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Abstract
An oat (Avena sativa L. ‘Otee’) cover crop was planted in nursery beds seeded with Acer ginnala Maxim., Celastrus scandens L., and Elaeagnus angustifolia L. and 21 Mar. 1985. Postemergence graminicide treatments were applied on 25 Apr. and 8 May after the nursery seedlings had germinated and when the oats were ≈15 and 38 cm tall. Treatments included fluazifop at 0.28, DPX-Y6202 at 0.11, haloxyfop at 0.28, and sethoxydim at 0.34 kg·ha-1. In 1986, the same herbicides, except DPX-Y6202, were applied alone to Sophora japonica L. seedlings grown in an oat cover crop. Six days later, imazaquin at 0.14 kg·ha1 or chlorimuron-ethyl at 0.009 kg·ha1 was applied alone and to plots that had previously received graminicide treatments. Acer and Celastrus seedlings in plots treated on 25 Apr. 1985 had greater dry weight than those treated on 8 May 1985. Date of herbicide treatment did not affect the dry weight of Elaeagnus seedlings. In 1986, graminicides provided complete control of oats, but broadleaf weed growth was subsequently released. Imazaquin and chlorimuron-ethyl provided control of pigweeds (Amaranthus sp.), but did not control lambsquarter (Chenopodium album L.) or purslane (Portulaca oleracea L.). Tree seedlings treated with haloxyfop alone, sethoxydim alone, or sethoxydim plus imazaquin had greater dry weight than those in the untreated controls. DPX-F6025 alone reduced seedling dry weight when compared to that of the untreated control. Chemical names used: (±)-2-[4[[-5-(trifluoromethyl)-2-pyridinyl)oxy]phenoxy] propanoic acid (fluazifop); (±)-2-[4-[(6-chloro-2-quinoxalinyl)oxy]phenoxy] propanoic acid (DPX-Y6202); 2-[4-[[3-chloro-5-trifluoromethyl)-2-pyridinyl]oxy]phenoxy] propanoic acid (haloxyfop); 2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one (sethoxydim); 2-[4,5-dihydro-4-methyl-4-(1-methylethyl) 5-oxo-1H-imidazol-2-yl]-3-quinolinecarboxylic acid (imazaquin); 2(([(4-chloro-6-methoxypyrimidine-2-yl)amino carbonyl]amino sulfonyl))benzoic acid, ethyl ester (chlorimuron-ethyl).
`Danka' black currant floral buds produce multiple low temperature exotherms (LTEs). However, the absence of visual injury symbtoms in the buds after exposure to subfreezing temperatures make it difficult to assess injury in these buds. A 2,3,5-triphenyltetrazolium chloride (TTC) reduction assay was used to determine whether LTEs corresponded to freezing injury of individual floral primordia or to the entire floral axis. Intact buds were cooled at 3C/n, removed at 3C intervals from -12 to -33C, and thawed on ice for 24 h. Duplicate samples were subjected to differential thermal analysis. Freeze injury Could not be measured with TTC in thawed, intact buds. However, incubation of excised floral primordia in TTC resulted in an all or nothing response. The number of LTES did not correspond to the number of floral primordia killed within a floral bud, but the median LTE did correspond with the temperature at which lethal injury of the whole inflorescence occurred. Therefore, preliminary results indicate that TTC reduction assay of individual floral buds is a fast, reliable technique to assess bud injury.
Abstract
Flurprimidol and XE-1019, applied at 15.0 and 2.5 mg/plant respectively, suppressed shoot dry weight and increased xylem pressure potential of Forsythia spectabilis Spaeth when drought was induced but did not affect leaf size or root dry weight. XE-1019 did not suppress growth when applied on 28 Aug. 1985. Plants treated with flurprimidol in late August had less shoot growth and higher xylem pressure potential than untreated controls or plants treated with XE-1019. Mefluidide applied as a foliar spray at 5000 mg·liter-1 on 25 June 1985 did not suppress growth or affect plant moisture status of forsythia. None of the growth regulators reduced the transpiration rate of forsythia plants. Chemical names used: N-[2,4-dimethyl-5-[[(trifluoromethyl) sulfonyl]amino]phenyl]acetamide (mefluidide); α-(1-methylethyl)- α-[4-trifluoromethoxy)phenyl]-5-pyrimidinemethanol (flurprimidol); (E)-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-ol (XE-1019).
Abstract
Chlorsulfuron was applied alone at 0.018 kg·ha−1 and in combination with 3.4 kg·ha−1 of oryzalin at rates of 0.018, 0.035, 0.070, and 0.140 kg·ha−1 to a mature ‘Chancellor’ grape (Vitis × sp.) vineyard. Oryzalin was also applied alone at 3.4 kg·ha−1. Oryzalin plus chlorsulfuron treatments provided excellent weed control. The vegetative growth of vines was reduced in the oryzalin plus chlorsulfuron treatments at rates of 0.07 and 0.14 kg·ha−1 as compared to the control. Oryzalin used alone and oryzalin plus chlorsulfuron used at the lowest rate were the only treatments that did not adversely affect vine growth or fruit quality. Chemical names used: 2-chloro-N-[[(4-≎ methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzenesulfonamide (chlor-sul-≎ furon); 4-(dipropylamino)-3,5-dinitrobenzenesulfonamide (oryzalin).
Abstract
Experiments were performed on ‘Cherokee’ blackberry (Rubus sp.) floral buds and cane tissue collected from field plantings on 12 Jan. and 18 Feb. 1987 to determine the susceptibility of floral primordia, phloem, and xylem to freezing injury after exposure to 16C for 0, 4, 12, 24, or 48 hr. Before rest completion in January, floral primordia, phloem, and xylem subjected to 16C were hardier than those tissues tested in February when rest was completed. Floral primordia and cane tissues dehardened slowly with time at 16C before rest completion. After rest was completed, the rate of deacclimation of floral primordia and xylem increased. Some blackberry canes were subjected to two thawing episodes at 16C for 4 hr. In January, phloem and xylem of canes thawed twice were as hardy or hardier than those tissues in samples thawed once. Conversely, two thawing episodes in February resulted in greater xylem injury than a single episode, but two episodes did not affect the hardiness of the phloem. The number of thawing episodes did not affect floral bud hardiness at either sampling date.
`Jonagold'/Mark apple (Malus domestica Borkh.) trees that were chip-budded in Washington and Illinois on 31 Aug. or 21 Sept. 1989 were sampled in Apr. 1990 to determine if magnetic resonance imaging (MRI) could be used to nondestructively examine vascular continuity or discontinuity between the rootstock and scion. Images could be placed into three categories based on signal intensity: 1) the rootstock, bud shield, and the bud or new scion growth had a high signal intensity; 2) the rootstock and the bud shield had a high signal intensity, but the scion had a low signal intensity; and 3) the rootstock had a high signal intensity, but the bud shield and scion had a low signal intensity. High signal intensity was associated with bound water in live tissue and the establishment of vascular continuity between the rootstock and scion. Azosulfamide staining and destructive sectioning confirmed that vascular continuity was established when the rootstock, bud shield, and scion had a high signal intensity in images, whereas budding failure occurred when the bud shield and/or the scion had a low signal intensity. Additional trees that had wilted or weak scion growth were collected from Illinois in June 1990. Parenchyma tissue was found in the scion adjacent to the bud shield that interrupted the vascular tissue. Poor scion growth on trees from the 21 Sept. budding in Washington may be attributed to insufficient growth of rootstock and/or scion tissues at the union in the fall.
Rhizomes of zoysiagrass (Zoysia spp.) were subjected to controlled freezing tests in Jan. and Mar. 1993 and 1994 to determine their low-temperature tolerance. In 1994, `Belair', `Korean `Common', `Meyer', and `TGS-W10' rhizomes survived temperatures as low as -18 °C, while rhizomes of `Sunburst' survived -14 °C. `Cavalier', `Crowne', `Palisades', `Emerald', and `El Toro' were killed at -10 °C or warmer temperatures. Entries surviving exposure to -14 to -18 °C in 1994 controlled freezing tests received post-winter survival ratings in the field of 6.7 to 8.7 (9 = 100% green). Entries killed at higher freezing test temperatures were slower to recover after winter in the field, with ratings of 2.0 to 3.0. Shoot number produced after freezing was a better measurement for assessing low temperature tolerance than was shoot mass. Controlled freezing tests, using regrowth as a measure of hardiness, appear to be useful for identifying low temperature tolerance of zoysiagrasses in the early years of a field study.
Researchers have collected a considerable amount of data relating to apple (Malus ×domestica) cultivars and rootstocks over the past 30 years, but much of this information is not easily accessible. The long-term goal of our working group is to increase access to this information using online technology available through eXtension. In eXtension, researchers and extension personnel are developing a community of practice (CoP) to increase the quality and amount of online information for individuals interested in our work [referred to as a community of interest (CoI)]. For this project, our CoI is broadly defined as commercial apple producers, nursery professionals, county extension educators, Extension Master Gardeners, home gardeners, and consumers. Our CoP is developing diverse educational tools, with the goals of increasing productivity, profitability, and sustainability for commercial apple production. Additionally, we will provide other members of our CoI access to research-based, reliable information on the culture of apples. We chose to begin our focus on cultivars and rootstocks adapted to the eastern United States and will add other U.S. regions as our resources and interest in our project grows.