Black Soldier Flies as a Value-Adding Tool within Organic Farming Systems

During the summer of 2012, BSF were raised exclusively in four ProtaPods™ (http://www.thebiopod.com/pages/pages/protapod.html) on private farmland in a location with access to a 4-acre organic garden, open broiler pasture, and an on-site red meat abattoir.  The ProtaPods were located underneath a solar voltaic array where they were shaded and protected from rain.  Egg traps were constructed from corrugated cardboard strips and secured with Velcro inside bins containing wet chicken feed, located throughout two hoop houses which contained chicks up to three weeks of age.  Egg clusters were collected daily and placed in a separate bin to hatch.  Filled egg traps were placed over a screen of ¼” hardware cloth and suspended over moist chicken feed.  A screen top prevented other flies from ovipositing in the bin.  When the hatched larvae were big enough to see they were dumped into the ProtaPods, rotating between the four active ProtaPods in sequence.  Mature larvae which migrated out of the ProtaPod and fell into a collection bucket were harvested on a daily basis.  The ProtaPods were fed a mix of about 75% meat scraps and 25% vegetable waste.  Broken raw eggs were fed as available.  Each ProtaPod was fed 2-3 pounds of material every other day during the peak of summer, and once a week in the fall when BSF activity levels decreased.  Over the winter months one ProtaPod was maintained and fed weekly inside an 82-square-foot heated plastic greenhouse, and the remaining three ProtaPods were left to enter dormancy.During the following summer of 2013 three of the four ProtaPods were relocated to a field containing compost windrows in active decomposition, situated between open cattle pasture and mixed hardwood forest.  This location was chosen to allow newly matured BSF greater proximity to the forest, where the majority of lekking and mating behavior is believed to occur (Tomberlin & Sheppard, 2001).  Young larvae and eggs were added to each ProtaPod to boost the active BSF colonies and attract gravid BSF females.  Egg collection traps were placed in and around each ProtaPod and eggs were collected daily.  Several additional egg  traps and the fourth ProtaPod were placed in an open 10’x40’ hoophouse which was constructed within a 1-acre orchard, situated between broiler pasture and a mixed hardwood forest containing a shallow pond.  All eggs that could be collected were reared as daily batches inside the hoophouse in shallow 15”x20”x5” bins.  Newly hatched larvae were fed a diet of moist chicken feed until they were one week old, then switched to increasing daily rations of ground cattle eviscerate originating from the abattoir.  Larvae were monitored for feed consumption and moisture on a daily basis and their feed rations were adjusted daily in order to provide no more feed than could be consumed over a 24 hour period.  Whole batches of mature larvae were harvested when the majority of larvae in the batch had turned black and stopped feeding.An experiment was conducted at the end the 2013 season to quantify bioconversion rates using the batch-rearing method.  In this experiment two batches of different sizes were created using 6,000 and 10,000 larvae held in 15”x20”x5” storage bins.  Initial population size was determined by weighing a small subsample of 20 larvae and projecting the weight of the total batch to attain the desired population.  The larvae were initially fed ground eviscerate at the rate of 1:1 in biomass (e.g., 30g eviscerate per 30g larvae).  After this point the feed amount was gradually adjusted at a rate that maintained the 24-hour consumption rule for each batch.  Larvae were fed exclusively ground eviscerate during the course of the experiment and the weight of each day’s ration was recorded.  As it was impractical to weigh an entire batch of larvae, samples of 20 larvae from each batch were weighed at regular intervals to determine average larval weight. The experiment was ended after 45 days, when the majority of the larvae were mature and were no longer feeding.  Each batch was screened to separate mature larvae from uneaten material and each component was weighed.  The net weight of consumed eviscerate material was determined by subtracting the weight of uneaten material from the total weight of feed rations over the 45-day period.  The conversion rate of eviscerate to larval weight was determined by dividing the net weight of consumed material by the final weight of mature larvae. Reference cited:  Tomberlin, J.K. & Sheppard, D.C. (2001).  Lekking behavior of the black soldier fly (Diptera: Stratiomyidae).  Florida Entomologist, 84:  729-730.