Observations on Spider Mite Damage Caused by Flareback from the Use of Systemic Insecticides, 1996

Abstract

Abstract Plots were established on 22 May 1996 at the W.D. Holley Plant Environmental Research Center located on the campus of Colorado State University, Ft Collins, CO. Individual experimental units consisted of 5 plants placed in short rows. Plot design was a CRD with 6 replications. Plots were treated oi separate dates for each treatment: 3 Jun for Marathon, 11 Jun for Disyston and 6 Jul for Admire. Soil drench plots were treated with approximately 0.34 L of total solution per plot. All treatments were watered immediately after application. Plots received irrigation in the form of overhead watering for ap proximately two months after initial treatments were applied. After this time, plots were watered throughout the remainder of the experiment by hand wa tering the plants from underneath. Plots were sampled on three different dates in September for the presence of spider mite damage. A visual estimate of the percentage of leaves per plot killed due to spider mite damage was recorded on each date. Symptoms of the phytoplasma disease aster yellows were also present at a low rate in the experimental plots, but did not confound the visual damage estimates. The plots were also sampled for the number of spi der mites present per plot on two different dates in September, 1996. Five leaves from each plot were bagged and returned to the laboratory for further pro cessing. At the laboratory, the leaves collected from each plot were passed through a mite-brushing machine and mites were collected in a 20mm X lOOmn petri dish. The petri dishes were freshly treated with hairspray to affix collected mites. The petri dishes were then frozen until required for counting mites at 40 X normal magnification under a dissecting scope with a gridded paper template underneath the dish.