Lateral thinking for a growing problem
Research into a peanut disease which is a particular threat on the Atherton Tablelands will include innovative trials with previously unheard-of green manure crops like fodder rapes and other brassicas.
Supported by growers through the GRDC, Queensland Department of Primary Industries pathologist Peter Trevorrow also plans to include waste from the ti-tree oil industry at Mareeba and Dimbulah in a range of organic amendments he intends to add to soil in his trial plots.
Other amendments will be lime —to adjust soil pH — poultry manure, more conventional green manures' and blood and bone meal.
Mr Trevorrow is targeting cylindrocladium black rot (CBR), which is caused by Cylindrocladium crotcdariae, a fungus that lives in soil alongside more beneficial organisms which assist thenodulation and nitrogen fixation of legumes.
CBR and sclerotinia rot, which is caused by Sclerotinia sclerotiorum, are the major soil-borne diseases of peanuts in north Queensland. But Mr Trevorrow said while sclerotinia is currently controlled by strategic applications of fungicide, there are no current chemical control options available for CBR, which is now widely distributed in both north and south Queensland.
The peanut industry is vulnerable because of its current reliance on high yielding but highly CBR-susceptible varieties. Breeding will hopefully provide a long-term answer, said Mr Tevorrow, but the current approach is to minimise damage through crop rotation and management.
Improving the soil profile
"In north Queensland CBR is likely to be more severe on soils with depleted levels of organic matter and of poor structure. Improvement in these areas may decrease the incidence of CBR and other soil-borne diseases," he said.
On the Tableland, it appeared environmental factors such as soil temperature and Wetter seasons were behind the CBR problem. Rotations with Rhodes and signal grasses, maize and sorghum as well as bare and weed fallows provided some relief, but not enough.
"That's why we are taking a couple of long shots with this line of research, including ti-tree waste in the soil amendments we plan to add and ploughing in the fodder brassicas as a green manure crop," Mr Trevorrow said.
Behind the research is work by John Kirkegaard at CSIRO Plant Industry, showing that a compound that exists naturally in brassica plants repels soil-borne diseases, (see Ground Cover issue 7)
"One of the attractions of green manure brassica crops is that they will be very short term, perhaps only eight weeks, and be able to be grown between summer-growing peanut crops if there is enough drizzly winter rain."
Subprogram 2.11.15 Contact: Mr Peter Trevorrow 070 92 8555