What is Diplodia Stem-end Rot of Citrus?
During flowering and fruiting, citrus trees can develop many fungal problems, but such issues also occur once the fruit is harvested and stored. These diseases are the worst because you have to watch all that hard work go to waste. Diplodia citrus rot causes decay of the fruit. It spreads in packed citrus and can cause widespread damage. Stem-end rot on citrus occurs most frequently in subtropical regions. The organism responsible is a fungus, Lasiodiplodia theobromae, which is harbored on the stems of the tree and transferred to the fruit. It occurs on all species of citrus in hot, humid areas. The fungus is latent on the fruit button until harvest where it reactivates. Citrus with diplodia stem-end rot seems to be most prevalent where there is a lot of dead wood on trees, high rainfall and temperatures, and where fungicides weren’t used regularly. Once fruit is in storage, untreated citrus can rapidly become rotten.
Signs of Diplodia Citrus Rot
The fungus invades the fruit where the button and fruit attach. At this site, discoloration will occur and rapidly advance to decay. Citrus stem-end rot will progress past the button to affect the skin and flesh of the fruit. The disease almost looks like brown bruises on the peel of the citrus. Discoloration follows into the fruit. Studies indicate the disease is more common when sanitation is inadequate and during lengthy degreening periods, when the skin of the citrus is forced to color.
Minimizing Stem End Rot on Citrus
Experts recommend reducing the time the fruit is exposed to ethylene greening agents. Certain fungicides are also used post-harvest to reduce the incidence of stem-end rot and other fungi. Other recommendations include:
Remove dead and diseased wood from trees.
Allow fruit to ripen on the tree longer.
Spray trees with a pre-harvest fungicide or drench the fruit in fungicide after harvest.
Lower degreening times and use less ethylene.
Store fruits at 50 degrees F. (10 C.).
