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Funded Project

Funding Program: IPM Partnership Grants

Project Title: Cultural Practices to Manage Bacterial Diseases in the Small-Scale Intensive Production of Fresh Market Onions

Project Directors (PDs): Christine Hoepting [1] Beth Krueger Gugino [2] Judson Reid [3]

Lead State: NY Lead Organization: Cornell University

Cooperating State(s): Pennsylvania

Undesignated Funding: $39,718

Start Date: May-01-2010 End Date: Apr-30-2012

No-Cost Extension Date: Mar-13-2013

Pests Involved: bacterial diseases

Site/Commodity: onions, vegetables

Area of Emphasis: cultural controls

Summary: Small-scale diversified fresh market vegetable growers who grow onions intensively are constantly challenged by yield losses due to bacterial bulb rots, which greatly compromise the profitability of the crop. If bacterial diseases cannot be managed, the profitability of this industry will not be sustained or expanded. The focus of this project is to evaluate, demonstrate and encourage adoption of cultural tactics to reduce bacterial diseases in small-scale intensive production of fresh market onions. We will evaluate the effects of mulch type and planting configurations on incidence of bacterial disease of onions, yield, bulb size, economic return and grower adoption. This project will be a cooperative effort among the Cornell Cooperative Extension Vegetable Program in New York, Penn State University, Cooperative Extension in Pennsylvania and two grower cooperators in New York and Pennsylvania. Successful demonstration of research-based recommendations to modify planting configuration and/or mulch type will result in 50 to 100% adoption of the 54 onion growers in the Finger Lakes region of NY and Lancaster County, PA. Consequently, losses due to bacterial rot and number of copper bactericide sprays will decrease, while yield, profitability and acreage of intensively managed sweet onions will increase, and more locally grown produce will be available to the consumer, and the small-scale fresh market onion industry will be sustained. Objectives: 1. To evaluate and demonstrate cultural practices including mulch type and planting configurations for managing bacterial diseases in small-scale intensive fresh market onion production. 2. To determine the economic feasibility of adopting cultural practices for managing bacterial diseases in small-scale intensive production of fresh market onions. 3. To increase grower knowledge about onion bacterial diseases and their management, and grower adoption of our research-based recommendations to use cultural practices as a component of an IPM program. Proposal

Interim Report: Nov-02-2011

Outcomes Objective 1 Results: Planting configuration field trials For tables, see full report in appendix. For interesting results regarding plant size, pest pressure, maturity and bolting, see full report in appendix. Bacterial bulb decay at harvest (Table 2): Although not significant, there was a general trend that as planting density increased, bacterial bulb decay at harvest decreased. In NY, 8 plant spacing with 3 rows per bed had 2 to 7.5 times more bacterial bulb decay than all other treatments. There was a trend that within the same plant spacing, 3 rows had 2 times and more bacterial bulb decay as 4 rows per bed. In PA, both of the narrow plant spacings (4 with 3 and 4 rows) had half as much bacterial bulb decay compared to the standard (6 plant spacing, 4 rows), representing 53% control of bacterial bulb decay. In PA, the bacterial pathogens most frequently isolated from symptomatic bulbs were Pectobacterium caratovora, Pseudomonas marginalis and Pantoea agglomerans. In NY, Burkholderia cepacia was most common with minor isolations of Pantoea ananatis. It is important to note that narrowing plant spacing was effective in reducing incidence of bulb decay for different species of bacterial pathogens. Yield and bulb size (Table 2): There was a significant trend that as plant density increased, marketable yield increased as a function of more bulbs being harvested per foot of plastic and fewer loses from bacterial bulb decay. Yield was much higher and bacterial rot much less in NY than in PA in 2010. In NY, 4 plant spacing with 4 rows per bed had significantly higher yield than all other planting configurations, while 8 plant spacing with 3 rows per bed had significantly lower yield than all other planting configurations. The 4 plant spacings also had significantly 6.5 and 3.7 times higher jumbo yield and 9.8 and 4 times higher medium yield than the standard with 4 and 3 rows per bed, respectively. The 6 plant spacing with 4 rows per bed had similar total and colossal yield, 2.7 times higher jumbo yield, and half as much rot as the standard. In PA, 4 plant spacing with 4 rows per bed had significantly 2.2 times higher marketable yield than the standard, and 1.5, 5.1 and 33 times higher jumbo, medium and small weight, respectively. In some markets it is difficult to sell such a high proportion of small and medium bulbs. For the Pennsylvania Simply Sweet marketing program, small and medium yield cannot exceed 30% of the total yield. The 4 plant spacing with 3 rows per bed had 1.8 times higher total yield than the standard, and had 1.6, 2.5 and 13 times higher jumbo, medium and small yield, respectively, which was not significantly different than the standard. Objective 1 Results: Alternatives to black plastic field trials For interesting results regarding plant size and pest pressure, see the full report in the appendix. Bacterial bulb decay (Table 3): All treatments had significantly lower Incidence of bacterial bulb decay at harvest than the black plastic, representing 59%, 71% and 75% control for reflective silver mulch, black biodegradable mulch and bare ground, respectively. The bacterial pathogens most frequently isolated from symptomatic bulbs were Pectobacterium caratovora, Pseudomonas marginalis and Pantoea agglomerans. Yield and bulb size (Table 3): Highest marketable yield occurred in the reflective silver mulch followed by the black biodegradable mulch, which were significantly 108  118 lb per 100 feet of bed higher than bare ground. Black plastic had significantly lower yield than all treatments. Bare ground had significantly 2.1  2.9 times and 1.5  3.4 times higher small and medium weight than all other treatments. Reflective silver mulch had the highest jumbo weight followed by biodegradable black, which had significantly 2.7  3.6 times higher jumbo weight than black plastic and bare ground. Colossal weight was low in this trial and although no significant differences occurred, reflective silver mulch had numerically the highest colossal weight. We suspect that the cooler temperatures provided by the reflective silver plastic and biodegradable black plastic mulches were less favorable for development of bacterial bulb decay and more favorable for healthy plant growth. Yield and bulb size of bare ground was lower than reflective silver and black biodegradable mulches despite excellent control of bacterial bulb rot because of competition from weeds; for bare ground to be a viable option, weeds must be controlled effectively. In the research farm trial, differences between mulch treatments with regard to both marketable yield and incidence of bacterial bulb decay were less conclusive (data not shown). Total marketable yield was significantly lower in the reflective silver plots compared to the black plastic and the incidence of bacterial bulb rot was numerically higher at 27% compared to 14% for the standard black. Soil temperature (Figure 1): Compared to the standard black plastic mulch, soil temperatures at the 1-2 inch depth were lower under bare soil by ~2 æC, lower under black biodegradable mulch by ~ 3-4 æC and lower under reflective silver mulch by ~ 6 æC during the majority of the season. Objective 2 Results: Economic analysis Planting configurations (Table 4): There was a general trend that as planting density increased, net economic return increased, which was a function of there being more bulbs to market per foot and lower incidence of bacterial bulb decay. At both locations, 4 plant spacing with 4 rows per bed had the highest economic return netting 1.4 times (variable and uniform pricing) and 2 times (uniform) to 5.5 times (variable) more per 100 feet of bed than the standard spacing in NY and PA, respectively. Note that the proportionately high small and medium weight in this planting configuration may not be easily sold in all markets. Also, 4 plant spacing with 3 rows per bed net higher than the standard by 1.1 (variable) to 1.2 (uniform) times, and 1.8 (uniform) to 1.9 (variable) times in NY and PA, respectively. In NY, 6 plant spacing with 4 rows per bed net similarly as 4 plant spacing with 3 rows per bed, but the 6 plant spacing with 3 rows per bed net slightly less than the standard planting configuration (8 plant spacing, 4 rows), despite having the same area per bulb (48 inch2). In this trial, we consistently observed 3 rows per bed had more bacterial bulb decay than 4 rows per bed. In both locations, planting densities that were lower than the standard net half to 3/5th as much as the standard, because they had the fewest number of plants per foot and the most bacterial bulb rot. Alternatives to black plastic mulch (Table 3): Compared to black plastic ($2.38 per foot), bare ground cost 18 times less, reflective silver plastic cost 1.8 times more and biodegradable black plastic cost 2.9 times more. All treatments had higher economic return than the standard black plastic. Reflective silver plastic had the highest net economic return at $166 and $279 per 100 feet of bed for variable and uniform pricing, respectively, which was 2.6 and 3.1 times higher than black plastic. Black biodegradable plastic had the second highest net economic return at $160 and $262 per 100 feet of bed for variable and uniform pricing, respectively, which was 2.5 and 2.9 times higher than black plastic. Bare ground net 1.9 and 1.7 times more than black plastic, but it should be noted that such a high proportion of small and medium weight may not be easily sold in some markets. Objective 3: Grower education and adoption Grower Educational Meetings During 2010 and the first quarter of 2011, we shared our 2010 research results at 8 grower meetings making 229 and 211 total contacts in PA and NY, respectively, and reaching an additional 160 participants nationally. For details, see full report in appendix. Publications Our research results were shared in articles that were published in two Cornell Cooperative Extension monthly vegetable newsletters in NY, and in the trade magazine, Onion World, which has international distribution. As well as in the proceedings of the statewide fruit and vegetable conferences in each of NY and PA, and in the professional journal, Phytopathology. For details, see full report in appendix. Grower Adoption In March 2011, Hoepting and Reid interviewed 15 growers in the Finger Lakes, Chautauqua County and Mohawk Valley in NY and in Northwestern PA. In 2011, all 15 of them experimented with narrow spacing on their farms, representing 100% grower adoption. In PA, two growers did not widen their spacing based on our results. Three growers in NY and 26 in PA experimented with alternatives to black plastic including reflective silver and white plastic on their farms in 2011. Additional Funding Leveraged: For every $1 of NEIPM Partnership money that we received for this project, we leveraged an additional $4.70 in research dollars totaling $187,032 to continue to develop a comprehensive Integrated Pest Management program for bacterial diseases of onion. For details, see full report in appendix.

Impacts Safeguarding human health and the environment: During the first year of this project, we identified two cultural practices that could very simply be adopted as part of an Integrated Pest Management program for bacterial diseases of onions. "After learning how narrowing plant spacing on onions grown on plastic can significantly provide 44 to 53% control of bacterial bulb decay at harvest, while increasing marketable yield by 1.2 to 2.2 times, in 2011, 15 growers in NY experimented with narrow plant spacing on their farms, and 2 growers in PA did not widen their plant spacing. "After learning how alternatives to black plastic mulch provided 59 to 75% control of bacterial bulb decay at harvest, while increasing marketable yield by 1.8 to 2.8 times, 3 growers in NY and 26 growers in PA experimented with reflective silver plastic and white plastic on their farms in 2011. "Adopting these techniques will eventually lead to a reduction in the heavy use of copper bactericides to control bacterial bulb decay in onions, especially in PA. For every spray that is eliminated, the Environmental Impact Quotient (EIQ) will drop by 9.5 to 14.4 units. For example, if a grower who currently applies a copper bactericide on a weekly basis from early May until harvest makes only half as many applications, the EIQ will drop by up to 72 units per growing season. An observation during the first year of this project provided preliminary information that led to a successful grant award that could ultimately result in reduced environmental pollution. In one of our field trials in PA, we observed a significant block effect where the block located at the bottom of a slope had 83% incidence of bacterial bulb rot at harvest, while the block located at the top of the slope had only 17%. This field was heavily manured, and presumably, nitrogen leached to the bottom of the slope where it favored the development of bacterial disease. Previously, Hoepting et al. in 2010 showed a strong relationship between rate of nitrogen applied and incidence of bacterial bulb decay at harvest in a study conducted on onions grown in muck soil. Further study of the relationship between manure use and/or soil fertility and bacterial diseases of onion is warranted. "In 2011, Gugino, Hoepting and Beer were awarded a Regional Integrated Pest Management Competitive Grant from the Northeast Region totaling $179,788 to identify factors associated with bacterial diseases of onion, including an investigation of the relationship with nitrogen. Gaining a better understanding of the relationship between soil nitrogen, bacterial diseases and optimal yield could lead to reduced nitrogen inputs in onion production, increased profitability and reduced water pollution. Economic benefits: Our studies showed that economic return increased 1.1 to 5.5 times representing $45 to $258 more income per 100 feet of bed by narrowing plant spacing by 2 inches. "By hosting our spacing trials, the grower cooperators made an additional $187 and $247 in PA and NY, respectively from the increased marketable yield on the total 120 feet (PA) and 180 feet (NY) of bed where the narrow plant spacing treatments were located. Our studies showed that economic return increased 1.7 to 3.1 times representing $60 to $189 more income per 100 feet of bed by using reflective silver plastic, biodegradable black plastic and no mulch instead of the standard black plastic mulch. "By hosting our trial, the grower cooperator in PA made an additional $153 on the 180 feet of bed that had an alternative to black plastic mulch. Growers who have been exposed to the results of this project are learning that they can manipulate plant size, maturity, yield and quality of their onion crop by adjusting the planting configuration and mulch type. Just as there is no rule requiring a grower to plant all of his onions the same variety, there is no rule requiring him to use the same planting configuration and mulch type for all of his onions either. When growers diversify these cultural practices, they consequently reduce their risk of losses from bacterial rots and undersized onions. "For example, based on his experimentation with narrow plant spacing, a grower in NY decided to plant 1/3 of his onions with narrow plant spacing. For his market, he wanted large bulb size as early in the season as possible, for which wide plant spacing suited this need best, because they would be pulled when they were immature and before the bacterial decay made its way into the bulb. However, he also wanted to store some of his onions to market in the fall and winter, for which the narrow plant spacing would produce bulbs with less bacterial rot at harvest that would store better, and since they were not being marketed out of the field, he could let them stay in the field to reach their full size potential. Implementation of IPM: Via our small-plot on-farm and research station field trials, we generated research results which proved that narrow plant spacing and alternatives to black plastic are viable cultural techniques that can be incorporated into an Integrated Pest Management program for bacterial diseases of small-scale onion production. Our outreach and educational efforts were significant: "During 2010 and the first quarter of 2011, we shared our 2010 research results at 8 grower meetings reaching 229 and 211 participants in PA and NY, respectively. "A newsletter article was published in two monthly newsletters of Cornell Cooperative Extension vegetable programs in NY, distribution of ~800. "An article was published in the international trade magazine, Onion World in January 2011. "Conference proceedings were published for the statewide vegetable conferences in both NY and PA. "In March, Hoepting and Reid interviewed 15 growers in the Finger Lakes, Chautauqua County and Mohawk Valley in NY and in Northwestern PA. Of these, 100% adopted narrow plant spacing on a portion of their onion acreage in 2011. As a result of our research, education and outreach, in 2011, 15 growers experimented with narrow plant spacing in NY and 2 growers were deterred from increasing their plant spacing. Three growers in NY and 26 growers in PA experimented with alternatives to standard black plastic. As a function of the exposure of this project, large-scale onion growers have questioned whether altering their planting configurations could help with managing bacterial diseases of onions, which has become one of the most important pest problems affecting onions in NY during the past decade. In 2011, Hoepting and Steve Beer, Cornell, conducted a large-scale on-farm trial to investigate the effects of seeding density, row spacing and nitrogen fertility on bacterial diseases of direct seeded onions grown on muck soil. In the future, the cultural technique of modified planting configurations to help manage bacterial disease of onions may also be adopted by large-scale onion growers. Currently, there are ~13,000 acres of large-scale onion production in NY and it ranks 6th in the United States.

Report Appendices Progress Report 2010 [PDF]

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