Root Awakening: Curry leaf plant infested with sap-sucking pests

My curry leaf plant keeps getting black spots under the leaves. I have cleaned and sprayed neem oil several times, but the spots keep reappearing. I have tried changing the pot and soil to no avail. What is this infestation and how can I stop it?

Prakash Menon

The black spots appear to be the larvae or pupae of a sap-sucking pest common in this plant species. Prune the infested parts if you do not want to use pesticides.

If your plant is grown under optimal conditions, it should be able to produce new growth that will replace the infested parts. Inspect your plant regularly and act promptly to stifle any pest infestations.

Environmentally friendly pesticides like summer oil can also be sprayed to manage the pest population. Ensure complete coverage of the plant and apply regularly to provide adequate control.

Move pot-bound plants to larger containers

My late father’s plants were thriving, but their leaves have started to turn yellow with brown patches. According to Google, these are copper plants (Acalypha wilkesiana).

This is happening across three different copper plants. We have removed the yellowing leaves, but the plants still look unwell. There are also beige patches on the soil’s surface.

Something similar happened to the plants last December, but on a smaller scale, and the plants bounced back with minor pruning. What is wrong?

Madeline Yeo

The pots seem too small for your plants. Pot-bound plants tend to dry up quickly, due to the limited amount of water that their growing mix can retain. As such, they wilt when they are thirsty. Plants usually will revive when given water, but the lower leaves will turn yellow and develop brown patches consequently.

You can move the plants into larger pots, which will have more soil volume and moisture levels at the root zone. You can also propagate new plants from short stem-cuttings as a back-up.

Monstera infected with a fungal disease

I bought my Monstera Albo seven months ago. A few weeks ago, the edges of the leaves turned brown with some yellow patches. Is the browning due to natural ageing or other issues? What can I do to maintain healthy foliage, and should I cut off the lower leaves?

Chng Ghim Hoon

The yellow spots look like a fungal infection, which can happen if the plant is grown in a shady location without proper air circulation. Infection can also occur if leaves are injured during handling and movement. Remove any injured leaves, as they will not recover.

Spray the plant with a fungicide to prevent the infection’s spread, and try to improve its growing environment to stop this issue from recurring.

To prevent your plant’s leaves from developing brown edges, ensure that its growing mix stays moist at all times. Do not let the plant dry out completely or grow in waterlogged conditions. Consider moving it to a bigger pot, which will be able to store more of the growing mix, so it does not dry out too fast. A pot-bound plant dries out faster.

Avoid over-fertilising. You may want to use slow-release fertiliser pellets to meet your plant’s nutrient needs and prevent salt build-up in the root zone.

Damaged leaf may have been resting on window glass

What is wrong with my Peace Lily? Some of its leaves, though not all, are turning black from the tips. I water deeply when its leaves droop and fertilise every few weeks. It gets filtered sunlight.

Diane Yeo

The large patch is likely due to an injury. Was the leaf resting on window glass that was exposed to sunlight? The heat from the window could have burned the leaf, and the damaged leaf should be cut and removed.

Move your plant a short distance away from the window so that this does not happen again. Rotate your plant periodically, as it will grow towards light over time in a high-rise setting.

The browning leaf tips on the rest of the plant need some attention. Letting the plant dry out totally, as well as overfeeding with fertiliser, can be possible reasons. Keep it moist. A change of growing medium, together with the use of slow-release fertiliser pellets, may benefit the plant.