Root Awakening: Plants attacked by sucking pests

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Plants attacked by sucking pests

My plants seem to be unwell. My Italian parsley plant (photo 1) has white patches on its leaves, while the bay leaf plant (photo 2) looks dried out. Then, at times, the leaves of the kaffir lime tree (photo 3) are curled. What is wrong?

Chew-Ping Cheah

Your Italian parsley appears to be attacked by sucking or rasping pests. They usually reside on the undersides of the leaves and are very small, making it difficult to spot them. Their bite marks cause a stippled pattern on the leaf.

You may want to use neem oil or summer oil to control the pest population. Spray the oil thoroughly on your plants. Repeated applications after several days may be necessary.

Also, grow your plants under optimal light conditions instead of placing them in the shade.

The bay leaf plant looks fine, except for the brown spots on its leaves. This could be a fungal disease that is often seen in plants grown in wet, lowland tropics.

You may want to shield the plant from excessive rain and grow it in a well-ventilated location and in well-drained soil. Place it in a pot so that you can move the plant easily out of the rain.

Lastly, the young leaves of your kaffir lime plant - it is also known as Limau Purut - may also have been attacked by sucking pests.

When sucking insects attack a developing leaf, the leaf will often become deformed over time.

To prevent this, check for any infestation regularly and treat it promptly - in the same manner as the Italian parsley plant.


Tip: Use stakes to support Chinese Rain Bell

The Chinese Rain Bell - its botanical name is Strobilanthes hamiltoniana - is a shrub. It has purplish flowers that droop from wiry, weak stems and grows up to 1.2m tall.

Because of its stems, the plant needs some support such as stakes. This shrub is ideal for growing in a semi-shaded outdoor location, with moist and well-drained soil. It can be grown easily from stem- cuttings.

Gloxinia needs more light

This gloxinia (below) has not flowered for nearly a year. It keeps growing horizontally. Why does this happen and how do I get it to flower?


Mint Goh

Your plant is suffering from a lack of light. It is best grown in an area where it can get at least four hours of filtered sunlight. Under the right light conditions, the plant, which is known botanically as Sinningia speciosa, will assume a more compact growth habit.

In the meantime, you can cut the plant, leaving at least a node or two growing above the soil level. New growth will emerge.

The tip of the stem can be potted separately and rooted. It will grow into a new plant.


Fungal disease cause of dying jackfruit

The fruit of my jackfruit tree always die prematurely. They look diseased (above). What should I do?

Low Bee Hua

It is likely that a fungal disease is affecting your developing jackfruit. This is a common problem in the tropics. In general, hot and humid conditions as well as rainy weather can lead to this problem.

One of the first things you can do is to prune the branches so that there is good ventilation within the crown. You should also remove and destroy diseased fruit that are still on the tree or have fallen off.

Lastly, spray a preventive fungicide such as Mancozeb to reduce the incidence of this disease.

Follow the recommended dosage and the withholding period, which is the time that must pass before you can harvest the fruit for consumption after applying the chemical.


Edible Blackie sweet potato

What is this plant (above)? Is it edible?

Andy Koh

This sweet potato plant is an ornamental variety with colourful leaves. Its cultivar name is Blackie.

Although edible, most ornamental sweet potatoes do not produce tasty tubers.

This plant grows best in the ground. It prefers a sunny spot with direct sunlight, which will bring out the deep purple shade of its leaves.

•Answers by Dr Wilson Wong, a certified practising horticulturist and founder of Green Culture Singapore ( He is also an NParks-certified park manager.

•Have a gardening query? E-mail it with clear, high-resolution pictures of at least 1MB, if any, and your full name to

A version of this article appeared in the print edition of The Straits Times on April 01, 2017, with the headline 'Root Awakening'. Print Edition | Subscribe