Submitted to: Biocontrol
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2010
Publication Date: 5/27/2011
Citation: Seagraves, M., Kajita, Y., Weber, D.C., Obrycki, J., Lundgren, J.G. 2011. Sugar feeding by coccinellids under field conditions: the effects of sugar sprays in soybean. Biocontrol. 56:305-314. Interpretive Summary: Many predatory insects are best described as omnivores, and foods like sugar and pollen are important components of their diets. Lady beetles are no exception, and it is thought that they rely heavily on sugar resources in the field although no one has ever quantified their feeding. Here, we applied sugar sprays to soybeans, and quantified the frequency of sugar feeding using gut content analysis (a procedure called the anthrone test) of common agronomic lady beetles in South Dakota. We found that all lady beetles tested regularly consumed sugar in soybean fields, even when it wasn’t applied mechanically. Moreover, the sugar-sprayed plots had greater numbers of lady beetles than the untreated soybeans, although soybean aphid populations were similar in the two treatments. This research makes that case that sugar feeding is very important for lady beetle populations in cropland, and suggests one way to conserve these beneficial species within agroecosystems.
Technical Abstract: Sucrose was applied weekly throughout the growing season at three U.S. locations (SD, MD, and KY), and coccinellids and aphids (Aphis glycines Matsumura [Hemiptera: Aphididae]) were sampled 24 h later. Total coccinellid densities were 50-77% greater in sugar-sprayed soybean than in untreated plots. Coccinella septempuncata L., Hippodamia convergens Guérin-Méneville, and Harmonia axyridis Pallas were more abundant where sugar was applied. Coleomegilla maculata (DeGeer) was found in equally low numbers in all treatments. Aphid densities were similar in both treatments, and only reached economically threatening levels in SD. Coccinellids digested sugar meals within 1 h of consumption (measured using the cold anthrone test). Despite this narrow window of detection, field-collected coccinellids frequently tested positive for fructose. Under natural conditions, sugar is commonly ingested by coccinellids and sugar sprays increase coccinellid densities and their consumption of sugar. Sugar sprays did not enhance biological control of aphids in this experiment.