Peas have the ability to establish symbiosis with nitrogen - fixing bacteria of the Rhizobium genus that have the ability to acquire atmospheric nitrogen. As the pea leaf weevil larvae feed on nodules, the benefits of these bacteria and the nitrogen top - dressing are questioned. The experiment with forage pea was set on the surfaces College of Agriculture in Križevci in 2014 with the aim of establishing an impact of the pea leaf weevil on the existence of nodules on plant roots and protein content in the surface mass and pea seed. The two level factorial experiment included the following factors: insecticide Force 1.5 G (treated - I and untreated I0) and nitrogen top dressing of 150 kg/ha of KAN (N and N0). The previous crop was wheat. In the autumn 200 kg/ha of fertilizer having the formulation of PK 20:30 was applied, while in the spring, before sowing, 150 kg/ha of NPK 15:15:15 was applied. The harvesting was completed on 17 March 2014 by a four-row pneumatic seeding machine PSK OLT for corn, which has an insecticide depositor, with 100 grains/m2, at a row spacing of 17.5 cm (three passages of the seeding machine) with Erby pea variety. At the beginning of pea flowering the nitrogen top-dressing was applied, after which a large amount of rain fell. The harvesting was completed on 2 July 2014. At the beginning of pea flowering dry weight nodule and nitrogen content in surface mass were determined. The values were not significantly different between I and I0 (0.13; 0.12 g dry weight nodule/plant and 4.08; 3.78 % of nitrogen). In the stage of pod formation, the nodules were eaten by pea leaf weevil larvae and it was not possible to determine their weight. The nitrogen content in the surface mass (2.60 - 2.79 %) and seed (3.36 - 3.62 %) was not significantly different among the researched factors. The data were statistically analysed by a variance analysis using Genstat 5 programme. Insecticide application did not meet the expectations. Therefore the impact of leaf weevil larvae could not be measured.