We Get Questions about pests, yes we do.
We ask people to send us photos, and they do, boy do they.
Q: cactus jungle,
here are the pictures. please note the white dots in the picture. what causes these? (lack of light or water, too much light or water?). also given the size of the smaller cacti, should any of them be transplanted to their own pots or can they all live together in the same pot as shown in picture 2 [not shown]? how much water should they be given being that they only get about 2-3 hours of direct sunlight? thanks for your help!
Thanks for sending the photos, they are quite clear: your Pachycereus has scale, an insect that attaches itself to the plant and sucks the juices out. This is treatable.
1. Spray the plant with neem oil to kill them. We mix 100% neem oil, which is safe for cacti. Don’t use the 70% solutions, like “Rose Defense,” which are not safe.
2. After 2-3 days, carefully clean off the scale with a q-tip dipped in alcohol.
Finally, your plants are all fine in the same pot, but they need more sun. Not enough light is making them prone to the scale. Slowly bring them into a location that gets more direct sun, waiting a week after they’ve been treated. I recommend a minimum of 4 hours of afternoon sun, which means near a west or south facing window.
Water every 3 weeks, drenching the soil and letting the water drain away. You should lift the pot up on pot feet or bricks so it is never sitting in water in the saucer.