Biological control of twospotted spider mites, Tetranychus urticae Koch (Acari: Tetranychidae), using Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseidae) on impatiens

The effectiveness of the predatory mite, Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae), as a suppressive agent of the twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), was evaluated on impatiens plants at predator:prey release ratios of 1:3 (high), 1:15 (medium) and 1:30 (low). Releases at each ratio were made at low and high initial T. urticae densities to determine if initial pest population size influenced the suppressive ability of the predator. After only one week, P. persimilis was reduced both the higher and lower T. urticae populations to negligible levels and kept damage to 5% or less, but only at the 1:3 ratio. At the medium predator:prey ratio, predators prevented spider mite numbers and damage from increasing, but did not reduce either. At the lowest ratio (1:30) spider mite populations and plant damage continued to increase. Both the medium and low ratios allowed unacceptably high levels of plant damage. A regression model indicated that a release ratio of 1:10 or higher should consistently reduce the pest population and associated damage to acceptable levels. However, if spider mites establish at high levels of infestation similar to those we tested experimentally, even releasing predators at a 1:3 ratio will not provide certain control. To reliably control damage from spider mites on impatiens, predators must be released as soon as spider mites are detected in order to reduce spider mite populations to non-detectable levels within one or two weeks of predator release

Computer acquisition and analysis of insect feeding monitor data

Electronic insect-feeding monitors are increasingly being used to study the feeding behavior of piercing-sucking insects in relation to host resistance and biotypes. The original AC design has been modified several times to simplify and expand the signal generator and signal processor. We report a method to improve the monitoring stage by using an MS-DOS computer to replace strip chart recorders. We present fragments of custom software in BASIC, C, and 8086 assembly language designed to simplify the collection and analysis of data. The analysis software allows a full range of operations to be performed on the data, including signal identification, frequency domain analysis, and filtering. We offer suggestions on integrating these fragments into customized software for different computer systems. An example using greenbugs, Schizaphis graminum (Rondani), on sorghums demonstrates that collection and analysis of feeding monitor data with the computer system is as accurate, faster, and less expensive than previously used systems