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(Lime plant infested with white flying insects PHOTO: GAN SING HAI)
Question: My lime plant was growing well and blooming before it became infested with white flying insects. I tried spraying the plant with white oil, but it has no effect on the insects. What are the insects and how do I get rid of them?
Gan Sing Hai
Answer: The pest is the whitefly, a type of sap- sucking insect. Whiteflies may appear if plants are stressed due to sub-optimal growing conditions.
The lime plant grows best in a sunny area. If you are growing it in a shaded location, give it at least four hours of direct sunlight daily.
For now, the most environment- friendly way to manage whiteflies is to use a strong water jet to wash them off the plant.Repeat the treatment if the infestation returns.
You can also use organic pesticides such as neem or summer oil, which suffocate the insects. The oils need to be sprayed regularly so that all pests and their young are eradicated.
Question: What is this plant (pictured) and can its fruit be eaten?
Jillian Toh
Answer: The plant is the golden variety of the edible papaya. Its botanical name is Carica papaya.
It has red petioles - a stalk that joins a leaf to a stem - that stand out against its yellow-green foliage. The edible fruitare best harvested after they ripen naturally on the plant.
Protect the ripening fruit from animals by wrapping them with a wire mesh. The Carica papaya plant can also be grown in a garden for its ornamental value.
Question: I bought a potted water lily from a nursery here and moved it into a larger container. The plant received four hours of afternoon sun every day. After a week of buying the plant, I buried a fertiliser pellet meant for lotuses and water lilies. The plant grew well, with new leaves sprouting for the first two weeks. However, the leaves started to rot. Why did this happen?
Leong Tuck Sum
Answer: Water lilies are sun-loving plants and need more than four hours of direct sunlight a day to be healthy. So, the rotting of leaves could be due to lack of sunlight.
Another reason for the rot could be that the plant is buried too deep in your new pot. The crown of the water lily must never be buried too deeply in the muddy substrate as this will cause it to rot.
Finally, ensure the fertiliser pellets are not applied too near the crown of the plant. You should use less than what is recommended on the product label as excessive fertiliser can burn and injure plants.
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.
Article by Natasha Ann Zachariah, originally appeared in The Straits Times.