194 Noack et al.: Efficacy of Imidacloprid in the Control of T. peregrinus maintained adequate control for at least two years (Figure 1). The initial sample established baseline populations for all treatments and confirmed there was no difference between any of the treatments at the beginning of the experiment. This sample was taken three days after administration of the imidacloprid and it would be unlikely the chemical would have been trans- located throughout the tree in that time. However, by the next sampling date, one month post-treatment, there was a significant decline in the T. peregrinus populations on all treated trees. The mean numbers of insects sampled on low and mid concentra- tion treatments were statistically less than those of the untreated trees. Trees treated with the high concentration, however, were not; but nonetheless their number had reduced considerably. By the third month, all treatments had significantly fewer insects than untreated trees and further, there was no difference in the control afforded by the different concentrations of imidacloprid. This trend was maintained for almost two years until Septem- ber 2006. Sampling at this time indicated the efficacy of low concentration application had diminished. By the final sample, September of the following year, there was no significant differ- ence between treatments and control. Although the trees were not surveyed between September 2006 and 2007, it is likely the control afforded by the high concentration application was im- pacting on T. peregrinus as their numbers were half that of any other group. Additionally, trees were visually monitored during this time and, although control and trees treated with the lower concentration of chemical displayed the characteristic reddening of the canopy, the trees in the high concentration group did not. The longevity of control attained in this experiment is comparable with the work of Frank et al. (2007) and Szc- zepanic and Raupp (2007) who established that soil ap- plication of imidacloprid provided at least two years pro- tection from Japanese beetles on little-leaf linden trees and hawthorn lace bugs on cotoneasters respectively. While this study’s results concur with the work of Cowles et al. (2006) in the longevity of control the chemical imidacloprid de- livered, they conflict in the efficacy of the chemical delivery sys- tem. Investigating the efficacy of imidacloprid in controlling the hemlock woolly adelgid on hemlock trees these workers addition- ally compared the efficiencies of delivery method and found that, while the soil application of imidacloprid controlled these insects for two years, trunk injection of the chemical was ineffectual. Cowles et al. (2006) compared the efficacy of three trunk in- jection protocols and three soil drench methods in controlling adelgids and analyzed imidacloprid residues in tree tissues from all treatments. In their own words the “precise relationship be- tween residues and efficacy are elusive.” This is demonstrated in an assay which determined concentration of imidacloprid in tissues from trunk injected trees was similar to that of the soil drench group, yet the control afforded by the former was ineffec- tual; and in another they found chemical residues in the tissues of trunk injected trees higher than the untreated which in turn was higher than the soil drench residues. Cowles et al. (2006) suggest possible reasons for the poor performance of trunk in- jection methods; there may have been an interaction between the hemlock sap and the injected formulation of imidacloprid which resulted in the active ingredient being precipitated out of the formulation by dilution of the solvent with sap or the chemi- cal may have been unevenly translocated throughout the canopy. Few investigations have been conducted on the control of insect pests by imidacloprid on eucalypt trees. This study’s re- sults compare favorably with those of Young (2002) who mi- croinjected eucalypts with imidacloprid [3 ml of 10% (AI) per 5 cm (2 in) of trunk diameter] to control red gum lerp psyllid. In his study imidacloprid treated trees showed a significant re- duction of psyllids for eight months. However, by the end of the experiment at 15 months, large variation in the control afforded by the treatment occurred between the trees. This worker ob- served that some trees had longer residual activity than others, and indicated several factors such as tree health, age, crown, and root structure may influence material uptake and distribution. The results suggest a constant and even translocation of chem- ical throughout the treated trees as standard errors (variation) were small within all treatment groups. In this trial the longev- ity and efficacy of control afforded by imidacloprid can prob- ably be attributed to a combination of the insect’s susceptibility to the chemical, and to the use of multiple injection sites which ensured an even distribution of chemical throughout the tree. CONCLUSION Trees treated with imidacloprid [SilvaShield SL, 20% (AI)] showed a significant reduction in populations of T. peregri- nus when compared to untreated trees. The study authors sug- gest microinjection of this chemical at a rate of 3 to 5 ml/10 cm (0.10 to 0.17 fl.oz/4 in) of dbh effectively controlled T. peregri- nus for two to three years. SilvaShield has been recently regis- tered for the control of T. peregrinus on eucalypts in Australia. Acknowledgments. Bayer Environmental Science is acknowledged for supporting this project and the Christian Rowe Thornett Postgraduate Scholarship for supporting the first author. The authors thank Mark Mc- Caughtrie and the Sutherland Shire Council for supporting this research. Also, thanks to Mark McCaughtrie’s team for managing the traffic and keeping the authors safe. Geoff Eldridge, Sidewinder Tree Injectors, for injecting the trees. The residents of Waratah Street, Sutherland are thanked for their patience. LITERATURE CITED Ahern, R.G., S.D. Frank, and M.J. Raupp. 2005. Comparison of exclu- sion and imidacloprid for reduction of oviposition damage to young trees by periodical cicadas (Hemiptera: Cicadidae). Journal of Economic Entomology 98:2133–2136. Albajes, R., C. López, and X. Pons. 2003. Predatory fauna in cornfields and response to imidacloprid seed treatment. Journal of Economic Entomology 96:1805–1813. Bai, D., S.C.R. Lummis, W. Leicht, H. Breer, and D.B. Satelle. 1991. Actions of imidacloprid and related nitromethylene on cholinergic receptors of an identified insect motor neurone. Pesticide Science 33:197–204. Carpintero, D.L., and P.M. Dellapé. 2006. A new species of Thaumas- tocoris Kirkaldy from Argentina (Heteroptera: Thaumastocoridae: Thaumastocorinae). Zootaxa 1228:61–68. Cassis, G., R.T. Schuh, and H. Brailovsky. 1999. A review of Onymoco- ris (Heteroptera: Thaumastocoridae), with a new species, and notes on hosts and distributions of other thaumastocorid species. Acta Societatis Zoologicae Bohemoslovacae 63:19–36. ©2009 International Society of Arboriculture
July 2009
| Title Name |
Pages |
Delete |
Url |
| Empty |
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success. You will be contacted by Washington Gas with follow-up information regarding your request.
This process might take longer please wait
