Sugar feeding by coccinellids under field conditions: the effects of sugar sprays in soybean

Sucrose was applied weekly throughout the growing season at three US locations (South Dakota SD], Maryland MD], and Kentucky 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.