Access Restriction

Author Liu, Tong-Xian
Source CiteSeerX
Content type Text
File Format PDF
Subject Domain (in DDC) Computer science, information & general works ♦ Data processing & computer science
Subject Keyword Onion Plant ♦ Seasonal Population Dynamic ♦ Life Stage Composition Thrip Tabaci ♦ Thrip Density ♦ Insecticide Application ♦ Life Stage Composition ♦ Onion Thrip ♦ Important Insect Pest ♦ Field Population ♦ Several Specie ♦ Daily Rainfall ♦ Major Factor ♦ Total Predator ♦ Total Thrip ♦ Early April ♦ 76-85 Larva ♦ Thrip Population ♦ Tabaci Population ♦ South Texas ♦ Visual Count ♦ Lower Rio Grande Valley ♦ Insecticide-treated Onion Plant ♦ Significant Correlation ♦ 10-28 Adult ♦ Absolute Count ♦ Developmental Stage ♦ Early Infestation ♦ Abundant Predator Specie ♦ Early February ♦ Weather Condition ♦ Consecutive Season ♦ Economic Threshold ♦ Untreated Onion Plant ♦ Predaceous Natural Enemy Population ♦ Caused Temporary Reduction ♦ Population Dynamic ♦ Orius Insidiosus ♦ Late March ♦ First Present ♦ Thrip Tabaci Lindeman
Abstract Onion thrips, Thrips tabaci Lindeman, is the most important insect pest of onions in the Lower Rio Grande Valley (LRGV) of south Texas. The population dynamics and life stage composition of T. tabaci populations and the predaceous natural enemy populations on onions were determined in three consecutive seasons from 2000 to 2002. T. tabaci were first present on onion plants in early February, increased in numbers gradually, and peaked in abundance in late March and early April. Visual counts of field populations revealed ≈75 % of total thrips and at least 77 % of total predators by absolute counts. Developmental stages of T. tabaci on onion plants consisted of 76-85 % larvae, <0.1 % pupae, and 10-28 % adults. Although insecticide applications reduced thrips density, an average of 92 thrips was found on each onion plant over the season, which far exceeded the economic threshold. Several species of predators were found on onion plants. Orius insidiosus (Say) was the most abundant predator species, with 37.4-74.5% on onion plants, depending on the season and insecticide application. There were significant correlations between predators and thrips densities on untreated onion plants (r = 0.7327-0.8234), but there were no such correlations on insecticide-treated onion plants (r = 0.0536-0.4537). It appears that predators were not a major factor regulating thrips populations. Of the weather conditions, temperature affected only the early infestation in January and February; and a daily rainfall of 1.8 cm or more caused temporary reduction of thrips densities on onion plants.
Educational Role Student ♦ Teacher
Age Range above 22 year
Educational Use Research
Education Level UG and PG ♦ Career/Technical Study