THE EFFICIENCY OF APHIDIUS ROSAE HALIDAY (HYMENOPTERA: APHIDIIDAE) IN REGULATING THE NUMBERS OF MACROSIPHUM ROSAE (L.) (HEMIPTERA, APHIDIDAE) ON PLANTS OF THE GENUS ROSA L.

Abstract

This is a fist report on the results of studies on the effect of the natural entomophagous parasitoid Aphidius rosae on the population dynamics of Macrosiphum rosae (L.) on plants of the genus Rosa L. in the arboretum and collection nurseries of the Polar-Alpine Botanical Garden located north of the Arctic Circle – in Kirovsk, in a protected area (67°39′05″N, 33°40′20″E, 387 m above sea level) and in Apatity, in an experimental site (67°56′41″N, 33°40′31″E, 175 meters above sea level). Average M. rosae numbers in the Kirovsk site varied in July and August from 5 to 60 individuals/leaf, and in Apatity in June, July, and August the population density of some colonies exceeded 90 individuals/leaf. In 2017, M. rosae mummies appeared in the Apatity experimental site in late May-early June on plants of Rosa amblyotis and R. rugosa. In the Kirovsk site, M. rosae mummies appeared only in August – September, mainly on R. rugosa and R. majalis. In 2018 and 2020, significant numbers of M. rosae mummies were observed from July to September in both sites. High biological efficiency (up to 90 %) was observed when the parasite : host ratio in the aphid colony was 1:30. However, the efficiency of A. rosae varies greatly among years, so constant monitoring is required for regulation and possible introduction to core infection areas. Our results evidence that the presence of natural entomophagous parasitoids A. rosae in M. rosae colonies on plants of the genus Rosa restrains the growth of the pest’s numbers to an environmentally safe level in the second half of the growing season and prevents mass outbreaks of the infection.