Ryegrass (Lolium spp.) is a troublesome weed in major wheat producing regions in the U.S. High diversity and adaptive potential are known to contribute to its success as a weed species and also create difficulties in correct species identification in fields. The objective of this research was to characterize diversity for 16 different morphological traits among 56 Lolium populations collected from wheat (Triticum aestivum L.) production fields across the Texas Blacklands region and identify specific Lolium species based on taxonomical characteristics. Populations were highly diverse (both at inter- and intra-population levels) for the traits studied, and a taxonomical comparison with USDA-GRIN reference samples revealed that all the populations were variants of Italian ryegrass [Lolium perenne L. ssp. multiflorum (Lam.) Husnot] with a few offtypes of perennial (Lolium perenne L.) or probable hybrids between the two species. Hierarchical clustering grouped the populations into 6 clusters based on their similarities for the morphological traits investigated. Principal component analysis showed that the variability for yield traits greatly contributed to the total diversity. Pre-flowering plant height (stage 10 on Feekes scale) was positively correlated with tiller count, shoot biomass, spike count, but not with total seed count/plant, whereas plant height at maturity (stage 11.3-11.4 on Feekes scale) was highly correlated with total seeds/plant. Further, basal node color was positively correlated with plant growth habit, regrowth rate, and leaf color. Leaf blade width was positively correlated with survival to pinoxaden and multiple herbicides, whereas, spike count was negatively correlated with survival to mesosulfuron. The high levels of intra- as well as inter-population variability documented in this study indicates the potential of this species to rapidly adapt to herbicides, and emphasizes the need for implementing diverse management tactics including the integration of harvest weed seed control.

The challenges for weed management have increased in rice cultivation due to the high number of cases of herbicide-resistant weeds, especially the widespread distribution of imidazolinone-resistant weedy rice. Therefore, there has been particular interest in preventive, physical, and cultural methods in recent decades. In this context, the adoption of the rice-soybean rotation is reported to be one of the most important factors for weed management in rice fields. Additionally, the use of a diversified crop rotation enables the implementation of a broader herbicide program, which is an important feature influencing weed population dynamics. Rice-soybean rotation has been adopted by farmers to control problematic weed species, reduce seed bank of troublesome weed species, and prevent rice grain yield and quality losses caused by its interference. This crop rotation scheme has brought several benefits when it comes to weed management; however, there are also some drawbacks when adopting this strategy such as the limited productivity of soybean and new weed species becoming problematic, such as Conyza species. Thus, this chapter explores the advantages and disadvantages of adopting crop rotation in Brazilian lowlands, and proposes a set of strategies to successfully implement crop rotation in lowland soils as a tool for weed management.

SUMMARYWe aimed to characterize the weed community in sprinkler irrigated rice, previously applied with residual herbicides for two years, as well as to infer about sustainability of the management applied to the fields based on an ecological approach. The experiment was conducted during the cropping seasons 2013/14 and 2014/15, under sprinkler irrigation. Rice was planted in the second-half of October, using the cultivar PUITA INTA CL. Herbicides were applied in pre- and post-emergence (sequential application) of crop and weeds. Ryegrass (Lolium multiflorum) was planted in winter. In May 2015, soil samples were collected for the soil seed bank study. Phytosociological characterization of weeds emerged from the seed bank was conducted from May 2015 to January 2016, until soil seed bank depletion. Echinochloa crusgalli, Fimbristyllis sp., Cyperus esculentus and Killinga brevifolia were the weeds to which most concern should be directed when growing rice under sprinkler irrigation in lowland areas of Southern Brazil. Their competition strategies are based on density. Herbicides used should be efficient in controlling at least these four weed species. A selecting action of herbicides on weed species was botanically characterized, as the weed species reported after two cropping seasons depended on the herbicide treatment applied.

The larval-pupal endoparasitoid Diachasmimorpha longicaudata (Ashmead, 1905) is considered one of the main biological control agents of fruit flies Ceratitis capitata Wiedemann (1824) and Anastrepha fraterculus Wiedemann (1830) in Central and South America. The application of pesticides for disease and insect-pest management in fruit species may have adverse effects on the parasitoid. The objective of this study was to evaluate the lethal and sublethal effects via residual contact of commercial pesticide formulations on D. longicaudata. The active ingredients thiamethoxam, indoxacarb, chlorpyrifos, deltamethrin, spinetoram, spinosad, phosmet, lambda-cyhalothrin, malathion, dimethoate, and methidationa showed high toxicity to adults (100% mortality) after 96 h and were classified as harmful (Class 4). In contrast, the formulations of azadirachtin (Agroneem 850 EC, Azact 2.4 EC, Azamax 12 EC, and Fitoneem 850 EC), chlorantraniliprole, bordeaux mixture, sulfur, lufenuron, lime sulphur, novalurom, and mancozeb were rated as innocuous (<10% mortality). In addition, the formulations azadirachtin did not reduce the parasitism and the emergence rate of the F0 generation, the same pesticides added to chlorantraniliprole, azadirachtin A+B (Agroneem 850 EC), and lufenuron did not cause reduction in parasitism and emergence rate of the F1 generation of D. longicaudata. The use of pyrethroids, organophosphates, spinosyns, oxadiazines, and neonicotinoids should be used with caution in IPM programs. While pesticides chlorantraniliprole, azadirachtin formulations, bordeaux mixture, lufenuron, lime sulphur, and mancozeb do not cause lethal and sublethal effects for D. longicaudata adults. The results of this study provide important information for use in integrated pest management programs for fruit fly management.

We aimed with this work to evaluate the efficiency of the herbicide [imazapic + imazapyr] in the weed control, especially of the jointvetch, and its reflex in rice plant establishment and grain yield. A field study was conducted, where treatments were: control without herbicide application; Kifix ® 140g ha -1 (24.5 g a.i. ha -1 imazapic + 73.5 g a.i. ha -1 imazapyr) and Kifix ® 280 g ha -1 (49 g a.i. ha -1 imazapic + 147 g a.i. ha -1 imazapyr). We evaluated crop emergence up to 25 days after sowing, crop plant height 12 days after emergence (DAE), jointvetch plant density 31 and 62 DAE, jointvetch dry mass 62 DAE and general weed infestation 62 DAE. At the end of the crop cycle we evaluated grains per panicle, panicle and 1000 grain weight, panicle density and crop grain yield. There is a risk of 15% reduction in the establishment of Clearfield ® rice plants when the maximum dose of the herbicide [imazapic + imazapyr] is applied pre-emergence, but under appropriate conditions, the crop development tends to compensate for this reduction in establishment. The herbicide [imazapic + imazapyr] is effective on jointvetch, but under high infestation conditions, as in the present study, a complementary herbicide application is required to achieve adequate control of jointvetch and avoid rice grain yield reduction due to competition.

In 2002, a survey carried out in rice paddies in the Rio Grande do Sul (RS) state reported the occurrence of nine species of jointvetch (Aeschynomene). Due to their semi-aquatic habit, some species adapted to irrigated rice fields, which led to their being considered the worst broadleaf weed in RS. Although farmers have successfully implemented weed management practices, Aeschynomene plants have reportedly escaped chemical control. This study aims to identify the species of Aeschynomene that occur in rice fields in RS and to evaluate the reasons why escapes are occurring. A survey was carried out by collecting mature seeds from individual adult plants. A questionnaire on the management practices employed in each field was administered to 54 farmers and 18 extension agents, each of whom was responsible for one of the surveyed rice fields. This survey found four species of Aeschynomene are present in rice fields in RS: A. denticulata, A. indica, A. rudis, and A. sensitiva. The results suggest that the explanation for escapes may lie in the management practices adopted by farmers, which are focused on the control of weedy grasses. Escapes are also associated with problems such as the lack of irrigation uniformity and out-of-stage, late herbicide applications.

O uso de agrotóxicos na agricultura é praticamente indispensável, contudo, estudos estimam que somente 45% do produto aplicado atinge a cultura, sendo que aproximadamente 30% sofrem deriva, 10% são perdidos por algum processo de transporte (lixiviação, volatilização e escoamento) e 15% atingem o solo. Além disso, do total aplicado, apenas 1% atinge o alvo, ou seja, patógenos, plantas daninhas e insetos. Embora avaliações de riscos de contaminação ambiental de agrotóxicos sejam obrigatórios para o registro e comercialização, frequentemente estudos relatam a presença destes em locais não alvos, sendo os corpos de água os principais prejudicados. Vários processos biológicos, físicos e químicos determinam o destino ambiental e a eficiência desses. Assim, diversos métodos experimentais podem ser utilizados para avaliar o comportamento de agrotóxicos no ambiente. Essa revisão objetiva resumir os métodos mais comumente utilizados para descrever e avaliar os processos nos quais o herbicida está sujeito quando presente no solo, bem como, as vantagens e desvantagens de cada um desses. No geral, em se tratando de destino de agrotóxicos no ambiente, os experimentos em laboratórios fornecem informações mais precisas, pois é possível controlar melhor as condições ambientais e isolar fatores de interesse. Mas é importante salientar que não existe um método mais eficiente, o que existe são métodos que podem fornecer um melhor resultado em determinada situação. Por tanto, a escolha do método vai depender do objetivo do estudo e da estrutura disponível.

No monocultivo de arroz, as espécies daninhas mais adaptadas a este sistema de produção aparecem em maior incidência na área. A rotação de culturas pode ser uma alternativa para auxiliar na redução do banco de sementes de plantas daninhas. Nesse sentido o objetivo do trabalho foi avaliar a dinâmica do banco de sementes de capim-arroz (Echinochloa spp.) e papuã (Urochloa plantaginea) em terras baixas, em combinações de rotação de culturas e do manejo de solo. Foram utilizadas as culturas de arroz, soja e sorgo, sob o manejo de preparo do solo convencional e sistema de semeadura direta, cultivado em faixas. Foi avaliado o banco de sementes de capim-arroz e papuã após dois anos de cultivo, na camada de 0-5 e 5-10 cm de profundidade. A densidade do banco de sementes de capimarroz e papuã foi superior no monocultivo de sorgo em relação ao cultivo de arroz. Não houve diferença do banco de sementes de plantas daninhas entre diferentes camadas de solo, exceto para o papuã no monocultivo de sorgo. O monocultivo de sorgo, sem aplicação de herbicidas em pós-emergência, em terras baixas incrementa o banco de sementes de capim-arroz e papuã.