We have a mandevilla plant on our outdoor balcony (above
ground level) that shows a number of little cotton wool-like balls at the point where two stems intersect. I suspect mealybugs. We are located in North York. Could you kindly advise as to how to treat the plant and get rid of the problem before it worsens?
Thank you very much.
Thank you for contacting Toronto Master Gardeners.
From your description, your plant is likely infested with mealy bugs.
Mealybugs are a type of scale insect. As they feed, they cover their bodies with a characteristic white, cottony substance for protection.
These pests damage indoor and outdoor plants by sucking out their sap. They also excrete honeydew over leaves and stems. This sticky exudate is an ideal growth medium for sooty mold which gives the plants a dirty sooty look. It also attracts other insect pests.
Your first line of defense is to physically remove as many mealybugs as possible from your Mandevilla. If the plant is small, you could remove the pests individually, knocking them into a container of soapy water. Or, you could spray the plant with a hard blast of water, collecting and disposing of the bugs that fall off, and then picking off and dispose of any adults that remain on the plant.
You can also apply an insecticidal soap, carefully following the manufacturer’s instructions.
Mealybugs can spread to other plants, and can be difficult to control. You will need to monitor all the plants on your balcony on an ongoing basis.
The following link provide additional information on mealy bugs and how to control them: Mealybugs- outdoors
Good luck in controlling this pest.