Effects of fungicides on the ultrastructure of the hypopharyngeal glands and the strength of the hives of Apis mellifera Linnaeus, 1758 (Hymenoptera: Apidae)

Abstract

Several crops of agronomic interest depend on bees' pollination, and Apis mellifera L (Hymanoptera: Apidae) is the most studied direct pollinator. Nevertheless, the use of pesticides in agricultural environments is common, including fungicides. Studies that seek to evaluate the effects of fungicides on the hypopharyngeal glands of bees, the site of royal jelly synthesis, are lacking. Thus, this work aimed to evaluate the effect of field doses of fungicides (Captan SC® and Zignal®), alone or in mixture, on the hypopharyngeal glands and their subsequent effect on the strength of hives. The evaluations were carried out under field conditions in three hives per treatment. For a period of one month, bee hives received feed containing sugar syrup, pollen and 1.2 mL of Zignal® and 3 mL of Captan SC® in the isolated treatments and 4.2 mL in the mixture. The action of fungicides on the hypopharyngeal glands was determined by transmission electron microscopy analysis in bees 7 and 15 days old, collected in the hives one month after exposure to fungicides. The strength of the hives was evaluated for six months based on the number of frames with adult bees, open and closed brood, and stored food. The results indicate that fungicides promote early degeneration of the rough endoplasmic reticulum and morphological and structural changes in mitochondria. In addition, a reduction in adult population, open and closed breeding and food stock was observed. More pronounced damage occurred when bees were exposed to the mixture of fungicides. Overall, it can be concluded that the presence of fungicides in bee diets promotes harm accentuated over time and compromises the survival of hives. It will be worth estimating the fungicide effects of the queen development and on the colony heath.