Title: Potential utilization of Spirulina microalga as a dietary supplement for the ladybird beetle Coleomegilla maculata Authors
Submitted to: Trends in Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 26, 2014
Publication Date: N/A
Interpretive Summary: We are exploring the potential of using native, generalist predators to suppress pest populations in high tunnels, greenhouses, plantscapes and crop fields. We are currently studying ladybird beetles as predators of spider mites, aphids and lepidopteran eggs and developing techniques to rear them at a lower cost using artificial foods and diets. We designed experiments to determine if a cyanobacteria microalga, Spirulina pratensis, could supplement and improve the quality of suboptimal diets for the omnivorous ladybird beetle Coleomegilla maculata. S. platensis is known for its high protein and vitamin content. Elemental analysis revealed that S. platensis had a higher nitrogen content (a measure of crude protein) than the suboptimal diets. Contrary to expectation, S. pratensis was not an effective nutritional supplement to the suboptimal diets. Moderate to high concentrations of S. platensis in the diets tended to have detrimental effects on C. maculata health. This new knowledge informs us that Spirulina does not boost the nutritional value of suboptimal foods.
Technical Abstract: A hindrance to wider adoption of augmentative biological control is the high cost of mass producing natural enemies, such as predatory insects. Cost reduction could occur by mass rearing predators on alternative foods and artificial diets rather than maintaining live prey and host plants. Many of the experimental foods and diets tested thus far are suboptimal, in comparison to optimal prey, and cannot serve as a standalone food source. In this study, we tested the hypothesis that Spirulina platensis (Cyanophyceae: Phormidiaceae), a protein- and vitamin-rich cyanobacteria microalga, could serve as a supplement to suboptimal diets for the omnivorous, ladybird beetle Coleomegilla maculata (Coleoptera: Coccinellidae). We conducted feeding bioassays to determine the effects of adding S. platensis powder to suboptimal food - synthetic pollen (Feedbee®) and a prototype artificial diet (based on vertebrate protein). We also determined the nitrogen, hydrogen and carbon content in dried samples of experimental foods. We discovered that S. platensis supplementation had little or no beneficial effect on increasing the quality of the synthetic pollen or the artificial diet. The higher nitrogen content (a measure of crude protein) of S. platensis, in comparison to synthetic pollen, artificial diet or Ephestia kuehniella (Lepidoptera: Pyralidae) eggs, did not mirror its usefulness as a supplement in either suboptimal food. S. platensis had detrimental effects on the health of C. maculata when used at moderate to high concentrations in this study. From this study, we surmise that a high protein content in food (as in Spirulina) does not necessarily ensure adequate development and reproduction in C. maculata.