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T.G. Beckman, W.R. Okie, and S.C. Meyers

Rootstock influence on bloom date and fruit maturation of `Redhaven' peach [Prunus persica (L.) Batsch] was studied over a 3-year period. Rootstock included seedlings (Lovell, Halford, Bailey, and Siberian C) and cuttings (GF677, GF655.2, Damas 1869, and `Redhaven'). Bloom dates of the various combinations differed in all 3 years, with a range of 3.6, 9.1, and 7.3 days in 1988, 1989, and 1990, respectively. Fruit development period differed each year with a range of 3.9, 5.8, and 4.4 days in 1988, 1989, and 1990, respectively. `Weighted-average harvest date also differed with a range of 3.6,2.9, and 5.6 days in 1988, 1989, and 1990, respectively. `Redhaven'/Lovell was the latest blooming and maturing combination in all 3 years of the study.

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Etaferahu Takele, Jewell L. Meyer, Mary L. Arpaia, David E. Stottlemyer, and Guy W. Witney

The effect of integrated applications of various irrigation and fertilization rates on productivity (yield and size) and returns of the `Hass' avocado (Persea americana Mill.) have been analyzed from 1987 to 1991 in western Riverside County. Eighteen treatment combinations comprised of three irrigation levels [80%, 100%, and 120% crop water use (ETc)], three N fertilizer levels (0.16, 0.7, and 1.4 kg/tree per year), and Zn (0 and 0.2 kg/tree per year) were included in the analysis. Using a partial budgeting procedure, returns after costs were calculated for each treatment combination. Costs of treatments, harvesting, hauling, and marketing were subtracted from the value of the crop. The value of the crop was calculated as the sum of crop returns in each size category. Three years of data on the relationship between irrigation and N showed 1) irrigating at 80% ETc would be ineffective even at very high water prices; 2) for groves where 100% ETc is sufficient, its application with either low or medium N would be beneficial; and 3) at higher irrigation (120% ETc), N application should be at or beyond the medium level.

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D. E. Stottlemyer, M. L. Arpaia, J. L. Meyer, G. W. Witney, and G. S. Bender

The influence of three irrigation treatments on flowering, yield, tree growth, root distribution, and leaf analysis of mature `Hass' avocado (Persea americana Mill.) was investigated over a six year period (1987-1992). Three irrigation treatments; 60, 80, and 100% of evapotranspiration (ETc) were applied using low-volume spray emitters. The differential irrigation treatments were maintained year round. Irrigation treatments did not affect the timing or intensity of bloom. Yield data from years 2-6 show a significant irrigation effect on cumulative weight and total number of fruit per tree. Trees receiving 100% ETc had higher yield/tree. This increased yield was due both to increased fruit numbers and individual fruit weight per tree. Tree growth was also significantly impacted by the irrigation treatments. Trees receiving 100% ETc exhibited the greatest amount of vegetative growth over the study. Yield efficiency (Kg fruit/m3 canopy) was not influenced by irrigation treatment. Irrigation treatment did not significantly influence nutrient analysis taken in the fall of each year.

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James W. Cross, Stacy A. Bonos, Bingru Huang, and William A. Meyer

Heat and drought are two major abiotic stresses causing a decline in quality in cool-season turfgrasses during the summer. The objectives of this study were 1) to determine whether genotypic variations in turf performance during summer stress in New Jersey is related primarily to heat tolerance or drought tolerance of tall fescue; and 2) to make selections of plants tolerant to summer stress for breeding efforts. Twenty-four tall fescue genotypes exhibiting differential performance during summer months in field conditions (12 summer stress-tolerant and 12 summer stress-sensitive) were selected from the germplasm pool present at the New Jersey Agricultural Experiment Station. Plants of these 24 genotypes were exposed to heat, drought, or heat + drought. There were generally no significant differences in turf quality, photochemical efficiency, relative water content, or electrolyte leakage between summer stress-tolerant and -sensitive genotypes, except in the heat treatment in which the summer stress-tolerant selections performed significantly better. The results indicate that the superior performance of the summer stress-tolerant plants under field conditions is mainly the result of superior heat tolerance.

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D.A. Rosenberger, T.L. Robinson, J.R. Schupp, C.A. Engle-Ahlers, and F.W. Meyer

Effects of three sterol-demethylation inhibiting (DMI) fungicides and a contact fungicide were compared over two years at each of two locations to determine if fungicide treatments had differential effects on productivity, fruit size and shape, or gross returns for `Empire' apples (Malus ×domestica Borkh.). Treatments were applied four to five times per year during the primary apple scab season. Effects of treatments were assessed by comparing fruit set efficiencies, number of fruit per tree, total harvested fruit weight, and fruit length: diameter ratios at harvest. No significant differences were noted among individual treatments in any of the four trials. However, when treatments were contrasted by grouping individual treatments, significantly larger fruit size was noted for triflumizole treatments vs. combined fenarimol and myclobutanil treatments in one of the four trials and for captan or mancozeb compared to fenarimol and myclobutanil treatments in two trials. None of the DMI fungicides compared in these trials had any consistent adverse affect on fruit size, total yield, or estimated gross return per hectare. We conclude that the plant growth regulator effects of DMI fungicides are inconsistent and are unlikely to have significant economic impact on commercial apple production.

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D.S. Gardner, T.K. Danneberger, E. Nelson, W. Meyer, and K. Plumley

Genetically transformed cultivars of creeping bentgrass (Agrostis stolonifera L. syn. Agrostis palustris Huds.) that are resistant to glyphosate have been developed by a collaboration of the Scotts and Monsanto companies. Prior to commercial release, we desired to determine if the transformed plants behave similarly to traditional creeping bentgrass except for the effects expected from the inserted gene, i.e., resistance to glyphosate. Therefore, studies were initiated on 23 June 2000 in Marysville, Ohio; 14 July 2000 in Middleton, N.J.; and 20 June 2000 in Gervais, Ore., to examine the relative lateral spread and competitive ability of several transformed lines of creeping bentgrass, non-transformed controls, and reference cultivars. Vegetative plugs of creeping bentgrass were transplanted into a mature stand of Kentucky bluegrass (Poa pratensis L.) or a uniform mixture of Kentucky bluegrass with perennial ryegrass (Lolium perenne L.). The plots were watered as needed to prevent moisture stress. Competitive ability of the transformed plants and reference cultivars were determined monthly by measuring the average diameter of the creeping bentgrass patch. On all observation dates, the transgenic lines, as a group, were smaller in average diameter (5.1-7.6 cm) compared to the reference cultivars (5.4-14.2 cm) and non-transformed control lines (5.9-10.2 cm). At the end of the observation period (Aug. 2001), no differences (P = 0.05) in lateral spread were observed between individual lines of transgenic bentgrass. Three lines of interest, ASR365, ASR368, and ASR333, had lateral spread rates that are similar to, or less than, that of their non-transformed parent and the conventional creeping bentgrass cultivars tested. Chemical names used: N-(phosphonomethyl) glycine (glyphosate).

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Bruce E. Branham, Glenn A. Hardebeck, Joseph W. Meyer, and Zachary J. Reicher

Annual bluegrass (Poa annua L.) is an invasive weed producing copious amounts of viable seed that compete with seedling turfgrasses during renovation. These field studies were conducted to determine the effectiveness of dazomet (tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione), a granular soil sterilant that breaks down in soil to release methyl isothiocyanate (MITC), for controlling the soil seed bank of annual bluegrass during turfgrass renovation. Field trials in Urbana, Ill., and West Lafayette, Ind., in Spring and Fall 2000 and 2001 evaluated dazomet rate from 0 to 504 kg·ha-1 and soil preparation techniques to determine the most effective practices to reduce annual bluegrass reestablishment into a creeping bentgrass (Agrostis stolonifera L.) seeding. The interval, in days, between dazomet application and creeping bentgrass planting was also examined to determine the optimal seeding time as measured by the level of annual bluegrass reestablishment. Spring trials generally gave poor results that were attributed to windy conditions resulting in rapid loss of MITC. The annual bluegrass soil seed bank was reduced 46% in spring trials compared to 78% in fall trials. Increasing dazomet rates reduced the absolute number of viable annual bluegrass seeds remaining in the soil. However, significant quantities of viable seed remained, regardless of dazomet rate. Annual bluegrass infested the renovated turf in all trials to varying degrees. Dazomet rates of 420 or 504 kg·ha-1 yielded the lowest rates of annual bluegrass reestablishment. Trials conducted in the fall at these rates resulted in annual bluegrass cover of 1% to 20% in the resulting turf. Creeping bentgrass planted at 1 day after dazomet application had significantly less annual bluegrass than when seeded at 7 or 9 days after dazomet application. Dazomet is a tool that can help reestablish a new turf with lower levels of annual bluegrass. However, eradication of annual bluegrass with dazomet is not likely and environmental conditions will dramatically affect the success of the sterilization.

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Peter J. Dittmar, Jonathan R. Schultheis, Katherine M. Jennings, David W. Monks, Sushila Chaudhari, Stephen Meyers, and Chen Jiang

The reason for internal necrosis occurrences in sweetpotato (Ipomoea batatas) storage roots is not well understood. This disorder begins internally in the storage roots as small light brown spots near the proximal end of the root that eventually can become more enlarged as brown/black regions in the cortex. The objective of this study was to determine the effect of ethephon and flooding on the development of internal necrosis in the sweetpotato cultivars Beauregard, Carolina Ruby, and Covington over storage durations from 9 to 150 days after harvest (DAH) when roots had been cured. Soil moisture treatments were no-flooding, and simulated flooding that was created by applying 10 inches of overhead irrigation during 2 weeks before harvest. Ethephon was applied at 0, 0.75, and 0.98 lb/acre 2 weeks before harvest. Overall, ‘Covington’ and ‘Carolina Ruby’ had greater internal necrosis incidence (22% to 65% and 32% to 51%, respectively) followed by ‘Beauregard’ (9% to 22%) during storage duration from 9 to 150 DAH at both soil moistures. No significant change was observed for either internal necrosis incidence or severity for ‘Beauregard’ and ‘Carolina Ruby’ over the storage duration of 9–150 DAH. However, there was an increase of internal necrosis incidence and severity 9–30 DAH in ‘Covington’, with incidence and severity remaining similar 30–150 DAH. Storage roots in treatments sprayed with 0.75 or 0.98 lb/acre ethephon had higher internal necrosis incidence and severity compared with the nontreated, regardless of cultivars at both soil moistures. This research confirms that sweetpotato cultivars differ in their susceptibility to internal necrosis (incidence and severity), ethephon applied to foliage can contribute to internal necrosis development in storage roots, and internal necrosis incidence reaches a maximum by 30 DAH in ‘Covington’ and 9 DAH in ‘Carolina Ruby’ and ‘Beauregard’.

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Etaferahu Takele, John A. Menge, John E. Pehrson Jr., Jewell L. Meyer, Charles W. Coggins Jr., Mary Lu Arpaia, J. Daniel Hare, Darwin R. Atkin, and Carol Adams

The effect of various integrated crop management practices on productivity (fruit yield, grade, and sire) and returns of `Washington Navel' oranges [Citrus sinensis (L.) Osbeck] was determined in the San Joaquin Valley of California. Seventy-two combinations of treatments comprised of three irrigation levels [80%, 100%, and 120% evapotranspiration demand (ETc)], three N fertilizer levels (low, medium, and high based on 2.3%, 2.5%, and 2.7% leaf N, respectively), gibberellic acid (±), miticide (±), and fungicide-nematicide (±) were included in the analysis. Using a partial budgeting procedure, returns after costs were calculated for each treatment combiition. Costs of treatments, harvesting, packing, and processing were subtracted from the value of the crop. The value of the crop was calculated as the sum of returns of crop in each size and grade category. The overall result indicated that returns after costs were higher for the +fungicide-nematicide treatment and also were generally more with increased irrigation. The combination of 120% ETc, +fungicide-nematicide, medium or high N, -miticide, and -gibberellin showed the highest return of all treatment combinations. Second highest returns were obtained with high N or with miticide and gibberellin used together.