A associação dos herbicidas glyphosate e diclosulam na dessecação pode diminuir a presença de plantas daninhas por maior período, favorecendo assim o desenvolvimento e a produtividade das plantas de soja. Objetivou-se verificar a eficiência do herbicida diclosulam associado ao glyphosate, na dessecação para plantio direto da cultura de soja RR, cultivada no sistema plante e aplique. A cobertura vegetal presente foi Urochloa ruziziensis com 4,4 t ha-1, distribuída uniformemente sobre a área experimental. O delineamento experimental utilizado foi o de blocos ao acaso com três tratamentos e 4 repetições. Os tratamentos constituíram-se na aplicação de glyphosate a 1,2 kg ha-1 de equivalente ácido (e.a.) + diclosulam a 25,2 g ha-1 de ingrediente ativo (i.a.) em pré-semeadura da cultura sem a aplicação complementar, glyphosate a 1,2 kg ha-1 de e.a. + diclosulam a 25,2 g ha-1 de i.a. em pré-semeadura da cultura + glyphosate a 1,2 kg ha-1e.a. em complementação e glyphosate a 1,2 kg ha-1 de e.a. em pré-semeadura + glyphosate a 1,2 kg ha-1 de e.a. em complementação. Foram avaliados os seguintes parâmetros: reinfestação inicial e densidade relativa de plantas daninhas aos 31 dias após a dessecação, reinfestação de plantas daninhas no período da colheita, dificuldade de colheita mecanizada, número de vagens por planta, peso de 1000 grãos e produtividade de grãos. A associação do herbicida diclosulam ao glyphosate auxilia no manejo inicial da comunidade infestante no cultivo da soja, sem, no entanto, dispensar a aplicação complementar do herbicida glyphosate.
The sugarcane borer, Diatraea saccharalis (Fabr., 1794) (Lepidoptera: Crambidae), is one of the main pests of sugarcane. This pest can reduce the quality and yield of the crop. Information on the quality and yield of cultivars in relation to the attack of sugarcane borer are necessary, since they guide the choice of the best materials for use in joint with other management tactics. Two field experiments were conducted in 2011 and 2012 to compare the quality and yield of 16 commercial sugarcane cultivars (IACSP93-3046, IACSP94-2094, IACSP94-2101, IAC91-1099, IACSP95-5000, IAC87-3396, RB92579, RB867515, RB966928, CTC2, CTC4, CTC9, CTC11, CTC15, CTC18 and SP86-0042) relative to the natural infestation of D. saccharalis. The experimental design was a randomized complete block with four replications. There was no difference between treatments for infestation index, with averages of 1.2 to 8.7% of bored internodes. Higher percentages of internodes with red rot were observed for CTC9, CTC2 and RB966928. The cultivars CTC4 and RB92579 infested with D. saccharalis resulted in lower technological quality, due the reduction in the contents of brix, apparent sucrose content (POL) and purity; and increase of the reducing sugars and, consequently, lower theoretically recoverable sugar (TRS). On the other hand, the lowest yields (t of cane ha-1) were observed for CTC18, IACSP94-2094, IACSP94-2101 and RB966928. Therefore, according to the hierarchical cluster analysis (UPGMA), the cultivars RB867515, CTC11, IAC91-1099, CTC15, SP86-0042, CTC2 and IACSP94-3046 were resistant to D. saccharalis.
The aim of this current study was to evaluate the mortality of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) nymphs by the combination between the entomopathogenic fungus Isaria javanica (Friedrichs & Bally) Samson & Hywel‐Jones and synthetic chemical insecticides. The bioefficacy of I. javanica and the insect growth regulators named spiromesifen and buprofezin was tested alone and in combination against B. tabaci nymphs under screenhouse conditions. The in vitro compatibility between these two control agents was previously assessed under laboratory conditions. The sublethal concentration (LC25) of these insecticides towards second‐instar nymphs was determined and then mixed with the fungal treatments to investigate the type of interaction. All I. javanica isolates at 5 × 107 conidia/ml inflicted nymphal mortality by up to 62.4%. The insecticides did not influence the germination and mycelial growth of the selected I. javanica isolate CG1282. In general, the insecticide–fungus combinations increased nymphal mortalities in comparison with their single counterparts. Combinations with the fungus and buprofezin or spiromesifen augmented nymphal mortality by 10% and 24%, respectively, in comparison with the fungus alone. Additive interaction was found with the combination of the I. javanica CG1282 at 1 × 106 conidia/ml and spiromesifen at 1.56 ppm, and additive and synergistic interactions were achieved with the fungus at 5 × 106 conidia/ml and spiromesifen at 3.12, 6.25 and 12.5 ppm. Additive interactions were also observed from mixtures of fungus at 5 × 106 and buprofezin at 3.12 and 6.25 ppm. Only combinations of I. javanica with spiromesifen reduced to some extent the mycosis on dead nymphs. The joint action of I. javanica with sublethal doses of these insecticides may be a promising tool to assist in the integrated management system for B. tabaci.
The rice stalk stink bug Tibraca limbativentris Stal, 1860 (Hemiptera: Pentatomidae) is an important pest of paddy rice (Oryza sativa L.) in South America. Current records of economic injury levels (EILs) and economic thresholds (ETs) for this insect are scarce. In this study, we determined EILs and ETs through cumulative insect-days of T. limbativentris adults in two phenological stages of paddy rice. Five field trials were established for the 2015/16 and 2016/17 crop season. To evaluate the relationship between insect-day and yield, rice plants were infested at V4 and R2 with adult male-female pairs of T. limbativentris. Mixed linear models were fitted utilizing the year and block as random factors to estimate the damage to plant, irrespective of the interference of environmental factors. The yield loss per insect-day was then used to calculate EILs using current market values and control costs. Rice grain yields were reduced by 5.91 kg/ha for each insect-day/m2 when infested during V4 stage, with EILs ranging from 3.88 to 11.61 insect-days/m2, while infestation during R2 stage resulted in a yield reduction of 3.16 kg/ha, with EILs ranging from 8.05 to 21.72 insect-days/m2. The results indicate that yield losses of paddy rice due to T. limbativentris infestation vary according to plant phenological stages and management should consider control cost and market value of rice. These EILs and ETs based on insect-days may be an efficient strategy for decision-making in the management of T. limbativentris on paddy rice.
The corn crop has a marked sensitivity to biotic and abiotic stresses. As a control method, basically, transgenic plants have been used in association with chemical control. However, frequent applications of insecticides affect the conservation of biodiversity, and consequently, the natural regulation of insect populations. Thus, the objective of the work was to compare the diversity of arthropodofauna associated with the cultivation of corn in organic and conventional systems. The experiments were carried out at Fazenda Nossa Senhora Aparecida, in Hidrolândia/GO, in two areas: one in a consolidated organic system and the other in a conventional system. The organic area (1 ha) was sown with the Creole variety Palha Roxa and no type of cultural treatment was carried out. The conventional area (10 ha) was sown with a transgenic hybrid resistant to the herbicide glyphosate 30F53VYHR and two chemical fertilizers were applied, for planting and cover, two applications of herbicides and an application of insecticide. To survey the arthropodofauna, in each area, two collections were made with six pitfall soil traps. The first collection was carried out in the vegetative stage and the second in the reproductive stage, approximately at 35 and 80 days after planting, respectively. The traps were kept in the field for a week. In addition, a collection with entomological net was carried out in 10 plants chosen at random. The collected insects were stored in plastic pots containing 70% alcohol and taken to the laboratory for quantification and identification. The data referring to the total of insects collected were submitted to the T test at 5% probability. In the two collected with pitfall traps, the largest number of arthropods was collected in the area of organic cultivation, with greater diversity of orders and families in this area. In the collection performed with entomological network, there was no difference between the places of cultivation. Organic crops provide better conditions for establishment and development for insects, especially those that spend some life in the soil. Therefore, the diversity of arthropods is greater in this cultivation system.
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