Investigations on invasive nematodes associated with complex insect pests from soil in corn in the environmental conditions of the Republic of Moldova

Corn is one of the major technical field crops in the Republic of Moldova, advantageous in bioecological and productive aspects, which is invaded annually by the harmful organisms with considerable parasitic impact. The phytosanitary control results, carried out annually and seasonally, comparatively in the corn plantations, notice a significant diversity of the specific diseases and of the invasive insects that seriously affect the plants from the germination phases until the harvest. In corn, were established the numerical density values (D. n.), comparative in different ecological areas, on average 15-280 (ex. /100 g soil), with an abundance by 5-25% higher in the autumn than in the spring. Phytoparasitic impact indices the frequency (F %) and intensity (I %) of the phytohelminthological disease level was estimated, being more advanced by 3-30% in the spring-summer period, observed differently depending on the area compared to the autumn period. The structure of parasitic phytonematode complexes was determined counting 20 species, included in 8 families and one order (Tylenchida), classified according to trophic specialization, with the predominance of endo-ectoparasites. It was established the diversity of the associated invasive insect species from the soil: 12 species, 8 families, 3 orders, also, with invasive ectoparasitic impact on corn plants, with the disease degree of 5-40%, detected in all phases of vegetation and sectors investigated.