The small bugs on your Calathea plant are likely to be either spider mites or mealybugs. Spider mites are tiny, red or brown bugs that spin webs on the leaves, while mealybugs are white, soft-bodied insects that cluster on stems and leaves.
Both of these pests can cause damage to your plant by feeding on its sap, which can lead to wilting, yellowing, and even death if left untreated. To get rid of them, there are several things you can try:
Use insecticidal soap or neem oil: These organic pesticides are effective against spider mites and mealybugs. Follow the instructions on the product label carefully and be sure to treat both the top and bottom of the leaves.
Wipe down the leaves: Use a damp cloth or cotton swab to remove as many of the bugs as possible from the plant. This won't get rid of all of them, but it will help to reduce the population.
Increase humidity: Spider mites and mealybugs thrive in dry conditions, so increasing the humidity around your plant can help to control their population. You can mist the leaves with water or place a tray of water near the plant to increase humidity.
Quarantine the plant: If you have other plants nearby, it's a good idea to isolate the infested plant to prevent the bugs from spreading. Keep the plant away from other plants for at least a few weeks to make sure the infestation is fully under control.
Remember to be patient, as it may take several treatments to completely eliminate the pests. Also, be sure to monitor your plant regularly to catch any new infestations early.