Apple russet is a ‘surface imperfection’ on the fruit, where a corky lesion, or discoloration has developed in response to various environmental, biological or chemical influences.

Russeting of the apple surface makes them less appealing to consumers, so apples with a lot of russet are rejected for the fresh market.

As part of developing products for use on apples, Zelam conduct trials to monitor russet levels to ensure that their products are completely safe.

 

 

 

Enviromental, biological or chemical influences. Russet is a condition in which cork tissue appears on the surface of an apple. Russet is more prevalent on lateral than on terminal fruit, on exposed than on shaded fruit, and on fruit from lower-altitude growing areas. Russet may also be genetic in nature, and cultivars such as Coxs Orange can be heavily russeted by harvest time. Some crop protection products including surfactants can be phytotoxic and increase russeting.

Trials are carried out in Taranaki on a research orchard, and in Hawke's Bay on commercial orchards, using a range of apple varieties. The trials are all of randomised complete block design, with 3-4 replicates. Typically 100 fruit from each of the 3 or 4 replicated plots are randomly sampled, and then sorted according to russet class and counted. The data is subject to rigorous statistical analysis.