The sustainability of the onion industry in New York is dependant on the ability of its growers to remain competitive. Risking the introduction of potentially devastating diseases that could drastically impact production is not sustainable. In this study, we investigated the economical feasibility of using locally grown transplants that are free of pests as an alternative to imported bareroot transplants that may be harboring Iris yellow spot virus (IYSV) and Botrytis allii. Onions grown from bareroot transplants proved to produce larger healthier plants with lower onion thrips infestation and 50% more jumbo size bulbs for 26 – 29% less cost per acre to produce. This translated into bareroots netting 29% and 26% more profit per acre than plugs, values of $1897.96 and $2155.95 for an early maturing yellow variety (cv. Ricochet) and a late maturing red variety (cv. Red Zeppelin), respectively. Achieving a high proportion of jumbo bulbs proved to be the most important factor in net profit. Further research and experimentation is required to determine whether locally grown transplants could yield a higher proportion of jumbo bulbs by manipulating plant spacing, and production and transplanting techniques.
The problem with onion growers importing bare-root transplants into New York is the risk of bringing in potentially devastating diseases of onions including Iris yellow spot virus (IYSV) and Botrytis allii. An alternative would be using locally grown greenhouse plug transplants. Unfortunately, the price of greenhouse plug transplants, which is approximately two to three times that of bareroots is a major deterrent to onion growers. However, there may be cost savings in labor and pesticides, and increased revenue due to increased yield and quality. Therefore, a thorough economic analysis that takes into consideration all aspects of growing onions from transplants was required.
Onions have the highest value of all vegetable crops produced in New York State and ranks sixth in the nation with a five year average value of $42.5 million. The majority of the 13,000 acres of onions are grown on muck soil in five regions across the state. Although yellow storage cooking onions compose the major type of onion grown in New York, acreage of red and sweet onions have increased considerably during the past decade. To remain competitive with the western United States with respect to large bulb size and early entry into the market, the production of onions from transplants has become a growing trend in New York. For example, in the Elba muck region, located in western New York, approximately 25% of the 3000 acres of onions were grown from transplants in 2005, up from less than 1% just 10 years ago. In addition, sweet onions, which are only grown from transplants is a relatively new venture in New York. New York growers typically import bare-root onion transplants from Arizona and to some extent, from Georgia and Texas.
IYSV is an emerging and potentially devastating disease of onion in the United States and the world. It was first detected in the United States in 1989, and when this project was initiated in November 2005, this disease occurred in eight western states and Georgia. In Colorado, IYSV spread rapidly from 5.6% (1 out of 18) of the sites tested in 2001 to 73.2% (41 out of 56) of the sites tested just three years later in 2003. Within fields, IYSV incidence is reported to range from 1-2% to 100%. IYSV generally results in a reduction in bulb size, especially in sweet and red varieties, and can delay crop maturity.
In 2004, researchers at Colorado State University detected IYSV in 0.0 to 4.4% of commercial onion transplant seedlings from locations in Arizona and California. It is possible that IYSV may be introduced to New York via infected transplant material from Arizona or other locations where the virus occurs. Onion thrips are prolific and challenging to control in New York. Therefore, it is conceivable that IYSV could have a devastating impact on the onion industry in New York should it be introduced on imported bare-root transplanted onions.
Botrytis allii is the causal fungus of neck rot, a storage disease of onions that deems bulbs unmarketable. B. allii is endemic, but it appears that major outbreaks of this disease (up to 80% loss in some varieties) have occurred in New York more frequently in association with the surge in the use of imported bare-root transplants, specifically in the very wet growing seasons of 2000 and 2004. In a preliminary study in 2005, Hoepting et al. found that 78% of imported bare-root transplant entries (variety by grower) evaluated had some degree of B. allii (range <1 to 100% of plants evaluated) before they were transplanted in New York. Comparatively, B. allii was not detected on any of the locally produced greenhouse plug transplants prior to planting or direct seeded plants that were sampled from the field during the growing season.
The sustainability of the onion industry in New York is dependant on the ability of the growers to remain competitive. Risking the introduction of a potentially devastating disease or increased frequency of storage rots that could drastically impact production is not sustainable. Therefore, it is critical that New York onion growers investigate the economical feasibility of using locally grown transplants that are free of pests as an alternative to imported bare-root transplants that may be harboring IYSV and B. allii.
In this study, we investigated the economic feasibility of using locally grown greenhouse plug transplants as an alternative to imported bareroot transplants for large scale onion production. We took into consideration all aspects of using the two types of transplants including initial price of the plants and expenses associated with shipping, labor, and use of equipment and pesticides. Contaminants including onion thrips (which vector IYSV) and Botrytis allii, the pathogen that causes neck rot of onion bulbs in storage, were quantified and differences in yield and bulb quality were included in the economic analysis.
Note to the reader: Tables referenced in this report are available from Northeast SARE by calling 802/656-0471 and requesting materials specific to ONE06-057.
A thorough comparison of quality, yield and economic feasibility of growing onions from plug and imported bareroot transplants on a commercial scale involved a collaborative effort among a muck onion grower and a Cornell Cooperative Extension Vegetable Specialist.
Experimental Design (Table 1): Comparisons were made using two onion varieties: i) an early maturing yellow variety that is grown from transplants specifically to gain earlier harvest and entry into the market when prices are high (c.v. Ricochet), and ii) a late maturing long-term storage red variety that is grown from transplants specifically to gain a bulb size advantage (c.v. Red Zeppelin). The grower cooperator procured treated seed and made the arrangements to have very similar seed lots of each variety grown from both bareroot and plug transplants. Enough plants were produced to grow approximately one acre of onions for each transplant type. Bareroot transplants were grown by Sunbelt in Buckeye, Arizona and commercial plug transplants were grown by Pudgie’s Greenhouse in Oakfield, New York. Local plug and imported bareroot transplants were planted side by side in the same field on May 5, 2006. Both transplant types were planted on 60 inch beds with 4 single rows per bed with 15 inch row spacing. Ricochet (yellow) bareroot transplants were planted singly with 3 inch plant spacing using an 8-row mechanical bareroot transplanter and a labor crew of 12 persons at a rate of $8.53 per hour (Figure 1). Red Zeppelin (red) bare-root transplants were planted singly with 4 inch plant spacing by hand into pre-poked holes. A 6 – 7 person labor crew was paid $0.015 per foot of planted row (Figure 2). All plug transplants were planted with three plants per plug/hole spaced 8 inches apart using a 4-row mechanical plug transplanter and a labor crew of 7 persons at a rate of $8.53 per hour (Figure 3).
Field Evaluations: Two weeks after transplanting on May 19, stand establishment, number of green leaves per plant, plant height and an overall plant vigor rating were taken from 10 randomly selected samples of 10 plants/plugs in a row. These evaluations (with exception of vigor ratings) were taken again 6 and 11 weeks after transplanting on Jun 16 and Jul 20 on 5 samples of 10 plants/plugs in a row. On Jun 16 and Jul 20, the number of Botrytis leaf blight (BLB) lesions per plant were counted on each plant per sample. Similarly, total number of onion thrips (OT) per plant were counted on Jun 16. OT numbers were too high to count on Jul 20 and Aug 11. About 10 plants per transplant type per variety with suspicious IYSV lesions were collected on Aug 11 and submitted to Marc Fuchs, Cornell Virologist, for IYSV analysis. Total number of purple blotch (PB) lesions per plant were counted on Jul 20 and Aug 11. Percent lodging was visually estimated on Aug 11. Ricochet and Red Zeppelin were harvested on Aug 17 and Aug 30, respectively. Five 5 x 5 ft sections were harvested per variety for each transplant type. Onions were pulled, windrowed for 7 – 14 days, topped, sorted into size classes (small, medium, jumbo and culls) and weighed. After natural curing, they were stored in a commercial onion storage. Significant differences among plug and bareroot transplants per variety were determined by a General Analysis of Variance (p = 0.05).
Transplant Inspection and Bulb Quality Evaluations: Prior to transplanting, 10 bundles (25-100 plants per bundle) of bare-roots were randomly selected per variety for a latent B. allii bioassay which was performed as previously described by Hoepting et al. 2006. Similarly, all plants in 2 randomly selected trays of plug transplants were collected and assayed for latent B. allii. After 3.5 months in storage, bulbs were evaluated for Botrytis neck rot and bacterial rots.
Economic Analysis: The grower cooperator kept detailed notes on the cost of seed, transplant production, shipping of transplants, labor and pesticide applications, and on the price of the different size classes of the two varieties. Only differences in the input costs were included in the economic analysis. Differences in stand establishment, yield, bulb size and quality out of storage were also included in the economic analysis. Cost estimates were made on a per acre basis. Due to the differences in plant population per acre, net differences were also estimated on a per 1000 plant basis.
Plant size and quality. Two weeks after transplanting, there were no differences between plug and bareroot seedlings with respect to plant height. Plugs had slightly more vigor than bareroots. Ricochet plugs had significantly more green leaves per plant than bareroots, while there were no such differences in Red Zeppelin (Table 2). Six weeks after transplanting, the bareroots had significantly more green leaves per plant and were significantly taller than the plugs in both varieties (Table 3). Eleven weeks after transplanting, there were no differences between plug and bareroots for number of green leaves per plant and plant height, except in the Ricochet variety, where the bareroots had significantly more green leaves per plant.
Initial stand establishment may be better with plugs compared to bareroots, because bareroots remain in a state of transplant shock for a longer period of time after transplanting. The time between pulling bareroot transplant seedlings and transplanting them is usually 7 to 14 days. Alternatively, growth of plugs is not interrupted. An advantage of bareroots being in transplant shock is that preemergent herbicides may be applied at high label rates within 2 days after transplanting, which allows for excellent weed control with minimal crop injury. There is much more risk of crop injury with plug transplants and growers can not use as high rates and do not have as many herbicide options. Thus, weed control may not be as good in plugs. Once bareroots grow out of transplant shock, they surpass plugs in size, which may be a result of less plant to plant competition (i.e. 1 vs. 3 plant(s) per hole/plug). Large healthy foliage translates into large bulb size.
Stand establishment (Table 4). Due to differences in plant spacing, plug transplants were planted at a higher plant density per acre (156,816 plants per acre) compared to red bareroots (104,544 plants per acre) and yellow bareroots (139,392 plants per acre) (Table 1). Mechanical transplanting of the plugs resulted in an average of 80.4% and 81.8% of a perfect stand stand for Ricochet and Red Zeppelin, respectively with only 44.7% and 45.2% of the holes planted with the correct number of plants (i.e. 3 per hole). In Richochet, 37.9% and 5.6% of the holes had two and one plant per hole, respectively, instead of three. There were an additional 3.1% skips, 3.4% small or struggling plants and 2.2% dead. In Red Zeppelin, 14.79% and 3.2% of the holes had two and one plant per hole, respectively, instead of three. There were an additional 4.4% skips, 5.2% small or struggling plants and 1.3% dead. Mechanical transplanting of yellow bareroot transplants resulted in an average of 89% of a perfect stand with 89% of the holes planted perfectly (i.e. 1 plant per hole). Five percent of the holes had an extra plant per hole and there were 7% skips, 9.8% small or struggling plants and 2.3% were dead. Hand transplanted red bareroots had 92.7% of a perfect stand with 79.3% of the holes being planted correctly (i.e. 1 plant per hole). Only 5.7% had an extra plant per hole and there were 7% skips, 9% small or struggling plants and 1.3% were dead.
Bareroot transplants had closer to perfect stand establishment compared to plugs, primarily due to a high percentage of holes planted with the correct number of plants per hole, especially when they were transplanted by hand (i.e. Red Zepelen). Alternatively, in the plugs there were a higher proportion of holes that had only two plants instead of three. Incidence of skips and small or struggling plants was higher in the bareroots, which was due to the plants being less uniform in size to begin with and the plants not being planted to moisture.
Pest pressure. There were no significant differences between plug and bareroot transplants with respect to number of BLB lesions per plant except on Jun 16 when the Red Zeppelin plugs had significantly more BLB than the bareroots (Table 3 & 4). Bareroot transplants had slightly more PB lesions per plant than the plugs with significant differences occurring in Red Zeppelin on Aug 11 (Table 4 & 5). Six weeks after transplanting, plug transplants of both varieties had significantly higher numbers of onion thrips per plant than the bareroots (Table 3). On Aug 11, Ricochet plug transplants visually had more thrips damage than bareroots (Figure ). One theory to explain this is that the wider plant spacing of the plugs are more favorable to thrips infestation, because thin stands improve host recognition. Another theory is that thrips preferred the plugs because these plants were less vigorous, as thrips pressure increases as plant stress increases. Cluster samples of both bareroot and plug transplants of both varieties tested positive for IYSV. Incidence of IYSV per transplant type or variety was not determined. This detection was one of the first in onion bulb crops in New York and the greater Northeastern United States.
Harvest and Yield (Table 5). No differences in maturity were noted between plugs and bareroots in the yellow variety, Ricochet. In the red variety, Red Zeppelin, the plugs matured faster than the bareroots. This may be due to the higher infestation of thrips in the plugs causing the plants to die down due to insect damage instead of naturally. Bareroots (Ricochet – 500 cwt/A; Red Zeppelin – 585.4 cwt/A) yielded higher than the plugs (Richochet – 457 cwt/A; Red Zeppelin – 503.8 cwt/A) for both varieties, especially Red Zeppelin, despite having lower plant populations per acre. Bareroots had almost twice as many jumbo and >4 inch sized onions compared to the plugs, which had 2.1 to 3.1 times more small and medium onions than bareroots. These results demonstrate that having 3 plants per plug/hole compromises bulb size due to plant to plant competition. It was observed that out of the three plants per plug/hole, often there were either two big and one small bulbs or one big and two small bulbs. In onions, jumbo-sized bulbs are worth more money than mediums, especially for red varieties. Perhaps, plugs grown with two plants per hole would produce more jumbo bulbs.
Botrytis allii contamination of transplants and storage quality (Table 6). In Ricochet, latent B. allii was detected in 60% of the bareroot samples with an average of 3.8% of the plants per sample infected (range: 1.6 to 20.7% infected plants per sample), compared to 0% in the plug transplants. Similarly, in Red Zeppelin, latent B. allii was detected in 73% of the bareroot samples with an average of 3.9% B. allii per sample (range: 1.1 to 11.6% infected plants per sample) compared to 0% of the plug transplants. Botrytis allii can cause neck rot of onion, a storage disease. Although, the 2006 growing season was not especially conducive to development and spread of B. allii in the field, our storage results showed that onions grown from bareroot transplants had three to four times higher incidence of neck rot (Richochet – 6.6%; Red Zeppelin – 11.7%) than those grown from plugs (Richochet – 1.6%; Red Zeppein – 3.5%). Incidence of bacterial bulb rots were low (0.9 – 5.1%) with plugs having only slightly higher incidences than bareroots. These results demonstrate the improved storage quality of onions grown from plug transplants compared to bareroots. When conditions are more conducive to development and spread of B. allii, neck rot could be a serious problem in storage. Why bareroot transplant production results in latent B. allii infections warrants further research as does producing bareroot transplants that are free of disease. Generally, yellow onions grown from transplants are sold out of the field or are only stored for a short term, therefore bulb quality during storage is not much of an issue. Alternatively, it can be a serious issue for red onions which are stored.
The thorough evaluations conducted during this project allowed for the discovery of suspicious lesions in plug and bareroot transplants in both onion varieties, which were later confirmed via molecular techniques to be IYSV. A preliminary detection survey conducted later in the season (not part of this project) showed that IYSV was present in 90% of the fields surveyed in western New York, indicating that IYSV occurred in the state prior to 2005. Ultimately, it is too late to prevent introduction of this disease to New York, and much research is warranted to ascertain the impact that it will have on onion production here. Whether imported bareroot transplants are infected with IYSV and whether this is an important source of inoculum now that IYSV is established in New York also warrant further research. Fortunately, this project has allowed us to gain some ground on how to optimize the cost and quality of using locally grown plug transplants as an alternative to importing bareroot transplants.
In 2007, Hoepting et al. will be investigating why bareroot transplants are latently infected with B. allii and are working with a transplant grower in Arizona to figure out if bareroots can be grown free of B. allii.
The importance of achieving jumbo sized bulbs proved to be the most important factor in net profit. The relationship between bulb size, plant spacing and plant population was also highlighted in this project. There is potential to manipulate and improve techniques for producing transplants and transplanting them into the ground, but it should not compromise bulb size. A couple of onion growers are experimenting with various techniques, including the production of locally grown bareroot transplants in a greenhouse.
Education & Outreach Activities and Participation Summary
Project awareness was created in mid-season (July 12, 2006) at the annual New York Onion Industry Council summer tour and meeting in Sodus (Wayne Co.) where 50 growers, Cornell research and extension professionals and allied industry representatives from all five onion growing regions across the state were in attendance. Field results and a pre-harvest demonstration were presented at a twilight meeting held in Elba on August 4, 2006 where 28 onion growers, Cornell research and extension specialists and allied industry representatives were in attendance from Orleans, Genesee and Steuben counties. On January 8, 2007, results were presented to fresh market vegetable growers at the Produce Auction Winter Educational Meeting in Penn Yan where about 100 fresh market growers were in attendance. Final results including the economic analysis will be written up as an Extension newsletter article, which will be distributed statewide, and may be presented at onion grower meetings during the 2007 season.
Economic analysis of transplant production and planting (Table 7). Cost of seed for plug transplants was 31.6% and 52.7% more expensive than it was for bareroots for Ricochet and Red Zeppelin, respectively, because it included an insecticide treatment (i.e. cyromazine) for onion maggot. In retrospect, this treatment was probably not needed and could represent an opportunity for savings. On a per-acre basis, the cost of plug transplant production was three times higher than it was for bareroots (including shipping costs of bareroots from Arizona to New York), a difference of about $599 per acre. Due to the different plant populations and transplanting techniques, it is challenging to directly compare the cost of transplanting between plug and bareroot transplants. Under the circumstances of this project, it cost about 1.5 times more per acre and 1.7 – 2.1 times more per 1000 plants to transplant bareroots than plugs, a difference of $203.95 and $162.98 per acre for Richochet and Red Zeppelin, respectively. The main reason for this difference is the increased cost of labor to transplant bareroots. Ricochet bareroots were planted with an eight-row mechanical transplanter, compared to a four-row transplanter that was used for the plugs. It took less time to plant an acre of bareroots (5 h, 48 min) than it did to plant an acre of plugs (6 h, 42 min), despite increased plant spacing, because less time was spent turning around with the eight-row transplanter. It cost more to plant the bareroots, because a 12 person crew was required for the eight-row bareroot transplanter compared to a seven-person crew for the four-row plug transplanter. It takes about six hours for six or seven crew persons to transplant by hand an acre of bareroot transplants. This is piece work and laborers make $0.015 per foot of row. The advantages to this method are that there is no minimum number of crew persons required for the process to function, skilled drivers are not required and this method had the closest to perfect stand of the transplanting methods. The disadvantage is that the work is very hard and most laborers prefer to sit on a mechanical transplanter.
Bareroots are treated prior to transplanting with a fungicide and an insecticide, which is labor intensive. Plugs are treated with an insecticide application in the field prior to transplanting. There is also an herbicide applied to bareroots that is not applied to plugs, because the risk of injury to the actively growing plug plants is too high. Therefore, the cost of pesticides and pesticide application for bareroots is 3.4 times more per acre, a value of $69.54.
Overall, savings in the cost of labor to transplant plugs and in pesticide use did not overcome the additional cost of treated seed and transplant production. Bareroot transplants cost $308.49 and $433.47 less per acre to produce and plant than plugs for Ricochet and Red Zepelen, respectively.
Economic analysis of net profit (Table 8). Bareroots netted 29% and 26% more profit per acre than plugs, values of $1897.96 and $2155.95 for Ricochet and Red Zeppelin, respectively. The major difference between bareroots and plugs was attributed to bareroots yielding twice as many jumbo sized bulbs as the plugs, which are worth more money, especially for the red variety.
There is opportunity for increased net profit of bareroot red varieties if the transplants were grown free of B. allii and had significantly less neck rot out of storage. Onion prices for the 2006 crop were 5 to 7 times the five year average. With lower onions prices and less differences in price among size classes, there could be less of a difference in net profit between plugs and bareroots. The growing season in 2006 was also very favorable for producing large onions. In a year with fewer jumbos and higher proportions of small and medium onions, there could also be less difference in net profit between plugs and bareroots. The percent return on bareroots from Arizona was fairly high in 2006. However, it is not always that good. For example, an untimely frost in Arizona in 2007 resulted in less than 50% return on bareroot transplants. The percent return on plug transplants is more consistent and reliable.
Areas needing additional study
The results of this project clearly showed that growing onions from bareroot transplants imported from Arizona was more profitable for New York growers than growing onions from locally grown greenhouse plug transplants. The main reason for this was that planting three plants per plug/hole with 8 inch spacing reduced the number of jumbo size bulbs by about 50%, compared to growing bareroot transplants singly with three- to four-inch plant spacing. Achieving jumbo size onion bulbs is the most important factor for increasing net profit. Unfortunately, in this study we also found that bareroot transplants imported from Arizona were latently infected with B. allii and resulted in twice as much loss out of storage due to neck rot, caused by B. allii. Further research is required to investigate the cause of this contamination and how to produce bareroot transplants that are free of disease. The widespread distribution of IYSV in New York suggests that it has occurred here undetected prior to 2005. Further research is required to ascertain whether imported bareroot transplants are an important source of inoculum of this disease and the impact of IYSV on transplanted versus direct seeded onions in New York. Further research and grower experimentation is required to determine whether onions can be produced economically from locally grown transplants. For example, the economic feasibility of growing plug transplants with 2 plants instead of 3 per plug/hole could be investigated. Also, experimenting with different transplanting techniques and configurations could be investigated further. Finally, it would be worthwhile to investigate whether bareroot transplants could be grown locally in New York under glass or high tunnels.