Hello. The conifer seems to be suffering from an aphid attack (Aphids - pest management). It is not possible to identify the white formations in the third photo (you can check if it releases a bleeding substance when crushed – Mealybugs in ornamental plants - pest management).
Thus, first of all, you can consider removing the severely deteriorated parts of the plant and those with a high number of pests. Afterwards, it is recommended to carry out 2-3 treatments with insecticides that have in their spectrum of control both pest species, such as (in a dose of 5 ml/10 L water) and (in a dose of 7.5 ml/10 L water), alternating every 7-10 days. To increase the effectiveness of the insecticides, it is recommended to add an adjuvant such as , in a dose of 2 ml/10 L to the solutions. Spray the mixtures as finely as possible so that they are distributed evenly on the plant. Detailed information on the best way to carry out phytosanitary treatments can be found in the following article: Phytosanitary treatments - environmental and labor protection.
While carrying out the treatments, you can also consider using a natural fertilizer that helps to improve the quality of the soil and supports the normal development of the root system, such as or , by watering at the roots. Additionally, 10-12 days after completion of the insecticide treatments, to increase the conifer’s resistance to the attack of plant pathogens and to stimulate its healthy growth, you may consider applying a fertilizer such as , by foliar spraying. Later, during the growing season, these fertilizers can be applied regularly, in accordance with the label instructions.
Additionally, in order to detect the presence of pests early and to be able to apply a treatment at an early stage of the attack, the regular use of specific adhesive traps (e.g. ) is recommended. The pests are attracted by the color of the paper and stick to the special adhesive.
More information on the care of these species can be found in our articles: Thuja, planting guide and care work; Conifers, planting guide and care work. Further, it is recommended to monitor the evolution of the conifer for a while, and in case other symptoms appear or those present worsen, we are waiting for your message accompanied by photos. In view of the above, it is not possible to say exactly how the conifer will develop in the future.