Sugar preferences of western corn rootworm larvae in a feeding stimulant blend

Feeding behaviour, feeding intensity and staying behaviour of neonate western corn rootworm larvae (Diabrotica virgifera virgifera LeConte) were evaluated in response to synthetic feeding stimulant blends to determine larval preferences among the three maize root sugars (glucose, fructose and sucrose) in the active blend and to determine whether any single sugar can substitute for the 3-sugar combination in a feeding stimulant blend. These experiments demonstrated the strong affinity that western corn rootworm larvae have for the natural sugars found in maize roots and also showed that sucrose is the most preferred of the three primary maize root sugars. The blend containing sucrose at 30mg/ml elicited feeding that was not significantly different than the natural glucose:fructose:sucrose blend. In subtraction bioassays, removal of sucrose from the blend resulted in significantly fewer larvae feeding. When the three-sugar blend was substituted with one of the number of various mono-, di- or trisaccharides, fewer larvae fed on all of the treatments compared to the blend with sucrose, except for the blend with maltose. In feeding choice tests, larvae preferred a blend containing sucrose over blends with either glucose or fructose, but larvae chose equally between a blend with sucrose and a blend containing the three-sugar mixture found in maize roots. Based on these results, a feeding stimulant blend with glucose (30mg/ml), fructose (4mg/ml) and sucrose (4mg/ml) elicits the strongest feeding response, but sucrose alone, in amounts equivalent to the total maize root sugar concentration (30mg/ml), could serve as a substitute for the 3-sugar mixture in a synthetic feeding stimulant blend.