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.
January 2006. Spotting on papaya fruit in Samoa, first thought to be caused by Corynespora. The spots are first seen on the leaves, then the petioles and fruits.
It was identified as Asperisporium caricae, Black spot disease. There should be numerous small black angular spots. Growth on media is limited, but the spores are easily recognisable. If the disease is heavy on the leaves it is likely to be the same on the fruit. Make slide preparations by scraping the surface of some of the spots on both leaves and fruit. For Asperisporium, look for small dark two-celled spores and short dark conidiophores in tight clusters (check in Ellis Dematiaceous Hyphomycetes p.273). For Corynespora, look for large light brown tapering spores with transverse septa on long conidiophores that are scattered singly over the surface of the spot (they are very pretty spores. See p.373 in Ellis).
The variety Sunrise is particularly susceptible to the disease.