Effects of aerially applied malathion insecticide on non-target insect orders in mountain ash forests of the Central Highlands of Victoria.  J. A. Harris.  June 1976.  15 pp. (unpubl.)

SUMMARY

This report contains the results of a survey during 1973 of the effects of malathion insecticide, applied from aircraft over mountain ash forest in the central highlands of Victoria on non-target insect orders. Collections were made of airborne insects within 2.4 m of the ground by means of Malaise traps before spraying, 4 days and 8 weeks after spraying, both inside and outside the target area. Samples of insects killed by spraying were collected on aluminium trays placed on the ground beneath trees around each Malaise trap.

The Diptera (flies), Hymenoptera (predominantly wasps), Coleoptera (beetles), and Hemiptera (bugs, leafhoppers) were the most abundant insects found in both Malaise traps and on aluminium trays. Within 4 days of spraying, significant reductions in numbers of airborne Diptera were observed at most sites, and at different sites for each of Hemiptera, Coleoptera, and Hymenoptera. Within 8 weeks of spraying, numbers of these orders at sprayed sites were again comparable to those at control sites, except at Limberlost Ridge, where the abundance of Diptera was significantly below that at the corresponding control site (Marney Hill). The samples of Diptera from both Limberlost Ridge and Marney Hill localities are presently being classified into families and species, to ascertain whether there has been a general reduction throughout the spectrum of Diptera, or whether only certain groups were affected.

The work has shown that the application of malathion over mountain ash forest at 560 ml 118% W/V a.i. in 11 l oil per ha does not cause long-term changes in the abundance of non-target insect orders below canopy, although it is very effective for phasmatids high up in tree crowns.

Also published:

Neuman, F.G., Harris, J.A. and Wood, C.H. (1977)  The phasmatid problem in mountain ash forests of the Central Highlands of Victoria.  For. Comm. Vic., Bull. 25, 43 pp.

Harris, J.A. (1981)  The effect of the insecticide maldison on Didymuria violescens (Leach) (Phasmatodea : Phasmatidae) and on the sub-canopy insect fauna in mountain ash forests of the Central Highlands of Victoria.  M.Sc.Thesis, Univ. of Melbourne, 237 pp.