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- Author or Editor: Elden J. Stang x
Selective flower removal was used in 1987 and 1988 to evaluate intraplant competition or inhibition within flowering uprights of `Searles' cranberry (Vaccinium macrocarpon Ait.). The lowest two flowers were removed from uprights at various stages of plant development in 1987. With one or both of the two earliest, i.e., lowest, flowers developing `into fruit, 25% of the remaining flowers matured into fruit. Removal of the earliest two flowers at preblossom or late blossom resulted in ≈ 46% fruit set for the remaining flowers. Slightly fewer upper flowers set (36%) when the earliest flowers and fruit were removed at early fruit development. In 1988, the lowest two flowers were removed at preblossom and natural insect pollination was supplemented by hand pollination. Hand-pollinated (upper) flowers set 58% when the lowest two flowers were removed, compared to 17% for the unthinned control. Yield and fruit numbers were lowered slightly as a result of flower thinning in both years. A significant amount of variation in fruit production was explained by the number of flowering uprights per unit of production area in both years.
`Raritan' and `Guardian' strawberry were grown in the matted row system with controlled plant densities of 1, 2, 3, 4 or 5 plants/0.09m2 for comparison to a non-thinned matted row averaging 9 plants/0.09m2. Nitrogen treatments were superimposed on plant spacings at 3 week intervals in preharvest and postharvest applications. Total seasonal available N was 0, 36, 54 and 76 kg/ha. Fruit yield per plant decreased as plant population increased. Berry size declined with increased plant population but number of fruit per plant was not influenced. For both cultivars, plant populations of 4 to 5 plants/0.09m2 resulted in maximum fruit yield. Number of branch crowns for all treatments was 2.5-3.5/plant in the second growing season. Branch crown numbers were reduced with higher plant populations. N effects were independent of plant population effects and did not compensate for lower yields at low plant populations in more or larger berries. Optimum water management may be more important than N fertilizer in determing strawberry plant growth and yield.
Spunbonded polypropylene fabric covers were applied over mature `Searles' cranberry (Vaccinium macrocarpon Ait. in the field during dormancy in 1989. Covers were selectively removed at 3 week intervals in April, May and early June after onset of growth. Plant canopy air temperatures under fabric were 5 to 6C higher than in exposed controls. Temperature differences up to 17C were measured in early June. Soil temperatures did not differ from the control until late May. Earlier greening of leaf tissue resulted in increased photosynthetic rates earlier in the growing season under fabric covers. Subsequent shoot dry weight was increased 5%; leaf size was not affected. A trend to increased fruit set (4 to 6%) with fabric cover treatments was observed when covers were applied for 6 or 9 weeks. Total fruit yield and anthocyanin content were not appreciably influenced by fabric covers.
Cranberries (Vactinium maerocarpon Ait), are Wisconsin's major fruit crop. Current annual production averages well over 45 million kg, and on-farm value exceeded $53 million in 1983. Wisconsin produced 40% of the United States cranberry crop in 1982; Massachusetts contributed 43%, and Oregon, Washington, and New Jersey produced 17%.
‘Earliglow’ strawberry (Fragaria × ananassa Duch.) plants were covered with 60% shade cloth in Wisconsin and Ohio during each of the following developmental phases: 1) check, no shade; 2) the runnering period after plant establishment; 3) flower initiation period in Fall 1983; 4) early growing season (from mulch-off until first flowering); 5) the fruiting period, 1984; and 6) constant shade. ‘Earliglow’ has a photosynthetic light response curve typical of a C, plant. Leaf dry weight per plant was decreased at both locations by constant shading during the fruiting period, just prior to plant sampling. Crown dry weight was reduced by constant shading. Leaf nutrient element contents of K, Ca, Mg, B, and Fe varied by location, but were not appreciably affected by shading treatments. Shading during the active runnering period resulted in increased total yield the following spring by 12% in Wisconsin and 17% in Ohio. In Wisconsin, increased total yield was the result of increased number of fruit in midseason harvests. Berry size was increased for constant shading or shading during fruiting, but yield was offset by lower fruit numbers. Usable fruit in Ohio on plants shaded during runnering was increased by 20% compared to the unshaded control. Constant shade resulted in an 18% and 46% reduction in total yield in Wisconsin and Ohio, respectively. Shading during the fruiting period resulted in yield reductions in both Ohio (13%) and Wisconsin (27%). Yield reductions were also noted in Ohio when shading occurred during early spring (21%), just prior to fruiting, or during flower formation (24%) the previous fall. Shading during the spring growth and fruiting period delayed fruit maturity and peak harvest 5 to 7 days.
Pollination and pollen tube growth were evaluated in two years as potential factors suppressing cranberry (Vaccinium macrocarpon Ait.) fruit set. Supplementing insect pollination with hand pollination increased fruit set from ≈30% to ≈38% in both years. The number of flowers per unit area was an important contributor to fruit set variation in one year. Cranberry uprights exhibited a temporal decline in fruit set when flowers were pollinated sequentially; the first flowers to open had a higher probability of fruit development than flowers opening later. Examination of stigmas indicated flowers receiving low amounts of pollen (<10 tetrads), or pollen that fails to germinate, are more likely to abort. An inadequate number of pollen tubes and lack of subsequent fertilization provides a partial explanation of fruit abortion in cranberry. Cranberry fruit set under existing field conditions appears to be limited, in part by insufficient pollination and pollen tube growth, with the latter apparently the result of intraplant competition for resources. Providing supplemental hand pollination increased cranberry yields in both years, 48% over natural insect pollination when the number of flowering uprights per unit area was high (≈3000/m2). A significant amount of yield variation was explained by the number of flowering uprights per unit area in both years.
A computer simulation was developed to analyze the economic feasibility of over-tree misting based on the interrelationships of daily temperature, bud development and corresponding effects of low temperature on apple (Malus domestica Borkh.) and peach (Prunus persica (L.) Batsch) flower bud kill in Ohio. Utilizing historical temperature data from 1940 through 1972, a revised model for estimating rest and bud development was constructed and the probability and extent of bud kill was simulated. Model validity was tested utilizing 1973-1976 temperature data. Using the 1940 to 1976 period, it was evident that the risk of substantial losses in revenue was reduced when over-tree misting was employed in all Ohio locations. Potential economic returns of the over-tree misting technology were greater for peaches than apples. Need for this risk reduction varies geographically in Ohio for apples and to a lesser extent for peaches.
A mechanized system for harvesting strawberries with minimal damage to fruit is proposed. Cultural requirements involve placing plastic or fiber mesh netting over the beds before growth of leaves and inflorescences begins, permitting leaves and fruit to develop above the netting. The prototype machine developed for the system mows off leaves, raises the netting, cuts off pedicels of fruit supported on the netting and delivers the fruit to a conveyor and bulk box before rolling up the netting for storage. The harvester is supported under and can readily be adapted to most conventional garden tracter designs. Observations on a small sample of fruit harvested by the machine suggest the possibility of a sizable reduction in amount of injury to fruit compared with earlier designs.
Uniconazole (UCZ) can control tree size by suppressing tree growth. Growth control of one year-old `Haralred' on MAC 9 `MARK' (dwarf) and EMLA 7 (semidwarf) rootstock was evaluated in the greenhouse. Uniconazole (65 or 130 mg/L) was sprayed 0, 1, 2 or 3 times at 3 week intervals. Total shoot growth was inhibited 31% and 24% on `MARK' and EMLA 7 rootstock, respectively, with 130 mg/L. Rootstock and scion diameter and number of leaves per tree were not affected by UCZ. Total leaf area on `MARK' rootstock increased when UCZ was applied once at 65 or 130 mg/L. On EMLA 7 two 130 mg/L sprays resulted in 22% less total leaf area compared to the control. UCZ applied three times reduced specific leaf weight on EMLA 7 trees 12% compared to the control. Branch angle was increased proportional to UCZ applications on semidwarf rootstock from 40° to 47°, and decreased on dwarf rootstock from 47° to 39°. Stomatal conductance increased 43% on `MARK' with 130 mg/L UCZ applied two times. Net photosynthesis of attached leaves did not differ. All UCZ treatments produced 18 to 56% fewer total flower clusters per tree than the control. UCZ appeared to delay bloom significantly.
The application of ethanol for enhancing effectiveness of ethephon under field conditions on cranberry (Vaccinium macrocarpon Ait.) fruit was tested during three seasons (1986 to 1988). The formulation containing ethephon plus the surfactant Tergitol (0.3% or 0.5%, v/v) and ethanol (2.5%, 5%, or 10%) consistently increased anthocyanin content in the fruit by 28% to 54% over the control. In general, fruit size was not affected by the ethephon treatment containing ethanol and Tergitol. The application of ethephon plus surfactant did not increase the anthocyanin content in the fruit. The presence of ethanol in the ethephon and surfactant mixture, however, consistently enhanced the fruit anthocyanin content by 21% to 40% as compared to ethephon plus surfactant. No adverse effect of various treatments on vine growth or appearance was noticed over the three seasons. Chemical name used: (2-chloroethyl) phosphonic acid (ethephon).