Preliminary research on cereal leaf beetle economic thresholds in maturing spring wheat 2006

Abstract

Cereal Leaf Beetle larvae (Oulema melanoplus (L)) appeared in leaf damaging numbers by June 1, 2006 in each of 2 spring wheat trials. Both trials were rated for CLB larvae per cent per M2 at boot stage on June 15, 2006. Flag leaf loss was calculated in terms of per cent destruction of leaf surface on July 1. In an effort to estimate wheat flag leaf per cent surface lost by cereal leaf beetle larval feeding, flag leaves were sampled from a 1/4 meter square area in each of 4 replicates per treatment. Length of flag leaf was measured in centimeters for each replicate and means were produced statistically by AOV. Levels of flag leaf per cent losses were broken out for each treatment, with percentages in 5 % differences. The tables show increased length in flag leaf and reduced flag leaf damage above 15% by some of the insecticide seed treatment. Effect on flag leaf reduction by mechanical means could relate to flag leaf damage and wheat yield from CLB feeding. The need for a mechanical damage experiment is obvious. From the data tables seed treatment insecticide treatments do affect flag leaf damage and flag leaf length. As a bi-product of the research, a field insectary was established on the trial site to protect the T. julius parasitoid wasp present in ca. 50% of the larvae collected by Terry Miller, WSU Insectary Manager.