New Zealand Journal of Ecology (2004) 28(2): 283-288

A simple gravimetric technique for estimating honeydew or nectar production

Short Communication
Roger J. Dungan 1
Jacqueline R. Beggs 2,3
David A. Wardle 4,5
  1. School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
  2. Landcare Research, Private Bag 6, Nelson, New Zealand
  3. Current address: School of Biological Sciences, University of Auckland, Private Bag 92 019, Auckland, New Zealand
  4. Department of Forest Vegetation Ecology, Swedish University of Agricultural Sciences, SE901 83, Umeå, Sweden
  5. Landcare Research, P.O. Box 69, Lincoln 8152, New Zealand

We describe a simple gravimetric technique for measuring the standing crop or production of carbohydrate-rich solutions such as honeydew or nectar. Simulated honeydew was sampled by absorbing droplets of solutions of known concentration and volume with dried and weighed pieces of filter paper. The change in mass of the paper after redrying provides an estimate of the total solution carbohydrates. This method was compared with a widely-used technique, whereby the volume and concentration of droplets is measured with microcapillary tubes and a sugar refractometer. A factor was derived to convert gravimetric refractometer readings (g sucrose 100 g-1 solution) to volumetric carbohydrate concentration (g carbohydrate 100 ml-1 solution) for the simulated honeydew solutions. There was no difference in the ratio of measured-to-expected carbohydrate mass between the two techniques, showing that the quick, easy, and accurate filter-paper method is appropriate for measuring carbohydrate-rich solutions.