Weather damage of barley
Weather damage of barley can take different forms including:
- kernel discolouration
- germ-end staining
- fungal staining or mould
- pre-harvest sprouting
- cleaved barley
- varietal purity
- grain quality.
Kernel discolouration involves the colour change from the light straw colour of bright grain to a deep yellow/tan coloured grain (or caramel colour when extreme). It involves the discolouration of the grain without, it seems, the involvement of fungi and is caused by light showers of rain, high humidity or even heavy morning dew.
The dark brown or black staining of the germ-end of the grain is referred to as germ-end staining or black point. Preliminary studies indicate that this staining may involve peroxidase enzymes rather than fungal activity.
Fungal staining or mould
The darker grey staining or appearance of distinctive spots of visible mould on the grain that appears after heavier rain, is associated with a number of fungi and is the more severe form of weather damage. Alternaria alternata is the fingi most frequently isolated on barley subjected to weather damage in WA.
Pink stained barley
Traces of pink stained barley grains were identified in grain samples from 2003 and 2004 harvests. Pink staining of barley can have a number of causes. The most obvious is the use of chemical applied as a seed treatment (ie. 'pickling'). However, pink and blue staining can be caused by coloured foam marker used as a spray guide when crop-topping (see photograph, Figure 1). Foam markers are considered to be weather fast and readily attach to organic matter including plant material. Pink staining can also occur as a form of germ end staining.
Grain with pink staining has a poor visual appearance which may be confused with grain that has been pickled, even if this was not the original cause of staining. It does not conform to grain hygiene standards required by regulatory authorities within Australia or importing countries. If stained grain is found on an export shipment, it can potentially lead to the entire cargo being rejected and jeopardise our valuable international markets.
To avoid affecting a stack and jeopardising our international markets, stained grain must not enter storage that contains barley that is destined for international markets. Growers should maintain good hygiene practises during harvest to prevent 'pickled' grain from contaminating grain deliveries. If growers use a ground spray rig to make a late application of either a herbicide or an insecticide, they should use white foam marker, rather than pink or blue foam markers, to avoid grain becoming stained.