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  • Author or Editor: Thomas Miller x
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Combinations of diuron, simazine, and terbacil were applied every year over 15 and 16 years to the same plots. Apple (Malu×domestica Borkh.) and peach (Prunus persica L.) trees then were planted 1 and 2 years following the last herbicide application. In general, apple-tree growth was not affected, but peach tree growth was reduced by some herbicide treatments. Peach-tree growth was reduced in plots treated with terbacil and soil organic matter was lowest in these plots. Time of last herbicide treatment did not affect apple- or peach-tree growth. The results indicated that reduced fruit-tree growth was associated with reduced soil organic matter and that residual terbacil may have inhibited peach-tree growth. Chemical names used: N′-(3,4-dichlorphenyl)-N,N-dimethylurea (diuron); 6-chloro-N,N′-diethyl-1,3,5-triazine-2,4-diamine (simazine); 5-chloro-3-(1,1-dimethylethyl)-6-methyl-2,4(1H,3H)-pyrimidinedione (terbacil).

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A series of experiments was conducted with apple (Malus ×domestica) and peach [Prunus persica (L.) Batsch] from 2003 to 2008 to evaluate the flower thinning efficacy of eugenol and a eugenol-based essential oil. Flower thinning effects by hand defoliation and alternative chemical agents were compared with eugenol in different years. Eugenol or the eugenol-based contact herbicide Matran 2 EC (or Matratec AG) produced noticeable phytotoxicity to floral parts and exposed leaf tissue within 15 min to 1 h after application and injury was proportional to rate. At the highest rates (8% and 10%), eugenol resulted in complete burning of all exposed tissue except bark tissue, in which there were no visible signs of injury. Within 3 to 4 weeks of application, phytotoxicity was difficult to observe even at the higher rates of eugenol. In companion experiments, hand defoliation of young leaves at bloom resulted in abscission of young fruitlets in apple, but not in peach, indicating that eugenol may cause thinning by multiple mechanisms. Ammonium thiosulfate (ATS) [49 L·ha−1 or 6.0% (v/v)] provided thinning in peach and showed little or no phytotoxicity, but the response was inconsistent. ATS was also inconsistent in thinning apple. The thinning response from monocarbamidedihydrogen sulphate (MCDS; Wilthin) at 3.2% (v/v) was inconsistent in peach. At the rate used, MCDS caused some phytotoxicity on peach. Applications of 1% to 2% eugenol appear promising, but good blossom coverage is critical for thinning. Furthermore, eugenol formulations need improvement to ensure uniform coverage for more predictable thinning.

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Application of nutrients to correct nutrient deficiencies in turfgrasses are often based on tissue analysis. Previous research has indicated that near infrared reflectance spectroscopy (NIRS) may be useful in tissue nutrient concentration determination since it requires minimum sample preparation and has been a reliable predictor of N concentration. The objective of this study was to evaluate the reliability of NIRS in determining P, K, Ca, and Mg concentrations in bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy]. Tissue samples were collected from Florida golf courses, representing different cultivars grown under various conditions and fertilizer regimes. Tissue samples were analyzed using NIRS and traditional wet chemistry (Mehlich-1 extracts analyzed using inductively coupled argon spectrophotometer) before results were statistically compared. Results from wet chemistry analysis averaged 15% lower than those obtained from NIRS. Although results for certain cultivars and elements were positively correlated (`Tifdwarf' Ca, r 2 = 0.72; P < 0.01), precision across all cultivars and nutrients was not sufficient (accounted for only 26% of variability) to indicate that NIRS would be an effective management tool for the elements evaluated in this study.

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Abstract

Peroxidase activity was determined in cucumber fruit (37 to 55 mm in diameter) subjected to mechanical stress followed by storage at 25C and 100% RH. Compared to unstressed, unstored control fruit, severe mechanical stress stimulated total extractable peroxidase activity after 24 and 48 hr of storage. Moderate mechanical stress or storage alone stimulated peroxidase activity to lesser degrees. Peroxidase isozyme analysis by native polyacrylamide gel electrophoresis showed that cucumber anodic peroxidases could be separated into slow-, moderate-, and fast-migrating groups. Both moderate and severe mechanical stress caused the appearance of a new slow-migrating peroxidase isozyme immediately after treatment. This slow-migrating isozyme disappeared after 24 hr of storage, then reappeared after 48 hr. Severe stress induced the appearance of two additional moderate-migrating peroxidases 24 hr after treatment. The same fast-migrating isozymes were also present in unstressed and moderately stressed fruits stored for 48 hr. Hence, using peroxidase as an indicator, it appears that mechanical stress induces an accelerated aging of processing cucumber fruit.

Open Access

Container-grown Cycas micronesica seedlings were purposefully infested with Aulacaspis yasumatsui and then installed at 0, 75, or 150 cm above the ground to investigate effects of infestation height on predation by Rhyzobius lophanthae. Significantly more scales on elevated seedlings were attacked by the predator. Our results indicate that lower predation at ground level by R. lophanthae may partly explain why the predator is not effectively controlling this armored scale epidemic on Guam. Ephemeral outbreaks of A. yasumatsui documented in quarterly surveys from Sept. 2006 until Aug. 2012 confirm the inadequate biological control. Our results illuminate the importance of fully evaluating the reliance on an alien predator as a solo biological control agent for an alien pest.

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Drought stress durations of 2, 4, and 6 days were imposed on Boltonia asteroides `Snowbank', Eupatorium rugosum, and Rudbeckia triloba to determine the effects on carbohydrate partitioning in the plant. Drought stress was imposed on 19 Sept. 1997 on 1.9-L containerized plants. Plants were planted in the field the day following release from stress. Crown and leaf samples of the three species were collected 21, 23, 25 Sept. 1997 and 30 Jan. and 4 May 1998 and were analyzed for low molecular weight sugars and fructans. The species differed in the time it took for longer chain fructans to break down to shorter chain fructans and low molecular weight sugars (glucose, fructose). The drought tolerant Boltonia and Rudbeckia had shifts from longer chain to shorter chain fructans by day 4 of stress. Boltonia had a change in carbohydrate partitioning in the leaf tissue, while Rudbeckia had a change in crown tissue carbohydrate partitioning. Eupatorium did not have a shift in longer chain fructans to shorter chain fructans in crown tissue until day six of stress. The slower shift from longer chain fructans to shorter chain fructans by Eupatorium, compared to Boltonia and Rudbeckia, could explain the lack of drought tolerance of Eupatorium. The shift from high molecular weight sugars to low molecular weight sugars suggests that the higher molecular weight sugars broke down to lower molecular weight sugars in response to drought stress.

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A large percentage of North American processing red raspberry (Rubus idaeus L.) is produced in maritime areas of western regions in Washington, British Columbia, and Oregon. Most of these raspberry plantings are caneburned; they are treated with herbicides in early spring to remove the first-emerging primocanes in an attempt to reduce their competition with floricanes during flowering and fruiting and thereby increase fruit yield. Trials were conducted in northwestern Washington to determine the effect of carfentrazone and oxyfluorfen applied for primocane management in three currently grown raspberry cultivars. Although caneburning did provide early season weed control in treated plots, weed control fell below 70% in the commercial ‘Meeker’ field more quickly each year: at 138 days after treatment (DAT) in 2010, 71 DAT in 2011, and 47 DAT in 2012, compared with greater than 80% control at the end of each season when the soil residual herbicide terbacil was applied. Oxyfluorfen provided longer suppression of primocane growth than did carfentrazone, particularly in ‘Cascade Bounty’ but also to a lesser extent in ‘Meeker’. Caneburning did not improve raspberry yield in five of the six tested years for ‘Meeker’, or in any of the five tested years for ‘Cascade Bounty’ or the single year for ‘Coho’, although the trend was for greater yield with caneburning across all cultivars. Oxyfluorfen improved 3-year ‘Meeker’ average yield 43% from nontreated raspberry in the commercial field trial, compared with a 29% increase with carfentrazone.

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Boltonia asteroides L. `Snowbank' (Snowbank boltonia), Eupatorium rugosum L. (eastern white snakeroot), and Rudbeckia triloba L. (three-lobed coneflower) were subjected to drought for 2, 4, and 6 days during the fall and spring. Leaf gas exchange, leaf water potential, growth, and carbohydrate partitioning were measured during drought and throughout the following growing season. Leaf gas exchange of B. asteroides was not affected by drought treatment in the fall, not until day 6 of spring drought, and there were no long-term effects on growth. Transpiration and stomatal conductance of R. triloba decreased when substrate moisture decreased to 21% after drought treatment during both seasons. Assimilation of drought-treated R. triloba decreased when substrate moisture content decreased to 12% during spring but was not affected by drought in the fall. There was a decrease in the root-to-shoot ratio of R. triloba that had been treated for 4 days, which was attributed to an increase in the shoot dry weight (DW) of treated plants. Reductions in spring growth of E. rugosum were observed only after fall drought of 6 days, and there were no differences in final DWs of plants subjected to any of the drought durations. Spring drought had no effect on growth index or DW of any of the perennials. Boltonia asteroides and R. triloba had increases in low-molecular-weight sugars on day 4 of drought, but E. rugosum did not have an increase in sugars of low molecular weight until day 6 of drought. Differences in drought response of B. asteroides, E. rugosum, and R. triloba were attributed to differences in water use rates.

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Abstract

A 6-parent diallel was used to study combining ability and type of gene action contributing to resistance in tomato (Lycopersicon esculentum Mill.) to anthracnose caused by Colletotrichum dematium (Pers. ex Fr.). The 6 parents, one set of F1, hybrids, and 5 selected reciprocal crosses were grown at 2 locations. Ripe fruit were harvested, puncture-inoculated with the pathogen, and subsequently evaluated for resultant lesion diameter. No reciprocal effects were found at either location for the 5 crosses studied. The analysis of variance for parent and F1 hybrid performance revealed a genotype × location interaction. Combining ability analysis based on the F1 hybrids alone indicated a significant general combining ability (GCA) effect. The specific combining ability (SCA) and GCA × location interaction mean squares were smaller than the GCA value but were still significant. Differential performance over locations of the hybrids of one line was primarily responsible for the GCA × location interaction. Analysis of variance and covariance of parental arrays indicated partial dominance in the direction of susceptibility. Narrow sense heritability for the trait was 70% over both locations.

Open Access

A nondestructive method was developed utilizing a modified Trebor 101 watercore tester to evaluate the internal quality of pickling cucumbers. The method involved measuring the relative amount of visible-infrared light passing through the longitudinal midsection of whole cucumber fruit. Light transmission was quantified on a unitless sigmoid scale from 1 to 10, with light transmission and scale values positively related. Immediately after hand harvest, size 3F (47 to 51 mm in diameter) cucumbers exhibited transmission values between 2 and 3, regardless of cultivar. Following a mechanical-stress treatment, which simulated bruising incurred during harvesting and handling of cucumbers, the internal quality of the fruit declined and was associated with an increase to a value of 6 in light transmission compared to non-stressed fruit. Light transmission increased as the severity of stress applied to the fruit increased, and high light transmission values were evident throughout a 48 h storage period at room temperature. Light transmission values increased as fruit diameter decreased, but values within a particular size class of undamaged, hand-harvested fruit were consistent. Machine-harvested fruit (size 3F), evaluated just before processing, exhibited light transmission values from 2 to 8, but the majority of fruit fell within the transmission range of 2 to 3. When fruit exhibiting different light transmission values were speared (cut longitudinally into sixths), processed, and then visually evaluated by panelists, spears prepared from fruit exhibiting high transmission values were judged to be of lower quality than those prepared from fruit exhibiting low transmission values. Visible-infrared light transmission may be a valuable tool for detecting poor quality cucumbers before processing, and could allow the mechanical selection of high quality fruit on a large scale basis.

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