The objective of this work was to compare the leaflet severity of Asian soybean rust in farms sown in December and February in the state of Mato Grosso. In the survey, 28 fields were sampled in 14 counties in the North, West and South regions of the state. A total of 40 leaflets were collected per plot, in randomized treatments with four replication and three crop phenological stages. Leaflet severity was assessed according to a diagrammatic scale. The data were expressed as leaflet severity, submitted to linear regression analysis, calculated the area under the disease progress curve (AUDPC) considering the three phenological stages sampled, and the means compared by the Tukey’s test. Leaflet severity was significantly higher in the fields sown in December than in February, as well the number of fungicides sprayings. Our results indicate that the proposed change in seeding time from December to February can be implemented by significantly reducing risks and in compliance with the principles of IN 002/2015.
Revista Brasileira de Entomologia 56(2): 228-239, junho, 2012 O Cerrado, bioma característico do Planalto Central, com grande diversidade de flora e de fauna, foi incluído na lista dos hotspots em diversidade do planeta pela Conservation Internacional (Mittermeier et al. 1999) devido a ameaças que vem sofrendo em virtude da ação do homem. As diminuições territoriais deste bioma ocorridas ao longo dos anos, em especial a partir da década de 1980, tem se tornado uma preocupação da comunidade científica.Vários trabalhos vem sendo desenvolvidos visando o conhecimento da entomofauna da região de Cerrado (Santos et al. 2004;Constantino 2005;Soares et al. 2010), mas poucos avanços ocorreram em relação ao conhecimento da ortopterofauna, principalmente no que se trata de Planalto Central e especialmente no estado de Mato Grosso, um dos grandes responsáveis pelas alterações deste bioma.Os gafanhotos constituem um dos maiores, e possivelmente o mais dominante, grupo de insetos herbívoros da Terra (Gangwere et al. 1997), características que os tornam insetos especialmente importantes para o sistema de defesa fitossanitária visando à proteção das plantas cultivadas. Apesar de 95% das espécies de gafanhotos não serem pragas, aquelas que são causam danos econômicos expressivos (Gangwere et al. 1997).No Brasil são relatadas pelo menos 20 espécies de gafanhotos com importância econômica ocorrendo em diferentes regiões geográficas (Lecoq 1991;Guerra 2001). Recentemente, Baeacris punctulatus Thunberg, 1824 foi relatada causando danos em lavouras mato-grossenses, em especial no município de Campo Novo do Parecis (Guerra et al. 2010). Esta espécie e outras sobrevivem durante o inverno (período de entressafra) em meio aos cultivos de milheto, sorgo, crotalária e girassol, culturas que depois de colhidas ou dessecadas dão lugar às lavouras de soja, passando esta a ser a alternativa de alimentação. ABSTRACT. Grasshoppers (Orthoptera, Acridoidea) in native savanna and crop areas in Chapada dos Parecis, Mato Grosso State, Brazil. We determined the composition and abundance of grasshoppers using sweep net sampling during three years at the Parecis Plateau, State of Mato Grosso, Brazil. The survey was done in areas with crops and native vegetation (savanna) with, respectively, 56 and 59 sites available in each environment. 3.031 individuals of grasshoppers were collected from 64 species distributed among the following families and subfamilies: Acrididae (49): Gomphocerinae (21), Ommatolampinae (10), Melanoplinae (6), Acridinae (4) Leptysminae (3), Copiocerinae (3), Proctolabinae (1) and Cyrtacanthacridinae (1); Romaleidae (1): Romaleinae (13) and Ommexechidae (1): Ommexechinae (2) and 1550 nymphs. The differences were significant between the number of species found in the savannas (61) and in cultived areas (16). However, the abundance of Acridoidea was significantly higher in crops than in savannas areas which was influenced mainly by two Acrididae's species: Baeacris punctulatus (Thunberg, 1824) and Orphulella punctata (De Geer, 1773)...
In on-farm trials, the foliolar severity of Asian soybean rust was evaluated in 44 areas, in three regions of Mato Grosso sown in December (2019) and February (2020). Several susceptible cultivars were used in different crop systems; insect pests and weeds were controlled with different management systems by the farmers. Forty soybean leaflets from four plots replications, demarcated at random in each field were taken. In laboratory foliolar severity was appraised. For rust control in the trials conducted in February, fungicides with efficiency greater than 60% were used consisting of DMIs, QoIs and SDHIs in double or triple mixtures, always adding multisites (chlorothalonil, mancozeb, copper oxychloride). The severity was greater in the fields sown in December (4.84% than in February 0.68%). The number of fungicides spraying/ha in December was 6.4 and February 4.6. It is discussed that through the use of multisites fungicides, the mutation potential in Phakopsora pachyrhizi is reduced and that the spores from areas cultivated in February, probably due to unfavorable environment, do not survive during the soybean free-period. Our results indicate that the sowing period can be changed from the end of December to February, since multisites fungicides are always used.
This review focus on the sensitivity reduction of Phakopsora pachyrhizi to site specific fungicides in the Brazilian state of Mato Grosso.The soybean grown area in this state in the 2018/19 growing season was 9,756,668 hectares. The main crop disease is Asian soybean rust that depending on disease severity may cause 80% yield reduction. The rust chemical control started in the 2002/003 season with site-specific fungicides applied solo and with 3.6 sprayings/ha/season. For these reasons, the fungus had sensitivity reduction to the fungicides DMIs, QoIs and SDHIs resulting in a short effective life. Anti-resistance strategies were not adopted to prevent or delay the development of soybean rust resistant population to site-specific fungicides. Reduced sensitivity to the target site has been observed for all site-specific fungicides involving cross and multiple resistance resulting in ineffective control. So far, eight mutations in Phakopsora pachyrhizi have been identified conferring reduced sensitivity to DMIs, QoIs and SDHIs but so far specific mutations are not considered in chemical control. The directional selection has occurred and has been aggravated season-after-season by the continuous use of site-specific fungicides in a large area, for 18 season and with more than three sprayings/area/season. The presence of soybean weed in one million hectares of cotton crop infected by rust aggravates the directional selection. Anti-resistance strategies should include sowing at the beginning of the recommended season, avoid the December season and replacing it by February, use of scientific criteria to time the first application and the use of multisite fungicides in all applications and in the entire area cultivated with soybean.
Multisite fungicides have been used for many years in fruit and vegetable crops worldwide. Cases of the fungi resistance development to these fungicides have been rare. From the 2002 season onwards, with the outbreak of Asian soybean rust in Brazil, caused by Phakopsora pachyrhizi, site-specific fungicides became the main weapon for its control. From 2002 to 2011, penetrant mobile site-specific fungicides were used and until today in double (DMI + QoI) or triple (DMI + QoI + SDHI) co-formulatoons in an area of more than 30 million hectares and with three sprays per area. This resulted, as expected, in the fungus sensitivity reduction, today with cross and multiple resistance to those site-specific fungicides. From the 2011 season in an attempt to recover control that for some chemicals and mixtures reached < 30%, research was started with site-specific + multi-site mixtures, taking as example Phytophthora infestans resistance development to metalaxyl in Europe showinig long-lasting solution found by the addition of multisite mancozeb. It is expected that the effective life of site-specific + multi-site mixtures may be as long in controlling soybean rust as it has been for potato, tomato and grape downy mildews. This review presents the concepts involved in the sensitivity reduction to fungicides. Some fungal species and fungicides involved are listed. Considering the P. pachyrhizi sporulation potential, the great soybean area sprayed and the number of sprays per area mainly with site-specific co-formulations and the reduced area sprayed with multisites, we discuss the need for annual monitoring of P. pachyrhizi sensitivity to the these chemicals.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.