WHEAT-BUG DAMAGE IN NEW-ZEALAND WHEATS - THE FEEDING MECHANISM OF NYSIUS-HUTTONI AND ITS EFFECT ON THE MORPHOLOGICAL AND PHYSIOLOGICAL DEVELOPMENT OF WHEAT

Adult Nysius huttoni White were placed in separate cages containing cultivars Rongotea and Karamu at the late anthesis, watery ripe and milky ripe stages of development. Between 84 and 99 % of the matured kernels were injured with the characteristic visible markings of bug‐damaged wheat. All the samples contained strong wheat‐bug proteinase activity as shown by the incubated SDS‐sedimentation test and the disappearance of HMW glutenin subunits from electrophoretograms. Grain infested at late anthesis was most severely affected with shrivelled kernels, high screenings, protein, free amino acids and α‐amylase, and low kernel weight, germination capacity and carbohydrate content. Grain infested at the watery ripe and milky ripe stages had values for the above properties closer to uninfested control wheat values. It was suggested that N huttoni sucked sap from lateral sieve tubes in the wheat ovary at late anthesis causing severe disruption to physiological development of the grain. Two commercial lines of wheat showed some characteristics of this effect. Copyright © 1990 John Wiley & Sons, Ltd