RESUMO-O sucesso de uma aplicação de herbicida está diretamente relacionado a uma boa deposição da calda no alvo, com o mínimo de perdas para o ambiente. Assim, o presente trabalho objetivou avaliar a deposição e o controle de plantas daninhas promovido pela aplicação de glyphosate em diferentes volumes de calda e com a adição do adjuvante nonil fenol etoxilado. O experimento foi conduzido em delineamento de blocos casualizados com quatro repetições, em esquema fatorial 3x2, sendo três volumes de calda (30, 60 e 150 L ha-1) e duas composições (com e sem adjuvante adicionado ao tanque). Inicialmente, foi realizada a caracterização físico-química das caldas pulverizadas. Foram avaliados, após a aplicação do glyphosate, utilizando pontas de pulverização hidráulicas de jato plano defletor: deposição de calda no alvo, perdas para o solo e controle de plantas daninhas. O adjuvante promoveu alterações de pequena magnitude nas propriedades físico-químicas da solução. Conclui-se que os menores volumes de calda proporcionaram maiores deposições nas plantas daninhas e menores perdas para o solo. O herbicida estudado proporcionou bom controle das plantas daninhas, independentemente da utilização do adjuvante e do volume de calda. Palavras-chave: deposição de calda, herbicida, propriedades físico-químicas, tecnologia de aplicação. ABSTRACT-A successful herbicide application is dependent upon a good spray deposition on the target, with a minimum loss to the environment. Thus, this study aimed to evaluate spray deposition and weed control with glyphosate using different spray volumes and with the addition of the adjuvant nonyl phenol ethoxylate. The experiment was conducted in a randomized block design, in a factorial model 3x2, with three spray volumes (30, 60, and 150 L ha-1) and two spray solution compositions (with and without adjuvant added to the tank). Initially, the physical-chemical properties of the solutions were evaluated under laboratory conditions. Spray deposition, loss to the soil, and weed control were investigated. The adjuvant promoted minor alterations in the physical-chemical properties of the solution. It was concluded that the lowest spray volumes showed the best weed deposition, and the lowest loss for the soil. The adjuvant did not alter the results. The herbicide provided a good weed control irrespective of the volume and adjuvant used. INTRODUÇÃO As plantas daninhas prejudicam o desen-volvimento e a produtividade de muitos cultivos agrícolas, principalmente pelo fato de compe-tirem com a cultura por água, luz, nutrientes e espaço físico. Os prejuízos em produtividade decorrentes dessa competição devem-se espe-cialmente ao fato de que nas áreas agrícolas as plantas daninhas geralmente ocorrem em densidades bem superiores às das espécies cultivadas (Bianchi et al., 2006).
Field experiments were conducted to evaluate the influence of preemergence (PRE) herbicides metolachlor at 1,700 g ai/ha, pyrithiobac at 70 g ai/ha, or pendimethalin at 840 g ai/ha applied alone or with fluometuron at 1,300 g ai/ha and glyphosate postemergence (POST) at 840 g ai/ha on seedling diseases in glyphosate-resistant cotton. Hypocotyl disease severity both years averaged across PRE herbicide treatments was greater after glyphosate application to four-leaf cotton than cotyledon cotton. The PRE herbicide treatments, particularly those including fluometuron, increased root and hypocotyl disease ratings compared with a nontreated control, and a sequential application of glyphosate did not further increase disease severity. Greenhouse experiments using soil infested withRhizoctonia solaniconfirmed findings from the field study showing that PRE herbicides can predispose cotton to greater seedling disease injury with no increased seedling disease severity associated with application of glyphosate. In the field study, glyphosate applied at cotyledon or four-leaf growth stages decreased disease severity on cotton hypocotyls both years. This inhibitory effect of glyphosate was less evident in the greenhouse study and may have been related to species of fungi present, infestation level, and differences in environmental conditions when compared with the field.
Cotton was planted 11 May into plots consisting of 2 rows (40 inch centers) X 25 ft at the Macon Ridge Location of the Northeast Research Station. Treatments were arranged in a RCB design with 3 replications. Insecticides were applied with a high clearance sprayer calibrated to deliver 10 gpa through TeeJet TVS 8001 flat fan nozzles (2/row) at 38 psi. The cotton plants were in the pre-square development stage and averaged 5-6 nodes at the time of treatment. Cotton seedlings were infested with tarnished plant bug adults at 2 h after treatment and again at 3 DAT by placing the insects in nylon mesh cages, and then securing the cage over the plant terminal. Two cages (1 per plant) were placed in each plot with each cage containing 5 tarnished plant bugs. Mortality of tarnished plant bugs was recorded 2 d after the plants were infested. No rainfall was recorded during this test. Data were analyzed with ANOVA, and means were separated according to DMRT.
Six insecticide treatments were evaluated against tarnished plant bugs in cotton at the Macon Ridge Location of the Northeast Research Station. Cottonseed was planted 1 May in 4 rows (40 inch centers) X 50 ft. Treatments were arranged in a RCB design with 4 replications. Insecticides were applied on 7 Jul with a high clearance sprayer calibrated to deliver 6 gpa through TeeJet TX-8 hollow cone nozzles (2/row) at 46 psi. Treatments were evaluated 3, 5, and 7 DAT by sampling the plots with a standard 15 inch diam sweep net. Also, to estimate actual mortality values for the treatments, field-collected tarnished plant bug adults were caged on 5 plants within each plot at 4 DAT. Five adults were introduced into a small nylon mesh cage which was placed over the plant terminal. Mortality of caged tarnished plant bugs was recorded 2 d after infestation (6 DAT). No rainfall was recorded during the test. Data were analyzed with ANOVA, and means were separated according to DMRT.
Granular in-furrow applications of Temik 15G were evaluated for control of seedling diseases with Terraclor Super-X, Terraclor, Terrazole, and Ridomil fungicides. The test was conducted at the Northeast Research Station, St. Joseph, LA. Plots were replicated 4 times in a RCB design and were 4 rows wide (40-inch spacing) X 65 ft. ‘Stoneville LA 887’ cotton seed was planted 17 Apr on a commerce silt loam soil which was sidedressed with 90 lb N/acre. Cotton seed was planted with a John Deere model 7100 series planter which was equipped with 10 inch seed cones mounted to replace the seed hoppers. The seeding rate was 4 seed/row ft and all plots received 0.5 lb (AI)/acre of Temik 15G. Granular in-furrow treatments and Pythium inoculum were applied with 8 inch belt cone applicators mounted to replace the standard granular applicators. In-furrow spray treatments were applied with a CO2 charged spray system through 25015 flat fan nozzles positioned in front of the press wheels. The spray tips were turned to spray across the furrow and were calibrated to deliver 5 gpa. Stand density was measured by counting all plants in a 10 ft section of an inside row on 5 May and all plants on the center 2 rows on 5 and 24 May. On 9 May, cotton seedling height and disease ratings were made on hypocotyls and roots by evaluating 5 randomly selected plants. In general, stem injury was caused by the fungal disease, Rhizoctonia solani. A rating system of 1 for no visible lesions, 2 for non-girdling lesions, and 3 for lesions that girdled the entire stem was used for stem injury. For root decay ratings (Pythium spp. symptoms) a scale of 1 to 6 was used (1 showing no visible symptoms and 6 showing 100% death of the root system). Pest control was initiated in Jun and continued on an “as needed” basis through Aug. Plots were harvested on 11 Sep. All 4 rows of the plots were mechanically harvested using a John Deere spindle type picker. Yields were converted to lb seed cotton/acre.
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