Effects of Transgenic Herbicide-Resistant Soybean Varieties and Systems on Surface-Active Springtails (Entognatha: Collembola)

Abstract

The degree of abundance and diversity of springtails (order Collembola) often indicates the extent of disturbance by various agricultural practices. We examined how transgenic herbicide-tolerant soybean varieties and their associated weed management systems affect the abundance of 21 surface-active springtail species during three successive soybean growing seasons. With six soybean varieties (three transgenic, three nontransgenic), we tested three weed management systems: (1) targeted application of speciÞc herbicides to the corresponding tolerant transgenic varieties; (2) conventional pre-and postemergence herbicide applications; and (3) mechanical cultivation. Each method posed its own potential costs and beneÞts to springtails. In targeted plots, springtail numbers were similar to or higher than those in conventional plots, suggesting that the later and repeated targeted applications to transgenic soybeans do not adversely affect springtail numbers in the short term. We attributed the observed treatment effect differences on springtail numbers to resultant differences in weed cover and degree of soil disturbance (indirect effects), rather than to any direct toxic effects of the herbicides. The treatments affected some species but not others; most of the affected species responded similarly to differences in weed treatment. Our results overall suggested no deleterious short-term effects of transgenic soybean targeted weed-management systems on abundance of the springtail species examined.

Spider mites associated to soybean in Rio Grande do Sul, Brazil

“…Such occurrence has been considered abnormal and could be associated with alterations of the soybean production system. Among the factors probably favoring the occurrence of mites are the use of new soybean cultivars, with favorable nutritional and morphological composition (Elden, 1997;Ali, 1999;Abraham, 2000;Rita & Lajos, 2001), increased use of glyphosate, which may reduce the biological diversity of the system and affect the arthropod population (Buckelew et al, 2000;Bitzer et al, 2002;Scursoni et al, 2006) and can be detrimental to entomopathogenic fungi (Morjan et al, 2002), pesticide use for pest management, which can influence, directly and indirectly, the spider mite population (Gerson & Cohen, 1989;Trichilo & Wilson, 1993;Grout et al, 1997;Childers & About-Setta, 1999;Sato et al, 2001Sato et al, , 2002James, 2003;Beers et al, 2005;Prischmann et al, 2005), and the occurrence of droughts (Flechtmann, 1972).…”

Ocorrência de insetos na parte aérea da soja em função do manejo de plantas daninhas em cultivar convencional e geneticamente modificada resistente a glyphosate

“…As diferenças populacionais verificadas sobre percevejos, lagarta-da-soja e lagarta falsa-medideira foram atribuídas à variação na composição botânica e não necessariamente à cultivar de soja modificada, pois ocorreram diferenças entre os tratamentos com plantas daninhas e não com as variedades modificadas ou convencionais. De forma similar, BITZER et al (2002) observaram que independente do cultivo ser com soja geneticamente modificada ou convencional a população de pragas sofreu maiores variações em função das práticas de manejo do solo e da composição da flora daninha.…”

Assessing the effects of cultivating genetically modified glyphosate-tolerant varieties of soybeans (Glycine max(L.) Merr.) on populations of field arthropods

“…4). Bitzer et al (2002) also suggested that the differences in the abundance of epigeal Collembola in GMHT soybean fields with different forms of weed management were caused by the beneficial accumulation of fresh organic matter from killed weeds rather than directly from herbicide toxicity. Homoptera were significantly more abundant between the rows in the GM plots, particularly with conventional weed control in the present study (significant V ×W interaction in Tab.…”