Issue link: https://read.dmtmag.com/i/138107
California growers WORRY ABOUT FIREBLIGHT These Bartlett pear trees in California have had to be drastically cut back to remove limbs infected with fireblight. It is often difficult to remove infected wood before the pathogen has spread into the trunk. Lack of antibiotics will limit where pears can be grown. Photo courtesy of rachel elkins, uc by Geraldine Warner Committed to Dedicated Service & Quality Trees For 75 Years & Counting Hickman: Reedley: 19701 Lake Road 21200 E. Dinuba Ave. Hickman, CA 95323 Reedley, CA 93654 209-874-1821 559-638-6675 800-654-5854 www.davewilson.com www.facebook.com/DaveWilsonNursery 16 July 2013 GOOD FRUIT GROWER hile Washington growers are concerned about how they're going to grow organic apples and pears without antibiotics to guard against fireblight, orchardists in other parts of the country are much more worried. The generally arid conditions in the Pacific Northwest limit the threat of the disease, which needs warm and moist conditions to become established. Some areas in the Midwest and eastern United States, which have more humid weather, simply can't grow pears because of fireblight. Some varieties are more susceptible to the disease than others, but in general pears are more susceptible than apples. Currently, the antibiotics oxytetracycline and streptomycin are growers' first line of defense, but chances are they won't be allowed in organic agriculture after October 2014. At its April 2013 meeting, the National Organic Standards Board rejected a petition to extend use of oxytetracyline for another two years. It is expected to reach a similar decision for streptomycin at its next meeting on October 22-24 in Louisville, Kentucky. California has about 450 acres of organic pears, mainly in the central valley. Fireblight is a perennial problem because of the humid climate and long growing season, reports Rachel Elkins, University of California pomology farm advisor in Lake and Mendocino counties. "I would say all of our organic growers in California are depending on antibiotics for fireblight control because we've got such vigorous growth," she said, explaining that the disease spreads quickly in vigorously growing trees. In Washington, growers can cut out diseased limbs to prevent the organism from spreading and killing the whole tree, but that's more difficult when it spreads much faster, she added. Also, whereas Washington conditions are not conducive to fireblight every season, California growers battle it year in year out. Another difference is that the fungal disease scab rarely develops in Washington's dry conditions, but it's a common problem in California. Antibiotics for fireblight can be tank mixed with scab treatments, such as copper, dithane, or ziram, but biological fireblight controls can't. That means an additional trip through the orchard. "It's whole different ball game in California than it is in the Northwest," she said. "You do not see a pear industry except where they can manage fireblight. If you can't manage fireblight, you're out of business." Even in Washington, the Concorde pear, which is very sensitive to fireblight, is hardly produced any longer. Elkins said that without antibiotics, the range of places where organic pears can be grown will be further limited. "Like anything else, where you grow something becomes a competitive issue," she said. "Where people can grow organics successfully, it will be done. Whether it's going to be done on the same farms, by the same people, in the same manner—that may not stay the same." • LISTING of antibiotics T he National List of Allowed and Prohibited Substances identifies substances that may or may not be used in organic agriculture. In general, synthetic substances are prohibited unless specifically allowed and nonsynthetic substances are allowed unless specifically prohibited. The National Organic Standards Board must review all substances every five years (known as a sunset review) to consider renewing, removing, or changing each listing. The antibiotics streptomycin and oxytetracycline were considered natural substances under several regional programs, including Washington and California's organic programs, before the National Organic Program was created. This was based on them being naturally occurring compounds produced by soil microorganisms. Timeline 1995: A Technical Advisory Panel to the NOSB concluded that streptomycin and oxytetracycline were natural products, but NOSB members unanimously determined them to be synthetic because the actual products used by growers were produced by microbial fermentation in commercial laboratories and then extracted and stabilized for eventual use. However, the NOSB allowed them to be used in organic apple and pear production to control fireblight for two years. The NOSB was to set up a task force to look into the materials further during those two years, but that was never done. 2006: The board renewed the antibiotics' listing until the next sunset review in five years' time. 2008: The NOSB approved a petition to add oxytetracycline hydrochloride to the national list, in addition to the oxytetracycline calcium formulation already listed. The board set an expiration date of October 21, 2012, removing oxytetracycline from the normal sunset process. 2011: At the sunset review for streptomycin, the board set a new expiration date of October 21, 2014. After reviewing a petition to remove the expiration date for oxytetracycline, it set the same expiration date for that product. 2013: At its April meeting, the NOSB denied a petition to extend use of oxytetracycline beyond 2014. It will consider the expiration date for streptomycin at its October meeting in Kentucky. —G. Warner www.goodfruit.com