Arboriculture & Urban Forestry 36(5): September 2010 avoided by only sampling branches with live leaves. In late Oc- tober or early November, after leaf abscission, dead branches in control trees were avoided by scraping a patch of bark before cut- ting a branch to make sure it was alive. In some cases when it was not possible to find three live branches, only one or two branches were sampled. If no live branches were found then the tree was excluded from branch sampling and the number of replications was reduced accordingly. The first live branch found in the up- per one-third canopy with a diameter of 4–12 cm was removed, and the remaining two branches were chosen to be as far away as possible from the first branch, and from each other, to main- tain canopy balance. Bark splits and emergence holes were not considered in branch sampling. Branch samples were dropped to the ground where side branches and twigs were removed. The branches were bundled and labeled for transport to Michi- gan State University’s Entomology Field Research Farm in East Lansing for processing. When branches were processed, a 0.65 m-long section in the center of each branch was marked for scrap- ing. The circumference of each branch was recorded at both ends of the scraped area. Surface area of each branch sample was de- termined by averaging the circumference of both ends, and us- ing the formula for the surface area of a cylinder (L2πR). EAB galleries and larvae were counted after clamping branch sections between the ends of a modified saw-horse and removing the bark with a drawknife and chisel. Branch samples were processed in a heated shed at the Entomology Field Research Farm. Annual can- opy thinning and dieback ratings were made in July each year by comparing the canopy of each tree with photographs in various stages of decline from 0% (healthy) to 100% (dead) in 10% incre- ments (Smitley et al. 2008). Each tree was rated by two or three individuals and averaged across observations to obtain an annual defoliation rating. When study trees were rated at >90% canopy thinning and dieback in July, they were excluded from branch sampling, and the trees were removed by the city during the winter. Treatment means were compared at each test site using the general linear models procedure (PROC GLM) of SAS 9.1 (SAS 2003). Levene’s test was used as part of the GLM procedure to test for homogeneity of variance. Percent data were transformed to arcsine square root (x) before analysis. Means were separated at the P = 0.05 level using Tukey’s op- tion in the MEANS statement. This performs a Tukey’s stu- dentized range test (HSD) when group sizes are equal and a Tukey-Kramer test when group sizes are unequal (SAS 2003). Troy Site 2005–2006 Street trees in a neighborhood in the northern part of Troy, MI, were used for this test. These trees were between 12 and 26-years- old and ranged in size from 18–61 cm diameter at breast height (dbh). The mean dbh was 35.6 cm. Trees in this test were planted and maintained by the City of Troy. The trees were located be- tween the street and the sidewalk, and were spaced a minimum 15 m apart and in no case did they overlap. Tree trunks were measured and marked with a metal tag during the final two weeks of April 2005. Lawns in the neighborhood were well-maintained and received natural rainfall, but very few were irrigated. Trees were grouped into 10 blocks of six trees based on location in the neighborhood. Each treatment was replicated 10 times with each replicate consisting of an individual tree. The treatments at this site consisted of five rates (0.10, 0.20, 0.40, 0.48, and 0.60 207 g ai/2.54 cm dbh) of emamectin benzoate formulated by Arbor- jet, Inc. (Woburn, MA, U.S.) and Syngenta Crop Protection, Inc. (Greensboro, NC, U.S.) as a 4.0 % ME. All trees receiving an em- amectin treatment were trunk-injected on May 25, 2005 using the Arborjet Tree IV™ system. The formulated insecticide was diluted 1:1 with water and put into a bottle pressurized to 3.16 kg/cm2 be- fore being injected through four evenly spaced sites on the lower trunk of each test tree. All treated trees received a single trunk injection treatment on May 25, 2005, with the exception of trees receiving the 0.1 g ai/2.54 cm rate, which were injected again May 23, 2006, at the same rate. Control trees were not injected or treated with any insecticide. Canopy thinning and dieback ratings were made for each tree on June 27, 2005, and June 15, 2006, as previously described. Upper branches were sampled using a bucket truck in October 2005, and the bark scraped as described. East Lansing Site, 2005–2009 Green ash street trees in East Lansing, MI, between 14 and 28-years- old with a trunk diameter between 25 and 61 cm (mean = 35.6 cm) were maintained by the City of East Lansing. Trees were located between the street and the sidewalk in seven different neighbor- hoods and spaced a minimum of 15 m apart to prevent canopy overlap. Tree trunks were measured and marked with a metal tag during the first week of August 2005. Study trees were located in well-maintained lawns, but very few were irrigated. Treatments were replicated 10 times with individual tree replicates. A descrip- tion of each of the four treatments in this test follows, including the formulation, type of application, rate, and application date. (1) TREE-äge (emamectin benzoate, Syngenta Crop Protec- tion, Inc.) was applied once at 10 ml/2.54 cm dbh (0.4 g ai) on September 27, 2005. To apply using the Arborjet Tree IV system, emamectin benzoate was diluted 1:1 with water and the solution was placed into a single pressurized 3.16 kg/cm2 bottle connected to four injection needles. At four evenly-spaced distances around the trunk at a height of 20–40 cm above the ground, four holes were drilled into the sapwood and a plastic septum (Arborjet #4 plug) was inserted, through which needles were placed for injec- tion. (2) Emamectin benzoate was applied once in spring 2007 at 2.5 ml/2.54 cm (0.1 g ai) dbh. Trunk injections were made with the Arborjet QUIK-jet™ micro-injector. The number of in- jection sites was determined by the formula: trunk cm dbh/5.08. Undiluted emamectin benzoate was injected in equal amounts through plastic septa. A rate of 0.1 g ai/2.54 cm dbh was injected on May 21, 2007. (3) Emamectin benzoate was trunk injected in spring 2007 at 5 ml/2.54 cm dbh (0.2 g ai). Injections were made once on May 21, 2007 with the micro-injector as previ- ously described. One tree was dropped from the test after the first year because the homeowner applied an additional insecticide treatment. (4) Control treatment, these trees were not treated. Annually in early July, and as previously described, can- opy thinning and dieback ratings were made for each tree. When branch sampling was included, the branches were pruned from the upper one-third of the tree canopy between September 19 and 26, 2006, October 8 and 12, 2007, or No- vember 4 and 10, 2008. Branches were collected, the bark re- moved, and EAB larvae counted as previously described. ©2010 International Society of Arboriculture
September 2010
| Title Name |
Pages |
Delete |
Url |
| Empty |
Ai generated response may be inaccurate.
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.
Downloading PDF
Generating your PDF, please wait...
This process might take longer please wait
