Assessment of the pure sowing of different legumes and in mixtures with grass on productivity and damage level by Sitona spp. and Otiorrhynchus ligustici (LINNAEUS, 1758) (Coleoptera: Curculionidae)

Abstract This work examined the impact on productivity of the cultivation system of perennial legumes such as sainfoin (Onobrychis viciifolia), bird’s-foot trefoil (Lotus corniculatus) and alfalfa (Medicago sativa), grown pure and in binary mixtures with cocksfoot and on damage caused by root pests of Sitona spp. and Otiorrhynchus ligustici. It was found that the productivities of aboveground and root biomasses in binary mixtures were significantly higher compared to the corresponding legume monocultures on average by 30.7 and 39.7% respectively in mixtures with sainfoin, by 15.0 and 73.1% in mixtures with bird’s-foot trefoil, and by 18.7 and 49.6% in mixtures with alfalfa. The weight of dry aboveground biomass in the pure leguminous crops slightly exceeded that of the corresponding leguminous components in the mixtures, whereas the productivity of cereal plants in mixed crops was significantly lower compared to the pure cocksfoot on average by 38.5, 47.0 and 51.7% in mixtures of sainfoin, bird’s-foot trefoil and alfalfa respectively. A similar tendency was observed with regard to dry root biomass. Damage to nodules by Sitona larvae in mixtures decreased significantly: on average by 33.5% (sainfoin + cocksfoot), by 50.3% (bird’s-foot trefoil + cocksfoot) and by 55.6% (alfalfa + cocksfoot) compared to pure grown legumes. The damage caused by Otiorrhynchus ligustici, as expressed by the length of gnawed furrows, in the mixtures with sainfoin, bird’s-foot trefoil and alfalfa decreased considerably - by 12.5, 77.8 and 59.5%, respectively - compared to the pure crops. The damage caused by the аlfalfa snout beetle had the most significant negative effect on aboveground and root biomass productivities. Mixed cultivation systems of forage crops are an economically and ecologically sustainable method of insect pest control.