Seasonal Changes in Size and Mite-Prevalence of a Bee Colony Exposed to Dinotefuran via Pollen Paste and Damaged by <em>Varroa</em> Mites

Abstract

Neonicotinoids, such as dinotefuran (DF), have caused a variety of problems, such as massive loss and winter failure of the bee colony, as a price for the benefit of reducing farm work, because it continues to maintain a high insecticide activity over a long period of time. In this study, a field experiment was conducted for about six months to investigate the effects of DF on bee colonies damaged by Varroa mites. This study examined the long-term changes in such as the size of bee colonies, the intake of sugar syrup (SS), intake of pollen paste (PP), which is a vehicle for administering DF, the intake of DF, the mite-prevalence of bees and the inside and outside temperatures of hive-boxes. The variation width of the inner temperature of the hive-box is less than that of the ambient temperature (Ta). The inner temperature of the hive-box is adjusted with about 30 ℃ of Ta as the boundary. If Ta is lower than 30 ℃, the inner temperature of the box is higher than Ta, and if Ta is higher than 30 ℃, it is lower than Ta. The temperature variation width of the DF-exposed colony is greater than that of the control colony. The average intake of SS per bee per day of the DF-exposed colony is more than that of the control colony. The average intake of PP per bee per day of the DF-exposed colony is almost equal to that of the control colony. These results suggest that bees do not avoid DF, and ingest PP without distinction between toxic and pesticide-free. In the period from the start of DF administration to the colony extinction, the intake of DF per colony is about 865 &amp;micro;g/colony, the intake per bee is 14 ng/bee, and the intake per bee per day is less than 0.1 ng/bee/day in this work. These intakes are much lower than the previous ones (60-65 ng/bee, 0.27-2.32 ng/bee/day). These discrepancies may be because attacks of mites and Japanese giant hornets hastened the colony collapse. Seasonal changes in mite-prevalence of honeybees is approximately the same regardless of the bee colonies. At the end of August (the start of attacks by Japanese giant hornets), the mite-prevalence will increase rapidly. Even if the number of bees damaged by mites turns to decrease, the mite-prevalence will continue to increase, with approaching 100% before bee colonies become extinct. In this study, it was found that the bee colony was collapsed by the intake of a smaller amount of DF due to the synergistic effect of DF and mite-damage. To prevent a bee colony collapse, not only to make an effort to minimalize the adverse effect on the bee colony of neonicotinoids such as DF with long-term residual effect and high insecticide properties, it is necessary to reduce the damage of mites as much as possible, while considering the synergistically adverse effects of neonicotinoids and miticides.

Evaluation of the appropriateness of pesticide administration-concentrations to honey beeApis melliferacolony in long-term field experiments and modest proposal

“…( 1), where values (P T , B T , D T ) other than P B in Eq. ( 1) are reported in papers already published by Yamada et al (2018a;2018b;2020b). P BD = P T ⁄ B T ⁄ D T (1).…”

“…We have conducted six long-term field experiments shown in Supplementary Table S2 to investigate the effects of neonicotinoid pesticides on bee ( Apis mellifera ) colonies (T. Yamada, et al, 2012, 2018 a , 2018 b , 2018 c , 2018 d ; T. Yamada & K. Yamada, 2020; Yamada, 2020). In these six long-term field experiments, sugar syrup (SS) and pollen paste (PP), which are foods of honey bees, were used as a vehicle to administer pesticides, which were dinotefuran (DF), clothianidin (CN), fenitrothion (FT) and malathion (MT), to a honey bee colony.…”

“…We have conducted six long-term field experiments shown in Table 2 to investigate the effects of neonicotinoid pesticides (neonics) on bee colonies 2012;2018a;2018b: 2018c2018d;2019;2020a;2020b). In these papers, the average pesticide intake per bee is calculated from the total pesticide consumption of the bee colony during the pesticide administration period and the total number of adult bees during that period.…”

“…2 to investigate the effects of neonico on bee (Apis mellifera) colonies (. Yamada et al, 2012;2018a;2018b;2018c;2018d;2020a, 2020b. These six longterm field experiments (2010-Experiment, 2011/2012-Experiment, 2012/2013-Experiment, 2013-Experiment, 2014/2015-Experiment, 2018 were conducted to investigate the followings, where the number of days in parentheses indicates the number of experimental days from the start date to the end date of the field experiment.…”

“…In conducting field experiments in an open system where it is difficult to control the experimental environment, we made the following efforts to reduce the influence of the experimental environment as much as possible (for details, see T. Yamada et al, 2012, 2018 a , 2018 b , 2018 c , 2018 d ; T. Yamada & K. Yamada, 2020; Yamada, 2020): (1) A pesticide-free drinking fountain was set up in the experimental site, and pesticide-free plants and flowers and trees were planted to prevent bees from ingesting pesticides from sources other than the experiment; (2) The control colony and the experimental colony were arranged alternately to reduce the influence of the location of the hive box on the experimental results; (3) In order to reduce the errors in the intakes of sugar syrup and pollen paste, and to reduce the measurement error of the numbers of adult bees and capped brood in the hive box and the dead bees in and around the hive box, immediately after dawn before the bees start foraging activities, measure the remaining amount of sugar syrup or pollen paste, and take photos of each side of all comb frames and the five walls in the hive box (can be checked repeatedly), using newly developed counting software as an adjunct to these photographs, the number of adult bees and capped brood were calculated from these photographs. And dead bees in and around the hive box were counted one by one and their number was recorded.…”