The damage from plant pathogens, especially from nematodes, viruses and fungi, steadily grows.
Even though the damage being done may be of various kinds, at the moment, you are talking collectively about 'damage'.
Phytosanitary is a very important issue in Russia now.
Complex infections are dominated in fields and in glass houses.
It is not clear what you mean here. Can you tell me in simple words what you mean by 'dominated'? What actually is going on with these complex infections?
Nurseries of horticulture and berries could serve as an indicator of negative processes in all Russian agriculture.
Again, in simple words, what do you want to say. For example, you jump from 'horticultural nurseries' ( a place where plants are grown) and combine that (in using 'and') to itemizing one actual plant...of all the fruits and vegetables in Russia! Your next paragraph suggests you mean hortiultural nurseries specifically researching raspberries.
Last year, we inspected the raspberry plantation of the Institute for Horticulture and unexpectedly found cysts of Globodera rostochiensis in the rhizospheres of raspberries there. We did not find Globodera in other plantations of the Institute (for Horticulture-omit - we know from the previous sentence which specific institute you are referring to.)