, spreading underground to attack and kill the roots, before causing the dead wood to decay.
With no chemical able to control the spread, the RHS advises gardeners to improve plant resilience by maintaining good plant health, making sure plants grow “in suitable conditions” and watering young plants less often but more thoroughly.
The UK’s record-breaking summer temperatures have also given rise to the glasshouse thrip, a tiny insect that can thrive in greenhouses.
Generally found in hot and dry conditions, this species of thrip has increasingly been able to survive in the south of the UK as the climate heats up.
Although the insects often do not cause noticeable damage, a garden infestation can cause mottling or spread plant viruses. Symptoms to look out for include silvery discoloured leaves, marked with small brown-red spots caused by the insects’ excrement. Worried gardeners should note that thrips can be controlled by natural garden predators, including the bug Orius laevigatus.
Sara Redstone, the biosecurity lead at RHS, said: “One of the best ways to maintain healthy plants year round is to let nature help in your garden. Gardens can play an important role in climate resilience and gardeners can maximise this by selecting and planting species which tolerate weather extremes in their local conditions.
“These resilient plants will be less stressed by the increasingly frequent harsh conditions we expect to see under climate change, and therefore stand a better chance of surviving disease.”