Use diluted soap solution to remove stains
How do I get rid of these white spots on the plant's leaves?
These white stains could be caused by garden chemicals applied on the plant during nursery production or when they were imported into Singapore. They could also be residue from water splashes from the ground or any dirty surface.
Try spraying a very diluted soap solution on the leaves to remove the stains.
Avoid using an overly concentrated soap solution as soap can dissolve the protective coating on leaves, causing irreversible injury to the plant.
Fungal disease possible cause of black patches
What is wrong with my plant? The leaves and flowers turn brown. I water it once a day and keep it in my bathroom.
The white structure is called a spathe - a modified leaf that is found at the base of the inflorescence of true flowers. If this plant has been with you for a while, the yellowing of the spathe is part of the ageing process.
The black patches on the leaves could be a sign of fungal disease. Remove affected leaves promptly.
It is vital to keep the plant's foliage dry. The bathroom can be an unsuitable display area as air circulation is often poor and light levels are low.
To manage the spread of the disease, increase air circulation and give the plant more light. It needs filtered sunlight for four to six hours a day. Using a fungicide such as Mancozeb may help to keep the situation in check.
Crush larvae early to deal with infestation
A week ago, white lines were seen on the leaves of my long bean plant. Now, the leaves are curly and have yellow dots. I do not want to use chemicals on the plant as I hope to harvest it for food.
Yew Poh Yok
Your plant is infested with leaf miners. They are the larvae of small flying insects that burrow in leaf tissue, making the white tracks. Leaf miners are difficult to control as contact pesticides are not effective in killing the larvae inside the leaves and sprays need to be timed accurately to kill adult leaf miners.
At the first signs of tunnel appearances, you can squeeze the leaf at the ends of the tunnels between two fingers to crush the larvae. This can be an effective means of control for minor outbreaks and a small collection of plants.
Remove and destroy badly infested leaves too. An environment-friendly and food-safe method to control leaf miner infestations is to use neem oil, which is a common method of pest control in home food gardens.
Neem oil reportedly affects the leaf miner's life cycle and reproduction. But note that it does not produce immediate results.
Tip: Brazilian Button's flowers a rare hue in the tropics
The Brazilian Button, from the Daisy family (Asteraceae), is a delightful plant to grow in the garden. Its botanical name is Centratherum punctatum.
When crushed, its coarsely toothed, green leaves emit a fruity scent reminiscent of pineapple or passionfruit. The plant produces bluish-lavender flowers - a rare floral colour in the tropics - when grown under full direct sunlight outdoors.
It can be used as a foreground groundcover plant. It should be pruned regularly to encourage a dense growth habit and is easily propagated using stem-cuttings. It is ideal for landscaping a fragrant or scented garden, as well as an English- themed garden in the tropics.
Wash pests off food plants with water
My tomato plant is infested with white flies. Is there a way to get rid of them without using chemical solutions?
White flies are sap-sucking insects that can be difficult to control in large infestations.
The most environment-friendly method to manage small infestations is to use a water jet to wash the pests off your plant. Organic pesticides such as summer oil and neem oil can also be used to smother the pests.
These methods can reduce but not eliminate the pests.
Avoid the use of systemic chemical insecticides - they may be more effective, but are often not indicated for use in food plants. They can also kill off beneficial insects and pollinators in the garden.
• Answers by Dr Wilson Wong, a certified practising horticulturist and founder of Green Culture Singapore (www.greenculturesg.com). He is also an NParks-certified park manager.
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