Hi All
Today I realized that my dwarf Meyer lemon tree leaves covered with black coat ,,,,what insecticide should I use to treat the problem
Please see attached photos
Thx
Hello @zillah
Sorry to hear that your dwarf lemon tree is suffering from black sooty mould. Your dwarf Meyer lemon is actually giving you a very clear signal about what is happening. The black coating on the leaves is sooty mould, which develops on the sticky honeydew produced by sap-sucking pests. In your photos, the culprit appears to be a significant infestation of scale insects attached to the stems. The good news is that this is a very common citrus problem and, with some attention over winter, your tree can recover very well.
For treatment, I recommend https://www.bunnings.com.au/ocp-500ml-eco-oil-concentrate_p2960092 , available from the store. Eco-Oil is specifically labelled for controlling scale insects on citrus and works by coating and suffocating the pests while remaining suitable for edible plants. It is made from botanical oils, is approved for organic gardening, and is effective against scale, whitefly, mealybugs and other sap-sucking insects. If you prefer a ready-to-use option, https://www.bunnings.com.au/ocp-750ml-ready-to-use-eco-oil_p2961639 is also available from Bunnings and is suitable for smaller trees.
At this time of year, my best advice for winter recovery is to focus on reducing the pest population rather than trying to force new growth. Start by gently removing as many scale insects as possible by hand or with a soft brush, then thoroughly spray the stems and both sides of the leaves with Eco-Oil, paying particular attention to the areas where the scale are clustered. Winter is actually a favourable time to do this because cooler temperatures reduce the risk of foliage burn and the tree is under less stress. Repeat applications according to the product directions, as newly emerging scale can hatch after the first treatment.
I would also avoid heavy fertilising during winter. Instead, keep the tree evenly watered, remove any dead or badly affected twigs, and allow as much sunlight and airflow around the canopy as possible. Once the scale infestation is brought under control, the sooty mould will gradually weather away or can be gently washed from the leaves. As spring warmth returns, you can then feed the tree with a quality citrus fertiliser to encourage fresh healthy growth.
Overall, your lemon tree is far from beyond saving. The flower buds visible in the photos are an encouraging sign that the tree still has plenty of vigour. By tackling the scale insects now and giving the tree a calm, steady winter recovery period, you should see a noticeable improvement in foliage health and growth as the weather warms.
Here is a handy guide: How To Grow And Care For a Lemon Tree
Please remember to wear personal protection such as gloves, goggles and a mask.
If you need further assistance, please let us know.
Eric
Thank you very much Eric for your help
