Select Presentations at Scientific Conferences (last 3 years)

An Assessment of Native Bee Diversity and Abundance in North Georgia Apple Orchards from 2010-2014. 2015 Southeastern Branch Meeting of the Entomological Society of America. Biloxi, MS. March 15-18, 2015. Oral Presentation by Mark A. Schlueter and Nicholas G. Stewart

Bees play a critical role in the pollination of fruit, nut, and vegetable commercial agriculture.   In the following study, native bee abundance and diversity was investigated from 2010-2014 in Georgia apple orchards.  The survey occurred over the entire growing season (March-September) with special emphasis on the apple bloom. Over 20,000 bees were collected using pan traps, vane traps, malaise traps, and sweep netting. 2010 was a traditional apple bloom dominated by mining bees (Andrena species).  In 2011 and 2012, the apple bloom occurred 2 to 4 weeks early.  During these blooms, much lower Andrena species were present; however, greater abundances of mason bees (Osmia species) and other non-Andrena bees were documented. In 2013, the apple bloom was 2-3 weeks later than the traditional bloom.  Interestingly, overall diversity and abundance were much higher than in the previous years.  In 2014, a traditional apple bloom took place and the Andrena species once again dominated the samples. In order to use native bees successfully in commercial agriculture, we will need to gain a better understanding of the abundance, diversity, emergence times, and pollination behaviors of the native bee species.   In Georgia, the mining bees appear to be good candidates to serve as commercial pollinators.


Osmia Taurus, O. Cornifrons, and Anthidium Manicatum in North Georgia: Three Introduced Bee Species Making Their Way Down South. 2015 Southeastern Branch Meeting of the Entomological Society of America. Biloxi, MS. March 15-18, 2015. Oral Presentation by Peter M. Schlueter, Nicholas G. Stewart, and Mark A. Schlueter

During a 5-year study of native bees at four North Georgia apple orchards and natural areas surrounding the orchards we collected 20,000 bees.  Each year there were 9-10 sampling events from March to October.  There were more than 150 species identified and over 30 new state records.  Three new bee species to Georgia: Osmia cornifrons (2011), Osmia taurus (2011), and Anthidium manicatum (2012) are of particular interest. O. cornifrons, known as the Japanese Orchard Bee, was introduced into Maryland by Batra (USDA) because of its great pollination successes. It is believed to be more than 100 times as efficient as the honeybee in pollination. Our study first detected O. cornifrons in Georgia in 2011.  To date, only a few specimens have been captured in GA.  It took almost 35 years to travel from Maryland to Georgia. O. cornifrons appears to prefer cooler climates than the southeast. Nesting studies in Georgia apple orchards performed in our study were never successful in getting O. cornifrons to nest in either artificial paper tubes or natural reeds. However, it sister species, also fro Japan, O. Taurus has faired much better in Georgia. It was first detected in 2011 in Georgia, and has steadily increased in numbers each year. The significant pest bee Anthidium manicatum was first collected in Georgia in 2012.  It was accidently introduced in New York in 1963.  Currently, it is very rare in Georgia; only 2 specimens have been collected by our survey. These high aggressive and territorial bees will reduce agricultural output by either disrupting the pollination behaviors of other bees or by simply killing them. Surveys are important tools that allow us to monitor important groups of organisms and alert us to the arrival of new species to the area.


Nesting Habits of Introduced and Native Mason Bee Species (Osmia species) in North Georgia Apple Orchards. 2015 Southeastern Branch Meeting of the Entomological Society of America. Poster Presentation by Peter M. Schlueter, Nicholas G. Stewart, and Mark A. Schlueter

Mason bees (Osmia species) are known to be efficient and reliable pollinators.  Mason bees and other native bees contribute $3 billon in pollination services each year to the U.S. economy. Several species of mason bees, including the native blue orchard bee (Osmia lignaria), have been successfully managed to serve in commercial fruit and nut pollination. For example, Osmia cornifrons and O. cornuta are 80 times more effective in pollinating apple flowers than the honeybee. Only 250-500 O. cornifrons are required per acre for pollination compared to 60,000 to 120,000 honeybees. Farmers throughout the United States clearly benefit from native bees, but change is coming.  A new species Osmia taurus has recently arrived in the southeastern United States from Japan.  It was first reported in the Baltimore area in 2002.  We documented the arrival of Osmia taurus to the state of Georgia in 2011. Since then our collection numbers have rapidly climbed with 1 specimen in 2011, 10 specimens in 2012, 20+ specimens in 2013 and 50+ specimens in 2014. Based on preliminary reposts from the Northeastern States, O. taurus appears to outcompete many of the native mason bee species, including Osmia lignariaWill this new “invasive” mason bee outcompete and replace the native species in the Southeast?  In order to measure nesting preferences and success of O. taurus (invasive bee) compared to O. georgica (common native mason bee in Georgia), we placed 24 nesting habitats in 3 different North Georgia apple orchards.  Nesting material consisted on wooden block with holes, wooden reeds (size: 5 mm to 9 mm), and Kraft paper tubes (sizes: 6mm and 7 mm). Osmia taurus choose larger nest tubes (p=0.001), produces larger cocoons (p=0.001), and has greater nesting success (low parasite problems) (p=0.001) than O. georgica. Larger offspring (larger pupa size) are laid first in the nesting tubes compared with the last offspring to be laid (p=0.001).  This is correlates with the current belief that female offspring are laid first and male offspring are laid last in the nesting tubes. The native Osmia georgica and O. taurus share many similar nesting behaviors.  However, the species do show some differences in nesting site choice, which may reduce nesting site competition. In conclusion, O. taurus colonization in Georgia will boost mason bees numbers and likely benefit agricultural production particularly in early blooming fruits (apples and blueberries).  Osmia taurus’ natural history and behaviors are well suited for Georgia and will likely result in a continuation of its species expansion and increased abundance. Earlier emergence and other competitive behaviors towards other mason bee species are likely to be a big challenge for the native mason bees.  Similar size species, such as O. lignaria will likely decline; however, smaller native species such as O. georgica will likely coexist.


Observing and Measuring the Pollination Effectiveness of Andrena crataegi  and other bees in Commercial Apple Orchards. 91th Annual Meeting – Georgia Academy of Science.  Augusta, GA.  March 28-29, 2014. Oral Presentation by Catherine G. Schlueter and Mark A. Schlueter.

European honeybees (Apis mellifera) are the major pollinators of fruits, nuts, and vegetables.  However, worldwide agriculture may be in jeopardy due to unprecedented declines in honeybees due to colony collapse disorder and other factors. The purpose of this study was to find a native bee replacement for the honeybee.  The first step was to conduct a survey of the native bees found in Georgia apple orchards.  Over 10,000 bees were collected and identified.  The second step was to measure the pollination characteristics of target bees: mining bees (Andrena species), bumblebees (Bombus species) and carpenter bees (Xylocopa virginica).  Honeybees (0.68 grams) and bumblebees (0.1-0.8 grams) carried significantly larger pollen loads than mining bees (0.01 grams).  However, all of the pollen on the mining bees was available for flower pollination compared to less than 4% of the honeybee’s pollen, since that pollen was packed away in the bee’s corbicula (pollen basket). Mining bees spent the longest time at the flower (16.1 seconds) compared to honey bees (6.8 seconds), bumblebees (<2 seconds), and carpenter bees (<2 seconds).  It was hypothesize that mining bees could successful replace the honeybee in apple pollination in Georgia.  Apple trees in four different orchards were selected for this experiment. Netting enclosures (cages), which kept out honeybee-size and larger bees, were placed over one of the selected branches (experimental group), while the other branch (control group) was left uncovered.  In August, mature apples were collected.  Each apple was measured for size (weight, circumference, and diameter), and each apple’s seeds were counted. Statistical analyses indicated that there were no differences between the control and experimental groups.  Andrena crataegi accounted for 72.5% of the native bees collected in the netting enclosures’ pan traps.  A. crataegi and the mining bees can provide a natural and sustainable agricultural alternative to the declining honeybee.


A comparison of pollination behaviors in bumble bees, carpenter bees, mining bees, and honey bees on apple and blueberry flowers. 61th Annual Meeting of the Entomological Society of America, Austin, TX. Nov. 9-14, 2013. Oral Presentation by Tatiana Rodriguez, Sterling Brown, Matthew Coger, Nicholas Stewart and Mark Schlueter.

Insect pollinators are key to producing over $15 billion in crops for the United States. Honeybees have been the main commercial pollinating insects for thousands of years.  However, native bees also play a key role in pollination.  It is estimated that they contribute $3 million to U.S. agriculture each year. Obtaining more knowledge about how efficient and effective native bees are at pollinating specific crops could reduce the effects of the current honeybee crisis.  Based on past years work in the orchards, it is believed that mining bees, bumble bees, and carpenter bees have great potential as native bee pollinators in Georgia.  One method to determine the effectiveness of native bee pollination is to measure the amount of usable pollen on the bees. This usable pollen would be in the form of body pollen that collects on the hairs of the bees. It is hypothesized that native bees was be equal or more efficient than honeybees in flower pollination based on their flower pollination behavior and body pollen distribution.  Over a period of 6 sampling days, we collected 20 bees of each group and recorded 3-5 pollination video clips for each bee group. The sampling days were during the blueberry and apple bloom periods. The majority of samples were taken from mid-morning by hand using 50ml conical tubes.  Statistical analysis (ANOVA test, p=0.0001) indicated that different bee species had significantly different amounts of usable pollen on their bodies at the apple orchards. Mining bees (Andrena species) carried the most usable pollen.  Other native bees (e.g. Bombus species) also exhibit higher usable pollen amount than the honeybee.  Most of the pollen collected by honeybees was safely tucked away in the bee’s corbicula (rear leg pollen basket) and not available for pollination. Mining bees spent an average of 16 seconds at each apple flower, which was much longer than the honeybees, which averaged 6 seconds at each flower. In addition, mining bees exhibited the highest flower interaction during pollination.  Mining bees often dived completely into the flower, resulting in the best pollen exchange opportunities. The results of the study support our hypothesis that native bees can be equal or more efficient than honeybees in flower pollination based on their flower pollination behaviors and body pollen distribution. Based on our data, it appears native bees are comparable to, and in many cases, better than the honeybee in terms of pollination behavior.


The identification of Andrena crataegi as the apple bee in Georgia. 61th Annual Meeting of the Entomological Society of America, Austin, TX. Nov. 9-14, 2013. Poster Presentation by Catherine G. Schlueter, Nicholas G. Stewart, and Mark A. Schlueter.

Commercial fruit and vegetable agriculture is dependent on honeybee pollination services.  However, the honeybee is in decline due to several factors such as Colony Collapse Disorder. In addition, costs for honeybee pollination services (i.e. renting honeybee hives) have increased over the past decades, adding to farmer production costs.  Is there an alternative pollinator to the honeybee?  In the present study, we have examined the abundance and diversity of native bees present in apple orchards in Georgia. We have documented over 100 species of native bees. The mining bee Andrena crataegi and its close relatives, the Melandrena, are the most abundant in Georgia apple orchards.  Netting experiments that isolated apple branches from honeybees found that native bees could pollinate just as efficiently as the honeybee.  In addition, over 90% of the bees responsible for the successful pollination of the apple trees were Andrena crataegi and the Melandrena bees.  Further studies show that the abundances of these bees can be boosted by adding trenches (nesting areas) around commercial orchards. Andrena crataegi, a communal ground nesting mining bee, has the potential to become a valuable commercial pollinator.


Diversity and abundance of native bees in orchards are significantly impacted by the timing of the apple bloom. 61th Annual Meeting of the Entomological Society of America, Austin, TX. Nov. 9-14, 2013. Poster Presentation by Nicholas G. Stewart, and Mark A. Schlueter.

In the following study, we compared variations in native bee abundance and diversity in Georgia apple orchards during different types of apple bloom.  During typical apple blooms (mid-April), mining bees (Andrena species) dominate the bee survey collections. However, during early blooms (mid-March), much lower Andrena species were present; however, greater abundances of Osmia species and other non-Andrena bees were documented. In following year, a typical apple bloom took place and the mining bees returned in good numbers.  Interestingly, overall diversity and abundance were much higher than in the previous years, perhaps due to the longer spread in food available due to the previous year’s early apple bloom.

The overall goal of this research collect evidence in support of how agricultural systems can depend entirely on native-based pollination systems. Knowing how severe aberrations in the apple bloom will affect the abundance of  “target” native bee taxa must be also understood in order to depend on native-based pollination systems in commercial agriculture.  When expected dominate bee groups fail to appear in their typical numbers during atypical bloom cycles, our data indicates minor bee groups which typically provide insignificantly to pollination services, may compensate for any lack of pollination the missing dominate bee taxa would have provided.


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