Search

Um experimento foi conduzido em São João da Boa Vista-SP, com o objetivo de determinar o período anterior à interferência (PAI) e o período total de prevenção à interferência (PTPI) das plantas daninhas na cultura da cana-de-açúcar. A cana foi plantada em abril de 1995, na época de plantio caracterizada por maior deficiência hídrica. A comunidade infestante presente foi variada, sendo Brachiaria decumbens e Panicum maximum as espécies mais importantes. Essa comunidade tendeu a apresentar acúmulo crescente de matéria seca durante todo o período de avaliação e reduziu em até 40% a produtividade de colmos da cana-de-açúcar. A cultura conviveu com a comunidade infestante até 74 dias após o plantio, sem sofrer redução significativa na produtividade (PAI). O período mínimo de controle para garantir a produtividade foi de 127 DAP (PTPI). Dessa forma, o controle das plantas daninhas foi crítico no período compreendido entre 74 e 127 dias após o plantio. A field trial was carried out in São João da Boa Vista, SP, to determine the critical time of weed removal and the critical weed-free period in sugarcane. The crop was planted on April 1995, at the beginning of the dry season. The species composing the weed community varied during the growing season. However, Brachiaria decumbens and Panicum maximum were the most important ones. Dry matter accumulated by the weed community increased during the entire period. Weed interference in sugarcane caused 40% of yield loss. Sugarcane grew along with the weed community up to 74 days after planting, without significant yield loss (critical time of weed removal). A minimal weed-free period of 127 days after planting was required to guarantee the sugarcane productivity (critical weed-free period). The critical period for weed control was between 74 and 127 days after planting.

Dois experimentos foram conduzidos com o objetivo de avaliar os efeitos de diferentes períodos de controle das plantas daninhas, sobre algumas características produtivas da cultura do amendoim. Os experimentos foram instalados no município de Taquaritinga-SP, em duas épocas de semeadura, sendo uma no cultivo "das secas", semeada durante o mês de março, e outra no cultivo "das águas", semeada durante o mês de setembro. Os tratamentos foram períodos de controle das plantas daninhas entre 017, 0-31, 0-45, 0-59, 0-73, 17-31, 17-45, 17-59, 17-73, 31-45, 31-59, 31-73, 45-59, 45-73 e 59-73 dias após a emergência da cultura. Foram mantidas duas testemunhas, uma sem controle e outra com controle das plantas daninhas durante todo o ciclo da cultura. A principal planta daninha, nos dois experimentos, foi Digitaria horizontalis. A comunidade infestante e a cultura foram influenciadas pela época de semeadura, modificando suas relações de interferência. No cultivo da época "das águas", os efeitos da convivência da comunidade infestante foram mais drásticos, afetando com maior intensidade a produtividade da cultura. Dentre as características produtivas avaliadas, o número de vagens por planta foi o principal fator na redução da produtividade. No cultivo "das águas", o controle somente foi necessário após os 45 dias iniciais de convivência, e na cultura "das secas", após os 59 dias, caracterizando os períodos anteriores à interferência. Nas duas épocas de semeadura o controle das plantas daninhas, realizado até 17 dias após a emergência, foi suficiente para garantir a produtividade da cultura semelhante à testemunha capina, caracterizando o período total de prevenção à interferência. Field trials were carried out to study the effect of weed control periods on some yield components of the peanut crop. Two experiments were carried out in Taquaritinga-SP, Brazil, one during the "dry season" (seeds sown in March), and the other during the "rainy season" (seeds sown in September). The treatments utilized were the following weed control periods: 0-17, 0-31, 0-45, 0-59, 0-73, 17-31, 17-45, 17-59, 17-73, 31-45, 31-59, 31-73, 45-59, 45-73 and 59-73 days after plant emergence. Two controls were used, one without weed control, and the other without weed interference during throughout the crop cycle. The major weed infesting both trials was Digitaria horizontalis. The infesting weed community and crop were affected by the seeding season, altering their interference relationships. In the "rainy season", the effects of the infesting weed community were more drastic, affecting peanut yield more intensely. Among the yield crop components evaluated, the number of pods per plant was the major factor in yield reduction. In the "rainy season" , control was needed only after 45 days of weed interference while in the dry season, only after 59 days, characterizing the critical times prior to interference. In both seeding seasons, weed control carried out up to 17 days after emergence was enough to maintain yield crop, being characterized as the critical weed-free period.

Made available in DSpace on 2022-04-29T08:46:49Z (GMT). No. of bitstreams: 0 Previous issue date: 1999-12-01 The leaf beetle Metriona elatior from Brazil-Argentina was screened in the Florida (USA) State quarantine facility as a potential biological control agent of tropical soda apple, Solanum viarum, a recently arrived weed species. Multiple-choice host-specificity tests were conducted in small cages (60 cm × 60 cm × 60 cm) using 95 plant species in 29 families. Adults fed heavily on the main target weed (S. viarum), and on turkeyberry, Solanum torvum (noxious weed of Asiatic origin); fed moderately on red soda apple, Solanum capsicoides (weed of South American origin), and eggplant, Solanum melongena (economic crop); and fed lightly on aquatic soda apple, Solanum tampicense (weed of Mexican-Caribbean-Central American origin), and on silverleaf nightshade, Solanum elaeagnifolium (native weed widely distributed). M. elatior adults laid 84 to 97% of their egg masses on S. viarum, and 3 to 16% on S. melongena. Non-choice host-specificity tests were also conducted in quarantine in which M. elatior adults and neonate larvae were exposed to 17 and 19 plant species, respectively. Tests with the neonates indicate that this insect was able to complete its development on S. viarum, S. torvum, S. melongena, and S. capsicoides. Although some adult feeding and oviposition occurred on S. melongena in quarantine on potted plants in small cages, no feeding or oviposition by M. elatior was observed in field experiments conducted in Brazil. Surveys in unsprayed S. melongena fields in Argentina and Brazil indicated that M. elatior is not a pest of S. melongena in South America. The evidence obtained from the South-American field surveys, Brazil open-field experiments, and Florida quarantine host specificity tests indicate that M. elatior causes significant feeding damage to S. viarum, and does not represent a threat to S. melongena crops in the USA. Therefore an application for permission to release M. elatior against S. viarum in the USA was submitted in October 1998. University of Florida Dept. of Entomology and Nematology, Gainesville, FL 32611 Universidade Estadual Paulista, Jaboticabal, Sâo Paulo State USDA-ARS S. Amer. Biol. Contr. Lab., Hurlingham Universidade Estadual Paulista, Jaboticabal, Sâo Paulo State