A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases <http://www.isid.org>
Date: Thu 4 Oct 2012
Source: FreshPlaza, Trinidad Express report [edited] <http://www.freshplaza.com/news_detail.asp?id=101527>
Melon farmers hit hard by crop disease
Because of continuous rains watermelon farmers in Kernahan [village of] Mayaro [county] lost thousands of dollars worth of watermelon crops. The coldness brought on the dreaded "gummy stem blight disease".
The dry season also brings the thrips insect [which] feeds on plants with commercial value. Farmers have now discovered a new threat to their melons, vertical cracks along the top half. None of the farmers knows what is destroying the crops throughout the area. When cracks appear the inside of the melon will be affected. A sample [is being] tested at the Ministry of Food Production, Land and Marine Affairs.
[Gummy stem blight (GSB) of cucurbits is caused by the fungus _Didymella bryoniae_ and is the most common leaf disease of watermelon. Symptoms include lesions on leaves and stems of seedlings.
The seedling may be girdled by the lesions and collapse, or be so weakened by the infection that it is never productive. Gummy stem blight requires prolonged moisture to become established and consequently is a serious problem in regions of high rainfall and glasshouse crops. The fungus also causes black rot if it infects the fruits.
Spores may be seedborne or spread by air currents, water from rain or irrigation systems, or mechanical means (including activities of insects, for example the thrips mentioned above). The fungus can survive between growing seasons in an over-wintering structure, and wild cucurbits or volunteer hosts may serve as pathogen reservoirs.
Disease management includes fungicides and use of certified GSB-free seed from reliable sources.
A suspected source of the GSB outbreak in Trinidad (for example contaminated seed or build up of local inoculum) is not reported in the story above. Fruit cracking, also mentioned in the report, may be due to a number of causes, including environmental factors.
Trinidad & Tobago:
Caribbean with location of Trinidad & Tobago:
GSB on watermelon leaf:
GSB on cucurbit transplants:
GSB on cucurbits, photo gallery:
Additional news story:
Gummy stem blight information:
_D. bryoniae_ taxonomy:
Gummy stem blight, watermelon - USA: new strains 20090521.1899
Downy mildew, cucurbits - USA (02): clarification 20071109.3633 Downy mildew, cucurbits - USA: (SC), new strain 20071023.3448]