Studies on the introduced smaller European elm bark beetle, Scolytus multistriatus, a potential vector of Dutch elm disease in Victoria

Summary

An account is given of the distribution, life history, flight activity and reproductive potential in Victoria of Scolytus multistriatus Marsham (Coleoptera: Scolytidae), and a strategy for control is discussed. Relevant biological data from the Northern Hemisphere are summarised. The beetle is established in north-eastern, central, south-western and south-eastern Victoria excepting East Gippsland. At an average mean monthly temperature of 15°C near Myrtleford, three generations of the beetle were produced per year, though at 5.6°C at Mt Hotham only one generation developed. Flight activity near Myrtleford commenced in mid-spring, peaked in late spring, mid-summer and early autumn, and practically ceased by late autumn; dispersal flights up to 10 km occurred. Fecundity per female averaged 52 eggs, and the annual reproductive potential per female exceeded 17 570 females.

Although the beetle has behaved essentially as an economically insignificant secondary phloem-feeding bark beetle, with three instars at the larval stage, it is important to urban forestry as a potential vector of Ceratocystis ulmi (Dutch elm disease). Should this disease be discovered, the following control measures would immediately be recommended: (1) strict adherence to a sanitation program, and (2) where elms have a special significance, a low-volume application during September and December of 1% emulsion of methoxychlor insecticide to the crowns of healthy elms, supplemented by mass-trapping of beetles using synthetic pheromone (‘Multilure’) baited traps in areas where levels of beetle populations are low.