Dave and I had a nice discussion off-line. I also apologize and don't want to mislead people into any new sort of fireblight treatment when it comes to commercial growing. I was merely sharing an experiment I did on one single tree in the hopes to gain a better understanding of how fireblight works. My results would not extrapolate to any large scale apple grower. My hope in sharing the results was to get feedback - and I finally received some of that.
My focus is on breeding, not commercial production, so I have about 80 apple trees with 450 varieties of apples. Because of our unique climate (largely freeze free yet high chill) we can grow a very large number of apples from low chill to high chill, and create interesting crosses. I am deeply concerned about fireblight in my orchard, given the large # of varieties, I have to be very careful and try to keep the orchard free of any potential vectors. We are not in a firebight prone area, since our late Springs are very cool and dry with night time temperatures well below 55F all the way into late June, this year was an exception, and a number of local growers experienced fireblight outbreaks due to a single week of warm and drizzly weather with night time temperatures in the 60's. The main thing I have learned from various off-line discussions is that the antibiotic coating is a waste of time, of course, except that it was useful for my experiment in that it demonstrated to me that the re-infection was coming from inside the tree. So now I understand that once fireblight has infected a tree, the fireblight bacteria is systemic in the cambium even if the tree shows no more signs of infection. Some of the articles I read suggest that the bacteria can travel some 5-6 feet below visible infection sites. So this leaves me with a number of questions: 1) How is it then that fireblight doesn't re-appear the next year given that the only control is to cut out visible infection in the Summer, cankers in the Winter, and blossom sprays + growth inhibitors in the Spring? 2) Doesn't cambium with high carbohydrate content inhibit bacteria growth? 3) what is the scientific method for detecting the bacteria? Microscope? ________________________________ From: Dave Rosenberger <[email protected]> To: Apple-Crop <[email protected]> Sent: Tuesday, July 14, 2009 6:27:19 PM Subject: Re: Apple-Crop: Fireblight Update Re: Apple-Crop: Fireblight Update My initial post was done in haste and was not very tactful. I have no interest in threatening anyone or in attempting to regulate pesticide use. I only wanted to be certain that readers recognize that home made remedies, while they may work, cannot be legally applied as pesticides in commercial orchards. I'm not certain, but I believe that EPA labeling is also required for chemical deer repellents. However, so long as Mo's Guiness Stout is used only to attract leprichauns and is not used directly as a deer repellent, we can probably assume that it will be exempt from labeling requirements. My comment about California in my earlier represented an unfinished thought: Given the state budget situations and government gridlock that seems to exist in both California and New York, both states may soon be expelled from the union and forced to survive as unstable and bankrupted 3rd world economies. Given that scenario, pesticide regulations may be the least of our concerns. Axel, I didn't >read it as Dr. Rosenberger threatening you, merely explaining >things. I learned something from his post. People are >interested in experimental results. But understand, this list is >geared toward commercial producers and researchers. That means >these folks are professionals. Although I'm not a serious >commercial grower myself (I sell a little fruit out my back >door) I can tell you most folks on this list are very >experienced, read up on the literature, and have been >experimenting with blocks of hundreds of apple trees. >Researchers on this list many times have multiple farms to use as an >experimental base.. It doesn't mean your research is >irrelevant. Research on one tree may have anecdotal value, and >can lead to testing on a larger scale. But keep in mind >fireblight has been researched for many many decades. I'm not >trying to be unkind, but the truth is, it's likely your methods have >been tried many times before. Mark >Angermayer KS > >----- Original Message ----- >From: Axel >>Kratel >To: Apple-Crop >Sent: Tuesday, July 14, 2009 1:36 PM >Subject: Re: Apple-Crop: Fireblight >>Update > >> >Sorry, I meant to say use retromycin sulfate, which is >>perfectly legal to use on plants, and even has the right EPA label, I >>just used neosporin as a way to keep the powder on the cuts. I thought >>neosporin had bactrin in it, apparently it doesn't. It would work >>equally well with silicon paste or any other pasty substrate. >> > >>>>But anyway, I am truly sorry I ever even posted this. If someone isn't >>even allowed to experiment and have someone on this list threaten with >>Federal law, well, then so be it, given that this is the second nasty >>E-mail I got, consider this to be my last post on this list. You >>people take yourself way too seriously. >> >>>>Good bye. >> > >> > ________________________________ >From: Dave >>Rosenberger <[email protected]> >>To: [email protected] >>Sent: Tuesday, July 14, 2009 10:24:09 AM >>Subject: Re: Apple-Crop: Fireblight Update >> >>>>I've enjoyed reading the postings and opinions concerning how to >>manage fire blight in Alex's Ernst Bosch apple tree. Those of us >>who have worked with or experienced fire blight know that this disease >>is very difficult to understand and manage. What works on one >>cultivar, in one year, or in one location may fail to work on another >>cultivar/year/location and what is cost-effective for one apple grower >>may be totally implausible in other economic models. Thus, I'm >>not going to debate Alex's observations. >> >>>>HOWEVER, I feel obligated to point out that within the boundaries of >>the United States (and I believe that still includes California), >>application of an antibiotic paste to pruning cuts is a violation of >>federal law. Any product used in that manner would require a >>federal pesticide label from EPA. That requirement applies to >>homeowners and hobby farmers as well as commercial growers. So >>far as I know, no antibiotic pastes are labeled for use on tree fruits >>to control fire blight. There are good reasons for these >>regulations, but I won't take time to discuss them. The bottom >>line is that using human or veterinary antibiotics on fruit trees or >>other crop plants is both illegal and potentially >>dangerous. > >>>>> I posted a while back on an Ernst Bosch Apple tree that came down >>with fireblight. I wanted to share with the group what had happened, >>although I must say that after reading the latest Illinois Fruits and >>Vegetable Crop news, I am grateful not to have to deal with the >>fireblight outbreak that the Midwest is experiencing this year. >>>>> >>>>> We are not in a fireblight prone area due to our cool, dry >>conditions, but this year, fireblight has broken out in a number of >>local orchards thanks to a warm and humid, rainy and drizzly week in >>May. So this has been a learning experience for me. >>>>> >>>>> I finally figured out how to deal with the fireblight infection, >>here is what I did: >>>>> >>>>> Since only one of my 200 trees (of which 80 are apple trees on >>MM111) came down with fireblight, my focus was to eliminate any >>further disease vectors, so removal of the tree is the only solution. >>However, I am a scientist by training, and my curiosity got me to play >>with the tree for a bit to try to understand what is going on. >>>>> >>>>> Here are some of the observations: >>>>> >>>>> Step one was to cut, but to my dismay, the infection returned, >>even after several cuts. Disinfecting the shears seemed irrelevant. >>The morning dew collecting on the cuts would often turn orange, and >>the drops would carry the infection to lower limbs. >>>>> >>>>> Step two was to try to figure out if the re-infection vector was >>external, or the bacteria was already systemic in the cambium. So for >>the next sets of cuts, my approach was to coat the cuts with a oily >>antibiotic paste with a bactrin base (bactrin is a wide spectrum >>antibiotic). The coating would prevent re-infection from external >>sources, but not if the bacteria is systemic in the cambium. Sure >>enough, another set of cuts lead to more infection, the ooze coming >>from under the paste. It only took 24 hours for the wood to turn >>orange under the paste, proof that the infection came from inside the >>tree, not from external sources or from the pruning sheers. >>>>> >>>>> Step 3 was to prune back radically, past the node of the infected >>branch. Upon close inspection, I discovered that the cambium had a >>darker shade, Cutting into the darker shaded areas revealed healthy >>wood, but the cut turned orange within 24 hours and would start to >>ooze. However, cutting several inches below any slightly darkened >>areas did not cause the wood to turn orange, and no re-infection took >>place. >>>>> >>>>> Step 4 was to douse the tree with antibiotic to make sure there >>is not any residual fireblight bacteria on the tree. I used a >>combination of bactrin and retromycin sulfate to treat the tree and >>surrounding mulch. >>>>> >>>>> At this point, it's safe to say the fireblight active infection >>is gone, although I believe the bacteria is still in the tree, but >>dormant for now even though there are no visible cankers. Since the >>tree is so young, I plan on removing and replacing it after the >>harvest this October. But before I do, I also plan on feeding the tree >>some heavy nitrogen to get it to grow and see if the new growth will >>show signs of re-infection. >>>>> >>>>> My conclusion for controlling fireblight is the following: the >>bacteria travels much, much further than 6-12 inches, and one must cut >>past any infected ambium: Chances are trees could carry fireblight >>even without showing any active signs of infection. >>>>> >>>>> 1) Always coat the cuts with an antibiotic oil-based paste to >>prevent re-infection from outside vectors. >>>>> >>>>> 2) The wood must be placed into a plastic bag immediately and not >>allowed to touch anything else. So it's a good idea to cover any >>oozing branch into a plastic bag and break off the branch, then do the >>pruning so no ooze droplet hits any other part of the tree. >>>>> >>>>> 3) Always disinfect the sheers in case the previous cut was into >>still infected wood. Preferred disinfection is a field heat treatement >>disinfector, which should be used anyway to prevent any sort of >>disease spread. You wouldn't want the doctor not to disinfect his >>surgical instruments before treating you, a plant is no different. >>>>> >>>>> 4) Always observe for orange discoloration under the paste for >>the next 24 to 72 hours. If the orange discoloration returns, the cut >>was made into more infected tissue, and you have to cut >>further. >> >>>>> 5) After any infected tissue is removed and discarded, the tree >>needs to be treated externally with an antibiotic to remove any >>residual bacteria. >>>>> >>>>> I cannot vouch that the above would work outside of Santa Cruz >>county; when I see the pictures of fireblight in the midwest, it makes >>me wonder how one would even deal with fireblight once it broke out, >>the only reasonable approach seems radical removal, and preventative >>spraying in the Spring. >> >> >>>>-- ************************************************************** Dave >>Rosenberger >>>>Professor of Plant >>Pathology >>Office: 845-691-7231 >>>>Cornell University's Hudson Valley >>Lab Fax: >>845-691-2719 >>>>P.O. Box 727, Highland, NY 12528 >>Cell: 845-594-3060 >>>> http://www.nysaes.cornell.edu/pp/faculty/rosenberger/ >> >> >> >>>>-------------------------------------------------------------------------- >> >>>>The 'Apple-Crop' LISTSERV is sponsored by the Virtual Orchard >>>><http://www.virtualorchard.net> and managed by Win Cowgill and Jon Clements >>>><[email protected]>. >> >>>>Apple-Crop is not moderated. Therefore, the statements do not >>represent "official" opinions and the Virtual Orchard takes >>no responsibility for the content. -- ************************************************************** Dave Rosenberger Professor of Plant Pathology Office: 845-691-7231 Cornell University's Hudson Valley Lab Fax: 845-691-2719 P.O. Box 727, Highland, NY 12528 Cell: 845-594-3060 http://www.nysaes.cornell.edu/pp/faculty/rosenberger/
