The numbers of Curculionoidea showed a growing tendency during the initial four years of alfalfa crop use for green fodder, but in the subsequent years they decreased significantly. The number of species increased with the plantation age.

Adults of Si tona humeralis Steph. damage leaves of alfalfa, causing bay-shaped leaf holes characteristic for the Sitona spp. The larvae damage root nodules, taproots and open the infection paths for pathogenic fungi which occur in soil and on the root surface which results in the withering of plants.

The influence of saponins isolated from alfalfa (Medicago sativa L.) leaves and glucosinolates isolated from mustard (Sinapis alba L.) seeds on the fertility of Colorado potato beetles (Leptinotarsa decemlineata Say) reared on potato leaves treated with these substances was tested. It was observed that both compounds restrained the process of egg laying however, the action of saponins was stronger.

Inoculation of tobacco cv. Xanthi nc or bean plants with the mixtures of benzothiadiazole (Bion) and tobacco mosaic tobamovirus (TMV) or alfalfa mosaic virus (AIMV), respectively did not show any inhibition of the number and size of the local lesions. Protective treatment of plants with Bion caused a significant decrease in disease incidence. In the case of tobacco cv. Xanthi nc and TMV or bean plants and AIMV that protective effect increased day by day and 6-7 days after treatment the production of local lesions was inhibited almost completely. Bean plants treated with Bion demonstrated resistance ranging between 60-90% also in nontreatcd parts. Bean and tomato plants pretreated with O.Ol% Bion were effectively (in 60-70%) protected against systemic infection by tomato black ring ncpovirus (TBRV).