Boxwood (Buxus spp.) is the most commonly cultivated woody ornamental shrubs in landscape settings and nursery production. Boxwood is grown for its attractive evergreen foliage and versatility in both formal and informal gardens. Meeting the high demand for boxwood plants worldwide has become challenging in recent years as the boxwood industry has been negatively impacted by a growing number of serious diseases and arthropod pests. Globally, the most common arthropods of concern are boxwood leafminer (Monarthropalpus flavus, Diptera: Cecidomyiidae), boxwood psyllid (Psylla buxi; Hemiptera; Psyllidae), Eurytetranychus buxi (Acari: Tetranychidae) and the invasive moth, Cydalima perspectalis (Lepidoptera: Crambidae). Moreover, major diseases of boxwood include boxwood blight (Calonectria pseudonaviculata, Hypocreales: Nectriaceae), Volutella blight (Pseudonectria buxi, Hypocreales: Nectriaceae), and Phytophthora root and crown rot (Phytophthora spp., Peronosporales: Peronosporaceae). These pests and diseases can lead to significant economic losses to growers and can decimate plants in landscape settings. Here we have reviewed recent research advances focused on the description and management of boxwood arthropod pests and diseases. Boxwood arthropod pests and diseases can be managed by implementing integrated arthropod pest and disease management strategies such as sanitary and cultural practices, genetic resistant cultivars, biological and chemical control methods. This information is provided to aid nursery producers, landscape industry professionals, and other stakeholders in developing integrated arthropod pest and disease management plans for boxwood.
Phytophthora root rot, caused by Phytophthora nicotianae Breda de Haan, is one of the destructive diseases of boxwood (Buxus sempervirens L.) and can affect all growth stages of field- and container-grown boxwood plants. Management is a problem and is only possible through an integrated approach. In this study, the efficacy of fungicides, biofungicides, host-plant defense inducers, and fertilizer were evaluated to manage Phytophthora root rot of boxwood. The objective of this experiment was to develop fungicide and biofungicide recommendations for Phytophthora root rot management in boxwood production. Field and greenhouse experiments were conducted in 2019 (Trial 1) and 2020 (Trial 2). The field experiment was arranged in a completely randomized design with four plots per treatment with five single ‘Green Velvet’ boxwood plants per plot. The greenhouse experiment was arranged in a completely randomized design with five single ‘Green Velvet’ container-grown boxwood plants per treatment. Plots/containers were inoculated with P. nicotianae grown on rice grains. Plant growth data such as height and average width were recorded at the beginning and end of the experiments. Total plant fresh weight and root fresh weight were recorded at the end of the experiments. Roots were assessed for root rot disease severity using a scale of 0% to 100% roots affected. Treatments used in both experiments were fungicides—ametoctradin + dimethomorph, fluzapyroxad, mefenoxam, oxathiapiprolin, pyraclostrobin, pyraclostrobin + boscalid; host-plant defense inducers—aluminum tris-drench, aluminum tris-foliar, potassium salts of phosphoric acid; biofungicides—Trichoderma harzianum Rifai strain T-22 + Trichoderma virens strain G-41, Bacillus amyloliquefaciens Priest; fertilizer—water-soluble nitrogen (nitrogen 5%) and soluble potash; and combination of water-soluble nitrogen, soluble potash, and T. harzianum Rifai strain T-22 + T. virens strain G-41. All treatments were drench applied except one of the aluminum tris, which was applied as foliar. The controls were nontreated, inoculated and nontreated, and noninoculated boxwood plants. In the greenhouse experiments, treatments that effectively reduced disease severity were pyraclostrobin, ametoctradin + dimethomorph, and oxathiapiprolin. In the field experiments, treatments such as pyraclostrobin, oxathiapiprolin, mefenoxam, fluzapyroxad, and combination of water-soluble nitrogen (nitrogen 5%), soluble potash, and T. harzianum Rifai strain T-22 + T. virens strain G-41 effectively reduced Phytophthora root rot severity. Oxathiapiprolin and pyraclostrobin are the chemical fungicides that were effective in both field and greenhouse experiments.
Oakleaf hydrangea (Hydrangea quercifolia) is an important ornamental plant grown in Tennessee. In May 2018, after late spring frost, cultivars Pee Wee and Queen of Hearts showed root and crown rot symptoms and identification and management of the disease was a major concern. The objective of this research was to identify the causal organism of this disease and develop management recommendations for nursery growers. Isolates from the infected root and crown parts were subjected to microscopy and the morphology of fungi resembled Fusarium. Molecular analysis was conducted by amplifying the internal transcribed spacer (ITS) of ribosomal DNA, beta-tubulin (b-Tub), and translation elongation factors 1-α (EF-1α) regions. Fusarium oxysporum was identified as a causal organism based on morphological and molecular analysis. Pathogenicity test was done to complete the Koch’s postulates by drenching containerized oakleaf hydrangea with conidial suspension. Experiments were conducted to evaluate different chemical fungicides and biological products with different rates for Fusarium root and crown rot management in container grown ‘Queen of Hearts’. Plants were inoculated by drenching containerized oakleaf hydrangea with 150 mL conidial suspension of F. oxysporum maintaining the concentration of 1×106 conidia/mL. Root and crown rot were assessed using a scale of 0-100%. Recovery of F. oxysporum was recorded by plating root and crown sections. Chemical fungicides such as mefentrifluconazole (BAS75002F), the low rate (1.09 mL/L) of difenoconazole + pydiflumetofen (Postiva), and the high rate (1.32 mL/L) of isofetamid (Astun) and biopesticide: the high rate (1.64 g/L) of ningnanmycin (SP2700 WP) effectively reduced Fusarium root rot severity and pyraclostrobin effectively reduced Fusarium crown rot severity in both trials.
Root rot caused by Fusarium oxysporum Schltdl. is a newly identified disease in oakleaf hydrangea. Some cultivars such as Pee Wee and Queen of Hearts grown in pot-in-pot container system showed root rot symptoms after late spring frost in May 2018 with 40% and 60% incidence in the infected nursery, respectively. This experiment was carried out to evaluate the tolerance among different hydrangea cultivars against root rot caused by F. oxysporum. Fifteen hydrangea cultivars from four different species were selected and rooted cuttings were prepared from new spring flushes. Twelve plants from each cultivar were transplanted in a one-gallon pot. Half of transplanted plants (6 - single plants) were inoculated by drenching 150 mL conidial suspension of F. oxysporum maintaining the concentration of 1×106 conidia/mL. Half of the plants remain non-inoculated (control) and were drenched with sterile water. After four months, root rot was assessed using a scale of 0-100% root area affected and recovery of F. oxysporum was recorded by plating 1 cm root in Fusarium selective medium. Fusaric acid (FA) and mannitol were extracted from the roots of inoculated and non-inoculated plants to see the effect and role on pathogenesis. Further, mannitol concentration was analyzed using absorption wavelength in spectrophotometer and FA was analyzed using high-performance liquid chromatography (HPLC). Results indicated that no cultivars were resistant to F. oxysporum. Cultivars from Hydrangea arborescens, H. macrophylla and H. paniculata were more tolerant to F. oxysporum compared to cultivars from H. quercifolia. Among H. quercifolia, cultivars Snowflake, John Wayne and Alice were more tolerant to F. oxysporum.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.