A network that helps people worldwide obtain rapid advice and information on crop protection, including the identification and management of plant pests.
PestNet is a network that helps people worldwide obtain rapid advice and information on crop protection, including the identification and management of plant pests. It started in 1999. Anyone with an interest in plant protection is welcome to join. PestNet is free and is moderated, ensuring that messages are confined to plant protection.
April 2006. A report of a disease of watermelon from Guyana, causing a blackening of the skin.
From the photos of the fruit, it looks like fruit blotch, caused by the bacterium Acidovorax avenae subsp. citrulli. This is a seedborne disease, and the pathogen survives well in the soil and is capable of attacking a number of cucurbits. There is little to do except switch to another source of seeds, and plant in fields that did not have the disease in the previous 3 years. The seed company should be told they are probably selling poor seed. A fermentation process is known to elimminate the seedborne bacterium. It may still be possible to eat the flesh of the fruit, although the fruit are unlikely to be marketable.
The bacterium used to be called Pseudomonas pseudoalcaligenes. There has been extensive work on the disease in the USA in recent years. Key workers for an Internet search are Schaad N for seed detection methods; and Walcott R and Gitaitis R for epidemiology/control.
A Google search will give many leads. Seed infections are a main source of disease and spread internationally.