Browsing by Subject "Bumblebee"

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    Chronic exposure of imidacloprid and clothianidin reduce queen survival, foraging and nectar storing in colonies of Bombus impatiens
    (2013-07) Scholer, Jamison D.
    The 20 year research focus on residue levels below 10 ppb of neonicotinyl insecticides found in nectar and pollen of seed-treated crops (corn, canola, and sunflower) has not demonstrated a reduction in bee colony health in most field studies. However, the label rate of neonicotinyl use on crops and landscape plants is much higher than seed treatments. In addition, crops and flowers can be retreated multiple times a season which can contribute to chronic exposure to bees at higher residue levels. In an 11 week greenhouse cage study with queenright colonies of Bombus impatiens Cresson, provided 0, 10, 20, 50 and 100 ppb imidacloprid or clothianidin in sugar syrup, neither neonicotinyl reduced production of brood, workers, and queens. Male production decreased in 10-100 ppb imidacloprid and 50-100 ppb clothianidin treatments. However, starting at 6 weeks queen mortality was significantly higher in 20-100 ppb imidacloprid or clothinaidin. The largest impact was the reduction in worker movement, consumption, number of syrup filled wax pots, and the addition of wax to the colony, which resulted in reduced colony weight. Queens and nest bees fed on the sugar syrup stored in wax pots that were filled prior to the start of the experiment. Foraging bees did not return sugar syrup to the nest, but remained on the floor of the flight box. We argue that queen mortality at 20, 50, and 100 ppb was related to lack of syrup in storage pots. We speculate that as queens started to die at week 6, workers in 20-100 ppb treatments produced fewer males and instead provisioned cells to produce new queens, since queen production was not reduced at higher doses, but male production was reduced. Since neonicotinyls in this and other studies were shown to reduce food consumption and foraging, wild bumblebee colonies that depend on workers to forage will be negatively affected by exposure to imidacloprid above 20 ppb. Solitary bees will be greatly impacted as the foraging queens solely provision the larvae.
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    Investigating Bumble Bee Nesting Habitat Preferences and Natural History Along the Lower St. Croix River
    (Spring 2024) Dolan, Chan
    The upper midwestern US is one of the most changed landscapes on the planet, where much of the native vegetation has now been converted to agriculture. This loss of habitat has negative impacts on a variety of species, including bumble bees (Bombus). Minnesota alone is home to 25 species of bumble bees, with numerous species at risk of extinction that can partially be attributed to habitat loss. In order to implement effective conservation action for these important insects, identifying their habitat requirements is key. Generally, bumble bees require three main habitat components to complete their life cycle: foraging habitat, overwintering habitat, and nesting habitat. The majority of bumble bee research has focused on foraging habitat and flower preferences of bumble bees, leaving a large knowledge gap regarding nesting and overwintering habitat. However, these aspects of the bumble bee life cycle are notoriously difficult to observe and the time required to locate such locations is often considered prohibitive, leaving them to be relatively understudied. This lack of information on the nesting habitat requirements of bumble bees has negative consequences regarding conservation action, as habitat needs cannot be adequately identified and therefore may be inadequately protected. In this thesis, I investigate the nesting habitat preferences of wild bumble bees in different habitat types along the Lower St. Croix River Valley in the US states of Minnesota and Wisconsin. I used a novel, systematic approach to locating bumble bee nests directly in their habitat, spending equal effort in each habitat to quantify bumble bee nesting habitat preference. I also document various aspects of bumble bee nest natural history including nest activity, survival, and interactions with other species, which is important for informing future research directions regarding nesting bumble bee biology and ecology. The findings from this study also inform the development of standardized nest searching protocol for finding bumble bee nests more efficiently.