Azaleas are one of the best known and well loved of the Spring flowering shrubs. Likewise the fragrant and delicate blooms of the Gardenia are an age old favourite in many gardens.
Unfortunately both plants are extremely susceptible to certain diseases.
The most common problems are:
Lace Bug on Azaleas - When a plant is affected by lace bug it will have a silvery look to the top of the leaf with a rusty underside. New leaf growth is a particular target for lace bugs. They tend to lay their eggs on leaf tissue from which the nymphs hatch and suck the sap from underneath the leaves.
Lace bug will rarely kill an Azalea so it is not necessary to spray it, but in a really severe case, insecticides are available. Products such as Confidor and Lebaycid are effective but are quite toxic chemicals, so proper care should be taken.
Scale on Gardenias
The sight of leaves covered with a black sooty mould fools many people into thinking a terrible disease has struck. This is not a disease. Sooty mould which usually comes hand in hand with the presence of ants is a sure indication that scale insects are attacking and spreading. They are tiny little creatures that can be seen clustered along the midribs of the leaves and sometimes along the plant stems.
Ladybirds are the natural predators of scale, however the presence of ants usually wards them off.
A simple remedy is a white oil emulsion which can be mixed with water and sprayed onto the plant. It can bought ready made or you can make your own.
White Oil Recipe:
- One part vegetable oil
- ½ part water
- Some washing up detergent
- Use a whisk for blending
- When using in the garden, dilute one part mixture to forty parts water
- Shake well before use
- Spray all the affected foliage and get as much underneath the leaves as possible.
- This thin film will suffocate the pests by sealing the outside edges and depriving them of oxygen.
- Take care not to spray during very hot weather as this can cause damage to the plant.
- There should be an improvement within two weeks.