The studies on biological control of damson-hop aphid (Phorodon humuli Schrank) on Marynka cultivar, using Aphidius colemani and Aphidoletes aphidimyza, were carried out in the hop-garden localised within Hop Experimental Station at Jastkow over the years 1998~2000. The efficacy of Aphidius colemani ranged from 5% to 65% and was found sufficient to control damson-hop aphid in the period before flowering i.e. to the middle of July, but it was not sufficient later. The efficacy of Aphidoletes aphidimyza ranged from 50% to above 90% and it was sufficient in one of the examined vegetation seasons. High air temperature and lack of rainfall reduced efficacy of both species, but especially that of Aphidius colemani. Animals and man; Control; Biological control; Nutrition; Diet; Prey; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Ecology; Predators; Habitat; Man made habitat; Land zones; Palaearctic region; Eurasia; Europe Aphidoletes aphidimyza (Cecidomyiidae); Control of; Evaluation; Insect prey; Phorodon humuli (Hemiptera); Cultivated land habitat; Poland; Jastow; Evaluation of use to control hemipteran host, cultivated land Aphidius colemani (Aphidiidae); Control of; Phorodon humuli (Hemiptera); Evaluation; Hemipteran hosts; Phorodon humuli; Cultivated land habitat; Poland; Jastow; Evaluation of use to control hemipteran host, cultivated land Phorodon humuli (Aphidoidea); Control by; Diptera & Hymenoptera; Hymenopteran parasites; Aphidius colemani; Plant hosts; Hop; Insect predators; Aphidoletes aphidomyza (Diptera); Cultivated land habitat; Poland; Jastow; Control by hymenopteran parasite & dipteran predator, evaluation, plant host, cultivated land none