Effects of Temperature and Density on House Cricket Survival and Growth and on the Prevalence of Acheta Domesticus Densovirus

SIMPLE SUMMARY: The growing world population demands an increase in food supply. Mass-rearing of insects can contribute to food production and recycling of nutrients. One of the insects that has a high potential as an alternative source of protein and other nutrients is the house cricket. However, cricket production faces various disease challenges, such as the Acheta domesticus densovirus (AdDV). This virus can cause high mortality in cricket colonies, and the triggers of virus outbreaks are not yet understood. Rearing crickets at lower densities and an optimal temperature may prevent viral disease outbreaks, but no studies examined the correlation between viral abundance and rearing densities and/or temperature. Therefore, this study examined the effect of different temperatures and rearing densities on cricket mortality and biomass and on the abundance of AdDV. In total, nine combinations of temperature (25, 30, 35 °C) and density (10, 20, 40 crickets) were tested. Higher rearing densities and temperatures resulted in higher total biomass produced per rearing unit and a minor impact on mortality. The results indicate that high rearing density can increase AdDV abundance, and that viral abundance is reduced at 35 °C. ABSTRACT: The house cricket, Acheta domesticus, is a commonly reared insect for food and feed purposes. In 1977, a report described a colony collapse, which was caused by the single-stranded DNA virus Acheta domesticus densovirus (AdDV). Currently, there are no confirmed A. domesticus colonies free of AdDV, and viral disease outbreaks are a continuous threat to A. domesticus mass rearing. Correlations between cricket rearing density or temperature and AdDV abundance have been hypothesized, but experimental evidence is lacking. Optimised rearing conditions, including temperature and density, are key to cost-effective cricket production. In this study, house crickets were subjected to different combinations of rearing density (10, 20, 40 crickets per box) and temperature (25, 30, 35 °C) to study the effect on cricket survival, biomass, and AdDV abundance. Rearing temperature affected had a minor effect on survival, which ranged between 80 and 83%. Total cricket biomass increased with higher temperatures and higher densities. Viral abundance in crickets at the end of the rearing period was variable; however, high rearing density seemed to result in higher AdDV abundance. At 35 °C, a temperature considered suboptimal for house cricket production, viral abundance tended to be lower than at 25 or 30 °C.