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W.T. Witte, M.T. Windham, R.J. Sauve, and P.C. Flanagan

Fifty-five accessions of commercially available crape myrtle cultivars were established with 10 single-plant replications during Fall 1993 and Spring 1994. Drip irrigation began on a regular basis May 1994 and plants were fertilized regularly. In contrast to the 1994 growing season with heavy powdery mildew infestation, little powdery mildew occurred in 1995. Mean growth index (GI = centimeter height + centimeter mean width) was calculated for each cultivar in Fall 1994 and 1995. Fastest growth occurred in `Tuskegee' and `Biloxi' (GI = 276, 246, respectively), followed by a group including `Tonto', `Comanche', `Choctaw', `Hardy Lavender', `Natchez', `Potomac', and `Tuscarora' (GI = 185 to 227). Slowest growth occurred in the group including `Pecos', `Seminole', `Baton Rouge', `Petite Orchid', `Bourbon Street', `Cherokee', `Monink Pink', `Moned Red', `Delta Blush', `Low Flame', `New Orleans', `Monow', and `World's Fair' (GI = 5 to 53). Data will be presented on powdery mildew ratings and physiological injury sustained during Winter 1995–96.

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M.T. Windham, W.T. Witte, R.J. Sauve, and P.C. Flanagan

Fifty-five cultivars of crapemyrtle were established in a cultivar trial with 10 single-plant replications during Fall 1993 and Spring 1994. Drip irrigation began on a regular basis on 18 May 1994 and plants were fertilized regularly. Powdery mildew appeared in July, and within 2 to 3 weeks maximum levels of infection occurred. Plants were rated using a scale of 0 (healthy) to 5 (totally mildewed). In the group of seven cultivars, most heavily infected (>2.8 rating), `Byers Wonderful White' was worst (4.1), followed by `Royalty', `Pink Lace', `Prairie Lace', `Petite Plum', `Firebird', and `Christmastime'. There were 21 cultivars with no mildew (0.0). Many of these were USDA–NA hybrids but also included `Hope', `Bourbon Street', `Glendora White', `Petite Snow', `Centennial Spirit', and `Hardy Lavender'. A few USDA–NA hybrids had slight mildew: `Potomac', `Powhatan', `Catawba', `Seminole', `Biloxi', and `Hopi' (<10% of foliage mildewed).

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W.T. Witte, M.T. Windham, R.J. Sauve, and P.C. Flanagan

Sixty accessions of commercially available lilac cultivars were planted May 1994 and immediately placed under drip irrigation and fertilized regularly. Powdery mildew appeared in July 1994 and was rated on a scale of 0 (healthy) to 5 (totally mildewed) in July, August, and September. Mean growth index (GI = cm height + cm mean width) was calculated for each cultivar in Fall 1994 and 1995. Fastest growth (GI = 75 to 45 respectively) occurred in the group including chinensis `Rothomagensis', meyeri `Dwarf Korean', reticulata `Ivory Silk', prestoniae `Isabella', `Mrs. Harvey Bickle', `Excel', `Katherine Havemeyer', `Mme. F. Morel', `Silver King', `Leon Gambetta', `Mount Baker', and microphylla `Superba'. Data will be presented on powdery mildew ratings for the 1995 season.

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William E. Klingeman, Gregory R. Armel, Henry P. Wilson, Thomas E. Hines, Jose J. Vargas, and Philip C. Flanagan

Mugwort (Artemisia vulgaris) is a perennial invasive weed species that has infiltrated row crops, turfgrass, ornamentals, and various noncrop areas. Currently, multiple mimics of indole-3-acetic acid can provide control of this species; however, these herbicides can damage certain sensitive ornamental plants. When applied at reduced rates, the p-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicides mesotrione and topramezone have demonstrated some selectivity among certain ornamental plants. Field and greenhouse studies were initiated to evaluate whether these herbicides could control mugwort when applied alone, or in mixtures with photosystem II (PSII)-inhibiting herbicides that often provide synergistic weed control. In the field, mesotrione controlled mugwort between 30% and 60% by 21 days after treatment when applied at 0.093 to 0.187 lb/acre. When the PSII-inhibiting herbicide atrazine was added, control increased to 78% and 79%. In the greenhouse, similar rates produced greater control in mugwort, and all mesotrione treatments limited mugwort regrowth by at least 95% when compared with untreated control. When HPPD inhibitor rates were reduced further, the addition of the PSII inhibitors atrazine or bentazon was not sufficient at providing acceptable control of mugwort.