The armored scales Hemiberlesia musae Takagi and Yamamoto, 1974 and Duplachionaspis divergens (Green, 1899) (Hemiptera: Diaspididae) were collected on the base of the stem and on leaves of sugarcane plants, Saccharum spp. (Poales: Poaceae), cultivated in plastic pots in greenhouses in the municipalities of Jaboticabal and Ribeirão Preto, São Paulo, respectively. This is the first report of D. divergens in Brazil and H. musae on Saccharum host plants.
Nitrogen fertilizers are one of the highest expenses in agricultural systems and usually a limitation to the productions of many agricultural crops worldwide. The intensive use of this element in modern agriculture represents a potential environmental threat, one of the many tools for the sustainable use of this resource without losing productivity is the use of plant growth-promoting rhizobacteria, especially nitrogen-fixing bacteria. However, in considering the competitiveness of the market, studies are still needed to determine the most efficient way to use this resource and if the nitrogen mineral fertilization is indeed substitutable. As a result, this study aims to deepen the scientific knowledge of the plant-microbe interactions by addressing their main characteristics and functionalities for plant growth and development and efficiency in the use of nitrogen. For this we reviewed relevant information from scientific works that address these issues.
Ammonia oxidation is the rate-limiting first step of nitrification and a key process in the nitrogen cycle that results in the formation of nitrite (NO2–), which can be further oxidized to nitrate (NO3–). In the Amazonian floodplains, soils are subjected to extended seasons of flooding during the rainy season, in which they can become anoxic and produce a significant amount of methane (CH4). Various microorganisms in this anoxic environment can couple the reduction of different ions, such as NO2– and NO3–, with the oxidation of CH4 for energy production and effectively link the carbon and nitrogen cycle. Here, we addressed the composition of ammonium (NH4+) and NO3–—and NO2–—dependent CH4-oxidizing microbial communities in an Amazonian floodplain. In addition, we analyzed the influence of environmental and geochemical factors on these microbial communities. Soil samples were collected from different layers of forest and agroforest land-use systems during the flood and non-flood seasons in the floodplain of the Tocantins River, and next-generation sequencing of archaeal and bacterial 16S rRNA amplicons was performed, coupled with chemical characterization of the soils. We found that ammonia-oxidizing archaea (AOA) were more abundant than ammonia-oxidizing bacteria (AOB) during both flood and non-flood seasons. Nitrogen-dependent anaerobic methane oxidizers (N-DAMO) from both the archaeal and bacterial domains were also found in both seasons, with higher abundance in the flood season. The different seasons, land uses, and depths analyzed had a significant influence on the soil chemical factors and also affected the abundance and composition of AOA, AOB, and N-DAMO. During the flood season, there was a significant correlation between ammonia oxidizers and N-DAMO, indicating the possible role of these oxidizers in providing oxidized nitrogen species for methanotrophy under anaerobic conditions, which is essential for nitrogen removal in these soils.
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In the state of São Paulo, the main sugarcane producing region of the world, two species of scale insects have frequently occurred, Aclerda takahashii (Kuwana, 1932) (Hemiptera: Aclerdidae) and Saccharicoccus sacchari (Cockerell, 1895) (Hemiptera: Pseudococcidae). To map the distribution and abundance of these species, 17 sugarcane producing fields, distributed in six mesoregions in São Paulo, were evaluated in August 2017 and, January, February, June and July 2018 during the ripening phase. The study on the seasonality of these species, by the presence or absence of the scale insects during the phenological cycle of the plant, was conducted between August 2017 and July 2018 in two sugarcane producing fields in the municipality of Jaboticabal, São Paulo, Brazil. The presence of S. sacchari was found in all the analyzed locations, and A. takahashii in twelve. Both scale insects showed significant difference of infestation in the node’s region of the stems during the ripening phase in one of the studied locations. The aclerdid presented significant difference by infestation in one site during the ripening phase of the plant. The pseudococcid infested a greater number of nodes in the following phases of development; vegetative, grand growth and ripening in both studied areas, but it was in one site during the ripening phase that presented the greatest difference. Although the pink sugarcane mealybug was more abundant than A. takahashii in both studies, there were no patterns of relationships between the numbers of individuals to geographical locations and temperature.
Saccharicoccus sacchari (Cockerell, 1895) (Hemiptera: Pseudococcidae) is globally disseminated on sugarcane plants. In Brazil, this species has been occurred in the same region as the occurrence of the fungal pathogen causing red rot, Colletotrichum falcatum Went, 1893 (Glomerellales). The objective of this study was to evaluate the hypothesis that this pseudococcid could act as a facilitator of the penetration of the phytopathogen C. falcatum. Species of this mealybug were reared at laboratory to infest sugarcane plants during the experiment. A total of 320 sugarcane plants were utilized for this study, 160 of CTC4 and 160 of RB86 7515 cultivars (cv.), each group subdivided into four treatments: (1) infested with mealybugs; (2) infected with fungal conidia; (3) infested with mealybugs and infected with fungal conidia; and (4) control.Biometrics of the plants, disease symptoms, Total Reducing Sugars (TRS) and Reducing Sugar (RS) were evaluated. To both cv., there was no difference in the height and diameter of the plants in all treatments; and only in "mealybug + fungus", significant difference on the lengths of the disease lesions inside the plants was found to each cv. as well as the levels of TRS and RS. The presence of the pseudococcid increased the incidence of the disease in both cv., although RB86 7515 was more susceptible to red rot than CTC4.
Sugarcane crops Saccharum spp. (Poales: Poaceae) produces different derivatives to the world: sugar, ethanol and bioenergy. Despite the application of pesticides, insect pests still cause economic losses, among these the pink sugarcane mealybug Saccharicoccus sacchari (Cockerell, 1895) (Hemiptera: Pseudococcidae) causing direct and indirect damage to the plant. This study assess the virulence of three entomopathogenic nematodes (EPNs) species and their symbiont bacteria against the pink sugarcane mealybug, under laboratory conditions. Fourteen treatments represented by control (distilled water), Heterorhabditis bacteriophora Poinar, 1976 (HB EN01) (Rhabditida: Heterorhabditidae), Steinernema rarum (Doucet, 1986) (PAM25) and Steinernema carpocapsae Weiser, 1955 (All) (Rhabditida: Steinermatidae) at concentrations of 25, 50, 75 and 100 infective juveniles (IJs)/insect, and the standard chemical product, thiamethoxam, were assayed. In a second experiment, the bacteria Photorhabdus luminescens (Thomas and Poinar, 1979), Xenorhabdus szentirmaii Lengyel, 2005 and Xenorhabdus nematophila (Poinar and Thomas, 1965) (Enterobacterales: Morganellaceae) at 3.0 x 109 cells/ml were assessed for each treatment. Ten replications were stablished, each one counting ten females/mealybugs inside a 10 cm Petri dish, amounting 100 individuals/treatment. All treatments were kept under stable conditions (25±1 ºC, H 70±10%, in the dark). All nematodes species infected S. sacchari. Steinerma rarum (PAM25) provided the highest mortality against the pink sugarcane mealybug (79.25%), followed by H. bacteriophora (HB EN01) (58.25%) and S. carpocapsae (All) (42.50%) (P<0.001). The mortality rate caused by X. szentirmaii, P. luminescens and X. nematophila were 40, 45 and 20%, respectively. Steinerma rarum (PAM25) has conditions to be a potential agent to be incorporate into the integrated pest management in sugarcane.
BACKGROUND The improvement of surface coverage and plant protection products deposition can be obtained by electrifying droplets, which are strongly attracted by plants, including the abaxial part of the leaves. Moreover, air assistance improves droplet penetration into the crop canopy, especially in the lower third of the plants. These technologies can help control soybean (Glycine max) whitefly, which preferentially lodges on the abaxial surface of the leaves. Thus, this study aimed to assess the effect of air‐assisted spraying and electrically charged droplets to control whitefly in soybean, besides assessing surface coverage, plant protection product deposition, droplet size, and crop yield. RESULTS Droplet electrification and air assistance did not change droplet size and uniformity classified as Fine. Surface coverage was not enhanced using air assistance and electrically charged droplets, where maximum coverage in the middle third of the plants was 4.55%. The results were not significant for spray plant protection products deposition. The number of nymphs per leaflet in the 2019/20 growing season was reduced with the used technologies, reducing from 10.9 to 3.0 nymphs per leaflet in the application with air‐assisted and charged droplets, but not enough to differ from the untreated. On the other hand, the reduction was significant from the first assessment in the 2020/21 growing season. CONCLUSION Air‐assisted spraying plus electrically charged droplets, under the conditions of this experiment which corresponds to the application carried out in production areas, were not effective to affect whitefly control and soybean yield in comparison to the conventional application method. © 2022 Society of Chemical Industry.
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