Question
I find on my rosemary plants a white sticky globule, is this a pest? If so which one, and how can I treat it ?

Answer
The only two pests that generally infest rosemary are aphids and mites. Either can be treated with an insecticidal soap for effective control.

But rosemary plants are also inflicted by a disease called powdery mildew. This fungal disease results in white blotches on the foliage of the plant. It is seldom fatal, but still should be controlled immediately once it is observed to prevent it from spreading. The best control for powdery mildew is copper fungicide.

If there are no holes in the foliage, I doubt you have aphids or mites. I would purchase a copper fungicide at your local garden center and spray at regular intervals. If you still suspect pests, you can also spray with an insecticidal soap. The two products can be used together.

I hope this answered your question. Please write again if I can ever be of assistance.

Regards,

Mike