Boxwood production.

Of 29 nurseries in the sample frame, a total of 25 clicked the link and 20 agreed to participate in the survey. Of these 20 responses, two were incomplete and 18 (62%) were completed in the first-round instrument. Members of the panel were from the states of Connecticut, Georgia, Illinois, Kansas, Minnesota, Oregon, Tennessee, Texas, and Virginia. Boxwood represented 14% of average total nursery sales for all the nurseries in the panel, which is higher than the percentage of boxwood share of total US broadleaf evergreens sold (7%) reported in the 2019 Census of Horticultural Specialties (US Department of Agriculture, National Agricultural Statistics Service 2020). As far as the types of boxwood operations, 80% of the panel members were involved in boxwood propagation, 55% were involved in field production, and 80% were involved in containerized boxwood production. Several respondents were involved in all three types of operations.

Asiatic boxwood was the most grown category (35%), followed by other hybrids (30%), less susceptible cultivars (23%), and American/English boxwood (11%). Common cultivars such as Golden Dream, John Baldwin, Baby Gem, Wedding Ring, Sprinter, Green Pillow, Hohman’s Dwarf, Grace Hendricks Phillips, Peergold, Cole’s Dwarf, Big Leaf Wintergreen, and Green Pillow fall into Asiatic boxwood category (Baysal-Gurel and Liyanapathiranage 2017; Ganci 2014; Ganci et al. 2013; Miller et al. 2016; Yoder et al. 2022). The results of this study are comparable to a previously published literature which indicates that the growers are shifting toward cultivating less susceptible boxwood (Omolehin et al. 2022). Asiatic boxwood category includes high to moderately resistant cultivars whereas American/English boxwood category includes cultivars highly susceptible to boxwood blight. The cultivars such as Aurea-pendula, Justin Brouwers, Vardar Valley, Suffruticosa, Scupi, Rotundifolia, Northland, Denmark, Handsworthiensis, Pendula, Newport Blue, Graham Blandy, Dee Runk could be included in English/American boxwood category (Baysal-Gurel and Liyanapathiranage 2017; Ganci 2014; Ganci et al. 2013; Shishkoff et al. 2015). Cultivars that could be included in the less susceptible category are National, Jim Stauffer, Gregem, Green Beauty, Nana, Winter Beauty, Wintergreen, Pinchusion, and Winter Gem (Baysal-Gurel and Liyanapathiranage 2017; Ganci 2014; Ganci et al. 2013; Miller et al. 2016). NewGen boxwood, included in the less susceptible category, was developed from the resistant cultivar breeding efforts as a response to the boxwood devastation caused by boxwood blight (Daughtrey 2019; McClellan 2019). The category of other hybrid cultivars could include Chicagoland Green^® Glencoe, Green Velvet, Green Ice, Green Mound, Green Gem, and Green Mountain (Baysal-Gurel and Liyanapathiranage 2017; Ganci et al. 2013; Ganci 2014; Miller et al. 2016; Shishkoff et al. 2015).

The proximity of the boxwood propagation facility to container or field production areas were compared and 50% of panel members responded that they had their propagation and production areas in the same nursery, 45% had the nearest boxwood container or field production area between 100 yards and 1 mile of the propagation facility, 10% had the nearest boxwood container or field production area within 100 yards of the propagation facility, and 5% had the nearest boxwood container or field production area more than 1 mile from the propagation facility. Cps conidia can sporulate on fallen or infected tissues and disperse to nearby crops during boxwood operations, whereas infected leaves blown into nearby fields also have the potential to germinate and cause further disease spread (Weeda and Dart 2012). The accidental movement of infected plant materials by the workers from production to propagation area or movement of pathogen inoculum via tools and equipment used in production, worker boots, gloves, or clothes (Bika et al. 2021; Daughtrey 2019; Gehesquière 2014) could potentially occur if propagation or production area are in close proximity. For this reason, the nurseries that had propagation and cultivation in the same area were at a higher risk of rapid disease spread and higher economic losses, whereas nurseries that maintained a greater distance (100 yards to 1 mile or more than 1 mile between production and propagation facilities) were comparatively at a lower risk.

Pachysandra (Pachysandra sp. Michx., Buxales, Buxaceae) and sweet box (Sarcococca sp. Lindl., Buxales, Buxaceae) are alternate hosts of Cps, and even if disease management measures are adopted to manage the Cps in boxwood, these alternate hosts can harbor the pathogen to establish a new infection cycle (Kong et al. 2017; LaMondia and Douglas 2015). Fifteen percent of the survey respondents grew sweet box, 20% grew pachysandra, and the majority of the respondents (70%) did not grow any of these plants with boxwood in the same nursery.

Twenty percent of the growers used smaller blocks to grow boxwood, whereas a majority (80%) did not produce boxwood in blocks. These smaller blocks of boxwood were separated by various tree and shrub species, grasses, Azalea (Ericales, Ericaceae), and Ilex (Aquifoliales, Aquifoliaceae) plants. It is recommended to produce boxwood in small blocks separated by a distance of 10 ft rather than using the whole available production area as a single block (Baysal-Gurel 2023; Dart et al. 2014; LaMondia et al. 2023).

The movement of infected plants, accidental spread of the sticky conidia by human factors such as use of contaminated cuttings tools, workers clothes, gloves, boots, equipment used in production are considered the main mechanisms of pathogen spread, but the spread could also occur by splashing rain, rainy storm, or irrigation from one plant to another plant (Baysal-Gurel and Liyanapathiranage 2017; Bika et al. 2021; Castroagudín et al. 2020; Douglas 2011; Henricot 2006; Kodati et al. 2022; LaMondia et al. 2021). The pathogen transmission via water could be minimized if a barrier of nonhost plant is used between each block of boxwood plants, which increases the diversity of plant species that will have a negative impact on the pathogen load. This lessens the rate of disease spread in the field and the disease does not spread as easily or quickly if the boxwood blocks were located next to each other without a barrier (Baysal-Gurel 2023; Hantsch et al. 2013; Mitchell et al. 2002). It is important to note that eradication measures are recommended when the boxwood blight is detected (Bush et al. 2016; Dart et al. 2014). Boxwood growers who do not use small blocks to grow boxwood are at higher risk of economic losses due to boxwood blight if Cps is accidentally introduced compared with growers who use blocking approach or use a single large block (production area). If smaller blocks are used in production and disease is detected in one block, only the plants from that block must be eradicated, which lessens the economic losses associated with boxwood blight.

Also, from these respondents, 42% followed a rotation plan after boxwood production, and 58% did not follow a rotation plan. When planting consecutive crops during a crop rotation program, 95% always completely cleaned out after each crop whereas 11% interplanted (planted another crop after boxwood) in the rotation program. A total of 63% of growers removed plant debris located under the plant rows immediately after each pruning, and 16% used other methods and 21% never removed any debris from the nursery. This indicated that panel members were aware of the potential of plant debris or pruned plant materials to be a source of new infections in healthy crops and aid in increased disease pressure. Sanitation is crucial in boxwood blight management as it helps to remove the Cps inoculum which could be surviving in the fallen plant debris (Palmer and Shishkoff 2014).

Unsanitized cutting tools could also spread Cps from one plant to another or, more specifically, cuttings prepared using unsanitized tools could carry the pathogen (Bika et al. 2021). When taking cuttings for propagation or pruning boxwood plants, 47% used a new or sanitized cutting tool after each block whereas 37% sanitized or used a new tool after each row, 5% used at each cut, 5% used at each plant, and 6% did not sanitize cutting tools. Forty-two percent of the growers treated boxwood cuttings with a sanitizing agent to eliminate plant pathogens and 58% did not use sanitizing agents. Additionally, 26% of members sanitized clothing, equipment, and vehicles between boxwood blocks, whereas 74% did not sanitize. The risk of spread of boxwood blight between fields of production within a production business is higher as the transmission of the pathogen could occur via human and animal movement and unsanitized cutting tools (Bika et al. 2021; Daughtrey 2019; Gehesquière 2014). The majority of the panel members did not sanitize clothing, equipment, and vehicles between blocks, which could be due to various reasons such as lack of awareness among the growers about the overall steps in sanitation that include cleaning the production area, and then using disinfecting agents to kill the plant pathogens (Hansen 2020), cost, and time associated with the sanitation (The HC Companies, Inc. 2023).

Diagnosis is a crucial first step in plant disease management (Castroagudín et al. 2020; Fry 2012). A majority of the panel members were involved in pathogen testing to reduce the further spread of the disease. Twenty-six percent of growers tested boxwood cuttings/plants within their company for the presence of plant pathogens, 58% sent them to a laboratory for testing, and only 26% did not test. Pathogen testing or diagnosis could be helpful in accurate diagnosis, early detection, monitoring the levels of disease or pathogen load, and applying necessary curative and quarantine measures that ultimately help in integrated plant disease management to minimize crop loss (Castroagudín et al. 2020; Malapi-Wight et al. 2016).

Plant health.

Phytophthora root rot, Volutella blight, boxwood blight, Fusarium root rot, and Pythium root rot were rated as the most problematic diseases faced by the panel members. Boxwood dieback, Macrophoma leaf spot, and nematodes were the least problematic in current boxwood production (Table 1). Phytophthora species are one of the most problematic and widely studied phytopathogens in nursery production which justifies the growers’ selection of Phytophthora as one of the current most problematic diseases in their production system (Mihajlovic et al. 2017; Parke et al. 2019).

Table 1.

Disease rating during current boxwood (Buxus sp.) production with 0 = no problem at all, 1 = least problematic to 10 = most problematic.

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Boxwood blight and Phytophthora root rot were rated as moderate to high threats to future boxwood production whereas Volutella blight, Pythium, Fusarium, Macrophoma, boxwood dieback, and other diseases were rated to be a low-to-moderate threat to boxwood production in the future (Table 2). The rapid spread of boxwood blight within the US states justifies the grower’s perception of boxwood blight being the worst threat they will encounter in the future (Daughtrey 2019; Ivors et al. 2012). In addition, Phytophthora is a soilborne pathogen often associated with water and is hard to manage, which justifies panel members’ anticipation of this being one of the problematic pathogens in the future (Parke et al. 2019; Redekar et al. 2019).

Table 2.

Extent of the diseases that pose a threat to boxwood (Buxus sp.) plant health in future production with 1 = no threat, 2 = low threat, 3 = moderate threat, 4 = high threat, and 5 = extreme threat.

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As listed in Table 3, a list of 17 items that could serve as sources of plant pathogens during boxwood production were assessed to better understand grower perceptions using the 5-point Likert scale. Twelve of 17 items had an average perception rating >3.5, with the highest rating for “boxwood transplants” (4.9 ± 0.2) compared with other sources such as cutting tools, nursery equipment, nursery bench, floor and sidewall surfaces, plant debris and culled plants, media and soil, trays, pots or containers, irrigation water, work clothing and shoes, visitors and nonemployees, worker hygiene, and other crops. The sources such as irrigation water, incoming plants, pots, potting media, and production field are already established critical control points in nursery crop production and have the potential to be the critical control points to decrease the spread of boxwood blight in nurseries (Parke and Grünwald 2012). Five lower ranked attributes of sources (rating below than 3.5) were animals (pets, rodents, and livestock), composted manure, pesticide applications, insects and bumblebees, and weeds. Interestingly, worker hygiene and animals are important factors in boxwood blight spread in production (Daughtrey 2019; Gehesquière 2014), whereas infected boxwood used in composted manure could be a source of new infections in healthy plants (Dart et al. 2014; Harvey et al. 2019; Lamondia et al. 2023; May 2023).

Table 3.

Perceptions of the panel composed of nursery growers regarding the knowledge of the items used in boxwood (Buxus sp.) production which could be sources of plant pathogens. The mean rating is based on a Likert scale from 1 to 5 (disagree to agree).

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Of the 31 boxwood production practices evaluated for their ability to limit/prevent plant disease introduction and spread, all had an average perception rating ≥3.5, indicating that these perceptions were important in the boxwood blight management practices (Table 4). The highest perception rating of 5.0 was recorded for cultural control methods, isolation and quarantine of incoming plants, inspection of incoming plant material, scouting for diseases, and removing infected and damaged plants. Although the panel members perceived that these practices could limit the pathogens in production, not all (100%) of them had fully adopted these practices as listed in Table 4, which could be due to a number of factors impacting adoption such as availability, accessibility, and cost-effectiveness (Balehegn et al. 2020; Senyolo et al. 2018). Majority of the panel members (≥50%) had adopted elimination, exclusion, and sanitation practices, promotion of worker hygiene, water management, and chemicals to manage diseases (Table 4). Some of the panel members (≥40% to 50%) had adopted provision of handwashing stations, limitation of vehicles at entry in production areas, using clean water all the time, and small-sized blocks for production (Table 4). The least adopted practices (<40%) were provision of crop-free period; provision of sanitary facilities; sanitization of carts, equipment, containers, and other items; provision of gloves/coats to the workers; provision of tire baths and foot bath at entry; treating water for plant pathogens; using certified cuttings; and use of biopesticides (Table 4).

Table 4.

Perceptions of the panel composed of nursery growers regarding the practices that can limit or prevent plant disease during boxwood (Buxus sp.) production. The mean rating is based on a Likert scale from 1 to 5 (disagree to agree).

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The panel members provided the highest ratings to the practice they were already conducting in their production system to be able to limit or prevent the plant disease. They were adopting the practices that in their opinion are helpful in preventing/limiting disease. The cultural control methods such as sanitation of cutting tools, containers, nursery equipment, and surfaces, along with chemical fungicide applications, biopesticides, and planting of resistant hosts are recommended for prevention of spread of boxwood blight (Bika et al. 2021; LaMondia et al. 2021; Palmer and Shishkoff 2014). Inspection, isolation, and quarantine of incoming plants, using certified pathogen-free cuttings are crucial for lowering the spread of boxwood blight because the infected plant material is the main mode of long-distance movement of boxwood blight. An example of this was the speculation of first introduction of boxwood blight to North America from infected plant material (Bartíková et al. 2020; Kong and Hong 2019; LaMondia 2015; LaMondia and Maurer 2020; Palmer and Shishkoff 2014). Sending samples for disease diagnosis in laboratory as early as possible is important to prevent further spread of the disease and recommended boxwood blight management measure (Castroagudín et al. 2020). Water in the production system contaminated with plant pathogens plays a significant role in disease outbreaks in the nurseries (Ristvey et al. 2019) and water mediated short-distance transfer of Cps has been verified by previous studies (Dart et al. 2014; LaMondia and Maurer 2020). Cps sporulates in the presence of moisture and the conidia are spread to neighboring plants by water splash, hence removing plant debris from production area and providing a crop-free period in the nursery are important to limit the further spread of Cps in production nurseries (LaMondia et al. 2021; LaMondia and Maurer 2020). Using clean water all the times, avoiding standing water in the production area, avoiding runoff water from holding areas, culling diseased plants from production areas, using smaller-sized blocks, monitoring/testing irrigation water for pathogens, and treating irrigation water for pathogens are important to prevent/limit the entry or spread of the pathogen. The stickiness of the conidia of Cps favors human/animal/equipment-mediated pathogen spread, thus excluding animals from the production area and providing worker gloves and clothes, vehicle tire baths at entry, handwashing stations, employee sanitation training, and sanitation facilities are important (Baysal-Gurel and Liyanapathiranage 2017; Bika et al. 2021; Dart et al. 2014; LaMondia 2015).

Members of the expert panel were familiar with processes and programs in boxwood production. Their mean ratings of familiarity of these practices were higher than 4.0 (on a 5-point scale), a value indicating that they were either familiar or very familiar (Table 5). Scouting and employee training was the highest practiced process (94%) among the panel members. Pesticide applicator training and certification were practiced by 89% of the panel members, whereas standard operating procedures for sanitations, best management practices and boxwood blight cleanliness program were practiced by 83% of the panel members. Tracing products or processes from initial to final stage was practiced by 67% of the panel members. Finally, 28% of the panel members practiced irrigation testing for plant pathogens (Table 5). As expected, the growers were extremely familiar with the processes/programs, which were already practiced by the majority of the respondents. Logically, processes/programs not familiar to the growers were not practiced. According to the methods and frequency of disease management techniques used in boxwood production in the past 12 months, 56% of growers had performed scouting and inspection activities 16 or more times, and 53% of growers had used sanitizers 16 or more times. Thirty-three percent used chemical control 16 or more times, and 55% used biological control one to three times.

Table 5.

Perceptions of the nursery grower panel regarding the extent they are familiar with the processes and programs in boxwood (Buxus sp.) production. The mean rating is based on a Likert scale from 1 to 5 (not familiar to very familiar).

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Good record-keeping for tracing plants from initial to final stages of production is a popular practice in production nurseries (Lebude et al. 2012), so the growers were very familiar with it. Some important and common components of integrated plant disease management are scheduling applications of pesticides and scouting; hence the growers were familiar with pesticide application training, certification, scouting, and employee training (Khachatryan et al. 2020; Lebude et al. 2012). With numerous publications of extension articles related to boxwood blight management, the growers were very familiar with best management practices (BMPs) and boxwood blight cleanliness programs because a holistic approach has been recommended to manage boxwood blight (Daughtrey 2019; Lebude et al. 2012; Palmer and Shishkoff 2014). Although growers were familiar with the importance of irrigation water treatment to prevent disease spread, some factors such as lack of readily available treatment technologies or the higher cost of establishment might be a hinderance to adopting them (Hong 2014).

Management and economic impact of boxwood production.

Growers mostly propagated cuttings in November, December, and January and transplanted rooted cuttings in March, May, June, and October. They grew boxwood in almost every month of the year and harvested boxwood (digging whole plants for commercial purposes) from February to June and August to November. They sold boxwood from February to November. Table 6 shows the percentage of boxwood loss during the propagation and finished stages during 2009 to 2019. The loss during the propagation stage increased from 3.6% to 3.8% from 2009 to 2019. The loss of boxwood in the finished stage increased from 2.9% to 4.3% from 2009 to 2019.The increase in loss of boxwood during propagation and the production stage from 2009 to 2019 is comparable to the decrease in the percentage loss of sales of broad-leaved evergreen shrubs, which included boxwood, from 2009 to 2019 (Rihn et al. 2021). These boxwood losses could be accounted for by several factors, such as occurrence of plant diseases caused by pathogens discussed earlier, insects and pests, and changes in soil conditions (Dhakal et al. 2022; Wayne 1979). The increase in percentage of boxwood production losses is parallel to the trend of decrease in percentage of total US boxwood sales from 2009 to 2019 studied by Hall et al. (2021), where these losses were analyzed to evaluate the impact on US annual sales of boxwood after the introduction of boxwood blight in 2011 as described by Ivors et al. (2012).

Table 6.

Percentage of boxwood (Buxus sp.) production loss (e.g., shrink, scrap, dump) during the propagation stage and the finished stage.

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Approximate annual yield (of all sized plants) was highest for propagation materials of boxwood of 84,455 followed by container production of 44,387 and field production of 4,408 plants. The approximate wholesale value was highest for container production of $1,853,077 followed by field production of $649,428 and nursery propagation of $284,231. Approximate retail value was highest for field production of $5,587,692 followed by container production of $2,879,231 and nursery propagation of $100,600. Sixty percent of growers sold boxwood using re-wholesalers/distributors, 56% sold using retail garden centers, 56% sold through landscape distributors, 16% through home centers, and 16% through direct sales to consumers.

In 2021, 39% of respondents earned annual income between $5.1 to $15 million, 17% between $15.1 to $25 million, 11% between $25.1 million to $50 million, 11% between $1 million to $5 million, and 11% less than a million by selling nursery products (Fig. 1). In addition, 6% of the respondents reported annual income between $50.1 million to $100 million, and only 6% reported more than $100 million (Fig. 1). A US green industry survey in 2018 by Khachatryan et al. (2020) reported that 82% of the respondents in the survey had less than $999,000 annual sales. They also reported that 14% had sales of $1 million to $4.9 million, 2% had between $5 million to $9.9 million, 1.6% had sales of $10 million to $50 million, and 0.4% had sales of $50 million or more. When comparing the percentages of income categories of our results with 2018 report, annual income was spread throughout more of the categories. It is important to note that the study by Khachatryan et al. (2020) comprised a large sample compared to our study, although the selected members in this study represent most of the states.

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Nursery’s approximate total gross sales in 2021 ($US).

Citation: HortScience 58, 8; 10.21273/HORTSCI17210-23

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Panel members sold 39% of their boxwood products to retail garden centers and 38% of their boxwood products to mass merchandisers such as Walmart, Menards, Aldi, and other retailers on average. Moreover, 37% of the boxwood products of the panel members were sold to landscape re-wholesalers (distributors). Some growers sold 50% of their total annual boxwood product using market channels other than those listed in the questions, such as their own retail centers or landscape department and wholesale growers (Table 7). In the study by Khachatryan et al. (2020), the most popular outlets for selling of nursery crops were re-wholesalers, landscapes firms and mass merchandisers which is similar to outlets of boxwood nursery products observed in this study.

Table 7.

The mean percentage (%) of total annual product by volume sold by growers in different market channels.

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Most of the growers agreed that they currently receive information about boxwood diseases via university extension services (100%), followed by the Internet (89%), and commodity or industry groups (78%) (Fig. 2). Additionally, 67% of growers obtained information from government entities, other producers and prints from industry, or mass media. Moreover, 61% obtained information from chemical/industry suppliers or distributors and 56% obtained information from printed references and books as well (Fig. 2). In this question, many growers indicated that they received information about boxwood via at least two or more options. The results of this study are similar to previous surveys regarding the most popular sources of information among the growers related to nursery production. Seminars and webinars from the university, university extension agents, and pest news on the Internet published by university extension system were the most followed source of information related to ornamental nursery productions in the United States because the growers exclusively used these channels to obtain information (Lebude et al. 2012). Among the different panel members, 94% of total respondents would like to get boxwood disease management information through direct e-mail and 78% via presentation or webinars (Fig. 3). In addition, 61% of the respondents preferred instructions via Internet information sites and 56% from workshops and training sessions (Fig. 3).

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Venues where growers receive information on boxwood disease management issues.

Citation: HortScience 58, 8; 10.21273/HORTSCI17210-23

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Percentage of growers most like to receive boxwood disease management information.

Citation: HortScience 58, 8; 10.21273/HORTSCI17210-23

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Among the panel members’ nurseries, family members, domestic laborers, and migrant workers worked full time, and only domestic laborers and migrant workers worked part time in the boxwood production. On average, about three family members, 78 domestic workers, and 42 migrant workers worked full time in the nurseries. Also, six domestic laborers and nine migrant workers were involved in working part time in nurseries (Table 8). The number of family members and domestic and migrant workers who were working full time and part time were more dispersed with the varying size of the industry. According to the US green industry survey conducted in 2018, national average number of employees per firm was 20.8, including 11 full-time/permanent employees, 7.5 temporary/part-time/seasonal employees, and 1.9 foreign national employees who were working under the H2A visa program in the US ornamental plant industry (Khachatryan et al. 2020). All the panel members reported that some of their employees were speaking both English and Spanish in nurseries. In addition to this, some other languages were also spoken. The average percentage of workers who spoke English was ∼34% (33.8 ± 17.7), Spanish was ∼66% (66.0 ± 17.6), and 5% of workers spoke other languages.

Table 8.

Employment status in nurseries in 2021.

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