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The present study aimed to evaluate the effect of silver nanoparticles (AgNPs) on the development of Colletotrichum lindemuthianum, the progression of anthracnose symptoms, and the growth of common bean plants. For this purpose, the fungal mycelial growth and conidial germination were assessed at AgNP concentrations of 0, 10, 30, and 50 mg·L−1 after seven days of incubation, as well as at 0, 0.1, 0.5, 1, 10, 30, and 50 mg·L−1 after 72 h, respectively. Bean plants of the IPR Uirapuru cultivar were sprayed at the V3 growth stage with AgNPs at 0, 10, 30, or 50 mg·L−1, either two days before, on the day of, or two days after inoculation. Conidial germination and appressoria melanization were measured on the leaf discs collected 24, 48, and 72 h after inoculation, and disease severity was assessed at 7 and 12 days post-inoculation. Another set of bean plants grown under the same conditions was used to evaluate growth promotion by AgNPs. For this, the plants were sprayed twice (with a seven-day interval), starting at the V3 growth stage, with AgNPs at 0, 10, 30, or 50 mg·L−1. Seven days after the second treatment, plant length and the fresh and dry weights of shoots and roots were measured, and the foliar pigments were quantified. The AgNPs did not reduce mycelial growth but completely inhibited the germination of C. lindemuthianum conidia. The severity of anthracnose decreased with the AgNPs in a dose- and application time-dependent manner, with the highest reduction (90%) observed when applied on the same day as an inoculation at 50 mg·L−1. This was strongly linked to a 70% decline in conidia germination and appressorium melanization on bean leaves. AgNPs at 50 mg·L−1 promoted plant growth by increasing the total length by 3%, as well as the fresh weights of bean shoots and roots by 17% and 90%, respectively, but did not affect the content of leaf pigments. [ABSTRACT FROM AUTHOR]

Stingless bees are of environmental and economic importance because they pollinate plants of agricultural and native interest. During foraging, bees can come into contact with synthetic insecticides, resulting in lethal and sublethal effects. Biological control using entomopathogenic fungi (EF) is an alternative to the use of synthetic insecticides. However, despite promising results in pest control, gaps in the activity of EF on nontarget organisms, such as stingless bees, have not been completely recognized. Thus, this work aimed to evaluate the effects of three bioinsecticides formulated from Beauveria bassiana (Boveril®WP), Metarhizium anisopliae (Metarril®WP), and Cordyceps fumosorosea (Octane®SC) on Melipona quadrifasciata, Plebeia droryana, and Scaptotrigona bipunctata (Hymenoptera: Apidae). Direct contact with the concentration of 107 conidia.mL−1 indicated a differentiated tolerance between bee species, as well as significant differences in mortality caused by these bioinsecticides. Melipona quadrifasciata showed the lowest tolerance to bioinsecticides, while S. bipunctata had the lowest mortality. According to the classification proposed by the International Organization for Biological Control, the Boveril®WP and Metarril®WP bioinsecticides were characterized as harmless to moderately harmful. Octane®SC caused mortality between 74.7 and 95% and was thus characterized as harmful to all three studied species. Although these bioinsecticides are selective for nontarget organisms, it is evident that the toxicity for stingless bees is dependent on the EF species used. Thus, its use must be carried out according to criteria that minimize damage to bees, effectively resulting in the development of sustainable agriculture. [ABSTRACT FROM AUTHOR]

Stingless bees are essential for the pollination of cultivated and native plant species. Anthropogenic activities in natural ecosystems trigger changes in the microclimate, impacting the flight activity of bees. Here, we examine the effects of some abiotic factors on the flight activity of some stingless bees. We installed four colonies of each species (Plebeia droryana, Scaptotrigona bipunctata and Melipona quadrisfasciata) in three distinct areas (predominantly urbanized area, mosaic of pastures with agricultural cultivation and mosaic of natural vegetation with fragmented landscapes) represented by different uses and land cover (L.U.L.C.). All observations were in the morning during three time slots. For each area, we recorded daily abiotic factors and measured the flight activity of bees entering and leaving the colony. P. droryana and S. bipunctata had similar flight activities, with less activity in anthropized areas. M. quadrifasciata showed the lowest activity among species in the three areas. The flight activity of S. bipunctata showed significant differences. Abiotic factors had significant differences between areas, light intensity had the greatest influence on flight activity among the three species. Our study indicates that stingless bees exhibit a pattern of behavior. However, the abiotic characteristics of a given ecosystem can affect the flight activity of each species based on its normative behavior. This is the first study to evaluate abiotic effects on the flight activity of P. droryana, S. bipunctata and M. quadrifasciata in southern Brazil. The results obtained here can contribute to the establishment of a conservation plan for stingless bee species and prevent future extinctions in a scenario of environmental changes. [ABSTRACT FROM AUTHOR]

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