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- Author or Editor: Daniel L. Ward x
Release LC (Abbott Laboratories), a commercial formulation of gibberellins, was applied to apricot, cling peach, freestone peach, nectarine, and plum varieties. Application was by commercial airblast sprayer. Fruit firmness was increased in the season of application in all crops. Meta analysis of the data indicated a maximum response for each crop differed over the rate range of 16 to 48 g a.i./acre. Changes in fruit soluble solids were slight. No differences in fruit color were observed. Reduction in flower bud density (thinning) was observed the following season. The reduction in bud density reduced the time required to hand-thin to a commercially acceptable level. A difference in thinning sensitivity to gibberellin was evident between crops.
G A3 sprays were applied to 10 primary scaffold limb replications with a handgun at three concentrations (25, 50, 100 mg/l), from May to September 1989. Flower bud thinning with G A3 applied in the year prior to bloom was examined for its effect on the developmental fate of lateral meristems. Limbs treated in late May had, on average, 45% more flower buds survive near-critical winter temperatures than did controls. During the period of greatest sensitivity to Flower Bud Density (FBD) reduction, GA3 treated limbs had vegetative bud densities (VBD) higher than control (on average 45% greater at 100 mg/l). On 9 June 100 mg/l reduced FBD by 78% compared to control and increased VBD by 57%, while on 6 July the same concentration. reduced FBD by 94% but VBD was increased by only 32%. These results appear to support the hypothesis that GA3 induced FBD reduction has more than one mode of action.
Preharvest fruit drop of apple [Malu×domestica (L.) Borkh.] can cause significant crop losses, but factors controlling date of individual fruit drop are unknown. In three types of experiments, we investigated the relationships among seed number/fruit, fruit weight, and day of year of drop. By shading in mid-May and stigma excision before bloom, we induced variability in seed number. Dropped fruit were weighed, and their seeds were counted daily from late August until all fruit had dropped. Nontreated trees were studied similarly. Regression analyses were used to assess relationships among day of drop, fruit weight, and seed number/fruit. Substantial variation in day of drop of individual fruit was not explained by seed number of the fruit in these experiments with `Smoothee Golden Delicious', `Redchief Delicious', and `Commander York'.
The effects of two pumpkin cultivars and five fungicide programs on cucurbit powdery mildew development and yield were evaluated in southern New Jersey from 2005 to 2007. Each year, five separate fungicide programs were applied to powdery mildew-tolerant cv. Magic Lantern or powdery mildew-susceptible cv. Howden pumpkin. The five fungicide programs applied season-long (10 applications per program) included: 1) protectant fungicides only: manzate + sulfur [Fungicide Resistance Action Committee (FRAC) codes M3 + M2] alternated weekly with maneb + copper hydroxide (FRAC codes M3 + M1); 2) standard program: chlorothalonil + myclobutanil (FRAC codes M5 + 3) alternated with azoxystrobin (FRAC code 11); 3) intensive program: maneb + myclobutanil (FRAC codes M3 + 3) alternated with [famoxadone + cymoxanil] (FRAC codes 11 + 27); 4) FRAC code 3 weekly: chlorothalonil + myclobutanil (FRAC codes M5 + 3) alternated with myclobutanil (FRAC code 3); and 5) FRAC code 11 weekly: chlorothalonil + azoxystrobin (FRAC codes M5 + 11) alternated with azoxystrobin (FRAC code 11). In each year, there were no significant interactions between the fungicide program and cultivar. In each year, area under disease progress curve values were highest when a FRAC code 11 fungicide was applied weekly compared with a FRAC code 11 fungicide applied in a weekly rotation with a FRAC code 3 fungicide or a FRAC code 3 fungicide applied weekly.
Visual examination of leaves at the end of each production season revealed there were no significant differences in powdery mildew development on the top (adaxial) or bottom (abaxial) sides of leaves in untreated subplots. Powdery mildew development was lower on the bottom sides of leaves when a Fungicide Resistance Action Committee (FRAC) code 3 fungicide was applied weekly compared with a FRAC code 11 fungicide applied weekly or when a FRAC code 3 fungicide was rotated weekly with a FRAC code 11 fungicide in each year of the study. There were no significant differences in total number of harvested fruit, number of harvested orange fruit, average weight of orange fruit, or percentage of harvested orange fruit between fungicide programs in each year of the study. Results of this study, based on arcsine-transformed area under disease progress curve (AUDPC) values and top and bottom leaf surface ratings, suggest that the weekly use of the FRAC code 11 fungicide lead to the development of practical resistance in the field population of cucurbit powdery mildew. Rotating a FRAC code 11 and FRAC code 3 fungicide weekly resulted in lower AUDPC values and powdery mildew development on the bottom side of leaves in 2 of 3 years of this study. However, based on AUPDC values and leaf rating values, the level of control obtained with the high-risk FRAC code 3 fungicide was less during each consecutive year. The immediate erosion of control (i.e., qualitative resistance) as observed with the FRAC code 11 fungicide or the gradual decline of control (quantitative resistance) as observed with the FRAC code 3 fungicide over three growing seasons shows the importance of being able to detect and understand the mechanisms of practical resistance development. This understanding will allow appropriate fungicide control recommendations to be made in a timely (i.e., real-time) manner. Importantly, fungicide resistance is most likely to develop on the bottom side (abaxial) of pumpkin leaves when effective, low-risk (nonmobile) fungicides (FRAC code M numbers) are tank-mixed with high-risk fungicides in cucurbit powdery mildew control programs. Tank-mixing fungicides that have a high risk for resistance development with protectant fungicides that have a low risk for resistance development remains critically important when controlling cucurbit powdery mildew and reducing the potential for fungicide resistance development. This is the first report of cucurbit powdery mildew developing practical resistance to a FRAC code 11 and FRAC code 3 fungicide in New Jersey.
A field study was conducted during the 2007 and 2008 growing seasons to determine and compare the susceptibility of 33 peach (Prunus persica L. Batsch) cultivars and advanced selections to rusty spot caused by Podosphaera leucotricha. During each season, the progression of peach rusty spot was monitored on three cultivars of varying susceptibility to determine when the epidemics had terminated. At that time, disease incidence and severity were estimated as percent infected fruit and number of lesions per fruit, respectively, for all cultivars in the study. Observations were recorded on fruit sampled from four replicate trees of each cultivar located in experimental plantings at the Rutgers Agricultural Research and Extension Center, Bridgeton, NJ. No fungicide sprays were applied to the trees during the study. Overall disease incidence values, estimated by averaging data from both years, varied widely across cultivars, ranging from 5% to 68% fruit infected. The three most susceptible cultivars were Autumnglo, Jerseyqueen, and Bounty, whereas the three least susceptible cultivars were Gloria, Harrow Beauty, and Sugar May. Results of Tukey-Kramer mean separation groupings and relative susceptibility rankings across both years were used to place cultivars into five disease susceptibility categories. The most susceptible cultivars were characterized as having yellow flesh with normal melting flesh texture and acidity, whereas less susceptible cultivars tended to have white-fleshed stony-hard subacid fruit. Among eight quantitative fruit characteristics examined for association with disease levels, ripening date, fruit weight at pit hardening, and fruit pubescence were found to be positively correlated with rusty spot development. Finally, the relationship between disease incidence and lesion density within the 0 to 0.5 incidence range, based on data from all cultivars in the study, agreed closely with former models derived from only a single cultivar.
In a conventional sophomore level course entitled “Organic Farming and Gardening,” 114 undergraduate students registered from years 2007 to 2009. Due to high demand and insufficient classroom space, this conventional curriculum was reformatted with identical course content into both a hybrid and a fully online version in which 361 students registered from years 2010 to 2012 and 336 students from 2013 to 2015. In comparing conventional instruction with hybrid and fully online versions over a 9-year period, few significant differences were found in final grades involving 811 students. Final class grade averages of these three learning systems ranged from 85.5% to 89.6% over their first 3-year spans. Over their 6-year span, the conventional class average of 89.6% was higher compared with 88.3% for the hybrid format and 86.8% for the online format. Student evaluation surveys assessed faculty performance with eight evaluative questions on a 1 to 5 scale from years 2012 to 2014. No significant difference existed between teaching in person vs. remotely, averaging 4.35 for the hybrid and 4.17 for the online. An additional eight questions measured educational methodology, technology, student confidence, and class satisfaction. There were no significant differences in comparing the combined averages of 4.12 for the hybrid format and 4.00 for the online version. Student responses indicated a significant preference overall for hybrid and online course formats compared with conventional methods. Registration numbers indicated an overwhelming choice for online education with an average class enrollment of 91.0 students compared with 38.0 students for conventional classes and 25.2 students for the hybrid format.
In this study, the effects of six nitrogen fertility programs and two bell pepper (Capsicum annuum) cultivars were evaluated for marketable yield and incidence of skin separation in fruit. In 2006 and 2007, bell pepper cultivar Aristotle, which is tolerant to the crown rot phase of phytophthora blight (Phytophthora capsici), and a susceptible cultivar, Camelot, were established in a split-plot design with cultivar as the whole-plot factor and fertilizer regime as the subplot factor. Each year, fertility treatments included 1) 180 lb/acre of soluble nitrogen (N) plus phosphorus (P) and potassium (K) as 20N–8.7P–16.6K, 2) 300 lb/acre of soluble N (4N–0P–6.6K), 3) 180 lb/acre of soluble N (30N–0P–0K), 4) 135 lb/acre of soluble N (30N–0P–0K), 5) 180 lb/acre of granular N (43N–0P–0K), and 6) 135 lb/acre of granular N (43N–0P–0K). Soluble fertilizer treatments 1–4 were applied weekly through drip irrigation during the production season. Granular fertility treatments 5 and 6 were applied after bed making but before laying black plastic mulch each year. Additionally, all plots received 180 lb/acre each of P and K (0N–2.6P–4.9K) plus 2 lb/acre of boron distributed season-long in weekly fertilizer applications. In 2006 and 2007, cultivar had no effect on marketable yield or percent marketable fruit. In 2007, the percentage of harvested fruit with skin separation was significantly higher in fertility programs 1 and 2 compared with program 5. In 2006 and 2007, there were no significant interactions between cultivar and fertility program for marketable yield per plot, fruit with skin separation, percent marketable fruit, or marketable yield per acre. In both years, harvest date has a significant effect on marketable yield per plot, fruit with skin separation, percent marketable fruit, and marketable yield per acre. The percentage of harvested fruit with skin separation was higher in phytophthora-tolerant ‘Aristotle’ compared with phytophthora-susceptible ‘Camelot’ in 2006 and 2007. Results of this study suggest that the development of skin separation in bell pepper fruit is more influenced by genotype than N fertility program.
From 2006 to 2008, four different production systems and five bell pepper cultivars (Capsicum annuum) with either no resistance (Alliance and Camelot), tolerance (Revolution), or resistance (Paladin and Aristotle) to the crown rot phase of phytophthora blight (Phytophthora capsici) were evaluated for the development of skin separation or “silvering” in fruit at a research facility and four commercial vegetable farms in southern New Jersey. Cultivar, production system, and year, each had a significant effect on the total percentage of fruit with skin separation and marketable yield. The percentage of bell pepper fruit with skin separation was higher in both phytophthora-resistant cultivars compared with the phytophthora-susceptible cultivars across all four production systems. Marketable yield was highest when bell peppers were grown in double rows on raised beds with black plastic mulch and drip irrigation compared with bell peppers grown on single rows on raised beds with black plastic mulch and drip irrigation and bell peppers grown on single rows on raised, bare ground beds with buried drip irrigation. Marketable yields were lowest when bell peppers were grown in single rows on high, ridged beds with overhead irrigation. Results of this study suggest that the development of skin separation or “silvering” in fruit is more closely associated with genotype than type of production system.
Preharvest abscission of apple [Malus ×domestica (L.) Borkh.] fruits causes significant crop loss in many years. In this study, fruit cutting was used to induce abscission in August and September. Abscission zones of `Redchief Delicious' Mercier strain fruits were sampled 0, 2, 4, and 6 days after cutting. Thin-layer-plate assays were developed and used to identify hydrolytic enzymes active in the abscission zone (AZ) after induction. Increased activity of cellulase, but not polygalacturonase, was detected in the AZ following cutting. Cellulase activity was consistently high in AZs 4 days after cutting. Both AVG (652 mg·L–1) and NAA (10 mg·L–1) applied 2 or 4 days after cutting delayed drop, but NAA delayed drop 1.6 days longer than did AVG. Fruits treated with AVG dropped over a longer period than did control or NAA-treated fruits. Chemical names used: aminoethoxyvinylglycine (AVG); naphthaleneacetic acid (NAA).
Sweet basil (Ocimum basilicum) is the most economically important culinary herb in the United States. In 2007, a new disease, basil downy mildew (BDM), caused by the oomycete pathogen Peronospora belbahrii, was introduced into the United States and has since caused significant losses in commercial basil production. Although no commercial sweet basils available are resistant to P. belbahrii, other species of Ocimum have exhibited potential tolerance, resistance, or both. The objectives of this work were to determine if leaf morphological characteristics including stomata density and leaf curvature correlated with infection of plants by P. belbahrii, and thus could be used as selected characters in plant breeding. In 2011, 20 Ocimum cultivars including sweet (O. basilicum), cinnamon (O. basilicum), clove (O. basilicum), citrus (Ocimum ×africanum syn. Ocimum citriodorum), spice (Ocimum americanum syn. Ocimum canum), and holy basils (Ocimum tenuiflorum syn. Ocimum sanctum) were evaluated for susceptibility to downy mildew. Sweet basils were determined to be the most susceptible; cinnamon, clove, and Thai types were moderately susceptible; and citrus, spice, and holy types were least susceptible to downy mildew. Using those same 20 Ocimum species and cultivars, stomata length and density and leaf curvature were measured and correlated with downy mildew incidence and severity. In general, basil species with higher stomatal densities had higher downy mildew incidence and severity. High stomatal densities were mainly found in the sweet, cinnamon, and clove basils. Citrus and spice species with longer stomatal lengths generally exhibited lower downy mildew incidence. Holy basil, the least susceptible of all Ocimum sp. to P. belbahrii evaluated in this study, had the greatest stomatal density and shortest stomatal length. Some sweet basil cultivars with the highest downy mildew incidence also had the greatest downward leaf curvature, whereas other sweet basil cultivars with moderate downy mildew incidence had leaves that were nearly flat or curved upward. Holy, citrus, and spice basils with low downy mildew incidence had leaves that were nearly flat or curved upward. This study suggests that leaf curvature and stomatal density and length affect downy mildew development and sporulation. Considerations of these leaf morphological characteristics may be useful phenotypic traits in breeding for downy mildew resistance in Ocimum.