Sugar beet is a main source of sugar, but the pest infestations reduce root quantity and sugar content. Post-harvest roots piled on the side roads before moving to the factories are being subjected to a variety of pests that may reduce root quality. So, the current study was carried out during 2012 and 2013 seasons at the Experimental Farm of Sakha Agricutlural Research Station for monitoring population size of major pests which attack roots of post-harvest sugar beet, and adverse effects on sugar content. Data indicated that the greatest population sizes in three plantations in both seasons were those of Diptera (mainly, Muscidae), Rattus norvegicus (Berkenhout, 1769) and Corvus spp. Moderate population sizes were those of Liogryllus bimaculatus L., while low populations were recorded for Lixus junci Boh., Scrobipalpa ocellatella Boyd., Agrotis ipsilon (Huf.) and Gryllotalpa gryllotalpa L. Also, the authors noticed that numbers of sheep were eating sugar beet roots greedily. Pest infestations resulted in highly significant losses in sugar percentage extracted from the damaged roots. It could be concluded that pests play an important role in reducing post-harvest sucrose.