Critical review of the efficacy of the Forests Commission’s anti-phasmatid operation during summer 1971 in mountain ash forests of the Victorian Central Highlands.  J.A. Harris and F.G. Neumann.  May 1972.  22 pp. (unpubl.)

SUMMARY

This report reviews the efficacy of the 1971 control operation against phasmatids whose progeny is expected to hatch in spring-summer 1972/73 in E. regnans forest within the Central Highlands of Victoria. It supplements rather than replaces an existing report on this project (71/1175) by analysing the levels of progeny in terms of densities of “sound-early” eggs in litter derived from the sprayed generation. Additionally, comparisons are made between population trends following control in 1971 with those from previous “peak”* years (1967 and 1969).

Overall, phasmatid control in 1971 was greatly superior to that in previous “peak” years. In 1971, a twenty-four fold increase in plague population level was avoided and the existing plagues were significantly reduced and in many stands to non-critical levels. Potentially critical levels of progeny, detected in winter 1971, were in many instances due to excessive insect residuals rather than to late spraying. A new criterion for respraying a locality on the basis of frass fall rates is proposed. The ratio acreage defoliated/acreage sprayed was 0.12 in 1970/71 compared with a much higher 0.41 in 1968/69. In localities sprayed within the recommended period, defoliation only occurred where insect residuals were excessively high. Also, no pre-control of oviposition was recorded from such stands.

*High levels of insect abundance occur every alternate year as a result of a predominantly two year life cycle in the Central Highlands.

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.