There are a small number of bugs that degrade diesel fuel. They tend to work together as a consortium. The most dominant micro-organism in diesel fuel is Hormoconis resinae (H. res.), previously known as Cladosporium resinae, which is commonly referred to as the Jet Fuel Fungus in aviation and the diesel bug in other industries.

High temperature, humidity, quality of diesel fuel, and water content all increase the growth potential of H. res.. The damaging effects of contamination by H. res. include corrosion of fuel tanks and fuel lines, as well as filter blockage. If infestations of the diesel bug or the Jet Fuel Fungus go unnoticed and untreated, the consequences in aircraft, boats, trucks, buses and non-road mobile machinery can be dramatic in both financial and safety terms.

The original fuel test created by Conidia was designed to detect both the presence and the level of Hormoconis resinae in aviation fuel. H. res. is a good predicator of kerosene contamination levels.

Fuelstat® resinae PLUS for detecting the Jet Fuel Fungus and the diesel bug have been designed to provide rapid results accurately indicating the levels of all organisms involved in contamination. This allows the test to be used in detecting the diesel bug or the Jet Fuel Fungus in all classes of aviation and diesel fuel.

All tests use immunoassay technology to deliver their results. High street pregnancy tests utilise the same technology. The Conidia test family share their accuracy and ease of use characteristics.