BROWN SPOTS COULD BE DUE TO A FUNGAL INFECTION OR SCALE INSECTS

I have a philodendron xanadu which has yellow spots on its leaves. The plant looks generally healthy. Please advise what I should do.

Hambali Leonardi

It can be difficult to identify the causative agent from the picture.

The brown spots could be either scale insects or fungal spots. Try scratching the spots off gently with your fingernail. If they can be removed, they are scale insects. If they cannot be removed, they are likely fungal spots which arise from the plant tissue.

For scale insects, you can spray a dilute solution of summer oil or neem oil on the leaves which suffocates the pests. You may still need to remove them gently with a sponge later on.

Be careful not to damage the leaves. Test the pesticide on one part of the plant to ensure the leaves are not sensitive to the pesticide.

If they are fungal spots, the marks are permanent. The improvement of the growing conditions, such as by giving your plant more sunlight and better air circulation and preventive application of a contact fungicide such as captan - available for sale in local nurseries - should reduce the chances of future infections.

POOR HEALTH OF JASMINE PLANT MAY BE DUE TO THE LACK OF SUNLIGHT

I bought this flowering plant two years ago. It flowered only once and grew to entangle the nearby railing and became weak, with leaves dropping. I pruned it, but now it hardly grows. How can I get it to bloom and grow healthily again?

Ernie Lim

It appears your plant is the jasmine (Jasminum sambac). It is quite sparse and lacking in vigour. A possible cause is the lack of sunlight, judging from the location where it is now placed.

Jasmine has to be grown under direct or filtered sunlight for at least six hours daily. With sufficient sunlight, the plant will be able to make food and produce new growth, which can eventually lead to the production of flowers.

Ensure that the plant is kept moist and not allowed to dry out when it is grown under sunnier conditions. Drying out of the root zone can cause the lower leaves of a plant to turn yellow and fall off.

• 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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