Honey bees are known for their wide global distribution, their ease of handling, and their economic and ecological value. However, they are often exposed to a wide variety of stress factors. Therefore, it is essential for beekeepers to maintain healthy bee colonies. In this context, a balanced diet is recommended to support the growth of strong and healthy honey bee colonies. The purpose of this review is therefore to provide an overview of the nutritional requirements of Apis mellifera and their importance for the maintenance of healthy bee colonies. An adequate diet includes the consumption of sufficient amounts of proteins, carbohydrates, lipids, amino acids, vitamins, minerals, water, and essential sterols, and a diet based on multi-floral pollen is desirable. However, when honey bee colonies are located near agroecosystems with lower resource diversity, both brood rearing and colony longevity may decrease, making them more susceptible to parasites and diseases. On the other hand, efforts have been made to improve the health of honey bee colonies with the help of nutritional supplements consisting of a variety of components. Nevertheless, studies have shown that even with these supplements, a lack of nutrients can still be an issue for honey bee colonies. Furthermore, future research should focus on identifying nutritional supplements that can better replicate natural diet diversity and assessing long-term effects on honey bee colony resilience, especially in low-flowering areas. This review discusses the interaction between nutrient requirements and the effects of supplements on colony health.

Melipona scutellaris is a Brazilian stingless bee that is important for pollinating wild flora and agriculture crops. Fungicides have been widely used in agriculture, and floral residues can affect forager bees. The goal of our study was to evaluate the effects of sublethal concentrations of pyraclostrobin on the midgut ultrastructure of M. scutellaris forager workers. The bees were collected from three non-parental colonies and kept under laboratory conditions. The bees were orally exposed continuously for five days to pyraclostrobin in syrup at concentrations of 0.125 ng a.i./µL (FG1) and 0.005 ng a.i./µL (FG2). The control bees (CTL) were fed a no-fungicide sucrose solution, and the acetone solvent control bees (CAC) received a sucrose solution containing acetone. At the end of the exposure, the midguts were sampled, fixed in Karnovsky solution, and routinely processed for transmission electron microscopy. Ultrastructural analysis demonstrated that both the fungicide concentrations altered the midgut, such as cytoplasmic vacuolization (more intense in FG1), the presence of an atypical nuclear morphology, and slightly dilated mitochondrial cristae in the bees from the FG1 and FG2 groups (both more intense in FG1). Additionally, there was an alteration in the ultrastructure of the spherocrystals (FG1), which could be the result of cellular metabolism impairment and the excretion of toxic metabolites in the digestive cells as a response to fungicide exposure. The results indicate that ingested pyraclostrobin induced cytotoxic effects in the midgut of native stingless bees. These cellular ultrastructural responses of the midgut are a prelude to a reduced survival rate, as observed in previous studies.

Various stressors reduce the health of honey bees (Apis mellifera) and colony survival. Therefore, there is an ongoing search for substances that strengthen bee immunity. Fungal extracts, which exhibit antimicrobial and antioxidant properties and mitigate viral infections, may prove to be such substances. The aim of this study was to determine how fungal extracts from Ganoderma lucidum (GL), Hericium erinaceus (HE), Inonotus obliquus (IO), and Trametes versicolor (TV) affect Carniolan honey bee longevity, antioxidant activity (CAT, GPx, GST, SOD, and TAC levels) and metabolic marker activity (ALP, ALT, and AST). Haemolymph for biochemical analyses was collected from bees at 7, 14, and 21 days after exposure to fungal extracts and stored at − 25 °C until analysis. GL treatment increased bee longevity by 16.4% compared to untreated bees (p < 0.0001). Bees fed with fungal extracts showed increased activities of metabolic markers and antioxidants after 14 and 21 days compared to bees only fed sugar syrup (p < 0.0001). Among all groups, bees fed IO had the highest levels of markers and antioxidants. This study demonstrates that including fungal extracts in the bee diet improves immune indicators in honey bees.

Given the current global agricultural system, honey bees are exposed to a complex network of stressors that can act simultaneously, making it challenging to maintain healthy colonies. Therefore, studies on natural products to improve colony health have increased in recent years. Among them, fungal extracts have been shown to be beneficial to honey bees. However, there remains a knowledge gap regarding lifespan and histomorphological studies in bees fed fungal extracts. Our current study aimed to assess the impacts of extracts from Ganoderma lucidum (GL), Hericium erinaceus (HE), Inonotus obliquus (IO), and Trametes versicolor (TV) on the lifespan and midgut of honey bees. Newly emerged Carniolan honey bees (Apis mellifera carnica) were fed 4% of each fungal extract until the death of the last individual to assess survival probability. For histomorphological analyses, bees were fed for 7, 14, and 21 days and sampled at these same time points. Then, the midguts were dissected and histologically processed for qualitative and semi-quantitative microscopic analyses. The results showed that the fungal extracts did not significantly affect honey bee survival, and that the histomorphology of the intestinal villi, digestive cells, and regenerative cells in bees treated with fungal extracts did not differ from that of untreated bees throughout the analyzed period. Similarly, no differences were observed in the midgut lesion index between bees treated with fungal extracts and the untreated group. Overall, the absence of harmful effects on lifespan and midgut suggests that feeding fungal extracts may be a potential alternative for supporting bee health.