During vigorous shaking, plant material will fragment to release Botrytis (if present) into solution. At this time, colored plant pigments may also be released, which can cause the test strip to have a background colour. However, the red test line (if Botrytis present) and the control line should be clearly visible. If this occurs, read the test as normal. However, if an excess of green plant sap / chlorophyll is observed to block reading or form a green line, the test is void and will need to be carried out again with less sample and / or less vigorous shaking.