Root Awakening: Summer oil, abamectin effective to fight mites on Mexican Petunia

Mexican Petunias may have mites or fungal disease

My Mexican Petunias have white patches on the leaves. What is this and how can I get rid of it?

Choo Hor Kan

The leaves of your Mexican Petunia (Ruellia simplex) could be infested with mites. See if you can spot them using a hand lens, as they are very small.

You can use summer oil or abamectin, which are pesticides that are effective against mites and can be used in rotation. But avoid the use of pesticides if there is a fish pond nearby, as they are highly toxic to fish.

Your plant could also have a fungal disease. Improve air circulation by selectively pruning plants. Apply fungicides such as copper soap, which is available for sale in local nurseries, to treat the issue.

Lemon may be infested with leaf miners and leaf hoppers

There are flies on the undersides of my 2½-year-old lemon plant’s leaves. The same thing happened in 2024 around the same time. Is this seasonal? Some leaves have curled and there are brown patches.

How do I limit the infestation? I sprayed Mapa Malathion 57, and water mixed with soap and vinegar, but without success.

Freddy Tan

The patches on the leaves of your lemon plant could be due to leaf miners, a common pest of this species. The small flying insects that were resting on the leaves may be leaf hoppers, which jump around for short distances when disturbed.

Both infestations can be managed by applying abamectin, which may be a more effective pesticide than what you have been using. Abamectin works via the translaminar mode, meaning it is partially absorbed into the leaf tissue.

Patches on Money Plant leaves may be an injury

Both my Manjula and Golden Pothos plants are on moss poles. They have grown taller and rooted in their poles, and are producing new leaves.  However, the Golden Pothos’ leaves on the middle part of the pole are turning yellow, while the white parts of the Manjula’s leaves are turning brown. What is wrong? Both plants are watered weekly and get indirect sun all day, as they are near a north-facing window. 

Sam Yeo

The exact cause of the patches is difficult to discern, but could be due to some form of injury. Note that the variegated portions of the leaves are more sensitive and prone to damage.

Were the plants moved from elsewhere to their current locations? Changes in light intensity can cause leaves to burn, especially if they are grown in a shadier location before being moved to a spot with higher light intensity.

Did you spray anything on the plants? Chemicals, pesticides or fertilisers can cause similar issues. Always test on a small part of the plant first to reduce the likelihood of pervasive damage. Also, use a more diluted version first, to be on the safe side.

Finally, was the plant allowed to dry out until the leaves wilted before rewatering? Plant tissues may be damaged or injured if they experience extreme moisture stress.

Aloe plant needs direct sunlight to thrive

My Aloe Vera plant has developed small dark patches. What is wrong? I give it as much sunshine as possible by placing it in the corridor. I water it weekly or fortnightly, and always check that the soil is dry before watering sparingly.

Chris Yap

The Aloe Vera plant needs at least six hours of direct sunlight a day. A lack of light will cause leaves to stretch and become soft and floppy. Leaves with such soft tissues will be prone to infection by pathogens, which appear as the patches described. You should move the plant to a sunnier spot.

Sapling could be the Kedondong

What is this plant? It looks like a fruit tree.

Lena Ong

From the picture and information given, the sapling could be that of the Kedondong (Spondias dulcis). It is a commonly grown fruit tree with pinnate leaflets similar to those seen in this picture. The plant needs well-draining soil and exposure to direct sunlight for at least six hours a day to thrive.