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Gary L. McDaniel

Suppression of scape elongation by paclobutrazol and ancymidol of potted `Paul Richter' tulips (Tulipa gesneriana, L.) under greenhouse and low light postharvest environments were compared. Soil” drench applications of paclobutrazol at 0.25 or 0.50 mg/15-cm pot were as effective as ancymidol at 0.50 or 0.75 mg/pot in limiting scape lengths at colored bud stage and at senescence. Paclobutrazol pre-plant bulb soaks at 2.5 or 5.0 mg·liter-1 prevented excessive scape elongation during low light exposure, whereas ancymidol bulb soaks were ineffective. Neither plant growth regulator reduced flower size or affected petal color. Paclobutrazol applied as a soil drench or as a bulb soak increased days required up colored bud stage up to 4 days, whereas neither chemical affected post-greenhouse, life of tulips. Chemical names used: (R*, R*)-(±)-β-[(4-chlorophenyl) methyl]-α-(1,1-dimethyl)-1H-1,2,4-triazol-1-ethanol (paclobutrazol) and α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol).

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Nicole A. Cardwell and Gary L. McDaniel

The pathogenesis-related protein, chitinase, is implicated in the resistance mechanisms involved in dogwood anthracnose, which is caused by Discula destructiva. Chitinase isozymes were isolated from Discula-inoculated Cornus mas, a highly resistant species, and from inoculated C. florida, a highly susceptible species. Chitinase activity was identified in C. mas on days 2-12 following inoculation, but was expressed only on day 8 following inoculation in C. florida. Both dogwood species expressed a constitutive chitinase level in noninoculated control leaves, but Discula-inoculated leaves of C. mas contained three chitinase isozymes, whereas C. florida leaves expressed only two. Molecular masses of isozymes were 21, 32, and 35 kDa for C. mas and 21 and 35 kDa for C. florida. Isoelectric focusing demonstrated three chitinase isozyme isoelectric points for C. mas (pI = 5.6, 6.8, and 8.9), but only two for C. florida (pI = 5.6 and 6.8). These differences in synthesized isozymes and rate of accumulation suggest that chitinase may have a role in the defense of dogwood against D. destructiva infection.

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Gary L. McDaniel, Effin T. Graham, and Kathleen R. Maleug

The effects of growth-retarding chemicals on stem anatomy were compared on poinsettia (Euphorbia pulcherrima Wind. `Annette Hegg Dark Red'). Micrographic examinations revealed that secondary walls of nonsclerotic phloem fiber cells were either completely or greatly reduced by retardant treatment. Wall thickening of phloem fiber cells was eliminated by paclobutrazol foliar sprays at 25 mg·liter-1. Fiber cell development was reduced, but not eliminated, by sprays of chlormequat and ancymidol at standard rates, while the triazole uniconazole at 10 mg·liter-1 permitted only limited fiber wall thickening. Chemical names used: (2-chloroethyl)-trimethyl ammonium chloride (chlormequat); α -cyclopropylα- (4-methoxyphenyl) -5-pyrimidine methanol (ancymidol); (E)-(p -chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl-1-penten-3-ol (uniconazole): and (R*,R*)- β -[(4-chlorophenyl)methyl]- α -(1,1-dimethylethyl)- 1 H-1,2,4,triazole-1-ethanol (paclobutrazol).

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William E. Klingeman*, Darren K. Robinson, and Gary L. McDaniel

Mugwort, or false chrysanthemum (Artemisia vulgaris L) is a well-adapted invasive plant that presents increasing management challenges to agricultural producers, Green Industry professionals and homeowners across portions of the eastern U.S. The ability of mugwort to regenerate from cut rhizome sections has not been adequately quantified for substrates that are typical of landscapes and nursery fields, container nurseries, and propagation beds. Cut rhizome sections were analyzed by rhizome color, length, and the presence or absence of a leaf scale. Media substrates included pine bark, sand, and soil. Rhizomes darken with time and color did not account for differences in growth among treatments. When grown in pine bark, sand, and soil substrates during 45-d trials, 85%, 78%, and 69% of 2 cm-long rhizome sections produced both roots and shoots. These results contrast with previous research. When rhizome fragments 0.5 cm long did not include a leaf scale, slightly fewer than 31% produced both roots and shoots in soil. Fewer rhizomes survived in soil, but root and shoot fresh masses of soil-grown rhizomes were greater than rhizomes that were regenerated in pine bark and sand. When rhizome sections had a leaf scale, survival, fresh masses of roots and shoots, shoot height, leaf number and root lengths were greater, regardless of substrate type. Root initials emerged in the internode between leaf scales and also adjacent to leaf scales. Shoot emergence preceded root emergence from rhizome sections. Growers, landscape managers and homeowners should scout regularly and initiate aggressive controls when mugwort populations are found.

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Gary L. McDaniel, William E. Klingeman, Willard T. Witte, and Phillip C. Flanagan

One-half (18 g·ha-1 a.i.) and three-fourths (27 g·ha-1 a.i.) rates of halosulfuron (Manage®, MON 12051) were combined with adjuvants and evaluated for effectiveness in controlling purple nutsedge (Cyperus rotundus L.) and for phytotoxic responses exhibited by two kinds of container-grown ornamental plants. Adjuvants included X-77®, Scoil®, Sun-It II®, Action “99”®, and Agri-Dex®. By 8 weeks after treatment (WAT), halosulfuron combined with X-77®, Agri-Dex®, or Action “99”® at the lower halosulfuron rate provided <90% purple nutsedge suppression. In contrast, Sun-It II® provided 100% control when combined with the higher halosulfuron rate. Nutsedge control persisted into the following growing season and halosulfuron combined with either Scoil® or Sun-It II® provided >97% suppression of nutsedge tuber production. Growth of liriope [Liriope muscari (Decne.) Bailey `Big Blue'] was not inhibited by Scoil® or Sun-It II® adjuvants in combination with the low rate of halosulfuron. However, regardless of the rate of halosulfuron or adjuvant used, initial foliar chlorosis was observed in both daylily (Hemerocallis sp. L. `Stella d'Oro') and liriope. All liriope receiving halosulfuron with X-77®, Scoil®, or Sun-It II® adjuvants recovered normal foliage by 8 WAT. By contrast, at 8 WAT some daylily still maintained a degree of foliar discoloration. In addition to chlorosis, all treatments reduced flower number in daylilies. The number of flower scapes produced by liriope was not affected by halosulfuron when in combination with either Sun-It II® or Scoil®. The high rate of halosulfuron combined with X-77® or Action “99”® improved control of purple nutsedge. However, this rate inhibited growth of both species, daylily flower numbers, and scape numbers of liriope, regardless of adjuvant. Chemical names used: halosulfuron (Manage®, MON 12051, methyl 5-{[(4,6-dimethyl-2-pyrimidinyl) amino] carbonyl-aminosulfonyl}-3-chloro-1-methyl-1-H-pyrozole-4-carboxylate); proprietary blends of 100% methylated seed oil (Scoil® and Sun-It II®); proprietary blend of 99% polyalkyleneoxide modified heptamethyl trisiloxane and nonionic surfactants (Action “99”®); alkylarylpolyoxyethylene, alkylpolyoxyethelene, fatty acids, glycols, dimethylpolysiloxane, and isopropanol (X-77®); proprietary blend of 83% paraffin-based petroleum oil, with 17% polyoxyethylate polyol fatty acid ester and polyol fatty ester as nonionic surfactants (Agri-Dex®)