Tanzania Journal of Agricultural Sciences 1999, Vol.2(1) : 115-125
Studies were conducted in the laboratory at RYe College, University of London, to investigate some aspects
of pre-infection structurai resistance on cashew leaf and flower sUlfaces. Using the Scanning,
Transmission Electron Microscppes and the light microscope, cashew leaf suTjaces were found to be
covered by a layer ofepicuticular wax, whichappeared to develop with age. Flower suTjaces werefound
to be covered by hairs of varying shape and length which appeared to help trap tiny mildew spores. Ihis
appears to explain why flower organs are extremely susceptible to mildew infection. Using artificial inoculation,
mildew in:ie"ction was possible on young leaves, but infection did not occur on older leaves.
Epicuticular waX layer observed on. cashew leaf suTjace, as a pre-infection resistance factor, appeared
to be responsible for inhibition of germination and development of O. anacardii on older leaves.