Ecology of diamondback moth in Australian canola: landscape perspectives and the implications for management

Abstract

The ecology of diamondback moth (DBM), Plutella xylsotella L. (Lepidoptera: Plutellidae), and records of its frequent, but sporadic, population outbreaks in the canola agroecosystems of southern and western Australia are reviewed. The migratory capacity of DBM, possible maintenance of pest populations on brassicaceous weeds and forage crops, resistance to commonly used pyrethroid insecticides, a lack of effective natural enemies (due to disruption by insecticides and difficulties associated with colonising the vast areas of canola crops) and suitable climatic conditions during critical phases of the crop cycle are all likely to contribute to the observed pest outbreaks. A greater understanding of the ecology of DBM in the canola landscape is fundamental to improving its management in the crop but relevant long-term DBM abundance data are currently lacking. Five critical research issues are identified: (i) improved understanding of the factors which determine regional movement patterns of diamondback in canola-growing areas; (ii) the development and implementation of flexible insecticide resistance management strategies; (iii) better understanding of canola crop colonisation by natural enemies of DBM and their population dynamics under current and alternative insecticide application strategies; (iv) greater appreciation of the interactions between DBM and its crop and weedy host plants; and (v) the development of validated simulation models to aid in the forecasting of possible DBM outbreaks. Each issue represents a significant challenge but all must be addressed if the development of a sustainable integrated strategy for the management of DBM in Australian canola is to become a reality.

Escalating insecticide resistance in Australian grain pests: contributing factors, industry trends and management opportunities

“…Control of H. armigera, P. xylostella and M. persicae is complicated by widespread insecticide resistance across multiple chemical groups and different agricultural industries. 12,15,16 This situation is similar to what is being observed in other countries. For example, M. persicae populations in Europe now possess resistance to a very large number of insecticide groups, which is hampering management efforts by farmers.…”

“…With the exception of H. destructor (a pest largely restricted to Australia and South Africa), these species are known to have resistance both in Australia and overseas (Table ). Control of H. armigera , P. xylostella and M. persicae is complicated by widespread insecticide resistance across multiple chemical groups and different agricultural industries . This situation is similar to what is being observed in other countries.…”

“…). This likely reflects the global status of these pests (and thus greater investment from agrichemical companies towards R&D) and the diversity of agricultural commodities each of these species attack …”

“…The impact of non‐selective insecticide applications on beneficial arthropods and their compatibility with IPM also need to be considered. Predators and parasitoids can play an important role in resistance management, especially when part of an established IPM program, as exemplified by P. xylostella management in Australian rape crops . If farmers were able to rely more on beneficial arthropods, fewer insecticide applications would be needed, reducing selection pressures.…”

“…This likely reflects the global status of these pests (and thus greater investment from agrichemical companies towards R&D) and the diversity of agricultural commodities each of these species attack. 16,28,29 For H. destructor, however, the story is very different. Only four unique MoAs are registered against this pest (Table 1).…”