Common Hydrangea pests & diseases

Common Hydrangea pests & diseases

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A basic guide to pests and diseases that affect Hydrangeas!

Hydrangeas are well known for there large impressive showy flowers and ability to change their flower colour from pink to blue because of the soil type.

Hydrangeas are generally pest and disease free but as with all plants sometimes they can be affected by diseases or pests. We have put together a list of the most common diseases and pests which you can refer to and try and identify any problems you may have.

Pests that may effect Hydrangeas

With hydrangeas, the most common pests and diseases include leaf spot which can be brought about by problems with water and soil. There is also a risk of powdery mildew when the plant doesn't get enough air circulation and there's too much water in the soil. Another risk is mold and aphids such as hydrangea scale so be cognizant of where you live and what issues you might face giving your soil environment and weather.

Hydrangeas are generally not affected to badly by pest but they can sometimes be affected by a handful of insects and other pests.

  • Aphids: These come in many forms and all though they are unlikely to kill a plant they can cause the leaves to curl by sucking the sap from the leaves which also leaves honeydue on the leaves that is a waste product of aphids. This can then lead to fungus forming on the leaves and aphids can also spread viruses.  Treatments include spraying with general pesticides or for a more organic approach try washing the leaves with soap. The soap clogs the pores of aphids and kills them.
Provanto 84436674 Ultimate Bug Killer RTU 1L
  • Up to 2 weeks control of a wide range of pests
  • Rapid action and long-lasting protection
  • Use on flowers and a wide range of edibles
  • Targets lily beetle, whitefly, scale, greenfly, red spider mite, blackfly, mealybug, thrips and leaf hopper
  • Use outdoors and indoors
  • Rose Chafers (beetles): Rose chafers are a beetle that is known for eating the flowers blossom of Hydrangea leaving small holes in the petals. They also eat the leaves between the veins of the plant causing further damage. The best organic way to try and prevent this is to check the plants and manually remove them from the plant. Pesticides can also be successful and have more immediate effects.
Bug Clear Ultra for Flowering Plants,Liquid Concentrate Insecticide and Acaricide, 200 ml
  • A contact and systemic insecticide that offers protection against a wide range of pests for flowering plants
  • Kills all major ornamental insect pests including whitefly, greenfly, blackfly and other aphids, scale insects, mealy bugs, red spider mites, caterpillars and lily beetles
  • Also offers a useful level of control of thrips
  • Its systemic action protects treated plants from such pests for up to three weeks
  • For use outdoors and in greenhouses and conservatories
  • Slugs and Snails: A pest everyone will be familiar with, there are not many plants that not affected by slugs but they will eat fresh new soft foliage. Slugs and can cause in slug traps which catch them at night and are very successful. Another highly successful way is to spread slug pellets around the garden.
Garland GAL13ST Slug X Trap, Green, 25x20x10 cm
  • A beer trap with a fearsome reputation
  • Each one can kill 40-50 slugs and snails a night
  • Fill with beer and the slugs are attracted to the smell
  • Once inside, they become disorientated and trapped in the inner maze
  • Lies flat to the ground - can be placed anywhere in the garden
  • Hydrangea Scale: Hydrangea scale is probably one of the most popular pests, they are usually identified by there oval white eggs that attach themselves to the stems of the plant. The pest such the sap from the plant and cause the plants to suffer and not growth as vigorously as they would. You can try to remove the eggs manually but this is a very hard option and may not be successful. Spraying with a pesticide is probably more effective and needs to be done around mid-July to kill the young nymphs.
Neudorff BugFree Bug and Larvae Killer, 750 ml
  • Active ingredient content 0.045 g/L pyrethrins and 8.25 g/L rapeseed oil
  • Ready to use spray to control mature insects, their larvae and their eggs
  • Effective against sucking and biting insects such as aphids, thrips, spider mites, whitefly, mealy bugs, scale insects, caterpillars, beetles and sheet wasp larvae
  • Suitable for a wide variety of ornamental plants, kohlrabi, apple and pear in home gardens and on allotments

Diseases that effect Hydrangeas

Mildew on Hydrangea
Mildew on Hydrangea

Mildew: Mildew is common on many garden plants and Hydrangeas at no exception. Mildew, as pictured left, is common in warm wet weather and is a type of fungus. Plants can be treated with a fungicide and sprayed as instructed in the back of the product packet. Having plants in an area where air can circulate around the plants will help prevent mildew.

FungusClear 18986 Ultra, 3 in 1 Action, Plant Protection Disease Control, 225 ml
  • Systemic protection and control of blackspot, powdery mildew and rust
  • Use on roses and other flowering or ornamental plants
  • Protects new growth and protects plants for over 3 months, when used at intervals recommended in usage instructions
  • Use between March to September
  • Apply using a garden pressure sprayer washed before and after use
Scotts Fungus Clear Ultra Gun! 1LTR
  • Ready-to-use hand spray
  • Gives systemic control of rose blackspot, powdery mildew and rust
  • Controls existing diseases and protects new growth
  • Quickly treats roses, garden flowers and decorative shrubs, trees and climbers
BOTRYTIS BLIGHTPetals turn brown and fall. Leaf spots form, especially where faded petals have fallen. Flower buds are killed before opening.Botrytis cinereaSpace plants to ensure good air circulation. Maintain low humidity. Avoid watering late in the day. Remove crop debris. Apply a fungicide to protect plants.
CERCOSPORA LEAF SPOTTan spots with reddish-brown halos develop on leaves.CercosporaApply a fungicide to protect plants. Water in a manner that keeps moisture off the leaves.
POWDERY MILDEWYellow areas form on leaves. These may become purplish. White, cottony fungal growth forms on the lower surface of the leaf.Erysiphe polygoniApply a fungicide to protect plants.
VIRESCENCEFlowers are green and may be stunted. Leafy shoots grow from the flower parts. Plants decline and die.PhytoplasmaDiscard infected plants. Maintain good insect control.
VIRUSESLeaves may be mottled, have yellow spotting, dead flecks, line or ringspot patterns. Plants may be distorted or have flower colour breaking, or few flowers.Hydrangea ringspot, tomato ringspot, impatiens necrotic spotPlant virus-indexed cuttings. Maintain good insect and mite control. Destroy infected plants.

Last update on 2024-06-16 / Affiliate links / Images from Amazon Product Advertising API

2 thoughts on “Common Hydrangea pests & diseases

  1. One of my there second year potted hydrangeas suddenly has white discolouring round all leaf edges. Not responded to general purpose bug spray. Pretty sure it is nowt scale or mildew. Any ideas/advice, please?

  2. I put too much malathion on my hydrangeas and now the flowers are brown. What do I do? Thank you for all the help you can give me

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