The role of predators and parasites in the natural regulation of lucerne aphids in Eastern Australia

(1) The impact of invertebrate predators on lucerne aphids (Acyrthosiphon kondoi (Shinji), Therioaphis trifolii (Monell) and Acyrthosiphon pisum (Harris) was studied in the Hunter Valley, New South Wales, Australia, using a selective insecticide to suppress predators. Aphid and predator numbers were monitored weekly over 2 years in unsprayed and carbaryl-treated plots. (2) The major predator groups were hemerobiids (Micromus sp.), coccinellids (Coccinella repanda Thunberg), predatory mites (Bdellidae) and syrphid larvae. (3) In 1980-81, predators had a significant effect on aphid numbers in late spring, summer and early autumn but not in late autumn. (4) There was no build-up of aphids in spring or summer of the second year (1981-82). When aphid numbers did increase, in autumn 1982, no significant impact of predators was demonstrated. (5) Parasitism by the braconid parasite Aphidius ervi Haliday became an increasingly important mortality factor for A. kondoi during the 2-year period. The high incidence of parasitism in the winter and spring in 1981 and 1982 was significant in preventing the spring build-up that had characterized populations of A. kondoi since its arrival in the Hunter Valley. (6) A. kondoi appeared to be sensitive to the stage of growth of the host plant, alate production increasing as the plant approached maturity, even when there were few aphids. (7) It was concluded that predators and parasites are capable of making a significant contribution to lucerne aphid control in a pest management programme.

[1]  W. Milne,et al.  THE IMPACT OF PREDATORS ON LUCERNE APHIDS AND THE SEASONAL PRODUCTION OF LUCERNE IN THE HUNTER VALLEY, NEW SOUTH WALES , 1986 .

[2]  W. Milne.  The release and establishment of Aphidius ervi Haliday (Hymenoptera: Ichneumonoidea) in lucerne aphids in eastern Australia. , 1986 .

[3]  E. Radcliffe,et al.  Effect of trichlorfon sprays and alfalfa (Medicago sativa L.) cultivars on pea aphid, Acyrthosiphon pisum (Harris). , 1984 .

[4]  S. J. Watson,et al.  Epidemiology of cereal aphids on winter wheat in Norfolk, 1979-1981. , 1984 .

[5]  D. Penman,et al.  Effect of temperature on the biology of bluegreen lucerne aphid, Acyrthosiphon kondoi , 1983 .

[6]  K. Sunderland,et al.  The effects of predator exclusion and caging on cereal aphids in winter wheat. , 1983 .

[7]  A. Watt,et al.  The role of cereal growth stages and crowding in the induction of alatae in Sitobion avenae and its consequences for population growth , 1981 .

[8]  P. Ridland,et al.  Seedling resistance to pea aphid of lucerne, annual medic and clover species in Victoria , 1981 .

[9]  R. Holtkamp,et al.  Heliothis species on three varieties of lucerne infested with blue-green aphid Acyrthosiphon kondoi Shinji. , 1980 .

[10]  P. Samson,et al.  BIOLOGY AND TEMPERATURE RELATIONSHIPS OF CHRYSOPA SP., MICROMUS TASMANIAE AND NABIS CAPSIFORMIS , 1979 .

[11]  M. Mackauer,et al.  THERMAL CONSTANTS FOR DEVELOPMENT OF THE PEA APHID (HOMOPTERA: APHIDIDAE) AND SOME OF ITS PARASITES , 1975, The Canadian Entomologist.

[12]  A. Dixon,et al.  Morph determination in the bird cherry‐oat aphid, Rhopalosiphum padi L , 1971 .

[13]  O. Sutherland.  The rôle of the host plant in the production of winged forms by two strains of the pea aphid, Acyrthosiphon pisum , 1969 .

[14]  R. Hughes,et al.  Population dynamics of the cabbage aphid Brevicoryne Brassicae (L.) (Homoptera:Aphididae in Vancouver, British Columbia : a quantitative study an synthesis of ecological relationships , 1982 .

[15]  E. Dietrick.  An Improved Backpack Motor Fan for Suction Sampling of Insect Populations , 1961 .