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Abstract
Seedling pecan tree [Carya illinoensis (Wangenh) C. Koch] roots were flooded for 28 days while trees were either dormant, beginning budbreak, or in active growth, plus an unflooded control. Flooding roots while trees were dormant did not affect growth and seldom affected leaf elemental concentrations compared to unflooded trees. Trees with roots flooded during budbreak usually had less leaf area and were shorter, with smaller trunks than unflooded trees. Leaf N and Fe concentrations were decreased immediately after flooding, but, 56 days after trees were drained, P, Ca, Mg, Zn, and Mn concentrations were greater than in unflooded trees. Leaf area, tree height, trunk diameter, and leaf and trunk dry weights were not affected by flooding during active growth. Root dry weight was reduced 31% immediately after trees were drained, and 48% 56 days after trees were drained compared to unflooded trees. Trees flooded during active growth had lower concentrations of N, P, K, Ca, Mg, Zn, Fe, and Mn immediately after flooding, but, 56 days after trees were drained, leaf elemental concentrations were not significantly different from unflooded trees.
The southern highbush blueberry (Vaccinium spp.) `Blueridge', `Cape Fear', `Cooper', `Georgiagem', `Gulf Coast', and `O'Neal'; the rabbiteye (V. ashei Reade) `Climax'; and the highbush (V. corymbosum L.) `Bluecrop' were evaluated for ovary damage following exposure of flower buds to 0 to 30C in a programmable freezer in Dec. 1993 and Jan. and Feb. 1994. The plants sampled were growing at the Univ. of Arkansas Fruit Substation, Clarksville. Damage was based on oxidative browning of the ovaries following an incubation period after removal from the freezer. With the exception of `Climax', a minimum temperature of –15C was required before bud damage was sufficient enough to differentiate among cultivars. All southern highbush cultivars and `Bluecrop' had superior hardiness compared to `Climax' at –15C in December, –20C in January, and –15C in February. Maximum hardiness of all cultivars was found in January. The hardier southern highbush cultivars were `Cape Fear' and `Blue Ridge'. Less hardy cultivars were `Gulf Coast, `Cooper', `Georgiagem', and `O'Neal', although the date of sampling affected the ranking of these clones for hardiness, especially for the February sample date. `Bluecrop' was not consistently hardier than the hardier southern highbush cultivars, except at the February sample date.
Several trials were conducted to compare standard and potential peach rootstocks. The NC-140 trial, with 'Redhaven' as the scion, included 'Halford', 'Siberian-C', 'Bailey', 'GF-677', 'GF-655.2', 'Damas', 'Citation', 'Lovell' and 'GF-43' rootstocks. All trees with 'Citation' as the rootstock died in the first three years. while 'CF-43' and 'Siberian-C' had low survivability and productivity. 'Damas' and 'GF-43' suckered profusely. 'Lovell' trees bloomed an average of one-to-three days later than all other entries. 'Halford'. 'GF-677', 'Bailey' and 'Lovell' had the highest yields. A trial comparing 'Loring' own-root and on 'Tennessee Natural' resulted in similar yields among stocks, but larger fruit and tree size with the own-root trees. 'Redskin' own-root and on 'Lovell' also resulted in similar yields among stocks, and larger tree and fruit size with own-root trees. A trial using the processing peach selection A-219 as the scion on `S-37' 'Chum Li Tao', AR-78118, 'Yarbrough Cling' and 'Lovell' resulted in highest yields and yield efficiency with 'Yarbrough Cling', 'Lovell' and 'S-37' rootstocks.
Ethrel sprays were applied at 50 or 100 ppm at approximately 40%, 70% leaf fall (10/16/89 or 10/24/89, respectively) or at both times on `Redhaven' and `Allgold' peaches. Bud hardiness was determined biweekly by differential thermal analysis (DTA). Stage and percentage of bloom open during the bloom period were subjectively estimated.
Spraying trees with 100ppm Ethrel at 50% leaf fall significantly increased bud hardiness at mid-winter compared to other treatments. After a mid-winter freeze (-21.7 C on 12/21/89), there was no significant difference between % bud survival of any treatments. But, trees treated with 50 or 100ppm Ethrel had 10-20% better bud survival than other treatments. Buds of the 2 cultivars had statistically similar hardiness although DTA analysis indicated that Redhaven had a .5-.8 C lower freezing point than Allgold in mid winter. This trend was reversed close to bloom with Allgold having .7 C lower freezing point than Redhaven. The time of full bloom was significantly delayed by treating trees with 100ppm at 40% leaf fall or 50ppm at both 40 and 70% leaf fall the previous autumn.
Geographical dispersion of production hampers watermelon integrated pest management (IPM) information delivery in Oklahoma. Melon Pest Manager (MPM) was created to educate and provide advisory information on IPM. Available at www.lane-ag.org, the site emphasizes information relevant to the area. MPM was conceived as Internet availability grew and was recognized to have potential for enhancing IPM implementation. Survey of producers suggested the value of Web-based information may depend on how easily it can be accessed. MPM was designed to provide easy access to watermelon IPM information. Compared to printed literature, web-based format is easier to revise and suited to presentation of information that applies yearly as well as that which may change frequently. MPM provides general discussion of melon IPM tactics and pest-identification and time sensitive information such as pest advisories and pesticide registration changes. MPM offers opportunity for novel presentation of educational information such as the real-time posting of field demonstrations. An initial challenge was to balance site development, promotion and education. Promotion and education followed placement of watermelon IPM tactic information on MPM but preceded advisory and pest identification. Pest identification links to existing sources are enhanced by material prepared for MPM. Progress is slowed by the need for expert intervention and the availability of images and descriptive information. Education on use of advisory resources (e.g., disease forecasters) is a high priority. However, availability and applicability of such products is dependent on the home site. The original concept envisaged mapping of pest activity using grower, extension agent and expert input. Time demands of other components of the site delay development of this aspect. Pest alerts are posted and distributed to county extension offices.