184 Percival and Banks: Water-retaining Polymer and Fungicide Combinations Guignardia Leaf Blotch Severity Guignardia leaf blotch severity was assessed visually in Sep- tember 2007, 2008, and 2009. Each tree was rated on a 0 to 5 rating scale, using a visual indexing technique and ratings on the scale: 0 = no leaf blotch observed; 1 = less than 5% of leaves affected and no aesthetic impact; 2 = 5%–20% of leaves affected with some yellowing but little or no defolia- tion; 3 = 21%–50% of leaves affected, significant defoliation (30%–50%) and/or leaf yellowing; 4 = 51%–80% of leaves af- fected, severe foliar discoloration and defoliation (51%–90%); 5 = 81%–100% of foliage affected with 91%–100% defoliation. The individual ratings for each tree in each treatment were used as a Guignardia leaf blotch severity index for statistical analysis. Mean Guignardia leaf blotch severity values for treat- ments were transformed using the arcsine–1 transforma- tion. All data were analyzed using ANOVA after checks for homoscedasticity were met using an Anderson- Darling test and the differences between means were separated by the Least Significance Difference (LSD) at the 95% confidence level (P = 0.05) using the Genstat for Windows 14th Edition program. Back transformed Guignardia leaf blotch severity values are presented here to ease interpretation of data (Blaedow et al. 2006). RESULTS Damaging outbreaks of Guignardia leaf blotch were recorded on control trees in both the 2007 and 2008 trials as indi cated by leaf blotch severity ratings of 4.6 on leaves of horsechestnut at the cessation of each growing season, respectively (Table 1; Table 2). None of the treated or control trees died as a result of leaf blotch attack during the course of the study, and none of the fungicide and water-retaining polymer combinations evalu- ated was phytotoxic to the test trees (data not shown). Efficacy as leaf blotch protectant compounds was demonstrated when fungicides were incorporated into a water-retaining polymer over the first growing season—i.e., observed pathogen severity was, in all cases, significantly lower (P < 0.05) compared to water dipped controls. In these cases, leaf blotch severity was reduced by 46%–65% (2007 growing season) and by 41%–67% (2008 growing season), respectively. Significant reductions in leaf blotch severity were mirrored by significant increases in leaf chlorophyll fluorescence as a measure of leaf photosyn- thetic activity (20%–29%, 2007 growing season; 32%–43%, 2008 growing season) and leaf chlorophyll content SPAD val- ues (40%–91%, 2007 growing season; 25%–58%, 2008 grow- ing season); (Table 3; Table 4; Table 5; Table 6). There were little differences in the magnitude of efficacy between fungi- cides and concentration applied where leaf blotch severity, leaf chlorophyll fluorescence, and leaf chlorophyll content were sta- tistically similar between treatments in both the 2007 and 2008 studies (Table 3; Table 4; Table 5; Table 6). Limited efficacy of any of the fungicide and water-retaining polymer combina- tions as leaf blotch protectant compounds was demonstrated the following year after application. In most cases, observed leaf blotch severity, leaf chlorophyll fluorescence Fv/Fm values, and leaf chlorophyll content were statistically comparable to water- treated controls. This indicates a fungicide and water-retaining polymer combination applied as a root dip at the time of plant- ing provides one growing season's protection. Application of ©2013 International Society of Arboriculture a water-retaining polymer root dip alone (i.e., no fungicide) had no effect on reducing leaf blotch severity at the cessation of both the 2007 and 2008 study. In all cases, observed leaf blotch severity, leaf chlorophyll fluorescence Fv/Fm values, and leaf chlorophyll content were statistically comparable to water-treated controls. Based on visual observation of leaf blotch severity, the greatest protection in both the 2007 and 2008 trials was provided by the synthetic fungicide penconazole applied as a foliar spray four times during the growing season. In both the 2007 and 2008 studies, leaf blotch severity was reduced by 100% (Table 1; Table 2). In addition, the highest chlorophyll fluorescence Fv/Fm and SPAD values as measures of leaf photo- synthetic activity and chlorophyll content respectively were recorded in penconazole foliar spray treated trees compared to water-treated controls and fungicide and water-retaining Table 2. The influence of water-retaining polymer (WRP) and fungicide combinations applied at the time of plant- ing for the control of Guignardia leaf blotch on leaves of horsechestnut (Aesculus hippocastanum L.) as measured by observed pathogen severity. Treatment Water (control) WRP WRP + Penconazole (0.15 g) WRP + Penconazole (0.30 g) WRP + Thiabendazole (0.15 g) WRP + Thiabendazole (0.30 g) WRP + Propiconazole (0.15 g) WRP + Propiconazole (0.30 g) WRP + Myclobutanil (0.15 g) WRP + Myclobutanil (0.30 g) WRP + Epoxiconazole (0.15 g) WRP + Epoxiconazole (0.30 g) WRP + Potassium Phosphite (0.15 g) WRP + Potassium Phosphite (0.30 g) Penconazole (spray) Leaf blotch severity 2008 4.6a 4.5a 2.5bc 2.2bc 1.8bc 2.0bc 1.8bc 1.7bc 1.5c 2.1bc 2.5bc 1.6bc 2.4bc 2.7b 0.0d 2009 4.1a 4.0a 4.3a 4.4a 4.2a 4.1a 4.4a 4.7a 4.0a 4.5a 4.9a 4.3a 4.7a 4.1a 4.2a Note: All values mean of ten trees. Also, lowercase letters indicate significant differences between means for each evaluation date (P = 0.05). Table 3. The influence of water-retaining polymer (WRP) and fungicide combinations applied at the time of plant- ing for the control of Guignardia leaf blotch on leaves of horsechestnut (Aesculus hippocastanum L.) as measured by leaf chlorophyll fluorescence Fv/Fm values. Treatment Water (control) WRP WRP + Penconazole (0.15 g) WRP + Penconazole (0.30 g) WRP + Thiabendazole (0.15 g) WRP + Thiabendazole (0.30 g) WRP + Propiconazole (0.15 g) WRP + Propiconazole (0.30 g) WRP + Myclobutanil (0.15 g) WRP + Myclobutanil (0.30 g) WRP + Epoxiconazole (0.15 g) WRP + Epoxiconazole (0.30 g) WRP + Potassium Phosphite (0.15 g) WRP + Potassium Phosphite (0.30 g) Penconazole (spray) Fv/Fm 2007 0.557a 0.569ab 0.669ac 0.721c 0.661abc 0.659abc 0.709bc 0.700abc 0.684abc 0.692abc 0.727c 0.714bc 0.667abc 0.688abc 0.807c 2008 0.506a 0.511a 0.497a 0.488a 0.522a 0.481a 0.505a 0.526a 0.501a 0.482a 0.490a 0.513a 0.518a 0.511a 0.516a Note: All values mean of ten trees. Also, lowercase letters indicate significant differences between means for each evaluation date (P = 0.05).
July 2013
| 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
