Keeping a colony healthy is a key challenge for insect mass production in industrial rearing facilities. A growing number of scientific papers investigate the ability of insects like the Black Soldier Fly (BSF) (Hermetia illucens) to convert organic wastes into high quality nutrients for feed and food. This bioconversion often involves survival in a wide variety of feed ingredients including ones with high contaminations in heavy metals, pesticides, viruses, bacteria etc. At the same time, ideal environmental conditions (warm temperatures and high air humidity) to rear the BSF may attract unwanted animals: other species of insects such as the housefly (Musca domestica) or the fruit fly (Drosophila melanogaster), but also, nematodes, mites, etc. These pests can compete on the feed source through rapid colonization thanks to short lifecycles and fast consumption of the substrate. They also introduce sanitary risks as they may carry pathogens which present a real danger to the entire colony but also for the staff rearing insects in industrial settings. An important knowledge gap remains on these potential pests, pathogens and parasites of the egg, larvae, pupae and adult stages of the BSF. This presentation shares our experience with a mite invasion our BSF colony suffered during summer 2019. Mites are tiny arthropods, barely visible without magnification, which belong to the class Arachnida and subclass Acari. They are potent threats to honeybees and to other wild fly colonies with Varroa destructor species as a well-known example. Harmless mites are also frequently found in cereal by-products stocks, common ingredients used in insect feed. We will detail the different steps that allowed us to identify mites in our facility, determine their specie and their provenance. After discovering a mite population in our BSF larvae growing boxes and on our adult flies, we evaluated their harmful nature and contacted researchers specialized in arthropods to identify and understand our aggressor. Furthermore, we investigated to what extent every BSF life stage was impacted by the mites. We performed on quarantined boxes and cages different experiments with potential inhibiting strategies such as oxalic acid exposure, zeolite spreading, feed heat treatments and frass sorting. We describe how we evaluated operational impacts and associated risks for our colony and how to control them up to complete eradication of the pest without stopping production. This is an opportunity to discuss our approach to this crisis, to give some guidance on operations and bio-security best practices and to share preventive measures. The need for more research and collaborations on this strategic matter for the future of insect farming is also hereby highlighted.

Black soldier fly (Hermetia illucens) larvae (BSFL) are capable of digesting a broad range of substrates and to convert them into protein-rich biomass. Differences in the nutritional composition of feeding substrates may result in differences in gut microbial profiles in the larvae, during the rearing cycle as well as at the end of the whole cycle. Moreover, depending on the insect developmental stage and the region of the gut, differences in microbial profiles may occur. General insight in these aspects may help to optimise the growth of larvae. When BSFL are reared to serve as ingredient in animal feeds, the highest added value can be generated by using low-quality (industrial) side streams as substrates, such as dried distillers grains with solubles (DDGS) and organic kitchen waste (swill). Therefore, the aim of this study was to rear BSFL on DDGS and swill, and monitor their microbiota in function of larval development and gut regions. Moreover, the growth rate of the larvae was compared with their performance on commercial chicken feed as control. During and after rearing, samples of the substrate, larvae, and residue were taken to monitor their bacterial biota. Four different gut regions were isolated from last instar larvae: the anterior, middle and posterior midgut, and the hindgut. The bacterial composition in the different gut districts for the three substrates are now being determined to study the community in each region and their similarity with the whole larvae. Also the bacteria in the substrates and in the residues will be determined to identify correlations. Illumina MiSeq sequencing targeting the 16S rRNA genes within the total DNA from the sample is currently being performed. This technology only provides relative abundances of bacterial genera present in the samples. Therefore, in addition quantitative real-time PCR (qPCR) is being performed, as this allows to transform relative into absolute abundances, giving a more realistic view on the bacterial community. As to growth performance, the weight gain of the BSFL was very comparable when reared on DDGS or chicken feed. After 14 days of rearing, the larvae reached a maximum weight of approximately 300 mg. Larvae reared on swill clearly grew slower and their weight did not exceed 200 mg, even after 21 days of rearing.

In sub-Saharan Africa, urban populations are projected to increase by 115% in the coming 15 years. In addition, economic growth and dietary shifts towards animal source foods have put high pressure and demand on agricultural production. The high ecological footprint of meat and dairy production, as well as high feed costs, prevent the livestock sector from meeting the increasing demand in a sustainable manner. Insects such as the black soldier fly (BSF) have been identified as potential alternatives to the conventionally used protein sources in livestock feed due to their rich nutrient content and the fact that they can be reared on organic side streams. Substrates derived from organic byproducts are suitable for industrial large-scale production of insect meal. Although efficient in waste management and in feed production, BSF larvae are very sensitive to the external environment such as temperature and rearing medium. Therefore, we studied the effect of temperature and substrate type, i.e., brewers’ spent grain (SG) and cow dung (CD), on the development and survival of BSF larvae. Both organic substrates were readily available in Nairobi, Kenya, the location of the experiments. In our experiment, 100 3–5-day-old BSF larvae were placed into containers that contained either SG or CD and further treated at temperatures of 15 °C, 20 °C, 25 °C, 30 °C, and 35 °C. The duration of larval development was recorded, and the prepupae were removed, weighed, and placed individually in separate, labeled, 35-mL plastic cups filled with moist sawdust. After emergence, 10 2-day-old adults (5 males and 5 females) from every replica per substrate were transferred into a cage (40 × 40 × 40 cm) and allowed to mate for 24 h at their respective temperatures. The laid egg batches were collected and counted, and the adult flies’ longevity was recorded. The data were subjected to a two-way analysis of variance (ANOVA) using the general linear model procedure. BSF larvae reared on SG developed faster than those reared on CD; the former also favored higher temperatures for their larval development and emergence into adults. The optimum range was 25–30 °C. With increasing temperatures, the longevity of adult BSF decreased, while the fecundity of females increased. Thus, it is possible to take advantage of the readily available SG waste streams in the urban environments of Kenya to produce BSF larvae-derived livestock feed within a short duration of time and at relatively high temperatures.

The type of waste that larvae feed on can impact their development time, performance and total biomass. This study investigated the effects of mixtures of chicken manure with fruit and vegetable pre-consumer waste on BSF larval development and bioconversion. As the proportion of chicken manure increased, individual larvae reduced in size while total development time increased. Bioconversion efficiency and total biomass produced decreased dramatically when chicken manure was greater than 40%. However, total chicken manure in the mixture did not impact survival of the larvae or waste reduction. Initial temperature and pH of the mixture during seeding also had a significant effect on larval development, survival, biomass production and waste reduction.

Black soldier fly larvae (BSFL) are known to dramatically alter the microbial community of their substrates. We hypothesized that recycling of the residue into the substrate, or inoculating the native substrate microbial community with concentrated, residue-derived microorganisms, would enhance BSFL bioconversion efficiency. The addition of the residue or residue-derived microbial communities decreased the BSFL bioconversion efficiency for tomato pomace and had no effect on the bioconversion of white wine pomace. Reasons for discrepancies between these results and previous studies include differences in substrate and inoculant microbial community composition. Larval gut and residue microbial community composition is being determined with DNA-based sequencing.