Plant growth regulator use in broad acre crops

There is little reliable information on how, why and on which crops plant growth regulators (PGRs) are currently used in Australia. Such information is needed to better link research and development with extension. Currently the four main classes of PGRs used in Australia include Ethephon (ETH), onium-types (chlormequat, CCC), and second and third generation PGRs; the triazoles (e.g. tebuconazole, TEB) and trinexapac-ethyl (TE), respectively. Of these, only CCC, TEB, TE are registered for use in cereals and none for canola. To better understand current usage of PGRs in grain crops, a telephone survey of 142 agronomists working across Australian grain growing regions was conducted. Participants provided information relating to PGR usage on the range of crops grown in their area, including, rates of application, reasons for use, response of crops/effectiveness, and a variety of other variables. The potential economic contribution of PGR to the grains industry was estimated from analysis of reported yield gains from application of PGR to wheat in the high rainfall zone (HRZ). Application of PGR with no change in yield from, for example, a 2.38 Mha area (representing 70% of the HRZ) would lead to a cost of around $70M. In contrast, there was an estimated net benefit of $35M and $138M for a 5 and 10% increase in grain yield in the HRZ. This research highlights the need to better understand use of and yield responses to PGRs under a range of climatic, regional and cultivation situations, through co-ordinated research and extension.