Sustainable Forages as an Alternative to Supplemental Feeding

Sustainable Forages as an Alternative to Supplemental Feeding

Summary

This beekeeping project is designed to study effective strategies for providing adequate nutrition to colonies, particularly during the spring build-up and the late summer dearth in Western North Carolina.  Spring nutrition is of paramount concern for bee breeders who need to stock mating yards at higher rates than what would generally be considered ideal so as to provide adequate drone saturation for breeding purposes.  Fall nutrition is equally important, since colonies are producing “winter bees” that are responsible for carrying the hive through the winter.  In Western North Carolina, fall is typically a time of limited resources.  Increasing stocking rates by offering supplemental feed can be an attractive alternative to managing dozens of small, scattered bee yards.  However, having a significant number of colonies competing for limited resources can cause a number of problems including robbing, parasite/pathogen transmission, and starvation.  The objective in season one is to address this concern conventionally by supplementing nutrition using sucrose and pollen supplements.

To this end, the decision was made to condense the project to one apiary of 40 colonies.  The chosen apiary is a winter yard that doubles as a mating yard in the spring.  The colonies used for the purposes of this project are production colonies, colonies being managed to produce a honey crop, and drone mother colonies, relatively large colonies who’s purpose is to produce significant numbers of male bees to service virgin queens being produced in-house.  Once breeding commences, these colonies are taken to production yards where they produce supplemental honey.  Following the honey flows, the colonies return to their original winter yard to start the cycle again.

• Winter/Mating Yard

Objectives/Performance Targets

Spring feeding is typically associated with one of two objectives: to stimulate brood production in an effort to “build-up” a colony for an upcoming honey flow, or secondly, to mitigate the risk of starvation if there is an imbalance between a colony’s nutritional needs and the available resources.  These nutritional needs are affected by the site and the weather.  At this project’s site in the spring of 2012, no supplemental feed was required.  Spring came early in 2012 and unfolded steadily and evenly without pronounced cold spells.  In contrast, the spring of 2013 was late and erratic.  January had the longest warm spell of the year with 13 consecutive days above average.  On January 13th, the nearest National Weather Service station recorded a temperature of 71 degrees–23 degrees above average!  Consequently, red maples began to bloom early and many colonies began to increase brood production.  However, February was the coldest month of the year followed by March which was the coldest month of the year in relative terms (departure from average).  March also had the longest cold spell of the year with 14 consecutive days below average at the end of the month.  Accordingly, the 40 colonies involved in this project consumed an average of 24.7 pounds of sucrose each between 3/4 and 4/15.  This equates to 6 gallons of 1:1 syrup at a cost of $10.87/colony.  In addition to sucrose, the colonies were also offered one pound of pollen supplement per week and frequently consumed less than half of the weekly ration.  The explanation behind this relatively slow protein uptake and justification for offering supplemental carbohydrates is evident in Figure 1A that graphs brood nest size at three different points in the six week feeding interval.  The graph is relatively flat, showing that these colonies were not necessarily “building up”, rather they were generally sustaining their earlier increase in population given the scarcity of resources due to the cooler than average weather.  This is somewhat surprising since an anticipated benefit of feeding in-hive versus forage-based feeding is that a colony’s ability to feed is not as dependent on the weather (e.g. bees can feed on a rainy day).  Nonetheless, the impact of the cool weather that characterized the spring of 2013 on colony “build-up” is easy to see in the data despite the in-hive supplemental feeding regiment.

One interesting sidenote discovered in the data in reference to a previous SARE project (#FS10-244), involves the fact that the colonies utilized for the project at hand unintentionally involved two different strains of honeybees.  These two strains have contrasting characteristics in terms of how they “build-up” in the spring.  One strain (herein referred to as the “hares”), wintered as a large cluster and “built-up” early on the premature red maple bloom.  These bees, although quick out of the gate, had a difficult time sustaining their large populations when resources waned due to the unseasonably cool weather that followed.  By contrast, the second strain (herein referred to as the “tortoises”), came through winter with smaller clusters.  Lacking a significant thermal mass, these bees had a delayed “build-up” that was slow and steady.  Counterintuitively, it was this later strain that went on to produce a decisively larger honey crop in contrast to the former strain, resulting in a “tortoise and the hare” scenario.  While both groups consumed the same amount of supplemental feed, they used the feed for different purposes.  The early expansion of the “hare colonies” out-paced the availablity of their resources.  Consequently, they used their supplemental feed to sustain their population.  By contrast, the “tortoise colonies” used their feed to supplement their even-paced growth.  The point here is not to advocate for one strain versus another, but rather to illustrate that different types of bees build-up differently in the spring and thus utilize supplemental feed differently.  The data suggests that there is a correlation between stock selection and nutritional demands as it relates to supplemental feeding.  Understanding this relationship could result in more effective feeding decisions.

• Figure 1A

Accomplishments/Milestones

The purpose of feeding in the fall is to prevent starvation during the late summer dearth and to provide adequate nutrition for colonies as they begin rearing winter bees.  Whereas in the spring, higher stocking rates are necessary for breeding purposes, in the fall, there are less incentives to stock yards as heavy.  Higher stocking rates increase competition for resources and promotes robbing behavior.  Robbing not only can mortally effect weak colonies, but also creates a context for pathogens to be transmitted from colony to colony.  In yards managed with reasonable stocking rates, the fall of 2013 was generally a year that required a reduction in the amount of feed required to keep colonies healthy.  This was due to a wet summer–July saw precipitation totals four times the monthly average.  The result was plentiful soil moisture that supported an extension in the bloom period for summer forages such as clover, and a substantial goldenrod flow in the fall.  However, nearly doubling our normal stocking rate for the purposes of this project, the circumstances at the project site were quite different.  Feeding at the scheduled rate of one gallon/week was inadequate to prevent starvation, robbing was a serious concern, and stress caused by nutritional deficiences/increased pathogen loads was common (see Figure 1B).  Only by following an aggressive feeding regime and continuing to feed beyond the ten week period called for by this project were colonies adequately prepared for winter.

For the purposes of this project, fall colonies were fed over a ten week period from 8/19 to 10/28.  Although the quantity was insufficient to maintain colony health as explained above, colonies consumed 41.5 pounds of sucrose or 10 gallons of 1:1 at $18.26/colony.  Pollen was also fed on a weekly ration of 1/2 pound per week at a cost of $1.76/colony.  There are also labor costs associated with feeding supplementally, including mixing, travel, and delivery costs.  These labor costs add up to an additional $1.08/colony.  Therefore, the sum of all the costs associated with the conventional fall feeding of colonies in season 1 was $21.10/colony (excluding the cost of equipment necessary with mixing and delivery).  This figure will be used to compare with alternative feeding strategies to be studied in season 2.

• Figure 2B

Impacts and Contributions/Outcomes

Throughout season one preparations were being made for establishing the forage plot required for the second season of this project.  An approximate six acre pasture adjacent to our mating yard was leased.  Soil samples indicated that fertility was substandard.  Following Extension recommendations, the field was burnt down using a glyphosate-based herbicide, drilled at 8 lbs/acre, and fertilized with a balanced fertilizer (17/17/17) at a rate of 115 lbs/acre.  An additional application of 230 lbs/acre will be applied in February.  These non-labor costs totaled $201/acre.  Labor costs associated with establishing the plot as described added up to $186/acre.

Planting occurred on October 3rd.  Despite this relatively early date (the reccommended planting period for rapeseed in this area is 10/1-10/15), the stand went into winter with less growth than what would be considered ideal.  The weather, specifically the lack of precipitation, was largely responsible.  September was the driest month of 2013 and the longest dry spell of the year occured between 9/26-10/7.  Ideally, rapeseed winters best after establishing 6-8 leaves of growth prior to the first hard frost.  Lack of rainfall and a hard freeze (19 degrees F) on 11/13 only led to an average of 4 leaves before dormancy.  Nonetheless, during a field evaluation with Extension on 11/26, the stand was determined to be on track for the purposes of this project.

Rapeseed is generally considered to be very winter hardy, however there are a number of variables affecting it’s ability to winter over successfully.  Planting date and the degree to which the stand becomes established before dormancy often receives the most attenetion.  Other factors include cultivar selection, some varieties winter better than others.  Little information is available for ‘dwarf essex’, the variety used in this project.  Improved canola varieties used in oilseed production are generally the focus of land grant university research.  We have successfully wintered trial plots of ‘dwarf essex’ rapeseed for three years in this region, however this season has presented unique circumstances in terms of weather.  The phenomenom known as the “polar vorex of 2014” brought record breaking low tempertures to the area on January 6th and 7th.  At the project’s location temperatures fell to 1 degree F with wind chill values below -10 degrees F, unfortunately there was no snow cover at the time to provide insulation.  These values followed December temperatures that were 4 degrees above the historical average.  Consequently, the rapeseed had tender growth that severely died back following this acute cold event (see photos).  At this time (early February), it is unclear how the “polar vortex” event will affect the planting.  Green at the base of the plants is encouraging despite significant foliar damage.  Nonetheless, the “polar vortex” event does draw attention to the unpredictability of weather and the potential consequences to honeybee forage plots like the one planted for the purposes of this project. This risk is not associated with the conventional feeding strategies outlined above which is clearly one of the most favorable advantages to feeding in-hive.

• Rapeseed Plot–post polar vortex (1/12/14)

Collaborators: