The honey bee, Apis mellifera, is the most important agricultural pollinator. Through pollination, they contribute at least $19.2 billion annually to the United States economy and they contribute an additional $4.74 billion through the honey industry (Calderone 2012; Matthew et al 2018). Despite their agricultural and economic importance, honey bee populations have declined by 61% in the US during the past 70 years (vanEngelsdorp and Meixner 2010). Beekeepers today expect to lose an average of 40% of their colonies yearly. In Indiana and Pennsylvania, annual losses can be as high as 60% (Kulhanek et al. 2017; Sadler 2018). The cause of elevated loses is largely attributed to pathogens and pests. Without a doubt, the ectoparasitic mite Varroa destructor causes the greatest damage among all the other apicultural stressors (Boecking and Genersch 2008). Mite control is therefore critical for honey bee survival.Beekeepers have responded to emerging pathogenic or parasitic threats, such as Varroa, by artificially selecting for resistance traits. The United States has a long history of breeding honey bees for traits that confer resistant or tolerant to pests and pathogens (e.g. Bailey 1968; Sugden 1982; Spivak and Gilliam 1998a, b; Rinderer et al. 2010). In addition, US bee breeders often incorporate other traits as well: docility (Langstroth and Dadant 1922; Meixner et al. 2010), higher honey production (Meixner et al. 2010), lower propolis production, and 'beauty' (Langstroth and Dadant 1922). There are dozens of beekeeper-driven breeding organizations around North America that aim to maintain stocks resistant to mites. These include the Ontario Bee Breeders Association in Canada, the Russian Honey Bee Breeders Association in the US, and the Heartland Honey Bee Breeders Cooperative (HHBBC) in and surrounding Indiana. PD Harpur is the Scientific Director of the HHBBC, a group of beekeepers dedicated to maintaining the 'Purdue Mite Biting' stock of honey bees that are resistant to Varroa destructor. This stock and others (e.g. 'Italian', 'Russian', 'Buckfast', 'Minnesota Hygienic', and 'Carniolan') are available for beekeepers to purchase and beekeepers pay a premium to receive colonies bred within specific stocks.Breeding efforts have had some success at increasing the frequency of resistance traits in honey bees (e.g. Stokstad 2019). Unfortunately, there are few extension recommendations for beekeepers about which stocks they should use in their operations. Nor are there data sets available that document stock performance--how well a given stock is expected to survive and thrive within a given location. This leaves beekeepers with only anecdotal evidence about which stock will be best suited to their needs. Ultimately, beekeepers have many stocks available to them but are often unaware of which is best for their operation.We propose a collaborative, stakeholder-driven project to address this urgent need for beekeepers in the Midwest and Northeast. We will undertake a large phenotyping study (N=400 colonies) comparing the health and profitability of four commercially-available stocks widely-used by beekeepers in our regions. Each stock will be sourced from known breeders early in Spring 2020, established as single colonies, and provided to beekeepers within Indiana and Pennsylvania. Every month for two beekeeping seasons (May - September 2020 and 2021), we will work with beekeepers to quantify health- and profit-associated traits for each colony. Our results, along with hands-on phenotyping demonstrations, will be provided to beekeepers through annual hands-on demonstrations at Purdue University and the Pennsylvania State University. Our work will accomplish two major objectives:Objective 1: Assess the health and profitability of four honey bee stocks within the Midwest and NortheastObjective 2: Disseminate our findings to beekeepers in the form of field days, hands-on workshops, extension materials, and peer-reviewed work.?