Pepper Elder is a common medicinal plant that occurs as a weed
I thought I planted mint seeds, but these sprouted. Are they mint? What are the tiny ball-like structures on the plants? I also spotted white insects which have white hairs and black spots and which seem to be harming the plants. What are they and how do I get rid of them?
The plant is Pepper Elder (botanical name: Peperomia pellucida). It is a weed that grows frequently in gardens and flower pots, and is sometimes grown as a medicinal herb.
It is not clear from the picture, but the small ball-like structures on the vertical stalks could be the fruits of the plants.
It is also not clear, from the picture, what the insects are. However, some scale insects - which appear as small, brown bumps - can be seen on the plants. They are sap-sucking pests that can weaken the plants over time if their population increases.
You may want to give your plants a little more light to increase their vigour. Organic pesticides like summer oil and neem oil may be used to control the pest population. They work by suffocating the pests, so good coverage and repeated applications are often required.
Ficus may be infested by thrips
I have had this plant for more than two years. It has been growing very well, but its new leaves recently turned dry. It is placed in my balcony which gets a lot of afternoon sun. What can I do?
The curled leaves of your Ficus may be due to thrips. Open up and inspect the curled leaves. Thrips in this case will appear as small, narrow insects that may be either translucent or black. They feed on plant tissue by rasping it and this causes developing leaves to become distorted.
You can prune affected leaves to cut down the pest population. Start spraying the plant with less toxic pesticides like neem oil, summer oil or pyrethrins. Good coverage and repeated applications are often required.
Entomopathogenic pesticides that contain the Beauveria bassiana and Metarhizium anisopliae fungi may also be used, but can be quite costly for hobbyists.
Dracaena lacking light for photosynthesis
I bought this Dracaena fragans from a nursery and placed it in the office for the past three weeks. Why are the leaves turning pale? The top layer of the growing media is coconut husk to prevent loss of moisture. What type of soil is best for the plant? Also, it does not get any sunlight at all.
Plants contain chlorophyll and need sunlight to perform photosynthesis, a process of making food to sustain the plant and produce growth. As such, they will not do well if they are grown in a place that has no sunlight or is too dim for them to perform photosynthesis. The pale new growth in your Dracaena is a sign of a lack of light.
Move your plant to a spot near the window, balcony or corridor where there is at least four hours of filtered sunlight daily. You can move the plant indoors for display for a few days before returning it to the sunlit site to recuperate.
Alternatively, you can install a grow light above the plant to provide the light it requires to thrive. Ensure the intensity is sufficient and switch the light on for at least 12 hours daily.
Increase pesticide applications to keep pest populations under control
About four months ago, I planted eggplant seeds I received from the National Parks Board. The leaves were green and healthy, but turned yellow after the plant was infested with bugs. A few flowers dropped off after they bloomed. I sprayed the plant with organic neem oil thrice - with each spray about two weeks apart - yet it is still infested with bugs. Similarly, my basil plant looked healthy a few months ago. I also harvested its leaves a few times. It is now infested with bugs too, and its new leaves are smaller, fewer and yellowish. I have used neem oil to reduce the pest population to no avail. Should I discard both plants? How can I prevent this from happening if I plan to replant both from seeds again?
Lai Kwai Kuin
The picture of the eggplant does not show clearly the pest issue mentioned.
For pest issues, it is best to nip them in the bud. Inspect plants daily and take action promptly. Depending on the pesticide used as well as the type of pest, it is important to know the life cycle and reproduction rate of the pest and apply the pesticide accordingly. There may be a need to increase the frequency of application for adequate control.
You may also need to combine it with other methods like washing the pests off plants and using pesticides that work via another mode of action. This applies also to the pest issues of your basil plant.
The basil plant appears very leggy with long stems that are devoid of lower leaves. It is probably pot-bound too - a situation where the roots have totally filled the container.
You may want to prune the plant selectively to promote new growth. Also, consider moving the plant to a larger pot for the roots to have more space to grow to support more aerial growth. You can propagate new plants using tip cuttings.
Ensure Desert Rose is grown under optimal conditions and rotate pesticides for better pest control
This plant was infested with red spider mites. I have been washing and spraying it with neem oil, but the mites reappear after a few days. How can I eradicate them? Also, the flower buds would appear but do not bloom.
Lim Eng Chong
The failure of flowers to develop fully may be due to a range of issues.
Ensure that the plant receives sufficient sunlight. The Desert Rose requires at least six hours of direct sunlight to grow well. Avoid stressing the plant, water it sufficiently and do not allow it to dry out excessively or give it too much water.
Also, protect it from rain as heavy rain can damage flower buds. Finally, check for pests such as thrips and aphids, which can feed on developing floral tissue, causing the buds to be aborted.
As for the spider mite issue, infestations can be difficult to control if the plant is stressed and not growing under optimal conditions. Pesticide applications may need to be repeated in close intervals for adequate control.
Also, pesticides such as summer oil that work via contact mode will need to cover the plant completely to be effective. Pests tend to hide in difficult-to-reach places.
Rotate this with other pesticides - such as abamectin, a miticide - for more effective control. Do not use miticides for prolonged periods as this can cause pest resistance, rendering it useless for spider mite control in future.
- Answers by Dr Wilson Wong, an NParks-certified practising horticulturist, parks manager and ISA-certified arborist. He is the founder of Green Culture Singapore and an adjunct assistant professor (Food Science & Technology) at the National University of Singapore.
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