Few control options
From the February 2008 edition of Agriculture Today.
Dr Stahlman is assessing the potential of some herbicides not currently available in Australia but which may have potential for registration and use in grain sorghum or sunflower.
Weed management is essential to successful crop production but grain sorghum and sunflower growers have few herbicide options for selective weed control.
Australian growers have even fewer options than US growers, however, international collaboration between a Kansas State University weed scientist and dryland cropping specialist and NSW Department of Primary Industries (DPI) district agronomists is helping identify and evaluate new herbicide options for Australian growers.
Professor Phil Stahlman is in Australia on a five month sabbatical, working with district agronomists Loretta Serafin (Tamworth) and Stephanie Belfield (Moree East).
"We are assessing the potential of some herbicides not currently available in Australia but which may have potential for registration and use in grain sorghum or sunflower here," Dr Stahlman said.
Dr Stahlman is based at the Tamworth Agricultural Institute and he, Ms Serafin and Ms Belfield are conducting summer crop field trials in grower paddocks near Moree, Quirindi and Tamworth.
"It is important to determine crop safety and weed control effectiveness under local conditions.
"It doesn’t matter how effectively herbicides control weeds if they cause unacceptable crop injury."
In sunflower, Dr Stahlman is comparing two non-registered herbicides with commercial standards - sulfentrazone (Spartan), registered in the US for control of specific broadleaf weeds in sunflower, soybean, and tobacco, and an experimental compound (KIH-485) that has performed well in US sunflower and corn trials.
A new active ingredient being developed by the BASF Corporation (BAS 800H) is being tested in grain sorghum along with dimethenamid-P (Outlook), available in the US but currently not in Australia.
"Based on my experience with these herbicides in Kansas trials, I think they may have a place in Australian agriculture too," Dr Stahlman said.
"Preliminary results are encouraging, especially the sunflower trials."
Neither sulfentrazone nor KIH- 485 injured sunflower in any of three trials, whereas a waterbased formulation of pendimethalin (Stomp*Xtra), the herbicide active ingredient most commonly used in sunflower, visibly injured sunflower in two of the three trials and caused stand loss in one of them.
Leaves of plants were pinched and exhibited a whitish-band across the first true leaves, and the stems of some plants were constricted immediately below the soil surface, eventually causing several of those plants to die.
In the grain sorghum trial, BAS 800H treatments caused minor chlorosis and considerable necrotic stripping of the outer leaves of a few plants, but later emerging leaves were unaffected.
Mid-season plant growth was stunted 10 to 20 per cent, depending on herbicide rates, but the stunting appeared to be caused more by dimethenamid- P than by BAS 800H.
"I doubt the observed effects will be reflected in lower grain yield, but we won’t know for sure until after harvest," Dr Stahlman said.
"Weed populations in all trials were too low to accurately assess weed control effectiveness, so additional work is needed to fully evaluate the value of these herbicides in Australian farming systems."
Dr Stahlman’s visit is funded by Kansas State University, NSW DPI, the University of New England, the Australian Centre for International Agricultural Research (ACIAR), and the Better Oilseeds Project, which is co-funded by the Grains Research Development Corporation and the Australian Oilseeds Federation.
Dr Stahlman will depart Australia at the end of February; before then he will speak at several grower updates across southern and northern Australia.
Contact Dr Phil Stahlman, Tamworth, (02) 6763 1100.
