Effect of alfalfa cultivation on the damage by Otiorhynchus ligustici Linnaeus (Coleoptera, Curculionidae)

Abstract

The effect of cultivation of alfalfa - alone and in mixtures with grass components (awnless bromegrass, cocksfoot and combination with both components) on the degree of root damage by Otiorrhynchus ligustici Linnaeus (Coleoptera, Curculionidae) and the productivity of dry aboveground and root biomass of crops was studied. The study was conducted at the Institute of Forage Crops - Pleven, Bulgaria and covers the period 2018-2020. It was found that mixed cultivation of alfalfa with grass components has been shown to reduce root damage by O. ligustici compared to alfalfa pure crop. The least preferred, with the lowest degree of damage was a mixture of alfalfa with cocksfoot (50:50%), where the number of gnawed furrows and holes, and the length of the furrows decreased by 70.5, 71.4 and 23.1%, respectively, followed by a mixture of alfalfa with awnless bromegrass (50:50%). The mixed cultivation of legumes and grasses has a positive effect on the development of grass components compared to their pure cultivation, as the values ​​of stem height, number of stems and root length have been shown to increase in mixtures. Cocksfoot in mixture with alfalfa has the highest values ​​on all three indicators studied. Thus, the mixed cultivation of alfalfa with grass components significantly increased the productivity of dry aboveground and root biomass of the individual components in the mixtures and ensures yield stability over the years.