Brazil is an extensive forest plants producer due to the edaphoclimatic conditions though; most part of the soils constituting Brazil's territorial extension possesses features as low fertility mainly in primary nutrients. Intimate relationships on rhizosphere are mandatory to take effect in order to plants capture and assimilate nutritional elements present in the soil such as the microorganisms present in it. Nitrogen fixing bacteria and arbuscular mycorrhizal fungi are responsible for most part of the organic matter decomposition in the soil and availability of essential nutrients to plants through symbiotic relationship. This relationship can be intensified by practices such as biodiversity enrichment and microbial fauna which occurs in agrosilvopastoral system. Results contribute to better comprehension on those systems towards grassland ecosystems and the vast soil living microorganisms contribution that live in it.

The present study aimed to assess the effects of the essential oil of Croton pulegiodorus Baill on eight populations of Sitophilus zeamais Motschulsky with different patterns of susceptibility to synthetic insecticides. Populations of S. zeamais were obtained from Sete Lagoas-MG, Jacarezinho-PR, Bom Conselho-PE, Garanhuns-PE, Jupi-PE, Lajedo-PE, São João-PE and Serra Talhada-PE. To estimate the lethal concentrations (LC 50 and LC 90 ) of oil for each population, fumigation tests were performed. The susceptibility of S. zeamais to the essential oil varied among populations. Garanhuns and Bom Conselho was considered the susceptibility patterns, presenting the lowest LC 50 (3.40 μL L -1 of air) and LC 90 (9.60 μL L -1 of air) for the essential oil, respectively. The population from Jupi exhibited the highest LC 50 (14.49 μL L -1 of air) and LC 90 (19.60 μL L -1 of air) for C. pulegiodorus. The resistance ratio ranged from 1.84 for the São João to 4.26 for the Jupi population. Thus, the essential oil of C. pulegiodorus showed fumigant activity, causing mortality in all S. zeamais populations used. O ÓLEO ESSENCIAL DE FOLHAS DE Croton pulegiodorusBaill APRESENTA ATIVIDADE INSETICIDA SOBRE Sitophilus zeamais Motschulsky RESUMO -O presente estudo teve o objetivo de avaliar os efeitos do óleo essencial de Croton pulegiodorus Baill sobre oito populações de Sitophilus zeamais Motschulsky com diferentes padrões de susceptibilidade a inseticidas sintéticos. As populações foram obtidas de Sete Lagoas-MG, Jacarezinho-PR, Bom Conselho-PE, Garanhuns-PE, Jupi-PE, Lajedo-PE, São João-PE e Serra Talhada-PE. Para estimar as concentrações letais (CL 50 e CL 90 ) do óleo para cada população, foram realizados testes de fumigação. A susceptibilidade de S. zeamais ao óleo essencial variou entre as populações. Garanhuns e Bom Conselho foram considerados padrões de susceptibilidade, apresentando as menores CL 50 (3,40 μL L -1 de ar) e CL 90 (9,60 μL L -1 de ar) para C. pulegiodorus. A população de Jupi apresentou as maiores CL 50 (14,49 μL L -1 de ar) e CL 90 (19,60 μL L -1 de ar) para C. pulegiodorus. A razão de resistência variou de 1,84 vezes para população de São João a 4,26 vezes para a população de Jupi. Assim, o óleo essencial de C. pulegiodorus apresentou efeito fumigante causando mortalidade em todas as populações de S. zeamais utilizadas. Palavras-chave: Produtos naturais. Euphorbiaceae. Curculionidae. Milho armazenado.

No abstract

The pupal parasitoid Tetrastichus howardi (Olliff) (Hymenoptera: Eulophidae) parasitizes pupae of sugarcane stalk borers inside the stalk. Parasitoids currently used for applied biological control of sugarcane stalk borers target eggs and larvae, and T. howardi will add mortality to the pest stage with high survival. Nevertheless, insecticide applications required to control sugarcane borers and other sugarcane pests can affect T. howardi parasitism. Survival, walking, evasion and parasitism of T. howardi females were evaluated in response to the dry residue of insecticides from different chemical groups: chlorantraniliprole, bifenthrin, spinetoram, ethiprole, fipronil and thiamethoxam. Females of the parasitoid were confined on sugarcane leaves containing residues of the insecticides at 2, 24, 48, 72 and 96 h intervals after application, and survival monitored during the 96‐h period with subsequent determination of parasitism in the laboratory. Furthermore, female walking behaviour was observed individually using half‐treated arenas with insecticides. Chlorantraniliprole was compatible with T. howardi irrespective of residual intervals and studied variables. Other tested insecticides did not allow parasitoid survival up to 96 h of confinement on dry residues and, consequently, parasitism. Locomotory activity indicated that parasitoid females might avoid residues of spinetoram and ethiprole. Females were released in cages containing spinetoram and ethiprole‐treated sugarcane plants with the chance to move to untreated plants, parasitized pupae placed on either treated or untreated plants within a 24 h exposure period, which resulted in offspring production. Females observed for 10 min for walking behaviour in a half‐treated arena with chlorantraniliprole, ethiprole, fipronil, spinetoram, bifenthrin or thiamethoxam exhibited 100%, 73.3%, 70%, 66.7%, 10% and 0% survival after 24 h, respectively. Chlorantraniliprole was compatible with T. howardi through the bioassays conducted, and parasitoids showed the ability to parasitize their hosts on spinetoram‐ and ethiprole‐treated plants moving away from the treated environment.

Drought and predicted changes in climate, such as increased atmospheric CO2 concentration and high temperature, may affect the growth and productivity of crop plants and generate varying responses, including morphological, physiological, biochemical and molecular changes. Water deficit negatively affects photosynthesis, while increasing CO2 can benefit plants and attenuate photo-oxidative damage, especially in C3 metabolism species. However, the excess heat associated with this increase can affect photosynthetic efficiency differently, depending on the species and/or variety studied. In addition, the responses to the combination of these factors are poorly understood and cannot be extracted directly from the effects of each of these agents applied in isolation. This review sought to address the isolated and combined effects of water deficit and climate change on agricultural production, reporting how plant metabolism is affected by rising temperatures and high CO2 concentration. This understanding is important to monitor the behavior of plants in the face of future climatic scenarios in order to develop strategies that can confer resistance to plants and ensure food security for agricultural production.