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  • Author or Editor: Christian A. Wyenandt x
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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.

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In 2001 and 2002, fall- and spring-sown, spring-killed or spring-sown living cover crops mulches were evaluated for their effects on pumpkin (Cucurbita pepo) number and weight, fruit cleanliness, and fusarium fruit rot (FFR; Fusarium solani f. sp. cucurbitae race 1). In general, the number and weight of orange (mature) fruit and total fruit weight were higher in bare soil (conventional), fall- or spring-sown, spring-killed cover crop mulches compared with spring-sown, living annual medic (Medicago spp.) cover crop mulches. In both years, pumpkins grown on fall-sown winter rye (Secale cereale), hairy vetch (Vicia villosa), winter rye + hairy vetch, and spring-sown oat (Avena sativa) produced fruit numbers and weights comparable to or slightly higher than bare soil (conventional) production, suggesting that these cover crop mulches had no effects on reducing pumpkin yield. The number and weight of pumpkins grown in spring-sown, living annual medic cover crop mulches were reduced in both years compared with the other cover crop mulches. On artificially inoculated field plots, percentages of groundcover at harvest and fruit with FFR were 89% and 5% in fall-sown winter rye (seeded at 90 lb/acre), 88% and 10% in fall-sown rye (50 lb/acre), 85% and 5% in fall-sown rye + hairy vetch (50 lb/acre each), 19% and 30% in fall-sown hairy vetch (50 lb/acre), 23% and 23% in spring-sown oat (110 lb/acre), 1% and 25% to 39% in spring-sown, living annual medics (40 lb/acre) and 0% and 46% in bare soil plots, respectively. Results suggest that cover crop mulches such as fall-sown winter rye, fall-sown winter rye + hairy vetch, or spring-sown, spring-killed oat killed and left on the soil surface may help reduce losses to FFR in pumpkin production.

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Although not considered an essential nutrient, silicon (Si) can be beneficial to plants. Si accumulator species such as pumpkin (Cucurbita pepo var. pepo) can absorb Si from soil. Si uptake may reduce plant susceptibility to fungal diseases such as cucurbit powdery mildew (Podosphaera xanthii and Erysiphe cichoracearum). We previously reported that wollastonite, an Organic Materials Reviews Institute–approved natural mineral, can increase soil Si level, increase soil pH, provide pumpkin plants with Si, and increase their resistance to powdery mildew. In this study, we examined the optimum application rate of wollastonite for pumpkins grown in pots and exposed to cucurbit powdery mildew. We confirmed that wollastonite has liming capabilities similar to regular limestone. Regardless of the application rates, wollastonite and limestone showed similar effects on soil chemistry and plant mineral composition. Pumpkin plants grown with the lower doses of wollastonite amendments (3.13 and 6.25 tons/acre) had the greatest tissue Si concentrations and demonstrated the greatest disease resistance. We conclude that wollastonite is a useful material for organic cucurbit (Cucurbitaceae) growers who want to increase soil pH and improve plant resistance to powdery mildew at the same time. Applying wollastonite at rates beyond the amount required to achieve a desirable soil pH for pumpkin production did not further increase Si uptake, nor did it further suppress powdery mildew development.

Open Access

The effect of preharvest application of a newly developed second-generation harpin product (2G-Harpin) on shelf life of fresh-cut lettuce (Lactuca sativa) was investigated. The lettuce plants were grown in three locations in the United States: Watsonville, CA, Cedarville, NJ, and Yuma, AZ, and treated 5 days before harvest at 140, 280, and 420 g·ha−1 (30, 60, and 90 mg·L−1). Lettuce processed and bagged were stored at 1 to 3 °C and evaluated for quality for 20 days. Lettuce from California treated with 2G-Harpin at 280 to 420 g·ha−1 consistently showed better visual quality and lower microbial population than the control. Overall results in New Jersey showed no major differences among treatments. In Arizona, microbial population was lower and visual quality was higher in lettuce treated at 280 and 420 g·ha−1 during part of the storage period. In further experimentation, we examined the phenolic content of lettuce harvested 1 and 7 days after treatment with 2G-Harpin. The results showed that phenolic content was higher in all treated lettuce than in the control lettuce after 24 h. Six days later, the levels fell back to the initial stage. Antioxidants capacity increased by 40% in head leaves when plants were treated with 280 and 420 g·ha−1 2G-Harpin, but no change was observed in outer leaves. Overall, it was revealed that a field application of 2G-Harpin can improve quality of fresh-cut lettuce under environmental conditions that need to be determined. Our results with phenolic content and antioxidant activity suggested that improvement in quality is probably the result of alteration of metabolites' composition and demonstrated that increased phenolics do not correlate with lower quality of fresh-cut products.

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Fusarium wilt of basil (FOB), caused by Fusarium oxysporum f. sp. basilici, is an economically damaging disease of field- and greenhouse-grown sweet basil. Growers have observed a resurgence of FOB and susceptibility in FOB-resistant cultivars. Because currently available chemical, biological, and cultural control methods are costly, unsustainable, ineffective, or challenging to implement, new strategies of FOB control are needed. Cold plasma is becoming an increasingly important experimental technology in the food and agricultural industry for pathogen decontamination. To understand the effect of cold plasma treatment on FOB incidence and severity, experiments were conducted by treating FOB mycelium, inoculated sweet basil seedlings, and seeds with various experimental cold plasma treatment devices, all using helium as a feed gas. Initial results indicated that while the cold plasma jet treatment did not result in a significant reduction in mean mycelial growth rate or virulence of the pathogen, direct cold plasma jet treatments on seedlings, as well as a cold plasma dielectric barrier discharge treatment on seeds, did exhibit varying efficacies against FOB. Control of FOB appeared to be strongly dependent on the exposure time to cold plasma. These findings can aid in the standardization of a cold plasma treatment for the commercial basil seed and transplant industry.

Open Access

Different basils (Ocimum sp.) and cultivars (28 in 2009 and 32 in 2010) were evaluated for susceptibility to basil downy mildew (Peronospora belbahrii) at the Rutgers Agricultural Research and Extension Center near Bridgeton in southern New Jersey. At the end of each growing season, seed was collected from individual plants and stored for potential downy mildew pathogen detection using real-time polymerase chain reaction (PCR) analysis. Most of the basil cultivars and breeding lines were showing symptoms of basil downy mildew infection at the time of seed collection before the first frost near the end of the production season. Symptoms of basil downy mildew were present on 25 of the 28 (89%) basil lines evaluated in 2009 and 26 of 32 (81%) basil lines tested in 2010 at the time of seed harvest, with sporulation evident on the abaxial surface of infected leaves. Real-time PCR analysis of seed collected from various infected plants detected P. belbahrii on seed of 14 of 25 (56%) basil lines tested in 2009 and 8 of 32 (25%) tested in 2010. Importantly, P. belbahrii was not only detected on seed of sweet basil (Ocimum basilicum) phenotypes but also on seed of ‘Spice’ basil (Ocimum americanum) in 2009 and ‘Sweet Dani Lemon Basil’ basil (Ocimum citriodorum), ‘Holy Red and Green’ basil [Ocimum tenuiflorum (form. sanctum)], ‘Lime’ basil (O. americanum), and again on ‘Spice’ basil in 2010 where no symptoms (i.e., no chlorosis or sporulation) were present on the leaves when seed were collected. This work demonstrates that basil seed, regardless of basil species and whether symptoms are visible on foliage of the basil plant or the plant is immune or resistant to downy mildew, can test positive for the presence of P. belbahrii using a real-time PCR assay following exposure of plants to the pathogen during the natural development of downy mildew under field conditions.

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