Aerial treatment of the Australian plague locust, Chortoicetes terminifera(Orthoptera : Acrididae) with Metarhizium anisopliae (Deuteromycotina : Hyphomycetes)

Between October 1999 and April 2000, nearly 4000 ha of nymphal bands and ad ult swarms of Chortoicetes terminifera (Walker) were aerially treated using a ULV oil formulation of strain FI-985 of Metarhizium anisopliae var. acri dum. During the mild weather (maxima 22-30 degreesC) of spring (October), t here was little change in nymphal bands during the first week but at all do ses between 25-100 g (1-4 x 10(12) conidia) ha(-1), the bands rapidly decli ned 9-12 days after treatment reaching > 90% mortality by 14 days. Metarhiz ium persisted for some time as there was 50% mortality of locusts fed veget ation collected from the treated blocks seven days after treatment. Persist ence was confirmed by the high mortality of bands that invaded from untreat ed areas and of nymphs that hatched on the plot five to seven days after tr eatment, though mortality was then delayed until early in the third week. D uring summer (January), temperatures were high (maxima 36-42 degreesC), and at all doses between 25 and 125 g (1-5 x 10(12) conidia) ha(-1), there was a rapid decline seven to ten days after treatment. By 12-14 days, there wa s a > 90% decline in numbers in most blocks which was confirmed by helicopt er surveys two weeks after treatment that found very few adults within or n ear treated areas. Mortality was delayed in the high dose where there were blockages of spray equipment during treatment. The clear demonstration that Metarhizium can suppress small local populations of C. terminifera led to the limited operational use of Metarhizium on an organic farm and in a Nati onal Park where nearly 2500 ha of bands and swarms were treated. Continued research is needed to develop a commercially viable product so that Metarhi zium can form a significant part of a programme of integrated pest manageme nt of locusts in Australia.