Pod Rot and Witches' Broom
pod or Moniliophthora roreri
Moniliasis or frosty
pod (Moniliophthora roreri) and witches' broom (Crinipellis
perniciosa) cause estimated losses of 5% and 21% respectively in global
cocoa production annually. On individual farms, up to 100% of a farmer's
crop can be lost in any one year and this has led to many farmers abandoning
their cocoa farms. The use of conventional chemical (copper fungicides)
and cultural control techniques (phytosanitary pruning) have failed to
halt the progress of these diseases. CABI scientists, Drs. Harry
Evans and Keith Holmes are
studying endophytes (mutualistic symbionts) that have the potential to
protect their host plants through multiple mechanisms: competitive exclusion;
induced resistance; antagonism or mycoparasitism. Dr.
Ulrike Krauss and her team based in Costa Rica investigate the exploitation
of mycoparasites/antagonists to reduce inoculum pressure of M.roreri
. Both approaches are being pursued using the principles of classical
biological control. Classical biological control involves returning to
the centre of origin of the target pest organism to find natural enemies,
in this case mycoparasites/antagonists, which have co-evolved with it.
In addition, molecular
studies of the M.roreri population are being undertaken (Drs. Krauss,
Evans, Mr. Phillips) to explain the spread of the pathogen and identify
its origin as well determine which isolates are suitable for screening
germplasm for resistance. Also, Dr.
Bateman is conducting trials in Central and South America in an effort
to make the application of biological and chemical preparations more effective
in controlling these diseases.