Western Australia Department of Agriculture researchers will trial a new test kit this season, which may be able to detect chocolate spot (Botrytis fabae) in faba beans before visible symptoms are present in the crop.

Chocolate spot disease is one of the most significant diseases affecting faba beans in Western Australia. Infection starts as small red-brown spots on leaves, stems and flowers. The spots on leaves and stems enlarge and develop a grey, dead centre with a red-brown rim or margin. Chocolate spot can kill flowers and stems. Spores will form on this dead tissue. Once the disease becomes established, it can rapidly spread within a crop. Aggressive development of stem infection late in the season can cause parts of the crop to lodge.

Chocolate spot starts as small red-brown spots on leaves and flowers. These enlarge and develop a grey, dead centre with a red-brown margin.

The test was developed by Dr Frances Dewey from the University of California at Davis and the University of Oxford, and is used to detect botrytis levels in grape juice/wine. The test kit works in a similar fashion to a home pregnancy test. When a chemical found in the cell walls of Botrytis is detected, a band appears in the window of the test kit. The speed with which the band appears depends on the level of Botrytis in the sample.

Department plant pathologist Jean Galloway recently travelled to New Zealand as part of a Grains Research and Development Corporation funded project to attend the 8th International Congress of Plant Pathology (ICPP) and a two day workshop on Botrytis at which the test kits were demonstrated. A collaborative project between the Department and Dr Dewey has been developed as a result of this trip. The test kits will be supplied to the Department's Northam Office for trial against chocolate spot this season.

Dr Galloway said it was not yet known whether the test would be applicable in Western Australia.

"Researchers are in the first stages of testing, but if the test is proved, the test could potentially be very useful for growers, as generally it is too late to spray the crop once the disease has been detected," Dr Galloway said.

"The kits could be used by faba bean growers to test their crops for chocolate spot disease before flowering to determine if there is a need to apply a fungicide spray," she said.

"Chocolate spot may be controlled by application of fungicidal sprays. As the greatest impact of this disease is through loss of flowers, the greatest increases in yield are achieved with sprays during flowering," she said.