Trunk injection with imidacloprid for controlling the erythrina gall wasp, Quadrastichus erythrinae (Hymenoptera: Eulophidae)
Date Issued
2011
Date
2011
Author(s)
Wang, Ting-Shuo
Abstract
Coral tree (Erythrina) is one of drought-tolerant plants which commonly grown in tropical regions. In many areas, coral trees are planted as street trees or shade trees. In addition, there are many elder coral trees are also commemorative for residents in some rural neighborhoods. But the native coral tree species in Taiwan get serious damage since the invasion of a new galling arthropod pest, erythrina eulophid wasp (Quadrastichus erythrinae). So far this galling wasp has spread across Taiwan. The Q. erythrinae spends entire larva stage in the gall tissues, and this characteristic makes it become difficult to kill with traditional chemical control methods. Therefore, in this study, trunk injection method, which is commonly used for forestry pest control, was employed to inject imidacloprid into gall tissues directly. For quantifying the necessary insection into a tree, finding out the correlation between tree diameters and imidacloprid dosage is the priority task to investige. Experiment result of Q. erythrinae emerge rate shows significant difference between imidacloprid treated group and untreated one, but it shows no difference when tree diameter is larger than 20 cm until one year later. According to the preliminary result, the number of major branches as a standard to estimate the suitable imidacloprid dosage will be used for the application of trunk injection on elder trees. The quantity of imidacloprid is based on tree’s diameter (when every additional 5 cm diameter is increased in branches, then we will inject additional 5 ml imidacloiprid). And picture-monitoring results show that damage stage drop down significantly in one month after injection. The injecting pits were also healed four months later. High performance liquid chromatography analysis presents a unique transition mechanism that imidacloprid can transport to the upper layer and reach lethal dosage in just three weeks. Even though the imidacloprid dosage in leaves drops down in several weeks, the low concentration still can affect the growth of Q. erythrinae. This study does not only present an effect evaluation of trunk injection control method for controlling Q. erythrinae, but also provides an useful reference for controlling other galling phytophagous pests.
Subjects
Quadrastichus erythrinae
trunk injection
damage stage
Type
thesis
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