Hello. The plant shows symptoms of a mite attack (small pests, hardly visible to the naked eye). Thus, for control, it is recommended to carry out 1-2 treatments, 7-10 days apart with an insecticide-acaricide such as , in a dose of 5 ml/10 L water, applied by foliar spraying (on the topside and underside of the leaves, as well as on the stem). In order to increase the effectiveness of the insecticide, it is recommended to add an adjuvant such as , in a dose of 2 ml/10 L to the solution. It is important to prepare a volume of the mixture corresponding to a single treatment (respecting the mentioned dosage), as the already prepared solution does not have a shelf life longer than 24 hours.
10-14 days after applying the insecticide treatment, it is advisable to apply a foliar fertilizer that supports the plants in overcoming periods of stress and contributes to maintaining their health, such as , applied directly by spraying, according to the recommendations on the label.
For further information on the care of this species please check our article: Calathea, plant care and growing guide.