Development and on-farm training of biologically based methods for integrated crop management of stone fruits in New England

Development and on-farm training of biologically based methods for integrated crop management of stone fruits in New England

Summary

In order to obtain isolates of bacteria (Xanthomonas arboricola pv. pruni =Xap) and bacteriophage (=”phage”), nineteen orchards in Connecticut, New York, and Massachusetts, were sampled for plant material obtained from peach, nectarine, and plum trees. A total of 121 plant samples were collected and tested for the presence of Xap as well as phage. From these, 23 Xap strains were obtained, purified, and stored. Additionally, 43 phage strains were obtained, identified as Xap-specific bacteriophage based on their ability to form phage plaques on Xap cultures. Laboratory studies were conducted to determine phage diversity, resulting in the conclusion that all 43 phage strains are functionally equivalent, based on cross-reactivity experiments using Xap strains lysogenic for a subset of 15 phage strains from the phage collection. A presentation on the goals, experimental plan, and research results to date was made in December 2010 to Connecticut growers at the annual meeting of the Connecticut Pomological Society. In January 2010, 60 O’Henry peach seedlings were potted and forced in the greenhouse. Efforts at effecting bacterial leaf spot (BLS) symptoms in the greenhouse were unsuccessful due to temperature and humidity limitations of available greenhouse space. All trees underwent a 750-hour chill period following forcing in the greenhouse in February 2011. Detached branch bioassays were attempted in the growth chamber, where conditions can be more accurately controlled. However, these efforts were also unreliable in producing BLS symptoms. Trees are current once again undergoing the necessary chill period in preparation for renewed efforts to effect BLS symptoms under controlled conditions, which are necessary in order to test the efficacy of phage in controlling these symptoms. Three experimental orchards of Sweet Dream peach trees were maintained through mid-summer pruning and replacement of dead trees.

Thirteen Connecticut growers with 150 acres of stone fruits were involved with IPM programs in 2011. All 13 growers adopted at least one new practice, in particular, the use of pheromone mating disruption for peachtree borer and lesser peachtree borer. The use of mating disruption alone resulted in the reduction of 788 pounds of active ingredient of chlorpyrifos, which is typically applied on a yearly basis for borer control. Ninety growers learned about the brown marmorated stink bug, a new invasive insect pest, at the Annual Meeting of the Connecticut Pomological Society in December, 2011. A total of 110 people attended a presentation on Development of Stone Fruit IPM Guidelines for the Northeast at the New England Vegetable Conference and Trade Show in Manchester, New Hampshire in December 2011. In addition, 80 growers learned about pheromone trapping for brown marmorated stink bugs at a twilight meeting in July, 2011.

Objectives/Performance Targets

Develop effective bacteriophage-based biological control strategy for controlling peach bacterial spot, which would provide an environmentally friendly and feasible alternative to the current chemical-based strategies. Additional target is a publication of the results of this project in a peer-reviewed scientific journal.

20 Connecticut stone fruit producers will adopt biologically-based integrated management techniques on 200 acres, such as mating disruption of peach tree borers, using traps and groundcover management to monitor and reduce tarnished plant bug populations, and better timing of fungicide and bactericide applications. This will result in savings of 2,000 pounds pesticide a.i. and $25,000 on production cost each year. In addition, they will substitute newer, less toxic, pesticides for some of the organophosphate and pyrethroid insecticides.

Accomplishments/Milestones

MILESTONE 1: Isolate 40 bacteriophages from New England stone-fruit orchards.
Progress: 23 Xap isolates and 43 phage isolates were obtained in the spring and summer of 2009 from a total of 19 orchards: two from New York, one from Massachusetts, and the remainder in Connecticut. Each phage was tested against the 23 Xap strains. Additionally, we have demonstrated that all 43 phages behave identically, and that phage immunity conferred through lysogenicity with one phage strain constitutes immunity to all 42 others. This experiment was repeated. An important conclusion from this result is that we will not have a mixture of genetically variable phage strains to use in the bioassays, greenhouse, and orchard trials.
MILESTONE 2: Ten phages that show potential as biological control agents based on preliminary laboratory tests will be evaluated in bioassays.
Progress: Further tests to identify any differences in virulence specificity among the phage strains confirmed the Milestone-1finding that all 43 phage strains are functionally equivalent in terms of their specificity to Xap strains.
MILESTONE 3: Five phages that show potential based on bioassays will be mixed together and used in subsequent greenhouse trials.
Progress: Sixty small O’Henry peach trees (O’Henry has very high susceptibility to Xap), which were used in 2010 for this same purpose, were given the necessary chill period and then forced in the greenhouse in February/March of 2011. Because the previous year’s attempts to infect individual trees with various Xap strains proved unsuccessful, this year we tried to reproduce BLS symptoms on detached branches, held in water, in growth chambers under conditions putatively ideal for infection in terms of light, temperature, and humidity. We were unable to reliably and reproducibly effect infections. There are no reports of this method being used in the scientific literature. The reasons for failure are unknown.
MILESTONE 4: Three phage-based treatments (phage mixture alone or together with other biological control agents) that provide equal or superior disease suppression compared to the currently used copper/antibiotic-based control methods in greenhouse trials will be chosen for further trials.
Progress: None.
MILESTONE 5: Two phage-based treatments that provide equal or superior disease suppression compared to the currently used copper/antibiotic-based control methods in orchard trials will be recognized as environmentally friendly alternatives).
Progress: Three orchards, each planted in April 2010 with 49 Sweet Dream peach trees on Lovell rootstock, were maintained through mid-summer pruning and replacement of dead trees.

MILESTONE 2 (90 Connecticut growers will receive a manual outlining IPM techniques and sustainable practices for stone fruit production).
Progress: A manual of IPM techniques and sustainable practices for stone fruit is under development. It will be produced and distributed to stone fruit growers in 2012.
MILESTONE 3 (Six growers will receive one-on-one training to help identify pests and learn about conventional and alternative methods of managing pests).
Progress: A total of thirteen Connecticut growers with 150 acres of stone fruits were involved with IPM programs in 2011. A range of farms was represented including one organic CSA (Community Supported Agriculture) farm. Seven growers with 30 acres of stone fruits received one-on-one field training throughout the 2011 season. Training included use of mating disruption for peachtree borer and lesser peachtree borer, use of pheromone traps for both borers and Oriental fruit moth, identification of diseases such as bacterial spot, peach scab, brown rot and X-Disease, identification of damage caused by Oriental fruit moth, borers, European red mites and tarnished plant bug; identification of chokecherries to aid in X-Disease management; and management options for all of the above pests. Three additional growers with a total of 35 acres of stone fruits received training on the use of mating disruption and trap monitoring for peachtree borers and lesser peachtree borers. Three additional Connecticut growers with 85 acres of stone fruit participated in the Eco Stone Fruit pilot project by following IPM protocols which were developed by the Co-PI and others through Red Tomato. Pheromone traps for the brown marmorated stink bug, a new invasive pest, were set up and monitored at 11 stone fruit orchards.
MILESTONE 4 (New stone fruit management guidelines and phage research will be discussed at the annual meetings of the Connecticut Pomological Society).
Progress: The following talk was presented.
Los, L. 2011. Management of the Brown Marmorated Stink Bug. Annual Meeting of the Connecticut Pomological Society. December 6, 2011. 90 growers were in attendance. The brown marmorated stink bug is a new invasive pest that attacks stone fruits and other crops.
MILESTONE 5 (40 Growers will attend a twilight meeting where new stone fruit IPM guidelines will be demonstrated).
Progress: Eighty people attended a fruit twilight meeting on July 14, 2011 and learned about the use of pheromone traps to monitor for the brown marmorated stink bug.
MILESTONE 7 (200 growers from the New England states will learn about the stone fruit management guidelines at the New England Vegetable and Fruit Conference in Manchester, NH)
Progress: The following talk was presented.
Los, L. 2011. Development of Stone Fruit IPM Guidelines for the Northeast. New England Vegetable and Fruit Conference and Trade Show. December 13, 2011. Manchester, NH. 110 people in attendance.

Impacts and Contributions/Outcomes

Forty-three phage strains have been obtained from stone fruit orchards in Connecticut, Massachusetts, and eastern New York. These are equally virulent on all 23 of the Xap isolates that were collected from the same distribution of orchards. Therefore, we are making progress towards our goal of developing a phage-based biological control strategy for controlling bacterial spot of stone fruit. Efforts to produce BLS symptoms, which failed in 2010 using whole trees in greenhouses, were attempted again in 2011 using detached branches in flasks of water in growth chambers, to allow for better regulation of conditions supportive of infection. These efforts were not successful. Three peach tree orchards that were planted in spring of 2010, each in a 7 x 7 arrangement, were maintained with mid-summer pruning and the replacement of any dead trees. These orchards are intended for use in orchard trials in spring/summer 2012, comparing phage against and in combination with two other methods, which will be chosen based on results of greenhouse/growth chamber trials. Once results are obtained from these experiments, we will publish the results and conclusions in a peer-reviewed journal, such as Phytopathology.

Ten Connecticut growers with 65 acres of stone fruit participated in one-on-one training in IPM techniques in 2011. Three additional growers with 85 acres participated in the Eco Stone Fruit project. All of the growers used mating disruption for peachtree borers and lesser peachtree borers. The use of mating disruption alone resulted in a decrease of 788 pounds of pesticide active ingredient of chlorpyrifos, an organophophate insecticide. The changes in pesticide applications due to the use of other IPM practices still need to be determined. In addition, the pesticide use changes for all other growers (those not involved in one-on-one training) will not be known until the post-project survey is conducted in 2012.
Other accomplishments not related to original milestones:
Lorraine Los was one of the lead scientists in the development of the IPM protocols of the Eco Stone Fruit project through Red Tomato. Red Tomato is a non profit organization which helps farmers sell their sustainably grown produce to supermarkets, distributors and other buyers. The protocols were revised in 2011 and were discussed at the Red Tomato Grower meeting on March 8, 2011. Three Connecticut growers participated in the Eco Stone Fruit program during the 2011 season.

Collaborators: