What Is Oleocellosis? What Causes Spots On Citrus Fruit

Oleocellosis of citrus, also known as citrus oil spotting, oleo, bruising, green spot and (incorrectly) “gas burn,” is a peel injury resulting from mechanical handling. The results are spots on citrus fruit that can have devastating financial consequences to commercial growers and shippers of citrus. What types of oleocellosis control can be used to manage the problem? Read on to learn more.

What is Oleocellosis?

Oleocellosis of citrus is not a disease but rather a phenomenon caused by mechanical injury that can occur any time during harvest, handling, or marketing. The injury causes greenish brown areas to arise on the fruit’s peel as a result of essential oils spilling over into the sub-epidermal tissues between the oil glands. It can affect oranges, lemons, limes, grapefruit, and other citrus types.

Symptoms of Oleocellosis of Citrus

Initially, citrus oil spotting is practically unobservable, but as time goes on, the damaged areas will darken and become more prominent. It is most common in humid regions or arid areas with heavy dew occurring during harvesting. Citrus peel oil from the mechanically injured fruit can also cause spotting on undamaged fruit that's stored with the damaged fruit. All types of citruses are susceptible to oil spotting. Smaller fruit size tends to be afflicted more often than larger sized fruit, and citrus that is picked when the dew is still on the fruit is also more susceptible to oil spotting. This type of injury to citrus is not normally a problem to home growers and is specific to larger scale commercial groves that utilize equipment to harvest and pack their citrus.

Oleocellosis Control

There are a number of methods to reduce or eliminate oleocellosis. Do not pick fruit that has touched the ground or that is still wet from rain, irrigation, or dew, especially early in the morning. Handle the fruit gently and avoid getting sand or other abrasive material on the fruit which can damage the peel. Don’t overfill pallet bins and use metal-shielded fruit picking bags which are smaller than the more commonly used citrus bags for lemons and other tender crops. Also, in the case of lemons, which are particularly vulnerable to oleocellosis, once harvested, leave them at the grove for 24 hours before transporting to the packing house. Also, commercial growers should keep the relative humidity in de-greening rooms at 90 to 96 percent, which will reduce the darkening of the oil spots. During non-de-greening season, hold the fruit in high humidity rooms at ambient temps without ethylene to reduce the darkening of the oil spots.