Browsing by Subject "Austriebsstörungen"

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Untersuchungen zur Bedeutung und Lebensweise phytophager Thripse (Insecta, Thysanoptera) als Verursacher von Austriebsstörungen an Reben als Grundlage zur Entwicklung umweltschonender Bekämpfungskonzepte
(2006) Wipfler, Rosi; Zebitz, Claus P. W.
Aim of this study was to gain basic knowledge of the biology of thrips pest species on grapevine. The results should provide the basics to develop environmentally compatible protection strategies. From 2002 to 2004, a monitoring of thrips infested vineyards was done in the vine growing region Palatinate. Thrips population dynamics and level of infestation were investigated in different newly planted vineyards and nurseries, as well as the damage caused by thrips. To answer the question, how and where thrips hibernate in vineyards, different collection techniques were tested to detect thrips in the soil and underneath the bark of vines. During the vegetation period, the flight activity of thrips was monitored in different vineyards and nurseries. Thrips species of vineyards, surrounding crops and shrubberies were compared to reveal possible ways of infestation by thrips on grapevine. Different insecticides were tested to control adult thrips and larvae in the field. Considering the collected thrips species, most striking result was the dominant abundance of the onion thrips, Thrips tabaci Lindeman, which caused most of the damage. The expected grapvine thrips Drepanothrips reuteri Uzel was of minor importance. Preferences for different grapevine varieties could not be found. Infestation mainly appeared in nurseries and newly planted vineyards. 30 different thrips species could be detected on grapevine. The results on level of infestation and phenology corresponded mostly with the literature data on D. reuteri. In the investigated vineyards, infestation was only detected in spring. In three years of investigation, infestation rates decreased from the middle of June onwards. The reason was mainly a migration of the polyphagous T. tabaci to other host plants. The detailed description and documentation of thrips infestation symptoms resulted in additions to already known symptoms. It was also possible to make further differentiations to infestation symptoms not caused by thrips. During the investigations it could be proved that different thrips species overwinter underneath the bark of vines and in the soil of vineyards. Therefore, thrips can rapidly infest vines in the following spring. Field experiments with yellow water traps showed that airborne adult thrips and thrips that actively migrate from surrounding crops are of major importance for the infestation of grapevines. Nurseries showed an increased risk of infestation, because they are usually located outside the grapevine areas and are surrounded by other crops. In this study it was not possible to gain any hint that thrips are transferred by grafted vine cuttings. The influence of shrubberies on thrips species in vineyards was of minor importance but needs further studying. It would also be of interest to investigate the influence of different culture techniques on the level of infestation and the phenology of thrips in vineyards. The insecticidal compounds spinosad, abamectin and imidacloprid proved to be effective to control thrips in the field. For newly planted vineyards, two treatments are recommended in spring: first against adult thrips at the beginning of May, and the second against the hatched larvae 14 to 21 days later. Treatment is necessary at levels of infestation of more than one thrips per shoot at the grapevine developmental stage BBCH 09 to 13, and with more than one thrips per leave at BBCH 14 to 17, respectively. Preventive treatment is recommended 1. for newly planted nurseries, if there is an increased risk of infestation because of surrounding crops with detected thrips infestation, and 2. at the beginning of budding for newly planted vineyards and one year old vineyards, especially if there was thrips infestation in the previous year and if predatory mites are absent. Control experiments in the laboratory could not be done, because it was not possible to establish a thrips colony to supply enough thrips material. The results of this study contributed to the approval of the compounds imidacloprid and abamectin for minor uses to control thrips on grapevine in 2006.