Mealybugs have a consistent urge to hide in groups underneath the succulent leaves, making it difficult to find and get rid of them. Mealybugs need to be treated with a stronger solution because they can be very difficult to get rid. Aphids are a more difficult pest to eradicate. Aphids are often found outdoors and easily accessible, making them an easy entry point for succulents. The brown spots are more like rust in appearance and may affect plant growth if not treated earlier. There are more 2000 species of cacti. These can be classified into two main groups: Opuntias, and Cactoids.