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 next time, and plant in fields that didn’t have the disease the previous 3 years. The seed company should be told they are very probably selling poor seed. A fermentation process is known to reduce the seedborne bacteria to practically zero. The fruits that are not too far gone are still edible, although they may not be marketable.
The bacterium used to be called Pseudomonas pseudoalcaligenes. There is extensive work in recent years from the USA. Key workers for a search are Schaad, N on seed detection methods; Walcott, R and Gitaitis, R on epidemiology/control.
A google search will give many leads. Seed infections are a main source of disease and its spread internationally.