RESUMO -O presente trabalho de pesquisa teve como objetivo identificar a composição florística de comunidades de plantas daninhas presentes em áreas agrícolas de várzea, manejadas em diferentes sistemas. O trabalho foi desenvolvido em áreas de produção de arroz irrigado das cooperativas: Cooperativas Mista Rural Vale do Javaés e Cooperativa Agroindustrial Rio Formoso, em Formoso do Araguaia-TO. Foram separadas três áreas de 1 ha, sendo: 1 -área sem rotação de culturas (arroz/pousio) há mais de cinco anos; 2 -área com rotação de culturas (arroz/soja) há mais de cinco anos; 3 -área com rotação de culturas (arroz/melancia) há mais de dois anos. Para caracterização e estudo fitossociológico da comunidade infestante foi utilizado, como unidade amostral, um quadro (1,0 x 1,0 m), lançado aleatoriamente dentro da área de estudo (método do quadrado inventário), por meio de um caminhamento em ziguezague. Na área sem rotação, foram identificadas 8 famílias e 16 espécies, destacando-se a família Poaceae com maior número espécies; Fimbristylis miliacea (Cyperaceae) foi a espécie com o maior índice de importância relativa (84,46%). Na área com rotação arroz/soja, foram identificadas 8 famílias e 12 espécies, destacando-se as famílias Poaceae e Cyperaceae com maior número espécies; Cyperus esculentus (Cyperaceae) foi a espécie com o maior índice de importância relativa (91,4%). Na área com rotação arroz/ melancia foram identificadas seis famílias e oito espécies, destacando-se as famílias Euphorbiaceae e Lamiaceae com maior número espécies; Physalis angulata (Solanaceae) foi a espécie com o maior índice de importância relativa (153,1%), seguida por Eclipta alba (Compositae) e Hyptis lophanta (Lamiaceae), com 40,45 e 37,6%, respectivamente.Palavras-chave: várzea, rotação de culturas, estudo fitossociológico, plantas daninhas. ABSTRACT -This research aimed to identify the floristic composition of weed communities present in lowland agricultural areas under different management systems. The trial was carried out in flooded rice areas of two different co-ops located in Formoso do

The starting point for generating a pest control decision-making system is a conventional sampling plan. Because the mites Polyphagotarsonemus latus and Tetranychus bastosi are among the most important pests of the physic nut (Jatropha curcas), in the present study, we aimed to establish sampling plans for these mite species on physic nut. Mite densities were monitored in 12 physic nut crops. Based on the obtained results, sampling of P. latus and T. bastosi should be performed by assessing the number of mites per cm(2) in 160 samples using a handheld 20× magnifying glass. The optimal sampling region for T. bastosi is the abaxial surface of the 4th most apical leaf on the branch of the middle third of the canopy. On the abaxial surface, T. bastosi should then be observed on the side parts of the middle portion of the leaf, near its edge. As for P. latus, the optimal sampling region is the abaxial surface of the 4th most apical leaf on the branch of the apical third of the canopy on the abaxial surface. Polyphagotarsonemus latus should then be assessed on the side parts of the leaf's petiole insertion. Each sampling procedure requires 4 h and costs US$ 7.31.

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Resumo -A diversificação do sistema produtivo depende de espécies com rápido crescimento, tolerância ao déficit hídrico, produção de biomassa, ciclagem de nutrientes e utilização humana e animal. Amaranth BRS Alegria: alternative for diversification of cropping systemsAbstract -Diversification of production systems depends on rapid growth, tolerance to hydric stress, biomass production, nutrient cycling and human and animal utilization. The grain amaranth species Amaranthus caudatus, A. cruentus and A. hypochondriacus, with light seed colour and no dormancy, present these characteristics. They are distinguishable from the weeds A. spinosus, A. hybridus, A. blitum and A. viridis, with dark and dormant seeds. Their grains, with excellent protein quality, can be used in gluten-free special diets and livestock feed. The A. cruentus BRS Alegria, the first recommendation for grain production systems in Brazil, originated from mass selection in the variety AM 5189 of the United States. In double-cropping, after soybeans, it showed average yield of 2,359 kg ha -1 for grain and of 5,650 kg ha -1 for total biomass, in 90 days from emergence to maturity.(1) Aceito para publicação em 12 de março de 2003.

One of the most promising plant species for biofuel production in Brazil is the physic nut Jatropha curcas. Major phytosanitary problems include the attack of two pest mite species, the broad mite Polyphagotarsonemus latus and the spider mite Tetranychus bastosi. Owing to pesticide-related problems, there is an increasing demand for sustainable environmental-friendly control methods such as biological control. In this study we evaluated the suitability of the predatory mite species Iphiseiodes zuluagai and Euseius concordis in controlling P. latus and T. bastosi on J. curcas. The number of T. bastosi killed by I. zuluagai was lower than the number of P. latus consumed.Euseius concordis preyed upon both T. bastosi and P. latus but the number of prey killed was always lower in comparison with I. zuluagai. However, P. latus and T. bastosi are suitable for the development of I. zuluagai and E. concordis as oviposition of both predators did not differ in relation to prey species. The preference of I. zuluagai for leaves of plants infested by either P. latus or T. bastosi, combined with the higher values for predation obtained by this predatory mite when fed on P. latus, compared to those values obtained by E. concordis, suggests that I. zuluagai can be more efficient than E. concordis in reducing populations of P. latus and T. bastosi under field conditions. Furthermore, we report here on the first record of predatory mites associated with P. latus and T. bastosi on native J. curcas plants in Brazil. In conclusion, we emphasize the crucial importance of predatory mites as agents of natural biological control of mite pests on J. curcas in small farms.

Spatial distribution studies in pest management identify the locations where pest attacks on crops are most severe, enabling us to understand and predict the movement of such pests. Studies on the spatial distribution of two mite species, however, are rather scarce. The mites Polyphagotarsonemus latus and Tetranychus bastosi are the major pests affecting physic nut plantations (Jatropha curcas). Therefore, the objective of this study was to measure the spatial distributions of P. latus and T. bastosi in the physic nut plantations. Mite densities were monitored over 2 years in two different plantations. Sample locations were georeferenced. The experimental data were analyzed using geostatistical analyses. The total mite density was found to be higher when only one species was present (T. bastosi). When both the mite species were found in the same plantation, their peak densities occurred at different times. These mites, however, exhibited uniform spatial distribution when found at extreme densities (low or high). However, the mites showed an aggregated distribution in intermediate densities. Mite spatial distribution models were isotropic. Mite colonization commenced at the periphery of the areas under study, whereas the high-density patches extended until they reached 30 m in diameter. This has not been reported for J. curcas plants before.

Resumo -O objetivo deste trabalho foi identificar ácaros na cultura de pinhão-manso e em espécies de plantas espontâneas associadas. Para isso, foram avaliadas a riqueza e a abundância de ácaros em plantas de pinhão-manso e em 14 espécies de plantas espontâneas associadas. As amostragens foram realizadas por meio de coletas mensais de folhas de plantas de pinhão-manso e de plantas espontâneas, nas entrelinhas do cultivo. Foram encontradas quatro espécies de ácaros predadores -Amblyseius tamatavensis, Paraphytoseius multidentatus, Typhlodromalus aripo e Typhlodromalus clavicus -, com potencial para uso no controle biológico de ácaros-praga na cultura do pinhão-manso, e duas importantes espécies de ácaros fitófagos -Brevipalpus phoenicis e Tarsonemus confususdesconhecidas como praga da cultura. Entre as plantas espontâneas avaliadas, quatro espécies -Hyptis suaveolens, Peltaea riedelii, Urochloa mutica e Andropogon gayanus -abrigam grande riqueza e abundância de ácaros predadores, enquanto oito destacaram-se pela diversidade de ácaros fitófagos.Termos para indexação: Jatropha curcas, controle biológico, fitófagos, plantas invasoras. Acarofauna in physic nut culture and associated spontaneous weedsAbstract -The objective of this work was to identify mites in physic nut culture, and in associated spontaneous weed species. For this, mite richness and abundance on physic nut plants and on 14 species of associated spontaneous weeds were evaluated. Samplings were done with monthy collections of leaves from physic nut plants and from weeds, between planting lines. Four species of predatory mites -Amblyseius tamatavensis, Paraphytoseius multidentatus, Typhlodromalus aripo and Typhlodromalus clavicus -, with potential for biological control of pest mites on physic nut culture, and two species of phytophagous mites -Brevipalpus phoenicis and Tarsonemus confusus -, not yet known as pests of the culture were found. Among the evaluated spontaneous weeds, four species -Hyptis suaveolens, Peltaea riedelii, Urochloa mutica and Andropogon gayanus -harbor great richness and abundance of predatory mites, whereas eight harbored a high diversity of phytophagous mites.

RESUMOO cresci ment o de Senn a obtusifolia foi estudad o sob con dições de casa-de-vege tação, num delineamen to inteiramen te casualizado com 4 repetições . As pla ntas cresceram em vaso s de 6 lit ros preenc hidos com areia e irrigad os com soluçã o completa A.E. all the plants had flowered . From the emergence to 63 days, the highest amount of dry matter was partitioned in the roots. Form this evaluation to the end of the cicle of sicklepod, the majority of the dry matter was partitioned to stems. The relative growth decreased quickly until 63 1Recebido para publicação em 13/01/97 e na forma revisada em 20/09/97.