Determination of mechanisms of host plant resistance to the Banks grass mite Oligonychus pratensis (Banks) (Acari: Tetranychidae) in selected maize inbreds

Abstract

Maize lines selected for resistance to the Banks Grass Mite were tested to determine which mechanisms of resistance were being expressed: Antibiosis, Nonpreference, or Tolerance. Inbred 3 and, to a lesser degree Inbred 2, expressed antibiosis when compared with Mo17, the susceptible check. None of the resistant inbreds expressed nonpreference when compared with Mo17 and no conclusive evidence was determined about expression of tolerance. Useful estimates of r[] values, the intrinsic rate of increase, could be calculated from data collected over a shortened period of time. Differences in r[] values calculated with and without the Jackknife method were so small as to negate the usefulness of the Jackknife method. The Wyatt and White method for calculating r[] values did not provide good estimates of r[] values for mites on resistant plants, especially when juvenile mortality was high. Greenhouse grown plants did not provide a satisfactory substitute for held grown plants.