212 Mmbaga and Oliver: Effect of Biopesticides on Foliar Diseases and Japanese Beetle In addition to foliar diseases, Japanese beetle adults can heavily damage roses, oakleaf hydrangea, and crapemyrtle. Feeding damage by adult Japanese beetle reduces the aes- thetic value of landscape plants (Figures 1). Insecticides like bifenthrin, carbaryl, cyfluthrin, deltamethrin, and lambda- cyhalothrin are routinely used to protect plants from Japanese beetle feeding (TOR 2005). In addition to feeding damage, Japanese beetle is also an important regulatory pest that im- poses serious shipping restrictions on balled and burlapped (B&B) nursery stock, and insecticides are routinely used to prevent grub infestations. The purpose of this study was to evaluate selected biopesticides for controlling foliar diseases and Japanese beetle adult feeding damage on roses, oakleaf hydrangea, and crapemyrtle. MATERIALS AND METHODS Plant Material and Experimental Design Plants were purchased from commercial farms: bare-root hy- brid T rose (‘Ain’t She Sweet’) from Upland, California, U.S.; and B&B oakleaf hydrangea (native unnamed selection) and container-grown crapemyrtle (L. indica) from McMinn- ville, Tennessee, U.S. The dormant plants were held in a cold room at 4°C (39.2°F) until the end of April when they were planted in field plots at Tennessee State University, Otis L. Floyd Nursery Research Center, McMinnville, Tennessee. Planting was done in six rows consisting of plots of four plants (one oakleaf hydrangea, one rose, one crapemyrtle, and one Photinia spp.) spaced 1 m (3.3 ft) apart. Plot spacing within rows was 1.54 m (5.1 ft) and row spacing was 3.0 m (9.9 ft). A total of nine biopesticides, two conventional fun- gicides, and one insecticide were arranged in a randomized complete block design with each treatment replicated six times (Tables 1–5). Application rates used are presented in Tables 1–5. All plants were watered as needed by drip irri- gation. A controlled-release fertilizer 14N–14P–14K was ap- plied in early May at a rate of 50 g (1.8 oz) per plant. In addition to field plots, roses were also planted in 11.4 L (3 gal) plastic containers using bark, peat, and sand (3:1:1) potting mix and maintained outdoors under 50% shade or in a controlled greenhouse environment at 25°C±3°C (77°F± 37.4°F). All shadehouse and greenhouse plants were watered daily by drip irrigation. A controlled-release fertilizer 14N– 14P–14K was applied in early May at the rate of 50 g (1.8 oz) per container. The experiments were set up as a randomized complete block design with six replicates of individual plants per treatment. Treatments applied were similar to those pre- viously described under field plots (Tables 1 and 4). All treatments for disease control in field, shadehouse, and greenhouse trials were initiated in early May soon after the first disease symptoms were observed in a few plants. Crape- myrtle budbreak occurs later than in roses and hydrangea, and plants were not sprayed until first disease symptoms were ©2007 International Society of Arboriculture observed. When adult Japanese beetles were detected in traps starting early June, the insecticide Sevin SL (Bayer Envi- ronmental Sciences, Montvale, NJ) was added in a tank mix with the fungicide trifloxystrobin (Compass, Olympic Hor- ticultural Products Company, Mainland, PA) to control in- sects in field and shadehouse trials. All treatments were ap- plied at 10- to 14-day intervals and sprayed to run off using CO2 powered sprayers with a flat-fan nozzle at 12 psi pres- sure (R&D Sprayers, Appaloosas, MS). Treatments were ter- minated in October. Disease Evaluation and Insect Feeding Damage Foliar diseases developed naturally without artificial inocu- lations. The main foliar diseases observed on roses were pow- dery mildew (S. pannosa) that appeared soon after budbreak in late April followed by black spot (M. rosae) that started in mid-June. Bacterial leaf spot (X. campestris) on oakleaf hy- drangea and powdery mildew (E. australiana) on crapemyrtle were observed soon after budbreak in mid-May. Entomospo- rium leafspot developed on photinia, but the evaluation was terminated as a result of death of plants after the first year. Disease severity was evaluated monthly from May to August using a 0–5 scale in which 11% to 10%, 211% to 25%, 326% to 50%, 451% to 75%, and 575% to 100% of plant foliage displaying signs and symptoms of disease (Horsfall and Barratt 1945). All data were analyzed using Statistical Analysis Systems (SAS) general linear models pro- cedure and analysis of variance (ANOVA) with spray treat- ments as the main effect (Schlotzauer and Littell 1987; SAS Institute 1990). Multiple comparisons among treatments for mean disease severity were performed using a series of t tests (Gomez and Gomez 1984; SAS Institute 1990). The least sig- nificant differences (LSD) were calculated according to Fisher’s protected LSD test at P 0.05. Japanese beetles adult feeding damage was visually evalu- ated from May through August. Percentage of total leaf area consumed was recorded using a 0–10 scale in which 0no damage and 10 100% feeding damage. The data on feed- ing damage were converted to percentages in which 1 10%, 2 20%, and so on. All data were square root trans- formed and analyzed by ANOVA with spray treatments as the main effect (Schlotzauer and Littell 1987; SAS Institute 1990). RESULTS Disease and Insect Feeding Damage Initial signs and symptoms of S. pannosa in roses were ob- served starting late April in the field, shadehouse, and green- house experiments. Initial symptoms consisted of slightly raised, blister-like areas that were often red-colored on the upper leaf surface of young leaves and later formed discrete patches of white powdery mycelia and conidiospores, which
May 2007
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