In most instances the speckled silvering leaves are caused by Azalea Lace Bug (Stephanitis pyrioides) which is native to Japan.
Lace bugs are sap sucking insects with lacy wings that congregate on the underside of leaves, a small number of these insects will not kill a plant and does not necessarily require treatment.
It is always best to try organic methods first. Check the health of your plants by looking at the undersides of some of the leaves, particularly in the spring and summer as the dormant eggs are hatching. If you catch the damage early you may simply be able to remove and carefully dispose of the effected leaves.
If the damage is severe the plants may require chemical treatment to kill the adults and break the lifecycle of this species. Many of the treatments to kill lace bugs may also kill off beneficial insects such as bees and ladybugs so treatment should be taken with care.
As with most tree pests and diseases plants are more susceptible if they are under stress. It is important to ensure the plant is appropriate for the area and plant health issues are addressed. Ensure adequate water, good soil condition and protection from severe weather. Both azaleas and rhododendrons generally prefer protection from full sun.
Other issues in rhododendron species, including azaleas, that might be causing health problems to these plants are:
- leaf miner
- powdery mildew
- greenhouse thrips
- whiteflies
- two-spotted mite
- leaf gall
- petal blight
- grey mould
- phytophthora root rot
- sunburn
Treetec can help with advice on diseases and offer chemical treatments for Azalea Lace Bug as well as other problems and diseases. If you require chemical treatment please note timing of the treatment is critical. It needs to coincide with the emergence of the first bugs from eggs usually around early springtime. Follow up treatments may also be required.
Please contact us for more information.