Aphids on Pencil Plant
I think this plant has a tough case of aphids. However, the insects have a brown hard cover. From the picture on this site of aphids, they look black like fleas.
Certified GKH Gardening Expert
If they have a hard outer shell, it could actually be scale bugs. Here is an article that you may find helpful: https://www.gardeningknowhow.com/plant-problems/pests/scale-bug-how-to-control-plant-scale.htm
At any rate, neem oil is an effective treatment. Here is more information: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm