Fireblight, antibiotics, and the NOSB
Resistant rootstocks won’t be widely available for several years, and they do not confer resistance to the top of the tree, where infections occur.
Antibiotics have long been key disease control materials for fireblight, one of the few uses of antibiotics in plant agriculture. These materials are natural compounds produced by naturally occurring soil microorganisms. For the past several decades, the most common control for fireblight has been the use of antibiotic sprays based on need using a predictive model of disease development.
The two antibiotic materials used are oxytetracycline (from the tetracycline group of antibiotics) and streptomycin. The former is primarily used in the Pacific Northwest, while Midwest and eastern growers rely on the latter. Streptomycin is now generally ineffective in the Pacific Northwest due to resistant disease strains, while oxytetracycline can provide 85 to 95 percent control if application is timed correctly. These materials have shown the best and most consistent control compared to other options, which include plant genetics, sanitation, removal of diseased limbs, nitrogen and water management, copper, and biocontrol products.
Biological controls have been researched and developed continuously since the 1980s, but to date, no single control alternative has proven equal to antibiotics. For example, Dr. George Sundin and colleagues at Michigan State University field tested several biocontrols over seven years in Michigan, New York, and Virginia, and reported in 2009 that “the prospects for biological control of fireblight in the eastern United States are currently not high due to the variability in efficacy of existing biological control options.” In the Pacific Northwest, oxytetracycline is applied when needed during the bloom period of apples and pears, and there is little evidence of residues on the fruit at harvest.
When the National Organic Standards were being drafted, the two antibiotics, both considered synthetic products because of their manufacturing process, were ultimately put on the National List of Allowed Synthetics with the specific annotation for use only for fireblight control in organic apples and pears. Materials on the list are reviewed every five years as part of the sunset process to determine whether their continued use is justified or whether a suitable organic-compliant alternative has become available. Given that these are the only allowed uses of antibiotics on organic foods, there has been pressure to phase them out. Various interests have put forward justification over the years, while growers have cited the lack of effective alternatives.
In 2006, the National Organic Standards Board decided by a vote of 7 to 4 to renew the two antibiotics until the next sunset review. Then, the NOSB received a petition in October 2007, to change the annotation to the use of oxytetracycline by adding another chemical form of it. This triggered a review independent of the sunset process (slated for 2011) and would have reset the sunset clock for another five years. On November 19, 2008, the NOSB changed the annotation to include calcium oxytetracycline as well as oxytetracycline hydrochloride, but also added the expiration date of October 21, 2012, thus removing it from the normal sunset process. The U.S. Department of Agriculture accepted this recommendation as a final rule in 2010. The majority of NOSB members appeared to support phaseout as soon as possible. Streptomycin was slated for sunset review in 2011 and a similar phase-out date was envisioned.
Washington State organic orchardists were surveyed in February 2010, regarding their likely response to this regulatory change. Eighty-two percent of the respondents said they would not be able to control fireblight without antibiotics in a high infection risk year (when the risk level exceeded 700-800 on the CougarBlight model), given the available alternatives. Many growers anticipated reducing their organic apple and pear production based on the loss of tetracycline. Organic growers in the Upper Midwest and Pennsylvania were also polled and generally said that antibiotics were a crucial tool of last resort for fireblight control.
Since Washington State produces the vast majority of organic fresh-market apples and pears in the United States, the loss of tetracycline would likely diminish the supply of these products at the same time that demand is still growing in domestic and international markets. And since the disease is not present in South America, a decrease in domestic supply would likely be replaced with imported fruit. In response, the Washington State Horticultural Association submitted a petition to the NOSB to remove the annotation regarding the phase-out date for oxytetracycline. The petition was put on the docket for the NOSB’s April 2011 meeting in Seattle, which also included the sunset review of streptomycin. The meeting location was fortuitous, as many affected growers were able to testify in person.
The testimony and discussions at the Seattle meeting were lengthy and illustrated the complexity of the fireblight disease. Most NOSB members had little understanding of the nature of the fireblight disease, the effective control options available, and the levels of risk and loss growers face with the disease. A significant part of the justification for the phaseout was based on presumed availability of alternative controls and resistant varieties and rootstocks. Alternative controls are registered for use, but have not performed consistently or with the same efficacy as antibiotics, as stated above.
According to Tim Smith, Washington State University Extension specialist and a world expert on fireblight, all pear cultivars, even those that are said to be resistant, are more or less susceptible to fireblight, especially when they are young. Apples have a wider range of susceptibility, but none are truly resistant. Red Delicious is one of the less susceptible apple varieties, but it is also one of the least desired by organic consumers. Gala and Fuji are produced on the most organic acres in Washington, and Gala is more susceptible. So, do growers choose a variety principally on the basis of consumer demand or a disease trait? An extension bulletin from Colorado State University states that “Cultivars of apple, crab apple, and pear differ in their degree of susceptibility to the bacterium.… Although some cultivars are less susceptible than others, no cultivar is immune to infection when the pathogen is abundant and conditions are favorable for infection.”
Thus, full resistance, or immunity, is not currently available for growers to utilize. A new project using marker-assisted breeding to find sources of resistance from Malus sieversii, a wild apple relative, could lead to National Organics Program-compliant resistant varieties in the future. The NOSB repeatedly referred to resistant rootstocks, especially the Geneva series from New York, as a reason to phase out antibiotics. These look very promising, but are not yet commercially available due to propagation problems.
The major tree fruit nurseries were interviewed during December 2011, and asked which resistant varieties they would recommend for commercial growers. They could not suggest a resistant variety for commercial growers, as none were known or accepted in the marketplace. And they could not provide any trees with Geneva rootstock before 2014 due to propagation challenges. Additionally, a resistant rootstock does not confer resistance to the scion (top) of the tree, which is where infections occur (primarily through the blossoms). And, you don’t switch a rootstock in an orchard like you change a wheat variety in a seed drill. Replanting an orchard involves an expense of $15,000 to $20,000 per acre. Introducing a new variety into commercial channels is a multimillion-dollar proposal that can take years.
The discussion around resistant germ plasm pointed out how complex this entire issue is and the challenge posed to members of the NOSB who typically do not have the technical background to understand it. This leaves organic growers quite vulnerable to the particular expertise and biases of the board members whose decisions can have a dramatic impact down on the farm. It suggests that growers need a better mechanism to ensure that their voices and concerns are heard by NOSB.
After much debate and numerous revisions to the committee recommendations, the NOSB voted to extend the expiration date for oxytetracycline to October 21, 2014. The same expiration was voted for streptomycin under the sunset review. The board asked the industry to set up a task force to monitor progress towards alternatives, which has been initiated by Washington State University and Michigan State University, with support from the Organic Trade Association. The Organic Tree Fruit Industry Working Group has provided updates to the NOSB to help them objectively assess whether suitable alternatives to antibiotics are ready by October 2014, and developed a series of fact sheets. New petitions for oxytetracycline and streptomycin have been submitted to NOP to initiate further consideration of the NOSB decisions.
The story of fireblight, antibiotics, and the NOSB illustrates some of the challenges of the organic standards process. The board members, all volunteer, are confronted with huge workloads that seem to continually grow larger. They generally do not have the technical expertise to evaluate many of the issues they are deciding on and must rely on expert input, stakeholder testimony, and fellow board member recommendations. They are trying to balance often conflicting interests of different stakeholders and not do harm to the organic sector. However, it is apparent that the biases of an individual or two on the board can shape recommendations to the board without there being adequate checks and balances from potentially affected parties.
Given the recent fireblight experience, the interests of growers need to be better represented in the process, and the board should be more proactive in soliciting representative grower input regarding decisions that could have large negative consequences. The realities of production and the market must be considered by the NOSB, and their decisions should allow for growers to make an orderly change of practice without undue disruption of their efforts to provide organic foods. Several board members themselves described how their own children will not eat the organic Red Delicious apples that they bring home, while the Galas are quickly devoured, confirming that less disease-susceptible varieties that no one wants to buy are not a solution to the fireblight problem.
NOSB members will take up the antibiotic expiration when they discuss the oxytetracycline petition at their next meeting in Portland, Oregon, on April 8 to 12. Again, this location allows for growers from the Pacific Northwest to testify in person, something that carries a lot of impact for the board. In addition, there will be a comment period beginning this month when written comments can be submitted. Certain advocacy groups are likely to gather comments from thousands of constituents and submit them.
Growers will likely never be able to match the numbers of comments from such groups, but need to have a substantial presence (hundreds of comments) for their perspectives to be given similar consideration, something that seldom happens. Getting organized as an “organic tree fruit constituency” now for the fireblight issue will pay dividends in the future as issues such as continued use of pheromone dispensers are likely to be debated by NOSB. While getting involved in the NOSB process can be quite time consuming, greater input by the organic community will definitely help improve the process over time.