Corn is one of the major technical field crops in the Republic of Moldova, advantaged from bioecological and productive aspects, which annually is invaded by the attack of harmful organisms with considerable parasitic impact. The results of the comparative phytosanitary control carried out annually and seasonally in corn plantations, note a significant diversity of 6 key diseases (common and dusty tall, forms of rottenness, helmintosporiosis, nigrosporiosis, diplodiosis) caused by 19 pathogens with significant and optional pathological specialisation and 15 species of harmful insects of orders Coleoptera, Lepidoptera Homoptera, corn specific polyphages and oligophages as well as for other cereal and technical crops, horticultural, invasive of major agro economical importance. The etiological structure and diversity of pathogens responsible for triggering corn diseases and associated harmful insect species have been estimated, with the determination of the impact of plant protection index, such as: Numerical density (D.n.), Attack frequency (F.%), Attack intensity (I%), estimation scales used to determine the impact after corn reaction to invasive attack of parasite and pathogen organisms.