Submitted to: International Colloquium on Invertebrate Pathology and Microbial Control Proceedings
Publication Type: Proceedings
Publication Acceptance Date: August 18, 2002
Publication Date: September 1, 2002
Citation: WRAIGHT, S.P. Phyllosphere ecology of Terrestrial Entomopathogenic Fungi. PROCEEDINGS OF THE INTERNATIONAL COLLOQUIUM ON INVERTEBRATE PATHOLOGY AND MICROBIAL CONTROL. 2002. v. 8. p. 72-77. Technical Abstract: Plant leaf surfaces (phylloplanes) and the microhabitat zones surrounding them (phyllospheres) comprise the largest biosphere-atmosphere interface on earth. Many biotic and abiotic factors interact at this interface to produce a highly variable and dynamic environment. These factors include wind, moisture, solar radiation, temperature, activities of microbial epiphytes and leaf-inhabiting invertebrates, allelochemicals and nutrient materials produced by the leaf and its inhabitants, and agrochemicals applied for disease and pest control. Although conditions prevailing in the phyllosphere are spatially and temporally variable, they are frequently or at least periodically favorable to entomopathogenic fungi, and many species exploit leaf surfaces as arenas for host infection. Most significantly, fungi rely on leaves to moderate moisture and temperature conditions and provide protection from solar radiation, isolation from competitors, and elevated sites for spore dispersal. Air movement stagnates at the leaf surface, creating a boundary layer of high humidity. Ventral surfaces usually generate a thicker boundary layer than dorsal surfaces because they are shaded, possess greater densities of stomata and trichomes, and often have contours or surface concavities that entrap humid air. Under hot conditions, leaves may be oriented to minimize solar irradiance, and evaporative cooling generated by increased transpiration can depress ventral phylloplane temperatures as much a 10°C below ambient. Under cool conditions, leaves may orient to maximize irradiance and maintain higher temperatures. Leaves produce waxes and other compounds that absorb germicidal UV-B radiation, making them highly effective solar radiation screens.