These studies were conducted on several central Texas agricultural producers?? properties, the Stiles Farm Foundation, the Texas Agricultural Experiment Station, and the Texas A&M University campus. First, an experimental herbicide from Dow AgroSciences, GF-884, was evaluated for effectiveness in controlling three annual and three perennial weed species in production pasture lands and hay meadows. Several rates of GF-884 were examined and evaluated against three registered pasture products and one non-selective herbicide. Next, GF-884 was assessed for tolerance on two common bermudagrass hybrids (Cynodon dactylon (L.) Pers.) at three progressive rates with and without adjuvant. Finally, the herbicides, picloram and fluroxypyr, were applied to common ragweed (Ambrosia artemisiifolia L.) to characterize their individual absorption and translocation and assess any influence one might have on the other. GF-884 applied at rates of 0.91 and 1.14 kg a.e./ha provided >85% and >75% control of the annual and perennial weed species evaluated, respectively. These same rates of GF-884 consistently provided control that was equivalent or better than thatachieved with the registered products. No differences were observed among treatments when shoots from the perennial species were evaluated 12 months following treatment application. The tolerance experiments utilized GF-884 at rates twice that used to evaluate weed control efficacy. These elevated rates did not result in discernable influences on yield or forage quality for either hybrid forage grass when compared to untreated areas. The efficacy and tolerance observations suggest that GF-884 applied at the highest recommended weed control rate can effectively control several annual and perennial weed species without imparting detrimental effects to the hybrid bermudagrass being produced. Finally, in the presence of fluroxypyr, 14C picloram absorption was maintained throughout all sampling intervals. Picloram applied alone, maximized 14C absorption at 6 HAT then declined significantly. At the final sampling, 14C from picloram applied alone was in greater concentration in the treated leaf and the root. Picloram significantly decreased absorption of 14C fluroxypyr. Fluroxypyr alone maintained 14C absorption throughout all samplings, whereas the combination maximized at 12 HAT. Initially, picloram limited 14C translocation, however at 6, 12, and 24 HAT this was not evident.

Submitted by RENATA THAYSA DA SILVA SANTOS null (renata_sol_2@hotmail.com) on 2017-09-19T19:23:31Z No. of bitstreams: 1 Dissertação pronta.pdf: 1297727 bytes, checksum: 9562b8aaaa9a30d19ffbb80afb4d3495 (MD5) / Approved for entry into archive by Monique Sasaki (sayumi_sasaki@hotmail.com) on 2017-09-20T17:21:48Z (GMT) No. of bitstreams: 1 santos_rts_me_bot.pdf: 1297727 bytes, checksum: 9562b8aaaa9a30d19ffbb80afb4d3495 (MD5) / Made available in DSpace on 2017-09-20T17:21:48Z (GMT). No. of bitstreams: 1 santos_rts_me_bot.pdf: 1297727 bytes, checksum: 9562b8aaaa9a30d19ffbb80afb4d3495 (MD5) Previous issue date: 2017-07-26 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O espalhamento das gotas sobre superfícies vegetais pode indicar eficiência na aplicação de herbicidas. Porém, o espalhamento de uma gota depende das características da calda fitossanitária, especificamente das propriedades físico-químicas e as suas interações com as superfícies onde as gotas se depositam. As propriedades físicas, como tensão superficial e ângulo de contato podem ser alteradas pela adição de adjuvantes ao tanque do pulverizador. Assim, o desenvolvimento de pesquisas que avaliem a interação dos herbicidas associados a adjuvantes é importante para a recomendação correta do adjuvante, uma vez que o adjuvante pode proporcionar maior espalhamento da gota sobre a superfície de diferentes espécies de plantas, e potencializar o controle. Nesse sentido foram realizados dois estudos, sendo o primeiro para avaliar a tensão superficial e o ângulo de contato em três espécies do gênero Sida. No segundo foi avaliado o ângulo de contato de seis espécies de plantas daninhas e a relação do ângulo com o controle de Lantana camara e Crotalaria incana, de ocorrência em pastagem, ambiente vastamente cultivado no Brasil, mas no qual são raros os trabalhos desta natureza. Concluiu-se que a adição do adjuvante lecitina ao herbicida aminopiralide + fluroxipir reduz o ângulo de contato das gotas sobre as superfícies adaxial e abaxial de Sida cordifolia e Sida glaziovii. E quanto menor ângulo de contato maior controle das espécies avaliadas. / The spreading of the drops on plant surfaces may indicate the possible success in herbicide application. However, the spread of a drop depends on the characteristics of the spray solution, specifically the physicochemical properties and their interactions with the surfaces where the drops settle. Physical properties such as surface tension and contact angle can be altered by the addition of adjuvants to the spray tank. Thus, the development of research that evaluates the interaction of herbicides associated with adjuvants is important for the correct recommendation of the adjuvant, since the adjuvant can provide greater spreading of the drop on the surface of different species of plants, and potentiate the control. In this sense two studies were carried out, being the first to evaluate the surface tension and the contact angle in three species of the Sida genus. In the second, was evaluated the contact angle of six weed species and the angle relationship with the control of Lantana camara and Crotalaria incana, a pasture, an area widely cultivated in Brazil, but in which works of this nature are rare. It was concluded that the addition of the lecithin adjuvant to the aminopyralid herbicide + fluroxypyr reduces the contact angle of the drops on the adaxial and abaxial surfaces of Sida cordifolia and Sida glaziovii. And the lower the contact angle the greater the control of the evaluated species.

Ionisable pesticides can be partially ionised within the range of natural soil pH and this strongly influences their reactivity in soils. This group includes important, worldwide contaminants of groundwater and surface waters. It is essential that their specific behaviour is recognised within risk assessment procedures. Experiments were carried out with ten pesticides (six acids and four bases) and nine arable soils (range in pH, texture and organic matter content) to advance the understanding and prediction of the behaviour of ionisable pesticides in soils. The main conclusions can be summarised as follows:<br />• Adsorption of ionisable pesticides tends to be stronger in soils with lower pH and containing more organic carbon. A regression equation including Log D (lipophilicity corrected for pH), the soil organic carbon content and a pesticide descriptor was selected to predict the adsorption of acids. The behaviour of bases was more complex and approaches specific to each compound seem to be required.<br />• There were some marked differences between the soils in their ability to degrade the different ionisable pesticides. The lack of consistent behaviour renders a global approach to prediction of degradation unrealistic. Distinct types of behaviour could however be distinguished according to the main route of degradation.<br />• Significant correlations between sorption and degradation were only observed for three pesticides out of ten, with faster degradation in soils with stronger sorption.<br />• A centrifugation technique was used to measure adsorption at realistic soil moisture contents and provides a robust characterisation of the fraction of pesticide available for leaching. Time-dependent adsorption was also assessed.<br />The increase in adsorption between one and seven days was not directly related to the level of adsorption although it was more important in soils containing more organic carbon.<br />Although specific interactions between pesticides and soils are still not fully understood, these results provide the basis for a more robust analysis of the behaviour of ionisable pesticides in the environment.