Economic feasibility of locally grown plug transplants as an alternative to imported bare-root transplants in onions

Economic feasibility of locally grown plug transplants as an alternative to imported bare-root transplants in onions

Summary

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 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 Iris yellow spot virus (IYSV) and Botrytis allii.

Objectives/Performance Targets

In this study, we are investigating the economic feasibility of using locally grown greenhouse plug transplants as an alternative to imported bare-root transplants for large scale onion production. We are taking 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 will be included in the economic analysis.

Accomplishments/Milestones

Both a yellow and a red onion variety grown from plug and bareroot transplants were evaluated for performance in side by side comparisons. Stand establishment, plant size and vigor, disease and onion thrips evaluations were made several times throughout the growing season. Final yield, bulb size distribution and quality out of storage were also evaluated.

Noteworthy Results:
Botrytis allii contamination of transplants – Bioassay results showed that latent B. allii was detected in 73% of the 15 bundles (~ 50-75 plants per bundle) with an average of 3.9% of the plants per bundle of the yellow bareroot transplant seedlings, compared to 0% in the plug transplants. Similarly, latent B. allii was detected in 60% of the bundles samples with an average of 3.8% B. allii per bundle compared to 0% of the plug transplants of the red transplant seedlings. Botrytis allii results in neck rot of onion, which shows up about a month after onions are in storage. Although, the 2006 growing season was not especially conducive to spread of B. allii, our storage results showed that onions grown from bareroot transplants had 3 to 4 times higher incidence of neck rot. These results indicate that growing onions from plug transplants results in improved storage quality.

Stand establishment – 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). Mechanical transplanting of the plugs resulted in 81% of a perfect stand due to 8.5% of the plugs containing only 2 instead of 3 plants per plug and an additional 1.7 – 2.9% of the plants containing only 1 plant per plug. In May, 2 – 4% of the plants appeared to be struggling and 0.7 – 1.7% were dead. At harvest, final stand in the plug transplants was 78 – 80% of a perfect stand. Mechanical transplanting of the yellow bareroot seedlings resulted in 93.7% of a perfect stand due to 2.3% of the holes having 2 instead of 1 plant and 7% of the holes missing plants. In May, 15% of the plants appeared to be struggling and 1.7% were dead. At harvest, final stand was 74% of a perfect stand. Hand transplanting of the red bareroot seedlings resulted in 99.3% of a perfect stand due to 5.7% of the holes having 2 instead of 1 plant per hole and 6.7% of the holes missing plants. In May, 10% of the plants appeared to be struggling and 1.7% were dead. At harvest, final stand was 92.7% of a perfect stand.

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 green leaves and were more vigorous than bareroots. Five and 8 weeks after transplanting, the bareroots were taller, had more green leaves and less onion thrips per plant than the plugs. Conversely, plug transplants had lower incidence of purple blotch.

Harvest and Yield – No differences in maturity were noted between plugs and bareroots for the yellow variety. In the red variety, the plugs matured faster than the bareroots. Bareroots yielded higher than the plugs for both varieties, especially the red one, despite having lower plant populations per acre. Bareroots had twice as many jumbo and colossal sized onions compared to the plugs, which had 1.5 – 2 times more small and medium onions. Generally, large bulb sizes and high yields are more profitable in onion production. This could be a major deterrent for the later season red varieties where large size is especially profitable. It should not be as much of an issue for the early yellow varieties. Reducing the number of plants per plug may improve the yield and size of onions grown from plug transplants, provided that it will be economically feasible.

Economic analysis – Is in progress.

Impacts and Contributions/Outcomes

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.

The thorough evaluations conducted during this project allowed for the discovery of suspicious IYSV lesions in the plug and bareroot transplants in both of the onion varieties trialed in this project, 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 New York 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.

Collaborators: