Good Fruit Grower

February 15

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Diseases & Disorders Growers have several choices in FIREBLIGHT CONTROL P ear and apple orchardists have a fairly broad field of products to use in controlling fireblight���and it should get even more crowded in the coming year with new registrations anticipated, says an Oregon State University plant pathologist. Several new products have registrations pending and could be registered in 2013, said Dr. Ken Johnson, who specializes in fireblight research at OSU in Corvallis, Oregon. Kasugamycin, a new antibiotic that goes by the name Kasumin, was registered in Canada in December and is awaiting registration from the U.S. Environmental Protection Agency. A new solubilized copper by Gowan Company called Previsto is also pending, along with a new technology that uses the plant���s own defenses. The systemic acquired resistance inducing agent is a Syngenta product called Actigard (see ���Turning on a plant���s defenses���). With the addition of the new products, growers will have several effective materials to protect their trees from the fireblight pathogen for a longer period���from dormancy to late bloom and even possibly tree rescue treatments in summer. Predictive models also help growers to better time sprays based on disease development. Here���s a rundown of today���s fireblight products and how they fit in an integrated control program, according to Johnson: Fixed coppers (several products available) applied during dormancy. Research studying fixed coppers applied at delayed dormancy with dorby Melissa Hansen mant oils has been encouraging, Johnson said. ���The coppers do have an effect in reducing the number of infected flowers at bloom,��� he said. ���Fixed copper is a sanitation treatment that delays the build-up of epiphytic pathogen populations.��� Additionally, three years of research in collaboration with University of California���s Rachel Elkins found no difference in russeting and fruit finish from the copper applications compared to dormant oils. ���This is some of the first data I���ve seen that shows that coppers can have an effect,��� Johnson said during a session at the Washington State Horticultural Association���s annual meeting. The research involved applying six pounds of active ingredient per acre at delayed dormancy in late March in California. Researchers used molecular scouting to detect the pathogen. Growers applied a full antibiotic program during the mid- to latebloom period. ���Initially, we couldn���t find fireblight in the early bloom, but as we moved to late petal fall, in the blocks where we didn���t spray the copper, 100 percent of the flowers sampled were infected,��� he said. ���Where we put the coppers on, infection was delayed, and we saw 30 and 60 percent infected, depending on the year.��� Through molecular scouting of rat-tail blooms, Johnson said that researchers have learned there is more risk presentin orchards in the summer than they previously thought. Biologicals. Three types of products are available and all are approved for organic use: bacterial stigma colonizers (BlightBan A506, Bloomtime Biological), yeast floral cup Two new fireblight products are coming��� hopefully soon. Apple and pear fireblight products Type Name Timing Fixed coppers Lime sulfur (used for apple thinning) CuOH, CuOCl, Cu2O Dormant Early bloom Biologicals BlightBan A506, Bloomtime, Blossom-Protect Early bloom Antibiotics Streptomycin, oxytetracycline, kasugamycin (pending) Early bloom Solubilized copper SAR inducer Phyton27 AG, Previsto (pending) Actigard (pending) Late bloom Late bloom, tree rescue Growth regulator Apogee (apples) Late bloom SOURCE: Dr. Ken Johnson, Oregon State University 8 FEBRUARY 15, 2013 GOOD FRUIT GROWER TURNING ON a plant���s defenses N ew technology is coming to the apple and pear industry to help control fireblight. Actigard is a systemic compound with a unique mode of action that mimics the natural systemic-activated resistance response found in many plants. When applied preventatively, much like vaccinations are given to humans to ward off certain diseases, Actigard stimulates or induces the plant���s natural defenses, turning on the genes that are involved in fighting off infection from various diseases. Actigard (acibenzolar-S-methyl), a product of Syngenta, is registered for other crops, including tomatoes, tobacco, and berry fruits. Registration is pending for apples and pears. In pome fruit, Actigard is applied late bloom or as a rescue treatment to help manage fireblight, said Dr. Ken Johnson, plant pathologist at Oregon State University. Research has shown improved fireblight protection when Actigard is used in combination with antibiotics, reducing strikes per tree by nearly half. ���That���s why we like Actigard���we���re cutting down blight incidence by 50 percent or so by going with a late application,��� Johnson said. ���In the blight business, that���s a meaningful response.��� One of the primary benefits to Actigard is its long residual life of seven to ten days during late petal fall, a time when antibiotics are ineffective, he said. ���You can use Actigard late for petal fall, rat-tail, and shoot blight in susceptible cultivars���it���s like using Apogee [plant growth regulator] but with no stunting of growth.��� Rescue But he���s also excited about Actigard���s potential as an aid for fireblight tree rescue and cleanup in an orchard, especially a new, young one. And, there may be potential for the material to protect rootstocks sensitive to fireblight, though more research is needed. Johnson has been experimenting with painting Actigard on trees after pruning branches with fireblight symptoms. In a small trial of Bosc pears (15 untreated and 10 treated trees), all trees were inoculated with the pathogen in April and the orchard then scouted for fireblight in early June. Trees with symptoms were pruned, painted, and sprayed with Actigard. Retreatment of cutting, spraying, and painting was done in late June on trees still showing symptoms. Fireblight in the control trees was cut out, but trees were not sprayed or painted. In October, the block was revisited to look for tree survival. Thirty percent of the trees that had fireblight cut out but no Actigard treatment were lost. Where trees were cut and sprayed, about 25 percent of the trees were lost���not much better than the control with cuts only, Johnson said. But where the trees were cut and painted with Actigard, only 10 percent were lost. ���Where we painted Actigard below the cuts���about 18 inches below the cut���we reduced the amount of blight,��� he said. Cuts were made about six to eight inches below the fireblight symptom. EUP label The U.S. Environmental Protection Agency has granted a ���crop nondestruct experimental use permit��� label for Actigard on pears and apples for the next two years. The experimental use permit label allows Actigard to be mixed with antibiotics as a spray and paint. Up to 150 acres in Washington, 60 acres in Oregon, and 30 acres in California can be treated. As part of the EUP permit, material used must be tracked, the department of agriculture notified (e-mail will suffice) when applied, and an administrative agent present during application. Researchers are working with industry to develop a list of qualified agents that can work with growers. Johnson said it is important to test the material to find out how it works in real-world settings. ���M. Hansen

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