Hudson Kagueyama Takano

Sumatran Fleabane (Conyza sumatrensis) Control in No-Tillage Soybean with Diclosulam Plus Halauxifen-Methyl

Due to the limited availability of selective herbicides to control Sumatran fleabane after soybean emergence, it is essential to develop new options that provide effective control prior to planting. A new herbicide formulation containing diclosulam + halauxifen-methyl was evaluated for effectiveness at two Sumatran fleabane plant heights (5 to 10 cm, and 10 to 50 cm) and for soybean selectivity when applied at 7 or 3 d before planting. Combined results from the two sites showed that diclosulam+ halauxifen, applied either alone or in a tank mixture with glyphosate, and the tank mixture of diclosulam + 2,4-D amine + glyphosate are effective at all rates tested to control Sumatran fleabane in preplant applications. Crop response was observed with applications 7 days before planting at only one of the sites. A rate-dependent crop response was observed for pre-plant applications performed 3 days before soybean planting. However, crop yield was not significantly affected for either timing across all rates. All rates tested of diclosulam + halauxifen in this study were considered safe to soybean. Nomenclature: Diclosulam; glyphosate; halauxifen, 4-amino-3-chloro-6-(4-chloro-2-fluoro-3-methoxyphenyl)pyridine-2-carboxylic acid; 2,4-D; Sumatran fleabane, Conyza sumatrensis (Retz.) E. Walker; soybean, Glycine max L. Merr.

Plantas daninhas como hospedeiras alternativas para Pratylenchus brachyurus

Uma das acoes indiretas exercidas pelas plantas daninhas na interferencia sob especies cultivadas e o potencial de hospedar agentes causadores de enfermidades. O nematoide das lesoes radiculares (Pratylenchus brachyurus) vem causando uma serie de danos em diversas culturas no Brasil. Para o manejo deste fitoparasita, o cultivo de diferentes especies de crotalarias tem sido empregado. O objetivo deste trabalho foi avaliar a hospedabilidade de plantas daninhas para P. brachyurus, bem como o efeito de supressao de diferentes especies de crotalaria. Para isso, foi instalado um experimento em casa de vegetacao no delineamento inteiramente casualizado em arranjo fatorial (2x17), com seis repeticoes. O primeiro fator consistiu na presenca ou ausencia da inoculacao do nematoide. O segundo correspondeu a dezessete especies vegetais, sendo onze plantas daninhas, quatro crotalarias (C. breviflora, C. juncea, C. ochroleuca e C spectabilis) e duas variedades de soja, as quais serviram como testemunha sendo hospedeiras de P. brachyurus. A inoculacao do nematoide das lesoes radiculares nao influenciou a altura de plantas e massa seca de parte aerea das diferentes especies avaliadas. Portulaca oleracea, Amaranthus viridis e Sida rhombifolia foram as especies com maior numero de nematoides por sistema radicular, e apenas a S. rhombifolia apresentou comportamento semelhante a testemunha (variedade de soja BMX Potencia RR®). Com relacao ao numero de nematoides por grama de raiz, os maiores valores foram observados para A. viridis, seguido por P. oleracea. Excluindo-se a C. juncea, todas as demais especies de crotalaria apresentaram-se como boas opcoes para o manejo em areas infestadas com P. brachyurus.

Growth, Development and Seed Production of Goosegrass1

E. indica is one of the most problematic weeds in the world because it is present in almost every continent, and there are reports of multiple resistance to herbicides by some biotypes. The objective of this paper was to analyze the growth, the development and the production of this plants seeds, in order to generate information about its biology that can be useful for management. The experiment was carried out in a greenhouse from May to September 2015. Sixteen samples were taken during the development cycle of the plant: 3, 10, 17, 24, 31, 38, 45, 52, 59, 66, 73, 80, 87, 94, 101 and 108 days after emergence (DAE). The response variables were based on a leaf area and dry matter of each one of the parts of the plant and the number of seeds produced per plant. At 12 DAE, 80% of the seedlings of E. indica had emerged, and each plant produced more than 120 thousand seeds, closing their cycle at 120 DAE. Between 38 and 43 DAE, the plant had fast emission of new tillers, exponential accumulation of the total dry matter and substantial increase of the absolute growth rate. Due to the data observed here, we concluded that the management of E. indica must be done preferably before 38 DAE due to the exponential growth after this period, preventing the plant from producing seeds and spreading to other places.

SELETIVIDADE DE HERBICIDAS APLICADOS EM PÓS-EMERGÊNCIA DA CROTALÁRIA

Weed control is essential to reduce or eliminate the interference of weeds on crops. Chemical control with the application of herbicides consists of the most used method, with this aim in grain producing areas. Information about the selectivity of herbicides to C. spectabilis (showy crotalaria) are scarce, which are critical for the management of this species as a crop. One field experiment was performed to evaluate the selectivity of herbicides applied in post-emergence of showy crotalaria. The herbicides bentazon (720 and 576 g ha), imazethapyr (106 and 79.5 g ha), pyrithiobac-sodium (84 g ha), flumiclorac (60 g ha), flumiclorac in sequential application (30 / 30 g ha), imazethapyr + bentazon (106 + 480 g ha), and clethodim + quizalofop (96 + 100 g ha) were applied in plants with four true leaves, also using a control without herbicide application. Pyrithiobac-sodium and flumiclorac isolated and the tankmix of imazethapyr + bentazon provided greater injuries to showy crotalaria, also affecting the final plant height. Pyrithiobac-sodium (84 g ha) was not selective to showy crotalaria. The herbicides imazethapyr (79.5 g ha), flumiclorac (sequential application), and bentazon (576 g ha), despite the association between clethodim + quizalofop, can be used for weed management in showy crotalaria crop.

Multiple resistance to atrazine and imazethapyr in hairy beggarticks (Bidens pilosa )

Resistance to herbicides is a serious threat to crop production worldwide, especially in agronomic crops and cereals. This research evaluated the possible occurrence of Bidens pilosa resistant to imazethapyr and atrazine in Brazil. The resistant biotype was collected from an area with a history of repeated application of photosystem II (PSII) and ALS inhibitor herbicides. The susceptible biotype was collected from an area with no history of herbicide application. Resistance verification experiments were carried out in the greenhouse. The treatments were arranged in a 3 x 8 factorial scheme, where the first factor was populations [susceptible (S), parent resistant (PR), and resistant F1 (RF1)]; and the second factor was herbicide dose (0, 375, 750, 1500, 3000, 6000, 12000 and 24000 g ha-1 for atrazine; or 0, 12.5, 25, 50, 100, 200, 400 and 800 g ha-1 for imazethapyr). The resistance factor to atrazine was 2.83 for PR and 5.55 for RF1. This population was more resistant to imazethapyr (>21-fold) than it was to atrazine. The recommended maximum dose of the herbicides did not control this B. pilosa population adequately. The data support the claim that B. pilosa population from this field in Quarto Centenario, Parana is resistant to two herbicide modes of action - PSII inhibitor (i.e. atrazine) and ALS inhibitor (i.e. imazethapyr). This is the first report of such case for this species, globally. Cross-resistance to other ALS inhibitors and other PS II inhibitors as well as the respective mechanisms of resistance to each herbicide are being investigated.

SELECTION OF HERBICIDES TARGETING THE USE IN CROP SYSTEMS CULTIVATED WITH SHOWY CROTALARIA

The increase in the area planted with Crotalaria spectabilishas occurred by several factors, highlighting the potential to reduce the nematodes, nitrogen fixation and the high production of biomass. By becoming a species sown as a crop, it is necessary to control the weeds that coexist with showy crotalaria. This change in the use of this crop creates the possibility of this specie becoming a weed. The aim of this study was to assess the potential use of herbicides applied in preemergence and postemergence of C.spectabilisfor different purposes (control of volunteer and selectivity plants). Three experiments were installed in a greenhouse (two with herbicides applied in preemergence - in soils with distinct textural categories; and one experiment with herbicides applied in postemergence). The results of the experiments with herbicides applied in preemergence showed that: amicarbazone, atrazine, diuron, metribuzin, prometryn, fomesafen and sulfentrazone showed effectiveness for control of C.spectabilis in clayey soil. Besides these, flumioxazin and isoxaflutole also showed potential to be used in the control of showy crotalaria in soils with loam texture. In relation to the postemergence herbicides, atrazine, diuron, prometryn, flumioxazin, fomesafen, lactofen, saflufenacil, amonio-glufosinate and glyphosate can be used aiming the chemical control of C.spectabilis. Herbicides chlorimuron-ethyl, diclosulan, imazethapyr, pyrithiobac-sodium, trifloxysulfuron-sodium, clomazone, pendimethalin, S-metolachlor and trifluralin applied in preemergence, and imazethapyr, pyrithiobac-sodium, flumiclorac, bentazon and clethodim applied in postemergence caused low levels of injury to C.spectabilis plants, making necessary the development of new searches to ensure the selectivity of these products.

SPECTRUM OF WEED CONTROL WITH 2,4-D AND DICAMBA HERBICIDES ASSOCIATED TO GLYPHOSATE OR NOT

ABSTRACT The possibility of using auxin mimics herbicides in culture postemergence applications contributes to weed management. This study aimed at evaluating and comparing the effectiveness of 2,4-D and dicamba herbicides on glyphosate resistant or tolerant weeds. The treatments were dicamba and 2,4-D doses with or without glyphosate. The evaluated weeds in the experiment were Richardia brasiliensis, Commelina benghalensis, Conyza sp. and Ipomoea nil. Herbicides were applied when weeds were in 4 to 6 and 10 to 12 leaves stages. Data referring to evaluations on day 30 after application were submitted to analysis of variance. Response-dose curves were obtained for herbicides, and C85 and C95 values were identified. Weed species showed different tolerance to dicamba and 2,4-D, and differences were more evident for C. benghalensis. The addition of glyphosate to the auxin mimic reduced the differences between them. For plants in less developed stages, regardless of the species, mixtures of glyphosate + 2,4-D or glyphosate + dicamba provided excellent levels of control. In general, considering equivalent doses, for R. brasiliensis, C. benghalensis and I. nil, 2,4-D herbicide was superior to dicamba. As for Conyza bonariensis, dicamba showed better control percentages.

Seletividade do Clomazone no Manejo Químico de Plantas Daninhas da Cultura do Algodão LL(r)

O amonio-glufosinate e um herbicida de amplo espectro de controle de plantas daninhas, porem nao apresenta controle residual no solo, o que limita sua utilidade quando usado isoladamente na cultura do algodao, havendo a necessidade de combinar diferentes herbicidas em mais de uma modalidade de aplicacao. O objetivo deste trabalho foi avaliar a seletividade de diferentes sistemas de controle quimico de plantas daninhas contendo clomazone na cultura do algodao LL(r). As misturas triplas em pre-emergencia apresentaram maior potencial de reducao no porte do algodoeiro. Recomenda-se utilizar misturas de dois herbicidas em pre-emergencia na cultura do algodao, com aplicacao de S-metolachlor em over the top, seguido de duas aplicacoes em pos-emergencia de amonio-glufosinate. Podendo-se inclusive utilizar pyrithiobac-sodium na primeira aplicacao em pos-emergencia.

Atividade Residual de Pyrithiobac-Sodium Aplicado ao Solo, Visando ao Controle de Plantas Voluntárias de Soja RR®

A presenca de plantas voluntarias de soja RR ® infestando lavouras de algodoeiro em segunda safra tem sido relatada com frequencia nos ultimos anos, havendo poucas informacoes disponiveis sobre o manejo desta especie no algodoeiro. O objetivo do presente trabalho foi avaliar o efeito da atividade residual do pyrithiobac-sodium sobre soja RR ® . O experimento foi conduzido em casa-de-vegetacao com delineamento inteiramente casualizado em arranjo fatorial (3x4)+1. O primeiro fator foi a epoca de aplicacao do herbicida (0, 10 e 20 dias antes da semeadura da soja), e o segundo as doses de pyrithiobac-sodium (28, 56, 84 e 112 g ha -1 ), alem de uma testemunha sem herbicida. A atividade residual do pyrithiobac-sodium sofre influencia da epoca da aplicacao, sendo que maiores periodos de permanencia do herbicida no solo resultam em menores percentuais de controle da soja voluntaria. Embora nao seja possivel obter controle total das plantas de soja RR ® voluntarias com doses de ate 112 g ha -1 , pode-se obter significativa supressao do desenvolvimento dessas plantas por meio da atividade residual de pyrithiobac .