Droplet deposition during spray and leaf pH in aquatic weed control

The morphological diversity of leaf surface and structures such as trichomes, stomata, cuticle, and waxes that exists among plant species can have great influence on the adherence and deposition of spray droplets, as well as on herbicide absorption. The aiin of this research was to study leaf pH and to evaluate wetting areas after applications of solution surfactants on the following aquatic weeds: Enhydra anagallis, Eichhornia crassipes, Heteranthera reniformis, and Typha subulata. The aquatic weeds were grown in reservoirs containing water under open air conditions and their leaf tissues were collected when the plants reached full development (before flowering). The mean leaf pH varied between 5.50 and 7.50; E. anagallis should be pointed out for presenting the highest pH values, of 6.68 and 7.02 on the upper and lower leaf surfaces, respectively. Surface tension reduction for glyphosate alone (5.0% v v(-1)), glyphosate + Aterbane BR (5.0% + 0.5% v v(-1)), glyphosate + Silwet L-77 (5.0% + 0.05% v v(-1)), and surfactants alone, Aterbane BR (0.5% v v(-1)), and Silwet L-77 (0.05% v v(-1)), were, respectively: 72.1; 28.7; 23.3; 37.3, and 22.1 mN m(-1).T subulata was the aquatic species with the highest upper and lower leaf surface wetting area.