Droplet deposition during spray and leaf pH in aquatic weed control

Abstract

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 aim 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. Key words: aquatic weed, glyphosate, surface tension, wetting DEPOSIÇÃO DE GOTAS DE PULVERIZAÇÃO E pH FOLIAR NO CONTROLE DE PLANTAS DANINHAS AQUÁTICASRESUMO: A diversidade morfológica da superfície foliar existente entre as espécies de plantas e a presença de estruturas foliares como tricomas, estômatos, cutícula e ceras podem exercer grande influência na aderência e deposição das gotas de pulverização, assim como na absorção do herbicida. Desta forma, o objetivo do presente trabalho foi estudar, em quatro espécies de plantas daninhas aquáticas (Enhydra anagallis, Eichhornia crassipes, Heteranthera reniformis e Typha subulata), a área de molhamento de gotas de pulverização nas superfícies foliares adaxial e abaxial, bem como o pH foliar. O experimento foi realizado em Botucatu-SP. As plantas foram cultivadas em caixas d'água sob condições de campo, e quando atingiram seu pleno desenvolvimento (antes do florescimento), foram realizadas as avaliações de pH foliar e da área de molhamento de gotas de pulverização. As tensões superficiais das gotas aplicadas (0,5 µL), apresentadas pelas soluções de glyphosate aplicado isolado a 5,0% v v -1 (Rodeo 480 g L -1 e.a. -produto comercial), glyphosate + Aterbane BR (5,0% + 0,5% v v -1 ), glyphosate + Silwet L-77 (5,0% + 0,05% v v -1 ), além das soluções com os adjuvantes isolados, Aterbane BR (0,5% v v -1 ) e Silwet L-77 (0,05% v v -1 ) foram respectivamente 72,1; 28,7; 23,3; 37,3 e 22,1 mN m -1 . As médias obtidas de pH foliar variaram entre 5,50 e 7,50, destacando-se a espécie E. anagallis com valores de 6,68 e 7,02 para as faces adaxial e abaxial, respectivamente. Dentre as plantas daninhas aquáticas avaliadas T. subulata foi a espécie que apresentou as maiores médias de área de molhamento nas faces adaxial e abaxial da fol...

Impact of tembotrione and flufenacet plus isoxaflutole application timings, rates, and adjuvant type on weeds and yield of maize

“…Tembotrione used alone or in mixture with flufenacet + isoxaflutole effectively controlled weeds, especially when applied twice (Gatzweiler et al, 2012). Based on our studies it can be concluded that the addition of adjuvants to the spray liquid was due to increased retention of the spray droplets on the weed leaves surface and also increased rate of absorption of the herbicide into the target plant (Costa et al, 2005). Adjuvant MSO plus fertilizer origin adjuvants (AMN, UAN) are typically applied with HPPD-inhibitor herbicides (tembotrione or mesotrione), and substantially improve weed control (Young et al, 2007).…”

Spray deposition on weeds of common bean crops

“…However, there were approximately 463.6 and 85.3% higher deposition on the weeds located between the rows than within the rows with the use of the TX (150 L ha , provided a spray deposition that was 34% higher for B. plantaginea plants at the 2-8 leaf stage and located between rows, when compared to the plants located in the rows of a soybean crop (V2-4 stage). It is important to emphasize that the diversity in leaf morphological that exists between B. pilosa and B. plantaginea, including the trichomes, stomata, cuticles and waxes, can have a great influence on the drop deposition and its adherence to the leaves and, consequently, on the absorption of the herbicide (Ferreia et al, 2002;Procópio et al, 2003;Monquero et al, 2001;Costa et al, 2005a;Costa et al, 2005b). However, there are few available reports on morphological studies related to leaf anatomy and correlated with drop deposition over weeds.…”

Surfactant droplet evaporation and deposition patterns on waxy leaf surface

“…The leaf morphology which varies with the plant variety and specie affects the droplet deposition formation and retention on leaf surfaces (De Ruiter et al, 1990;Smith et al, 2000;Beattie and Marcell, 2002;Costa et al, 2005;Brewer, et al, 2007). The structures of leaf surface include cuticular wax, veins, hairs and other protrusions.…”

“…The penetration performance of insecticides, herbicides or fungicides into plant tissues largely depends on the wettability of leaf surfaces while the wettability is influenced by the topography on the leaf surfaces (Kannan and Sivakumar, 2008). Surfactants are usually used in spray mixtures to increase the leaf surface wettability and droplet spreading capability (Foy, 1993;Ryckaert et al, 2007), resulting in less pesticide use (Kirkwood, 1993;Costa et al, 2005). However, excessive use of surfactants might not produce uniform residual coverage on hydrophobic surfaces after post-evaporation (Pierce et al, 2008).…”