Toxicity Evaluation of Selected Plant Water Extracts on a Honey Bee (Apis mellifera L.) Larvae Model

Abstract

So far, larval rearing in vitro has been an important method in the assessment of bee toxicology, particularly in pesticide risk assessment. However, natural products are increasingly used to control honey bee pathogens or to enhance bee immunity, but their effects on honey bee larvae are mostly unknown. In this study, laboratory studies were conducted to determine the effects of including selected aqueous plant infusions in the diet of honey bee (Apis mellifera L.) larvae in vitro. The toxicity of infusions from three different plant species considered to be medicinal plants was evaluated: tansy (Tanacetum vulgare L.), greater celandine (Chelidonium majus L.), and coriander (Coriandrum sativum L.). The impact of each on the survival of the larvae of honey bees was also evaluated. One-day-old larvae were fed a basal diet consisting of distilled water, sugars (glucose and fructose), yeast extract, and freeze-dried royal jelly or test diets in which distilled water was replaced by plant infusions. The proportion of the diet components was adjusted to the age of the larvae. The larvae were fed twice a day. The experiment lasted seven days. Significant statistical differences in survival rates were found between groups of larvae (exposed or not to the infusions of tansy, greater celandine, and coriander). A significant decrease (p < 0.05) in the survival rate was observed in the group with the addition of a coriander herb infusion compared to the control. These results indicate that plant extracts intended to be used in beekeeping should be tested on all development stages of honey bees.