Laboratory and field tests for risk assessment of metsulfuron-methyl-based herbicides for soil fauna.

Metsulfuron-methyl is one of the most used sulfonylurea herbicides, being applied alone in pre-emergence and with a mineral oil (as adjuvant) in post-emergence. In risk assessment of pesticides, ecotoxicity tests have been applied to assess the effects of products and mixtures under laboratory conditions, but they are limited in their ecological relevance when compared to field assessments. Considering the differences between laboratory and field exposure, and the lack of data on the effects of metsulfuron-methyl in natural soils, this study consisted in a set of tests to assess the ecotoxicity of this herbicide applied alone, combined with an adjuvant (mineral oil) and the adjuvant applied alone, both under laboratory and field exposure, with artificial and natural soil respectively. Reproduction tests with four non-target soil invertebrates species were performed in laboratory, while two experiments were performed in field evaluating avoidance behaviour, feeding activity, mesofauna abundance and pesticide residual. Laboratory results showed that metsulfuron-methyl alone is not a threat to soil fauna on the recommended doses. However, the presence of mineral oil as adjuvant showed ecotoxicity to Eisenia andrei, Enchytraeus crypticus and Proisotoma minuta on laboratory tests. Field evaluations indicated that metsulfuron-methyl and the adjuvant do not impaired the feeding activity of the soil fauna. The low abundance of native communities could be related to soil management. Results showed that laboratory and field evaluations are necessary to better understanding of the effects of pesticides to soil fauna and adjuvant addition should be considered on pesticides risk assessment.

Do recommended doses of glyphosate-based herbicides affect soil invertebrates? Field and laboratory screening tests to risk assessment.

Despite glyphosate-based herbicides are widely used in agriculture, forestry and gardens, little is known about its effects on non-target organisms. The present work evaluated the ecotoxicity of four formulated products (Roundup® Original, Trop®, Zapp® Qi 620 and Crucial®) on soil invertebrates. Screening ecotoxicity tests were carried out with soil and oat straw collected in a field experiment, besides laboratory-spiked soils. Screening tests included avoidance behaviour of earthworms (Eisenia andrei), collembolans (Folsomia candida) and isopods (Porcellio dilatatus) in single and multispecies tests; reproduction of collembolans (F. candida), and bait lamina in field. Non-avoidance behaviour was observed in standard tests (earthworms) in soil, neither in multispecies tests (earthworm + isopods) using oat straw, while for collembolans it occurred for the product Zapp® Qi 620 even at the recommended dose. Reproduction of F. candida was not impaired even at high doses in laboratory-spiked soils. Feeding activity on bait lamina test was impaired in treatment corresponding to the red label product, Crucial®. Results showed the relevance of bait lamina test on screening the impact of herbicides in the field. The findings highlight the importance of considering different formulations for the same active ingredient in risk assessment of pesticides.

Alternativas para o controle de soja RR® voluntária na cultura do algodoeiro / Alternatives for the control of voluntary soybean RR® in cotton crop

Com o advento do cultivo de algodão em segunda safra, o controle de plantas voluntárias de soja RR® tornou-se uma operação indispensável na cotonicultura. Assim, o presente trabalho teve por objetivo avaliar a eficiência de diferentes alternativas de controle químico de plantas voluntárias de soja RR®, mediante a avaliação de herbicidas empregados no algodão. Foram instalados dois experimentos em casa de vegetação, sendo um com plantas de soja em estádio V1 e o outro em V2. Foram avaliados 21 tratamentos, sendo que estes compostos pela aplicação isolada e em mistura dos herbicidas pyrithiobac-sodium, amonio-glufosinate, glyphosate e trifloxysulfuron-sodium em diferentes doses. As variáveis analisadas foram: controle aos 7 e 28 dias após a aplicação dos herbicidas (DAA); matéria seca e altura das plantas aos 28 DAA. Os resultados demonstraram que nenhuma das misturas entre os herbicidas apresentaram antagonismo no controle de soja RR®. Diferentes níveis de supressão podem ser obtidos pela aplicação dos herbicidas avaliados, porém, apenas o amonio-glufosinate isolado ou associado ao pyrithiobac-sodium controlou todas as plantas voluntárias, independentemente do estádio de aplicação. Em geral, a soja apresentou maior tolerância aos herbicidas testados quando em estádio de crescimento mais avançado.

With the advent of cotton cultivation in the second harvest, the control of volunteer soybean GR® has become an indispensable operation on cotton. So, this study had to evaluate the efficiency of different alternatives to chemical control of volunteer plants RR® soybean, through an assessment of herbicides used in cotton. Two experiments were established in greenhouse, one with soybean plants in stage V1 and the other in V2. There were evaluated 21 treatments, compounds by alone and in mixture of herbicides pyrithiobac-sodium, amonio-glufosinate, glyphosate and trifloxysulfuron-sodium at different rates. The variables analyzed were: control at 7 and 28 days after herbicide application (DAA), dry weight and plant height at 28 DAA. The results showed that none of the mixtures showed antagonism between the herbicides in control of GR® soybeans. Different levels of suppression can be obtained by application of the herbicides evaluated, but, only the amonio-glufosinate, isolated and associated with pyrithiobac-sodium controlled all volunteer plants, regardless of the application stage. In general, soybean was more tolerant to herbicides while in more advanced growth stage.