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. Therefore, these efforts have been abandoned; established researchers who have worked on this disease for over 20 years have reported similar difficulties with effecting disease symptoms in greenhouse settings. Three experimental orchards of Sweet Dream peach trees were maintained through mid-summer pruning and replacement of dead trees.

Twelve Connecticut growers with 145 acres of stone fruits were involved with IPM programs in 2012. All 12 growers used pheromone mating disruption for peachtree borer and lesser peachtree borer and four of them used mating disruption for Oriental fruit moth. The use of mating disruption for peachtree borers alone resulted in the reduction of 870 pounds of active ingredient of chlorpyrifos, which is typically applied on a yearly basis for borer control. Eighty-eight growers learned about stone fruit IPM from five posters displayed at the Annual Meeting of the Connecticut Pomological Society in December, 2012. Outreach on stone fruit IPM was also provided through 28 Fruit IPM updates via Email to over 190 growers. Field surveys were conducted for two new invasive pests, the spotted wing drosophila and the brown marmorated stink bug. Surveys requesting information on current stone fruit IPM practices were mailed to Connecticut stone fruit growers as part of the Verification Plan for this project. The results of this survey will be compared to the pre-program survey to determine changes in IPM practices since the beginning of the project.

Objectives/Performance Targets

The original objectives of this project were to develop an 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. An additional objective was to compare the phage-based method to current copper and antibiotic based methods. However, the absence of genetic diversity among naturally occurring phage populations, and the inability to produce BLS symptoms in a controlled greenhouse setting, have resulted in the decision to revise the objectives to abandon further phage experiments, and to incorporate a randomized orchard trial of the most commonly used copper and antibiotic based control 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), were used in 2010 and 2011 for purpose of testing phage efficacy in controlling BLS Attempts in both years to infect individual trees or detached branches (there are no reports of this method being used in the scientific literature) with various Xap strains proved unsuccessful, regardless of efforts to maximize favorability of conditions. The reasons for failure are unknown, but corroborate anecdotal information from veteran researchers in this field. Unable to reliably and reproducibly effect infections, these efforts have been abandoned.

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 in Milestone 5.

Progress: None. The phage-based treatments will not be incorporated into the 2013 biocontrol trials.

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 tested in orchard settings.

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 in 2011 and 2012.

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 2013.

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: The one-on-one grower training visits were primarily conducted during the first three years of the grant in 2009, 2010 and 2011. However, IPM training continued with two growers with a total of 3 acres in 2012. 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.
In 2012, the primary goals of the project were 1) to continue to work with growers on the use of mating disruption for stone fruit pests and; 2) to continue with education and survey for two new invasive pests of stone fruits, spotted wing drosophila and brown marmorated stink bug. A total of twelve Connecticut growers with 145 acres of stone fruits received training on the use of mating disruption and trap monitoring for peachtree borers and lesser peachtree borers in 2012. Four of these growers (34.5 acres) also used mating disruption for Oriental fruit moth. Three of the growers with 85 acres of stone fruit participated in the Eco Stone Fruit project by following IPM protocols which were developed by the Co-PI and others through Red Tomato. Eight farms with stone fruits were monitored for spotted wing drosophila. A large number of adult flies were captured in vinegar baited traps but larvae were only found infesting cherry fruit in one location. In addition, a black light trap for the brown marmorated stink bug (BMSB) was used at one stone fruit orchard where BMSB was found the previous year.

MILESTONE 4 (New stone fruit management guidelines and phage research will be discussed at the annual meetings of the Connecticut Pomological Society).

Progress: Five posters describing Stone Fruit IPM were developed and displayed.

Concklin, M. and L. Los. 2012. Stone Fruit IPM Guidelines. 5 individual posters. Annual Meeting of the Connecticut Pomological Society. December 4, 2012. 88 growers were 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, and have therefore been abandoned.

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 were originally intended for use in orchard trials in spring/summer 2013, comparing phage against and in combination with two other methods, which will be chosen based on results of greenhouse/growth chamber trials. Due to the inability to produce BLS symptoms in greenhouse settings, and the absence of phage diversity, field research in 2013 will involve randomized trials of current copper/antibiotic methods, and not phage. Once results are obtained from these experiments, we will publish the results and conclusions in a peer-reviewed journal, such as Plant Disease.

Twelve Connecticut growers with 145 acres of stone fruit participated in IPM programs in 2012. Three of these 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 and four used mating disruption for Oriental fruit moth. The use of mating disruption for peachtree borers alone resulted in a decrease of 870 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 completed. Field surveys were conducted for two new invasive pests, the spotted wing drosophila and the brown marmorated stink bug.

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 2012. Three Connecticut growers participated in the Eco Stone Fruit program during the 2012 season.
As part of the Verification Plan for this grant, final surveys were mailed to stone fruit growers in October with a follow-up mailing in December. The results of this survey will be compared to the pre-program survey to determine changes in IPM practices since the beginning of the project. The Co-PI was the editor of the stone fruit sections of the 2012 New England Tree Fruit Guide. Stone fruit IPM and pesticide information were revised. Outreach was also provided through Fruit IPM updates via Email to over 190 growers. Twenty eight Email updates included information on stone fruit IPM.

Collaborators: