Location: Carl Hayden Bee Research Center
Project Number: 2022-21000-022-072-I
Project Type: Interagency Reimbursable Agreement
Start Date: Jul 1, 2024
End Date: Jun 30, 2025
Objective:
The purpose of this award is to predict when colonies should be put into cold storage for overwintering based upon weather conditions in the fall. Colonies that are put into cold storage must contain ‘winter bees’. Among the attributes that enable winter bees to withstand long periods of confinement in the hive, these bees have enlarged fat bodies and occur in colonies that have stopped rearing brood in the fall. Our study will test a working hypothesis that the number of hours that bees spend in cluster (i.e., when ambient temperatures are less than or equal to 10 degrees C) is related to the amount of brood they rear. We will determine if brood rearing declines as hours in cluster accumulate in the fall. We also will determine if time in cluster and decline in brood rearing is related to an increased storage of lipids and decrease in protein in the fat body. The cessation of brood rearing and enlarging of fat bodies are characteristics of winter bees. Our previous studies have shown that bees in colonies that have stopped rearing brood in the fall have higher lipid and lower protein concentrations than those rearing brood at the same time of year in southern latitudes. We will collect data to determine if our observations on brood rearing and fat body metrics can be predicted based upon the number of hours with temperature less than or equal to 10 degrees C. If so, a decision tool for beekeepers could be developed to predict when colonies should be put in cold storage based on location and weather conditions in a given year.
Approach:
This study will include data collected in three temperate (State College, PA, East Lansing, MI and Pullman, WA) and two southern locations (Tucson, AZ and Auburn, AL) beginning in late summer (baseline measurements) and continuing into the fall. At each location, frames of bees and brood will be measured to determine if and when brood rearing ends. Mites per 100 bees will be recorded and varroacides will be applied as needed. Nosema spore counts will be made, and treatments will be applied if the counts average greater than 1 x 10 (to the 7th power) spores per bee. Hourly weather data (temperature, wind speed, and rainfall) will be recorded at each site beginning in July until the end of the sampling period in late fall. Colonies at PSU, MSU, WSU, and CHBRC will be overwintered in cold storage facilities and will be measured and sampled again when they are removed in late-winter or spring. Fat body metrics (weight and protein and lipid concentrations) will be determined from monthly samples of colonies at each site.
Using the hourly weather measurements particularly temperature, we will determine the number of hours that bees are exposed to temperatures < 10oC and in cluster. We then will use colony size data (frames of bees and brood), and fat body metrics to test for relationships between increasing hours that bees spend in cluster and frames of brood in colonies using linear and non-linear curve-fitting techniques. If significant relationships exist, algorithms will be derived to describe brood area as a function of accumulated cluster hours. Brood area data then will be used to test for relationships with fat body metrics using linear and non-linear curve-fitting techniques. Our previous studies of fat body metrics and brood production while colonies were in cold storage indicated that the decline in fat body lipid levels was positively related to the amount of brood that was reared.
