RHS reveals pests and diseases ranking for gardeners

This year's RHS pest and disease ranking has been revealed, showing which diseases and pests are a concern for gardeners.

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The 24th annual pest and ideas ranking shows that box tree caterpillar has topped the pest ranking for a third year in a row. It also shows that the pest has become more widespread and resulted in more enquiries than the rest of the top five combined.

Honey fungus is the most prominent garden disease - a pattern repeated since the ranking began in 1995 - although there was a drop in enquiries between 2018 and 2019.

The alder lead beetle returns to the top ten for the second time and is now the fifth most popular pest enquiry in 2019. The beetle can cause defoliation of alder, its main host.

Apple and pear scab are of increasing concern to gardeners and the same fungi are responsible for blossom wilt in spring and brown rot in summer. Black rose spot also took a place in the top ten, which is surprising given how familiar this disease, and its management, is for gardeners.

The top ten pests for gardens in 2019

1. Box tree caterpillar
2. Vine weevil
3. Slugs/snails
4. Fuchsia gall mite
5. Alder leaf beetle
6. Woolly aphid
7. Rosy apple aphid and Viburnum beetle
8. Glasshouse red spider mite
9. Plum leaf-curling aphid

The top diseases for plants in gardens in 2019

1. Honey fungus
2. Phytophthora root rots
3. Box blight
4. Pear rust
5. Brown rot of fruit
6. Leaf spot and canker of Prunus
7. Apple and pear scab
8. Rose black spot
9. Blossom wilt of fruit trees
10. Powdery mildew of Prunus

Matthew Cromey, Principal Scientist at the RHS, said: "Pests and diseases are among the main challenges we face as climate change affects our gardens and horticulture more widely.

"As the UK’s gardening knowledge bank, our research will help increase biosecurity and provide best practice. We want to develop a nation of gardeners equipped and motivated to deal with the challenges of our changing world."