Honey bees are constantly threatened due to the wide use of pesticides. This study presents the effects of deltamethrin on the mortality, olfactory learning, and memory formation of the native Saudi bee Apis mellifera jemenitica. Topical and oral application of realistic field and serial dilutions of deltamethrin (250, 125, 62.5, and 25 ppm) caused significant mortality at 4, 12, 24, and 48 h posttreatment. Bee mortality increased with the increasing concentration of insecticide at all tested posttreatment times. Highest mortality was observed at 24 h and 48 h after both exposure routes. Food consumption gradually decreased with increasing concentration of deltamethrin during oral exposure. The LC₅₀ of deltamethrin was determined at 12, 24, and 48 h for topical (86.28 ppm, 36.16 ppm, and 29.19 ppm, respectively) and oral (35.77 ppm, 32.53 ppm, and 30.78 ppm, respectively) exposure. Oral exposure led to significantly higher bee mortality than topical exposure of deltamethrin at 4 h and 12 h, but both exposure routes were equally toxic to bees at 24 h and 48 h. The sublethal concentrations (LC₁₀, LC₂₀, and LC₃₀) of deltamethrin significantly impaired the learning during conditioning trials, as well as the memory formation of bees at 2, 12, and 24 h after topical and oral exposure. Thus, deltamethrin inhibits learning, and bees were unable to memorize the learned task.

The honey bee, a significant crop pollinator, encounters pesticides through various routes of exposure during foraging and flower visitation. Considering the potential threat of pesticide poisoning, the indigenous Saudi bee Apis mellifera jemenitica is susceptible to the risks associated with acetamiprid, a neonicotinoid insecticide. This study investigates the acetamiprid-induced effects on the survival, olfactory learning, and memory formation of A. m. jemenitica through two exposure routes: topical application and oral ingestion. Field-realistic and serially diluted concentrations (100, 50, 25, and 10 ppm) of acetamiprid led to notable mortality at 4, 12, 24, and 48 h after treatment, with peak mortality observed at 24 h and 48 h for both exposure routes. Bee mortality was concentration-dependent, increasing with the rising concentration of acetamiprid at the tested time intervals. Food consumption following oral exposure exhibited a concentration-dependent pattern, steadily decreasing with increasing concentrations of acetamiprid. Oral exposure resulted in a substantially higher cumulative mortality (55%) compared to topical exposure (15%), indicating a significant disparity in bee mortality between the two exposure routes. The 24 h post-treatment LC₅₀ values for acetamiprid were 160.33 and 12.76 ppm for topical application and oral ingestion, respectively. The sublethal concentrations (LC₁₀, LC₂₀, and LC₃₀) of acetamiprid were 15.23, 34.18, and 61.20 ppm, respectively, following topical exposure, and 2.85, 4.77, and 6.91 ppm, respectively, following oral exposure. The sublethal concentrations of acetamiprid significantly decreased learning during the 2nd–3rd conditioning trials and impaired memory formation at 2, 12, and 24 h following both topical and oral exposure routes, compared to the control bees. Notably, the sublethal concentrations were equally effective in impairing bee learning and memory. Taken together, acetamiprid exposure adversely affected bee survival, hindered learning, and impaired the memory retention of learned tasks.

The impact of agrochemicals on pollinators, especially honey bees, has drawn significant attention due to its critical implications for worldwide food stability and ecosystems. Given the potential threat of insecticides to honey bees, bees may encounter multiple insecticides simultaneously during foraging. This study investigated the toxic effect of an insecticide mixture (IM) containing acetamiprid (neonicotinoid) and deltamethrin (pyrethroid) on the survival and cognitive appetitive performance of Apis mellifera jemenitica, a vital native pollinator in arid regions of Saudi Arabia. The lethal concentration (LC₅₀) was determined by assessing bees’ mortality rates following exposure to IM through topical and oral routes. Significant bee mortality occurred at 4–48 h post treatment with IM through both exposure routes, showing a trend of increased mortality with higher IM concentrations compared to the control bees. Throughout all tested times, topical exposure proved relatively more effective, resulting in significantly greater bee mortality compared to oral exposure to IM. Food intake declined progressively with rising IM concentrations during oral exposure. The LC₅₀ values of IM at 24 h after treatment were 12.24 ppm for topical and 10.45 ppm for oral exposure. The corresponding LC₁₀, LC₂₀, and LC₃₀ values were 3.75 ppm, 5.63 ppm, and 7.54 ppm for topical exposure and 2.45 ppm, 4.04 ppm, and 5.78 ppm for oral exposure, respectively. The combination index (CI) revealed a synergistic effect (0.43) for topical exposure and antagonistic effects (1.43) for oral exposure, highlighting differential toxicity dynamics. IM exposure significantly impaired cognitive acquisition and memory reinforcement in honey bees, as demonstrated through behavioral assays, indicating potential neurotoxic effects. Learning and memory formation significantly declined at 2, 12, and 24 h after exposure to sublethal concentrations of IM through both topical and oral routes. Thus, evaluating the interactive impact of multiple pesticides on bees’ health and cognitive function is essential, particularly in regions where diverse agrochemicals are routinely utilized.

Vairimorpha ceranae and Vairimorpha apis are widespread microsporidian pathogens of honey bees, yet information on their occurrence in the indigenous Arabian honey bee, Apis mellifera jemenitica , remains limited. This study investigated the prevalence and seasonal dynamics of Vairimorpha spp. in A. m. jemenitica colonies from arid and semi-arid regions of Saudi Arabia. Nine regions were screened using species-specific PCR, while monthly microscopic spore counts assessed seasonal dynamics over one year. V. ceranae showed significantly higher prevalence (77.8% to 100%) than V. apis (11%) within both climatic zones (Fisher’s exact test, P < 0.001). Pairwise comparisons revealed significant localized variation among most regions in V. apis prevalence (Fisher’s exact test, P > 0.05). Co-occurrence analysis demonstrated a significant positive association between V. ceranae and V. apis (ϕ = 0.42, P = 0.003), with all V. apis infections occurring as co-infections with V. ceranae . Seasonal spore loads differed significantly among months (ANOVA, F = 2.47, p = 0.015), declining during spring and reaching a maximum in December, while remaining relatively low overall (3.0 × 10 ⁴ –3.2 × 10 ⁵ spores per bee). These findings demonstrate the widespread establishment of V. ceranae in A. m. jemenitica populations, the restricted distribution of V. apis , and relatively low infection intensity (spore count/bee) under Saudi Arabian conditions, providing a baseline for future investigations of host–pathogen interactions and disease ecology in A. m. jemenitica under challenging environmental conditions.

Saudi acacia (Talh) honey, produced from the nectar of Acacia gerrardii trees prevalent in Saudi Arabia, is regarded as one of the most distinguished varieties of honey in the region. Locals use it extensively, for therapeutic and medical purposes, and it is also incorporated into various foods. This study examined two key quality indicators hydroxymethylfurfural (HMF) level and diastase activity (DN) in fresh Talh honey. Adherence to guidelines is crucial for the health and purity of honey. Measuring the HMF and DN is important because elevated HMF or reduced DN may indicate prolonged storage, poor conditions, overheating, or adulteration. These indicators also reflect how effectively beekeepers maintain honey quality during extraction, storage, and marketing. The mean HMF levels were 2.93±1.0 and 1.32±0.3 mg/kg in the first and second years, respectively, while the mean DN values were 12.49 ± 0.1 and 19.3 ± 1.8 Schade units in the same years, respectively. These results were well within local and international standard requirements. Such measurements are valuable for assessing honey quality, which is essential for both worldwide trade and medical use. The present study therefore provides baseline information on acacia (Talh) honey.