The purpose of this study was to analyze the relationship between light intensity, cannabis (Cannabis sativa L.) yields, and profitability. We also look for evidence that spectrum differences across broad-spectrum horticulture lights and general-purpose LEDs affect the relationship between yield and light intensity. Finally, we discuss the financial return of increasing light intensity in order to increase yields. We found that yields increase linearly with light intensity up to at least 1500 µmol m -2 s -1 , which is at least twice the intensity that is most commonly used by cannabis growers. That relationship did not appear to be influenced by spectrum quality differences among the lamps included in the study. Finally, for all the intensity ranges that we considered, the value of the gain in yields from increasing light intensity far exceeded the cost of using more electricity.

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Cannabis (Cannabis sativa L.; Rosales: Cannabaceae) is a newly legalized crop and requires deeper insights on its pest communities. In this preliminary study, we identified a thrips species affecting indoor-grown cannabis in Canada and tested its impact on plant yield. We used three levels of initial infestation (zero, one, and five thrips) on individual plants grown in two growing mediums: conventional substrate or substrate containing the biostimulant Bacillus pumilus Meyer and Gottheil (Bacillales: Bacillaceae). We found that the onion thrips, Thrips tabaci (Lindeman) (Thysanoptera: Thripidae), is proliferating in indoor-grown cannabis. Furthermore, our results showed that fresh yields were higher for the plants that initially received zero thrips compared to those that initially received five thrips. Moreover, the biostimulant only marginally helped reduce the impact of thrips. We highlight the importance for growers to carefully monitor thrips infestations in indoor-grown cannabis. Finally, we emphasize the need for more research related to the impact of pests on cannabis yields and safe means of pest control for this strictly regulated crop.