June 2010. A root rot of Jatropha from Mali. Well cared for, healthy, 2 m meter tall Jatropha have been attacked by a pathogen just after the first rains in May. The plants died within 2 weeks. The pathogen either enters at the stem base and then invades the stem and the root, or it enters through the roots. The bark of the root and stem become yellow inside, the root becomes moist, and rots with a strong smell.

In response, a member wrote: Jatropha is quite susceptible to Phytophthora which infects via the roots killing the crown and often moving some distance up the trunk above soil level. It is favoured by wet conditions and the photos are what you would expect from an advanced stage of infection. So it sounds like that may be the problem. It may possibly be P palmivora which is prevalent in tropical areas.

Control under those conditions is very difficult. Good drainage is essential, but with very heavy rain even that may not be enough. Growing on mounds would help. If the cuttings are raised in a nursery it is very important that that area is disease free, otherwise the disease will simply be carried on new plants. Chemical control in the field may not be an option, but if it were to be considered then one of the phosphonate (phosphorus acid) products would probably be the best choice applied as a foliar spray.

Confirmation of the diagnosis came from Vietnam, but suggesting that if a chemical remedy was sought, it would be best to get the correct identity established first. There was also a suggestion to use EM, as this in combination with garlic, onion and ginger has been used with success against Fusarium on Jatropha.

Soil drainage as mentioned above is also important. The Vietnam experience with Jatropha is that in heavy clay soils, and other soil types that have poor drainage, plants are always susceptible to root rots.