Effects of red versus white wheat bran on rate of growth and feeding of some stored-product beetles

Abstract

The red pigment in the seed coat of hard red spring wheat is produced by phenolics. Most of the wheats grown in western Canada are hard red spring varieties; however cultivars with a whiter seed coat are being developed for their better milling and baking attributes. Because phenolics serve to protect some plants against insect attack, we compared the susceptibility of white and red spring wheat to attack by stored-product insects. Tenebrio molitor (Tenebrionidae) larvae reared on red wheat bran gained less weight than larvae reared on white wheat bran but this insect has a long developmental period and does not attack sound grain. Tribolium castaneum (Tenebrionidae) pupal weights were not affected by the type of wheat milled products on which the larvae fed. A feeding bioassay showed that red bran did not act as an antifeedant for T. molitor, T. castaneum, or Sitophilus oryzae (Curculionidae). However, it acted as a feeding stimulant for Rhyzopertha dominica (Bostrichidae), which is related to wood-boring insects. It is unlikely that white wheat in storage would be more prone to insect damage than red wheat. Key words: Bran, colour, wheat, phenolics, stored-product insects