SummaryModern agriculture often involves the use of pesticides to protect crops. These substances are harmful to target organisms (pests and pathogens). Nevertheless, they can also damage non-target animals, such as pollinators and entomophagous arthropods. It is obvious that the undesirable side effects of pesticides on the environment should be reduced to a minimum. Western honey bees (Apis mellifera) are very important organisms from an agricultural perspective and are vulnerable to pesticide-induced impacts. They contribute actively to the pollination of cultivated crops and wild vegetation, making food production possible. Of course, since Apis mellifera occupies the same ecological niche as many other species of pollinators, the loss of honey bees caused by environmental pollutants suggests that other insects may experience a similar outcome. Because pesticides can harm honey bees and other pollinators, it is important to register pesticides that are as selective as possible. In this manuscript, we describe a selection of methods used for studying pesticide toxicity/selectiveness towards Apis mellifera. These methods may be used in risk assessment schemes and in scientific research aimed to explain acute and chronic effects of any target compound on Apis mellifera. Métodos estándar para la investigación toxicológica en Apis mellifera ResumenLa agricultura moderna a menudo implica el uso de plaguicidas para proteger los cultivos. Estas sustancias son dañinas para los organismos objetivo (plagas y patógenos). Sin embargo, también pueden dañar a animales que no son objetivo, como artrópodos polinizadores y entomófagos. Obviamente los efectos secundarios indeseables de los plaguicidas sobre el medio ambiente deben ser reducidos al mínimo. Las abejas occidentales (Apis mellifera) son organismos muy importantes desde el punto de vista agrícola y son vulnerables a los impactos inducidos por los plaguicidas. Contribuyen activamente a la polinización de los cultivos y de la vegetación silvestre, lo que hace posible la producción de alimentos. Como Apis mellifera ocupa el mismo nicho ecológico que muchas otras especies de polinizadores, la pérdida de las abejas melíferas causada por contaminantes ambientales sugiere que otros insectos pueden experimentar un resultado similar. Ya que los plaguicidas pueden dañar a las abejas y a otros polinizadores, es importante registrar los plaguicidas que sean lo más selectivos posible. En este artículo, se describe una selección de los métodos utilizados para el estudio de la toxicidad y el efecto selectivo de los plaguicidas hacia Apis mellifera. Estos métodos se pueden utilizar en sistemas de evaluación de riesgo y en la investigación científica para explicar los efectos agudos y crónicos en Apis mellifera de cualquier compuesto objetivo.

This study was aimed at evaluating the effect of a microbial pest-controlling product (MPCP) with the active substance Bacillus thuringiensis ssp. aizawai (strain: ABTS-1857) on adults and larvae of honeybees. To determine the contamination levels of Bt spores in different matrices, a colony-feeding study under semi-field conditions was performed. Furthermore, two chronic adult trials and a chronic larval study were conducted under laboratory conditions to test the effects of different concentrations of the plant protection product (PPP) on the development and mortality. Possible modifications of the chronic oral toxicity test were assessed by additional pollen feeding. Our results showed that Bt spores were detected in all matrices over the entire test duration in different concentrations, decreasing over time. The survival of adult bees and larvae was negatively affected in laboratory conditions after a chronic exposure to the MPCP depending on the tested concentrations. Moreover, the earliest sign of bee mortality, resulting from exposure to ABTS-1857, was recorded only after 96 h at the highest tested concentration. Pollen feeding to adults significantly increased the survival of the treated bees. In conclusion, the PPP with the Bt strain ABTS-1857 showed an effect on the mortality of adults and larvae under laboratory conditions. Further studies with Bt-based PPPs under realistic field conditions are necessary to evaluate the potential risk of those MPCPs on honeybees.

The ongoing debate about glyphosate-based herbicides (GBH) and their implications for beneficial arthropods gives rise to controversy. This research was carried out to cover possible sublethal GBH effects on the brood and colony development, adult survival, and overwintering success of honey bees (Apis mellifera L.) under field conditions. Residues in bee relevant matrices, such as nectar, pollen, and plants, were additionally measured. To address these questions, we adopted four independent study approaches. For brood effects and survival, we orally exposed mini-hives housed in the “Kieler mating-nuc” system to sublethal concentrations of 4.8 mg glyphosate/kg (T1, low) and 137.6 mg glyphosate/kg (T2, high) over a period of one brood cycle (21 days). Brood development and colony conditions were assessed after a modified OECD method (No. 75). For adult survival, we weighed and labeled freshly emerged workers from control and exposed colonies and introduced them into non-contaminated mini-hives to monitor their life span for 25 consecutive days. The results from these experiments showed a trivial effect of GBH on colony conditions and the survival of individual workers, even though the hatching weight was reduced in T2. The brood termination rate (BTR) in the T2 treatment, however, was more than doubled (49.84%) when compared to the control (22.11%) or T1 (20.69%). This was surprising as T2 colonies gained similar weight and similar numbers of bees per colony compared to the control, indicating an equal performance. Obviously, the brood development in T2 was not “terminated” as expected by the OECD method terminology, but rather “slowed down” for an unknown period of time. In light of these findings, we suggest that chronic high GBH exposure is capable of significantly delaying worker brood development, while no further detrimental effects seem to appear at the colony level. Against this background, we discuss additional results and possible consequences of GBH for honey bee health.

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In agricultural crops, honey bees may be exposed to multiple pesticides. However, in field realistic conditions mixtures of products classified as harmless to bees can lead to a synergistic increase of toxicity on honey bees, as known for ergosterol biosynthesis-inhibiting (EBI) fungicides combined with pyrethroids or neonicotinoids. For substances like fertilizers, usually no information on potential side effects on bees is available. Initially, effects from tank mixes containing insecticides, fungicides and fertilizers were investigated under laboratory conditions by use of a spray chamber contact test. For selected combinations, higher tier studies were carried out. Mixtures containing thiacloprid, boscalid and dimoxystrobin with boron fertilizers showed no increase of mortality. In contrast, tank mixes of thiacloprid formulations and EBIfungicides resulted within 24 h in synergistic mortality increase in laboratory, semi-field and field. Actually, a short time interval of 24 h between individually applied potentially synergistic products like pyrethroid insecticides and EBI fungicides led to an increase of mortality up to 100% under laboratory conditions, indicating that the detoxification was still ongoing, resulting in an increased susceptibility for other stressors during the metabolization process. In conclusion, tank mixtures do not always lead to an increase of honey bee toxicity. However, former published findings about synergistic impacts between neonicotinoides and EBI-fungicides could be confirmed. The findings of our and other higher tier studies finally prompted the competent regulatory authority (BVL) to regulate these mixtures by restriction NB6613 since September 2018. Nevertheless, the investigation of potential interactions between mixing partners and their additive or synergistic effects are the basis for a better understanding and a logical risk assessment to ensure protection of honey bees.Keywords Honey bees Á Tank mixtures Á Synergistic impacts Á Contact exposure Á EBI-fungicides