There are times when small organisms can cause major shocks to normal life. Several years ago the international trade in pelargoniums was brought almost to a halt by a bacterium – Ralstonia solanacearum. This pathogen causes bacterial wilt in Pelargonium (and brown rot in potatoes), and is listed as a quarantine pathogen. Import of all pelargoniums into the United States was stopped, with huge impact on the growers in East Africa and Europe.
Since this outbreak, growers all over the world have put in place rigorous hygiene measures to prevent future problems. At the heart of good hygiene is routine monitoring, and a key tool to support visual inspections is the Pocket Diagnostic on-site test for R. solanacearum.
The major source of potential infection with Ralstonia is irrigation water. Leading growers with propagation nurseries in East Africa take enormous care to disinfect irrigation water; Selecta Klemm, for example, uses a three step process involving chlorine and slow-sand filtration. However, even with this level of cleanliness, routine monitoring is carried out diligently.
Torsten Mundus, supply chain manager with Selecta Klemm is responsible for the 100 million Pelargonium cuttings taken by the company’s growers each year for rooting in Europe and the USA. ‘The mother plants are inspected weekly by trained scouts. The scouts are on the lookout for any wilting plants, but they also take small samples from the lower third of random plants for Ralstonia testing.’ Any positive results from the on-site test are confirmed by laboratory diagnosis because of the economic consequences of the disease. Since the results of Pocket Diagnostic tests are stable, tests that have been run become a lasting record of monitoring, and an important part of the quality control audit trail.
It is the scouts themselves who use the Pocket Diagnostic tests. They test for both Ralstonia, and Xanthomonas hortorum pv pelargonii, another bacterial pathogen causing wilting symptoms. Xanthomonas does not have quarantine status, but it does cause more severe economic damage than Ralstonia.
The high level of mother plant monitoring plays two important roles, says Mr Mundus. ‘Firstly, it provides in-house reassurance that crop health is not being damaged by Ralstonia or Xanthomonas. Secondly, the records we have from monitoring with Pocket Diagnostic tests become part of the report we need to gain United States Department of Agriculture (USDA) certification for export of our cuttings to the United States. The test results confirm the clean condition of our plant material.’
Reference to USDA certification is significant. Back in 2003 when the Ralstonia crisis was at its height, the USDA compared the performance of several rapid tests. Their preferred test in terms of speed and clarity of result was the Pocket Diagnostic product. Users can take confidence that six years later the test is performing as well as ever, and helping to keep international trade flowing.