Applying trinexapac-ethyl (TE) is a common practice for growth suppression and quality improvement of ultradwarf bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy] putting greens. Previous research suggested that growing degree-days (GDD) effectively predict the suppression of creeping bentgrass (Agrostis stolonifera L.) putting greens following a TE application, and additional research showed similar results on ultradwarf bermudagrass putting greens. Whereas temperature may be the main factor influencing turfgrass suppression following a TE application, it is likely that other environmental factors affect suppression as well. The objective of this research was to identify the optimal variable unit for predicting suppression, particularly the maximum suppression point (MSP), after a TE application on a 'MiniVerde' ultradwarf bermudagrass putting green. Tested variable units included calendar days (DAT), GDD (base temperatures of 0-12˚C), soil temperature (2.5 cm), global horizontal irradiance (GHI), and photosynthetically active radiation (PAR). The GDD with a base temperature of 0˚C (GDD 0) model predicted suppression better than the GDD with a base temperature of 10˚C (GDD 10) model, GHI model, and PAR model. According to the GDD 0 model (pseudo-R 2 , .564; SE: 0.195), the MSP occurred at 262 GDD 0 with a suppression magnitude of 61%. The models did not indicate a rebound period following the single TE application. 1 INTRODUCTION Applying trinexapac-ethyl (TE) to ultradwarf bermudagrass putting greens [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy] is a common practice. Trinexapac-ethyl Abbreviations: DAT, calendar days after treatment; GA, gibberellic acid; GDD 0 , growing degree-days with a base temperature of 0˚C; GDD 10 , growing degree-days with a base temperature of 10˚C; GHI, global horizontal irradiance; MSP, maximum suppression point; PAR, photosynthetically active radiation; TA, trinexapac acid; TE, trinexapac-ethyl; WAIT, weeks after initial treatment.

Southern crabgrass [Digitaria ciliaris (Retz.) Koeler] is an annual grass weed that commonly infests turfgrass, roadsides, wastelands, and cropping systems throughout the southeastern United States. Two biotypes of D. ciliaris (R1 and R2) with known resistance to cyclohexanediones (DIMs) and aryloxyphenoxypropionates (FOPs) previously collected from sod production fields in Georgia were compared with a separate susceptible biotype (S) collected from Alabama for the responses to pinoxaden and to explore the possible mechanisms of resistance. Increasing rates of pinoxaden (0.1 to 23.5 kg ha−1) were evaluated for control of R1, R2, and S. The resistant biotypes, R1 and R2, were resistant to pinoxaden relative to S. The S biotype was completely controlled at rates of 11.8 and 23.5 kg ha−1, resulting in no aboveground biomass at 14 d after treatment. Pinoxaden rates at which tiller length and aboveground biomass would be reduced 50% (I50) and 90% (I90) for R1, R2, and S ranged from 7.2 to 13.2 kg ha−1, 6.9 to 8.6 kg ha−1, and 0.7 to 2.1 kg ha−1, respectively, for tiller length, and 7.7 to 10.2 kg ha−1, 7.2 to 7.9 kg ha−1, and 1.6 to 2.3 kg ha−1, respectively, for aboveground biomass. Prior selection pressure from DIM and FOP herbicides could result in the evolution of D. ciliaris cross-resistance to pinoxaden herbicides. Amplification of the carboxyl-transferase domain of the plastidic ACCase by standard PCR identified a point mutation resulting in an Ile-1781-Leu amino acid substitution only for the resistant biotype, R1. Further cloning of PCR product surrounding the 1781 region yielded two distinct ACCase gene sequences, Ile-1781 and Leu-1781. The amino acid substitution, Ile-1781-Leu in both resistant biotypes (R1 and R2), however, was revealed by next-generation sequencing of RNA using Illumina platform. A point mutation in the Ile-1781 codon leading to herbicide insensitivity in the ACCase enzyme has been previously reported in other grass species. Our research confirms that the Ile-1781-Leu substitution is present in pinoxaden-resistant D. ciliaris.

Trinexapac-ethyl (TE) is commonly applied to ultradwarf bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy] putting greens for growth suppression and secondary benefits. Improperly timed reapplications will reduce the benefits of TE, but knowing when to reapply is difficult because suppression duration is affected by environmental conditions, especially temperature. In another experiment we determined that GDD with a base temperature of 0˚C (GDD 0) was the most precise unit for predicting the maximum suppression point (MSP) after a TE application on a 'MiniVerde' ultradwarf bermudagrass putting green. The model suggested that the MSP occurred at 262 GDD 0 after the TE application. The objective of this second experiment was to test GDD 0 reapplication intervals for an extended period of time. We included four GDD 0 intervals (100, 200, 400, and 600) and two TE rates (0.022 and 0.044 kg a.i. ha −1). We hypothesized that reapplying TE before the MSP would result in a consistent suppression magnitude from day to day (i.e., consistent daily growth), which should be an ideal growth pattern for turfgrass managers. The 100-and 200-GDD 0 intervals yielded consistent suppression magnitude throughout the experiment, and suppression magnitude increased with the higher TE rate. In contrast, the 400-and 600-GDD 0 intervals allowed fluctuation in suppression magnitude from day to day. Discoloration occurred after initial applications and was more severe for the higher TE rate. Abbreviations: DAIT, days after initial treatment; GA, gibberellic acid; GDD 0 , growing degree-days with a base temperature of 0˚C; GDD 10 , growing degree-days with a base temperature of 10˚C; MSP, maximum suppression point; TE, trinexapac-ethyl.

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Potassium fertilizer and irrigation management in the progress of fungal diseases and yield of watermelonAmong the major diseases of watermelon, gummy stem blight (Didymella bryoniae) and downy mildew (Pseudoperonospora cubensis) stand out because they cause great losses in productivity and fruit quality. To investigate the influence of potassium fertilization on the progress of gummy stem blight and yield of watermelon and the influence of the water depth and the interval of irrigation in the progress of mildew, two assays were carried out under field conditions in Gurupi, Tocantins state, Brazil, in 2009 and 2010. The assay I was carried out in blocks and the treatments consisted of three doses of potassium applied (0, 50 and 100 kg/ha using KCl) and 12 replications. We evaluated the severity of gummy stem blight through a scale and the production data and fruit quality. In the assay II, we used a randomized complete block design with four replications in a factorial 3 x 3, three irrigation levels (100, 300 and 500 mm of water during the crop cycle) and three irrigation intervals. We evaluated the severity of downy mildew addition, the production and fruit quality. Doses of potassium did not affect the progress of gummy stem blight and the number, weight and fruit quality. The irrigation applied influenced the progress of downy mildew. Higher levels of severity of downy mildew were observed in plants cultivated under irrigation with levels of 500 mm of water. The amount of water applied also significantly influenced the production and fruit quality. We observed the presence of more crooked or deformed fruits in plants kept under water using a level of 100 mm. The highest total and marketable yield were obtained in plants irrigated with the level of 500 mm of water.

stomatal conductance, leaf area, leaf anatomy measures (width of palisade and spongy parenchyma, length of central vein, adaxial and abaxial width of central vein, length of vascular bundle, width of vascular bundle), and stem diameter. A higher tolerance was observed in BRS Valiosa RR to moderate hydric deficit conditions when they occurred in soybean stage V2. The BRS Valiosa RR cultivar presents a better morphologically and anatomically adaptive response to moderate hydric restrictions of up to (−0.07 MPa) when they occur in the first weeks of plant development.

-Saflufenacil is absorbed by the plant leaves and roots, thus the residual permanence of this herbicide can cause losses to the crop plants. Therefore, the objective of this study was to evaluate the selectivity of the saflufenacil herbicide, applied singly and in combination with glyphosate, on coffee and citrus plants grown in a sandy soil. Two experiments were implemented and conducted in completely randomized design with four replications. The chemical treatments consisted of three sequential applications, with directed spraying of saflufenacil at rates of 0.035, 0.07 and 0.105 kg a.i. ha -1 , glyphosate at rate of 2.160 kg a.e. ha -1 , the two herbicides combined at the same rates, and a control without chemical treatment. The saflufenacil applied singly and in combination with glyphosate was selective for coffee and citrus plants, which presented no visual toxicity symptoms. The sequential application of saflufenacil, singly and in combination with glyphosate did not affect the growth of coffee and citrus plants. The saflufenacil has potential for use, in combination with glyphosate on controlling many weed species in coffee and citrus areas without any interference on the development of these species.Keywords: Development. Directed spraying. Herbicide. Phytotoxicity. SELETIVIDADE DO SAFLUFENACIL ISOLADO E EM ASSOCIAÇÃO COM GLYPHOSATE EM CULTURAS DE CAFÉ E CITROSRESUMO -O saflufenacil é absorvido pelas folhas e raízes das plantas, por isso a permanência residual deste herbicida pode provocar prejuízos para as plantas cultivadas. Portanto, este trabalho teve como objetivo avaliar a seletividade do herbicida saflufenacil aplicado isolado e em associação com glyphosate, em plantas de café e citros cultivadas em solo arenoso. Foram instalados e conduzidos dois experimentos no delineamento inteiramente casualizado, com quatro repetições. Os tratamentos químicos consistiram de três aplicações sequenciais, com jato dirigido de saflufenacil nas doses de 0,035, 0,07 e 0,105 kg i.a. ha -1 , de glyphosate na dose de 2,160 kg e.a. ha -1 , e da associação dos dois herbicidas nas mesmas doses, além de uma testemunha sem tratamento químico. O saflufenacil aplicado isolado e em associação com glyphosate foi seletivo para plantas de café e citros, não apresentando nenhum sintoma visual de intoxicação nas plantas. A pulverização sequencial de saflufenacil isolada e em associação com glyphosate não afetou o crescimento das plantas de café e citros. O saflufenacil tem um potencial de uso em associação com glyphosate para fornecer controle de muitas espécies de plantas daninhas em áreas de café e citros sem nenhuma interferência no desenvolvimento destas espécies. Palavras-chave:Desenvolvimento. Jato dirigido. Herbicida. Fitointoxicação.