Laser-guided variable-rate intelligent spray technology is anticipated to reduce pesticide use in production of crops and safeguard the environment. However, the ability of this technology to effectively control insect pests and diseases of crops must be validated before it becomes part of integrated pest management programs. Abilities of three different intelligent sprayers were tested to control pest insects and plant diseases at one fruit farm and two ornamental nurseries in Ohio during three consecutive growing seasons. The same sprayers with disabled intelligent functions were used as conventional constant-rate applications for comparisons. Test crops were apple (Malus pumila), peach (Prunus persica), blueberry (Vaccinium sect. Cyanococcus), black raspberry (Rubus occidentalis), crabapple (Malus sp.), maple (Acer sp.), birch (Betula sp.), and dogwood (Cornus florida). There were five insects and six diseases total involved in the investigations in the fruit farm and two nurseries. The field tests showed the intelligent spray applications reduced pesticide and foliar fertilizer use by ≈30% to 65% on average during the 3-year experiments. At the same time, intelligent spray technology was similar or more effective than conventional spray technology when controlling insects and diseases on a variety of crops. These results demonstrated that intelligent spray technology was environmentally friendly and more effective for control of insect and disease pests in fruit farms and ornamental tree nurseries.
Liming Chen, Heping Zhu, Leona Horst, Matthew Wallhead, Michael Reding, and Amy Fulcher
Marcela Miranda, Xiuxiu Sun, Christopher Ference, Anne Plotto, Jinhe Bai, David Wood, Odílio Benedito Garrido Assis, Marcos David Ferreira, and Elizabeth Baldwin
Coatings are generally applied to fruit as microemulsions, but nanoemulsions are still experimental. ‘Nova’ mandarins (Citrus reticulata) were coated with shellac or carnauba (Copernica cerifera) microemulsions or an experimental carnauba nanoemulsion; these were compared with an uncoated control during storage for 7 days at 20 °C. Coatings were also tested on ‘Unique’ tangors (C. reticulata × C. sinensis) stored for 14 days at 10 °C followed by a simulated marketing period of 7 days at 20 °C. Fruit quality evaluations included weight loss, gloss, soluble solids (SS), titratable acidity (TA), pH, SS/TA ratio, internal CO2, O2, fruit juice ethanol, and other aroma volatile content. Sensory visual shine and tangerine (C. reticulata) flavor rank tests after storage were conducted, followed by an off-flavor rating. The carnauba waxes resulted in less weight loss compared with the uncoated control and shellac coating during both experiments. There were no differences in gloss measurements of ‘Nova’ mandarins; however, shellac-coated fruit ranked highest for shine in a sensory test. For ‘Unique’ tangors, initially, shellac showed the highest gloss (shine) measurement; however, at the end of storage, the nanoemulsion exhibited the highest gloss, although it was not different from that of the microemulsion. Similarly, after storage, the nanoemulsion ranked highest for visual shine, although it was not different from that of the microemulsion. There were only minor differences in SS, TA, pH, and SS/TA among treatments. The internal CO2 gas concentration and juice ethanol content generally increased and internal O2 decreased during storage. The highest levels of CO2 and ethanol were found for the shellac treatment, as was the lowest O2, indicating anaerobic respiration. There were only minor differences among the other coating treatments; however, they were only sometimes different from those of the control, which generally had the highest O2, lowest CO2, and lowest ethanol. Shellac and the carnauba microemulsion also altered the volatile profile more than the control and the nanoemulsion did, especially for ‘Unique’ tangors. For ‘Unique’ tangors, the control and nanoemulsion ranked highest for tangerine flavor and had the least off-flavor at the end of storage. Among the coatings tested, the carnauba emulsions demonstrated less water loss, imparted more sustainable gloss, and caused less ethanol production than shellac, with the nanoemulsion exhibiting higher gloss measurements, less modifications of the atmosphere and volatile profile, and, consequently, better flavor compared with the microemulsion.
Sabin Khanal, Sarah R. Hind, and Mohammad Babadoost
Bacterial spot, caused by Xanthomonas spp., is one of the most important diseases of tomato in Illinois. Field surveys were conducted during 2017–19 to assess occurrence of bacterial spot in commercial tomato fields. Severity of foliage and fruit infection was recorded, and symptomatic samples were collected from three-to-five cultivars in three different farms in each of northern, central, and southern regions of Illinois. Severity of symptomatic foliage ranged from 0% to 91% (average 36.7%) and incidence of symptomatic fruit ranges from 0% to 30% (average 10.8%). During the surveys, 266 Xanthomonas isolates were collected and identified as Xanthomonas gardneri and X. perforans using Xanthomonas-specific hrp primers. Eighty-six percent of the isolates from the northern region were identified as X. gardneri, whereas 73% of the isolates from southern region were identified as X. perforans. Isolates from the central region were identified as X. perforans and X. gardneri 53% and 47% of the time, respectively. Multilocus sequence analysis using six housekeeping genes (fusA, gap-1, gltA, gyrB, lepA, and lacF) revealed the endemic population of X. gardneri and X. perforans. In addition to Xanthomonas, nine non-Xanthomonas bacterial genera were isolated from the samples, with most of the isolates classified as Microbacterium, Pantoea, and Pseudomonas.
Melissa Moher, Max Jones, and Youbin Zheng
The majority of commercial Cannabis sativa L. (cannabis) cultivators use a 12.0-hour uninterrupted dark period to induce flowering; however, scientific information to prove this is the optimal dark period for all genotypes is lacking. Knowing genotype-specific photoperiods may help to promote growth by providing the optimal photoperiod for photosynthesis. To determine whether the floral initiation of cannabis explants respond to varied photoperiods in vitro, explants were grown under one of six photoperiod treatments: 12.0, 13.2, 13.8, 14.4, 15.0, and 16.0 hours per day for 4 weeks. The percentage of flowering explants was highest under 12.0- and 13.2-hour treatments. There were no treatment effects on the fresh weight, final height, and growth index. Based on the results, it is recommended that an uninterrupted dark period of at least 10.8 hours (i.e., 13.2-hour photoperiod) be used to induce flowering for the ‘802’ genotype. In vitro flowering could provide a unique and high-throughput approach to study floral/seed development and secondary metabolism in cannabis under highly controlled conditions. Further research should determine if this response is the same on the whole-plant level.
Qinglu Ying, Chase Jones-Baumgardt, Youbin Zheng, and Gale Bozzo
Microgreens are specialty vegetables that contain human health-promoting phytochemicals. Typically, microgreens are cultivated in controlled environments under red and blue light-emitting diodes (LEDs). However, the impact of varying the proportions of these light qualities on the composition of diverse phytochemicals in indoor-grown microgreens is unclear. To address this problem, the levels of chlorophylls, carotenoids, ascorbates, phenolics, anthocyanins, and nitrate were examined in arugula (Eruca sativa L.), ‘Red Russian’ kale [Brassica napus L. subsp. napus var. pabularia (DC.) Alef.], ‘Mizuna’ mustard (Brassica juncea L.), and red cabbage (Brassica oleracea L. var. capitata f. rubra) microgreens following cultivation under LEDs supplying varying proportions of blue light (5% to 30%) and red light (70% to 95%). Varying the proportion of blue light did not affect the extractable levels of total chlorophyll, total carotenoids, or nitrate in all four microgreen species. Generally, the levels of reduced and total ascorbate were greatest in arugula, kale, and mustard microgreens at 20% blue light, and a minor decrease was apparent at 30% blue light. These metabolite profiles were not impacted by the blue light percentage in red cabbage. Kale and mustard accumulated more total phenolics at 30% blue light than all other blue light regimens; however, this phytochemical attribute was unaffected in arugula and red cabbage. The total anthocyanin concentration increased proportionally with the percentage of supplied blue light up to 30% in all microgreens, with the exception of mustard. Our research showed that 20% blue light supplied from LED arrays is ideal for achieving optimal levels of both reduced and total ascorbate in all microgreens except red cabbage, and that 30% blue light promotes the greatest accumulation of total anthocyanin in indoor-grown Brassicaceae microgreens, with the exception of mustard.
Guohui Xu, Lei Lei, and Hexin Wang
Mark K. Ehlenfeldt
Hong Su, He Zhang, Chaoxia Wang, Jianquan Huang, Jiayin Shang, Na Zhang, Dan Wang, and Kai Li
The addition of pulverized grape pruning wood to grape soils has a positive effect on fruit quality. However, its effects on the soil microecology of the root zone and the growth of the grape plants are not fully understood. To address this, ‘Shine Muscat’ grapes were cultivated in media consisting of garden soil and crushed grape pruning material at different mass ratios [100:1 (T1), 50:1 (T2), 30:1 (T3), 20:1 (T4), and 10:1 (T5)] and in garden soil without the pruning material, as a control. The changes in the plant fresh weight, leaf area, soil and plant analyzer development (SPAD) value, root development, soil organic carbon, microbial biomass carbon, and soil enzyme activity were determined over time. High-throughput sequencing technology was used to determine the soil bacterial community structures. The pruning supplementation increased the grape plants fresh weight, leaf area, and SPAD values. The T2 and T3 treatments increased the grape root length, surface area, and the projected area and number of the root tips; the soil organic carbon content, microbial biomass carbon content, soil invertase activity, amylase activity, and β-glucosidase activity were also significantly increased. The addition of the grape pruning material was found to increase the bacterial diversity and richness 60 and 150 days after treatment. At the phylum level, Proteobacteria, Acidobacteria, and Actinobacteria were the dominant groups, and the grape pruning material increased the relative abundance of the Acidobacteria and Actinobacteria after 60 and 150 days. The relative abundance of the Actinobacteria in the T2 treatment was 1.7, 1.3, 1.5, and 1.3 times that of the control, after 60, 90, 120, and 150 days, respectively. The T2 treatment was identified as the optimal treatment for grapes in the field because it improved the soil microecology and promoted root and tree development the most compared with the other treatments tested.
Rhuanito S. Ferrarezi, Arun D. Jani, H. Thomas James III, Cristina Gil, Mark A. Ritenour, and Alan L. Wright
The prevalence of Huanglongbing (HLB) in Florida has forced growers to search for new management strategies to optimize fruit yield in young orchards and enable earlier economic returns given the likelihood of HLB-induced yield reductions during later years. There has been considerable interest in modifying orchard architecture design and fertilizer and irrigation management practices as strategies for increasing profitability. Our objectives were to evaluate how different combinations of horticultural practices including tree density, fertilization methods, and irrigation systems affect growth, foliar nutrient content, fruit yield, and fruit quality of young ‘Valencia’ sweet orange [Citrus sinensis (L.) Osbeck] trees during the early years of production under HLB-endemic conditions. The study was conducted in Fort Pierce, FL, from 2014 to 2020 on a 1- to 7-year-old orchard and evaluated the following treatments: standard tree density (358 trees/ha) and controlled-release fertilizer with microsprinkler irrigation (STD_dry_MS), high tree density (955 trees/ha) with fertigation and microsprinkler irrigation (HDS_fert_MS), and high tree density with fertigation and double-line drip irrigation (HDS_fert_DD). Annual foliar nutrient concentrations were usually within or higher than the recommended ranges throughout the study, with a tendency for decreases in several nutrients over time regardless of treatment, suggesting all fertilization strategies adequately met the tree nutrient demand. During fruit-bearing years, canopy volume, on a per-tree basis, was higher under STD_dry_MS (6.2–7.2 m3) than HDS_fert_MS (4.3–5.3 m3) or HDS_fert_DD (4.9–5.9 m3); however, high tree density resulted in greater canopy volume on an area basis, which explained the 86% to 300% increase in fruit yield per ha that resulted in moving from standard to high tree density. Although fruit yields per ha were generally greatest under HDS_fert_MS and HDS_fert_DD, they were lower than the 10-year Florida state average (26.5 Mg·ha−1) for standard tree density orchards, possibly due to the HLB incidence and the rootstock chosen. Although tree growth parameters and foliar nutrient concentrations varied in response to treatments, management practices that included high tree density and fertigation irrespective of irrigation systems produced the highest fruit yields and highest yield of solids. Soluble solids content (SSC) and titratable acidity (TA) were lower, and the SSC-to-TA ratio was highest under STD_dry_MS in 2016–17, with no treatment effects on quality parameters detected in other years. Both drip and microsprinkler fertigation methods sufficiently met tree nutrient demand at high tree density, but additional research is needed to determine optimal fertilization rates and better rootstock cultivars in young high-density sweet orange orchards under HLB-endemic conditions in the Indian River Citrus District.
Yongjun Yue and John M. Ruter
The genus Pavonia is one of the largest genera in the Malvaceae species; it is mainly distributed in South America. Three species of Pavonia were identified based on different flower colors and potential for landscape use in the southeastern United States. These species produce a large amount of seed at the end of the blooming season, which is not ideal for ornamental use. To reduce the seed set, gamma irradiation was used for mutation induction and propensity to induce compactness and sterility. A preliminary study indicated that the seed of Pavonia hastata would germinate at irradiation rates up to 2000 Gy. Seeds of three species were treated with six different dose rates ranging from 0 Gy to 1000 Gy to determine the ideal rate for Pavonia breeding and how gamma irradiation affected seed germination. M1 (the first mutant generation) P. lasiopetala and P. missionum were sown in 2018 and planted in the field at the University of Georgia Durham Horticulture Farm on 1 May 2019, as were M2 (the second mutant generation) seeds of P. hastata. Seed germination in 2019 showed no significance due to treatment but significance due to species and species by treatment interaction. Field evaluation performed in 2019 indicated that height was not influenced by irradiation for any of the three species but that the width index was. Flower diameter and leaf area of P. missionum became smaller as the irradiation rate increased, but the other two species showed no trends. Chlorophyll mutations were observed on P. hastata at the 1500 Gy level, which has attractive traits for ornamental use.