Towards sustainable disease management in northeastern apples using risk forecasts and cultural controls

Final Report for LNE12-315

Project Type: Research and Education
Funds awarded in 2012: $201,078.00
Projected End Date: 12/31/2015
Region: Northeast
State: Massachusetts
Project Leader:
Daniel Cooley
Stockbridge School of Agriculture
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Project Information

Summary:

From 2012 through 2014, collaborating researchers, Extension specialists and commercial apple growers in New England tested methods for reducing primary inoculum for the major apple disease, apple scab (causal agent Venturia inaequalis) and the impact of delaying the first apple fungicide application of each growing season. Educational programming promoting sanitation was done through the same period, as well as training in using web-based tools to follow inoculum maturation.

Growers were also trained in how to measure the amount of inoculum in their orchard using the potential ascospore dose (PAD) method, and shown how to translate their PAD index to the amount of time that they could delay the first fungicide application the following spring. At the beginning of the project, a grower survey determined the extent to which growers in New England were using sanitation practices to manage apple scab and whether growers were delaying their initial fungicide application according to inoculum estimates. A follow-up survey in 2015 assessed similar data.

Collaborators performed research and demonstration trials at three university research farms (MA, NH, and ME) and six commercial orchards (MA, NH, ME, CT and VT). A total of 33 commercial blocks were compared to blocks in the same orchard sprayed used conventional timing, usually starting at bud-break. In the delay blocks, growers eliminated from one to three fungicide applications a year (mean 1.9) while scab incidence at harvest was the same in both delay and conventional blocks (1.1% vs. 1.2%).

The percent of farms practicing at least some orchard sanitation to reduce scab inoculum increased from 67%  to 74% of those responding to the verification survey (74 farms and 57 farms respectively), while the number of acres using sanitation increased from 44% to 57% of those responding (1389 acres and 796 acres respectively). The percentage of growers doing a PAD index increased from 15% to 24% of respondents (16 growers and 16 growers), though the percentage of growers planning to delay to at least the tight cluster growth stage decreased from 16% of respondents (17 growers) to 9% (6 growers). Growers cited a reluctance to risk scab infections particularly early in the growing season, and the time required to do a PAD index as major reasons behind the low adoption rate of delaying the first fungicide spray, in spite of the demonstration that the method worked in comparison tests. Most growers used sanitation, usually flail mowing in fall or spring, stating that it was a relatively inexpensive and easy way to reduce scab risk. This demonstrates that growers are generally very risk-averse when determining what methods to use for apple scab management.

Introduction:

Apple growers in the Northeast have maintained excellent working partnerships with researchers, Extension and private professionals over the past thirty-five years, making their orchards more environmentally and economically sustainable through use of integrated pest management. However, management of the most threatening disease, apple scab caused by the fungus Venturia inaequalis, continued to depend heavily on fungicides.

Many years ago, reductions in the number of fungicide sprays were achieved by switching from prophylactic applications made before infection periods to use of newer DMI and strobilurin fungicides with post-infection activity. Unfortunately, scab strains resistant to the post-infection fungicides have evolved and those materials are no longer reliably effective. As a result, from 1998 to 2008, growers returned to frequent, protective applications and fungicide use for scab management increased.

This project used three linked tactics that have been shown to effectively manage scab and reduce fungicide use:

  • Measuring the amount of scab inoculum (potential ascospore dose or PAD)
  • Reducing scab inoculum using sanitation
  • Employing weather-based decision support systems (DSS) to track infection

Growers and crop advisors worry that these methods require more effort and expense, and that reducing the number of fungicide applications will expose them to unacceptable risk. We argue that demonstration of efficacy and practicality of these methods in controlled research settings and in commercial orchards will increase use of these methods, reverse the trend of increasing fungicide use, and serve as a model for implementation of reduced fungicide methods in organic and conventional orchards throughout the Northeast. This project gave growers an understanding of the feasibility and reliability of these practices through education, research evaluation, and grower demonstrations.

The growth stage at which apple trees need protection against scab varies with the amount of inoculum. Scab inoculum consists of spores called ascospores, and can be estimated as a potential ascospore dose, PAD. Almost all the scab spores that will infect an orchard are in leaves from the previous fall lying on the ground within 100 feet of the tree. If the PAD in an orchard is high, infection can occur as soon as there is green tissue present in the spring. But if the PAD is sufficiently low, there is no risk of infection until one or more weeks later. Without risk of infection there is no need to apply a fungicide. The length of this delay period from green tip varies, depending on ascospore maturation, which can be estimated by models in decision support systems (DSSs).

Growers can destroy much of the inoculum in an orchard, over 95% in many cases. This tactic, generally called sanitation, can be carried out in two ways, flail mowing and/or applying urea to leaves. With flail mowing, growers use a flail mower to grind up leaves after they have fallen, either in the fall or early spring before bud-break. Urea applications are made either to leaves on the tree after harvest, or to fallen leaves in the fall or spring. These tactics may be combined.

Sanitation reduces the risk of scab, and reduces the chance that scab will become resistant to fungicides. It is good IPM. Therefore, this project recommended growers use sanitation in every apple orchard every year, even if the orchard did not qualify for a delayed spray the following spring.

Disease forecast models based on weather data can reduce uncertainty in making scab management decisions. However, collecting weather data and using forecast models can be complicated and intimidating. The internet and electronic weather monitoring technology have made it easier to get timely, accurate forecasts for apple scab.

In New England, four decision support systems are used:  NEWA (the Network for Environment and Weather Applications) managed by the New York State IPM Program; Ag-Radar managed by the University of Maine Extension; the commercial product SkyBit (ZedX, Inc., PA); and the commercial product RIMpro (BioFruit Advies, Netherlands). These tools allow growers to closely monitor estimates of ascospore maturation and availability and apple scab infection periods. However, growers have been slow to adopt them, largely because they don’t know how to use them and are not sure that they will help their scab management program.

Growers rely on tangible evidence of success and practicality before adopting new management tactics. At pre-season workshops growers learned the techniques and scientific background for scab sanitation, PAD estimation, the delayed spray protocol, and use of DSS tools. Training was necessary but on-farm use was even more valuable.

Performance Target:

Our objective has been to work with New England apple growers to improve apple scab disease management in three specific areas:

  • Improve methods of measuring scab inoculum in the field,
  • Reduce scab inoculum by increasing and improving sanitation methods (urea sprays and leaf-chopping),
  • Make better use of decision support systems (DSS) to track infection risks.

At the end of the project, we had sufficient resources to allow us to add an additional objective:

  • Build a smartphone app to guide growers in the selection of environmentally sound pesticide options

These objectives have been met by a combination of university and commercial orchard research and demonstration trials, grower collaborations, educational events and publications, and grower surveys. By performing measurements of scab inoculum in the field with growers during 4 fall seasons, we were able to demonstrate to > 50 growers that a 2-3 acre block of trees could be indexed in about 30 minutes.  Even more growers (approx. 75) saw the efficacy of increasing and improving sanitation methods and subsequently adopted these methods. There was a progression from using rotary mowers to using flail chopper mowers and to getting the equipment in closer to the trunks of the trees. More than 60 growers received individual training in the use of decision support systems (DSS) and more than twice that number received information about these tools at meetings and workshops.

Performance target: Fifty apple growers will document adoption of scab management alternatives on a total of 500 acres, reducing their fungicide use and maintaining or reducing scab incidence in those blocks. Our calculations indicate that this should save a total of from $50,000 to $75,000 in production costs per year.

Adoption of scab management alternatives did occur for at least 50 growers.  The most widely adopted have been the sanitation practices and the use of DSS. Not as many growers have regularly adopted urea spraying or delayed first spray programs. With increased knowledge of how the disease works and how the weather data and disease models influence the disease risk, a large number of growers are saving sprays by only spraying when the risk is moderate or high.

Cooperators

Click linked name(s) to expand
  • Jon Clements
  • George Hamilton
  • Glen Koehler
  • William MacHardy
  • Renae Moran
  • Cheryl Smith
  • Arthur Tuttle

Research

Materials and methods:

During the fall seasons of 2011-2014 project scientists assisted grower collaborators with PAD assessments in blocks of apples trees in every New England state except RI. By 2014 there were 22 orchards in the project. Blocks of apple trees averaged 2 to 3 acres each and included scab susceptible cultivars such as MacIntosh, Cortland, and Macoun, as well as cultivars with some scab resistance, such as Empire and Honeycrisp.

Between leaf fall each year and the green tip bud stage each spring, flail mowing sanitation was performed at commercial and university orchard sites, and urea applications were done at most sites. Blocks of apple trees that had low levels of overwintering inoculum using the fall PAD index received delayed fungicide applications in the spring. That is, they did not get a fungicide spray at the green tip bud spray as would be used in a conventional scab management program, but instead the first scab spray was delayed. Guidelines recommended delay until tight cluster to the pink bud stage, or until after two scab infection periods, whichever came first. The delay could be adjusted according to estimates of ascospore maturity, where approximately 10% of the seasonal inoculum load was considered a threshold. In some cases, under unusually dry conditions, ascospore maturation stopped while tree growth continued, and some sprays were delayed until bloom. All growers and researchers monitored scab infection periods carefully using a DSS, usually NEWA or AgRadar. Leaf scab incidence was evaluated in both delayed and control blocks during June or early July, and fruit scab incidence was evaluated just before harvest. Control blocks were in the same orchards as delay blocks, but did not receive sanitation treatments and received fungicide sprays starting at green tip.

Blocks of apple trees that had too much overwintering scab to qualify for a delay were used in a sanitation test. These blocks got maximum amounts of sanitation (two passes with a flail mower and a urea application), and received a full fungicide program starting at the green tip bud stage. Control blocks received little or no sanitation and the same fungicide programs. All blocks were assessed for leaf scab in June and for fruit scab just before harvest.

To assess grower adoption of the recommended scab management practices, we did two surveys, one concurrent with the start of the project and a second at the end of the project. Both surveys were distributed to commercial apple grower email lists in the six New England states.

To develop the smartphone app, a list of registered pesticides was evaluated according the Eco Apple Protocol (IPM Institute of N.A. https://ipminstitute.org/projects/northeast-eco-apple/). A hierarchical design built around apple phenology was used to match pesticides to pests, giving the grower of recommended pesticides for a given time and pest. Pesticides not allowed under the Eco Apple protocol were not included in the options.

Research results and discussion:

The project was originally planned to start in early spring 2012 and to run through two growing seasons, but due to delays in funding it did not start officially until later in 2012. Because we had data and sufficient resources, we decided to go ahead and start the research and demonstration work in early spring 2012 and then continued for three full field seasons. At the end of the project, we had resources that allowed us to add an additional objective, building a smartphone app that would guide growers in the use of apple pesticides. The project concluded in the summer of 2016.

Milestones

  • 300 apple growers receive an on-line survey about current practices. 100 growers return the survey and identify impediments to adoption. (Mar. ’12).  
  • 50 growers attend one of two four-hour workshops that explain apple orchard sanitation, elimination of early season fungicides, and decision support systems (hereafter ‘scab management alternatives’ or SMA). (Mar. ‘12).   Done during growing season.
  • 15 growers agree to participate as test sites for the delayed scab fungicides in ’13 and to work with decision support in ‘12; (Mar. ‘12). Done, we exceeded this number.
  • 100 growers attend twilight meetings at commercial orchards or field days at university farms and learn about SMA. (Jun. – Aug. ‘12.) Done, we exceeded this number.
  • 30 growers and orchard advisors attend one of three fall sessions demonstrating inoculum measurement method (PAD) and fall urea treatment. 20 growers measure PAD in their orchard and begin orchard sanitation (Oct. – Nov. ’12).
  • 100 growers who responded to first survey receive a second survey to determine changes in understanding of and willingness to use SMA. 80 growers return survey. (Jan- Feb. ‘13). Done in 2014.
  • 200 growers learn results of spring ‘12 fungicide delay experiments on university farms by attending educational winter meetings, through newsletters, and publication in Fruit Notes (Nov. ‘12 – Mar. ‘13). Done.
  • 50 growers, including cooperators, attend 2nd year workshops to discuss SMA, answer specific implementation questions before 2013 growing season, and suggest modifications (Mar. ’13).
  • 15 growers eliminate at least one fungicide spray in their orchard by following protocol. (Apr. – Jun. ‘13). Only 11 of the 20 growers had low enough PAD counts to eliminate the early season spray, but these 11 did the elimination.
  • 3 growers host twilight meeting at demonstration sites (one each in MA, ME, NH) (Jun. ’13). 75 growers attend meetings and learn about SMA.
  • 200 growers learn results of spring 2013 fungicide delay experiments on university farms and grower demonstration blocks by attending educational winter meetings through newsletters, and publication in Fruit Notes (Nov. ‘12 – Mar. ‘13).
  • 100 New England apple growers access on-line decision support (Feb. – Jul. ’13).  Done and exceeded.
  • 300 apple growers receive an on-line survey about current practices. 100 growers return the survey; 50 of the respondents document the number of acres of orchard sanitized, number of fungicide applications eliminated by use of delayed scab spray strategy, and their degree of satisfaction with the approach. (Dec. – Feb. ’14).
  • We repeated the milestones for 2014, and increased the number of grower sites to 22.
  • Build a working version of a smartphone app designed to guide growers in the selection of the most ecologically sound and effective pesticide options. Done

Results

2012: Project scientists assisted grower collaborators with potential ascospore dose (PAD) assessments during Fall 2011 in preparation for the beginning of the study. Between leaf fall in Nov. 2011 and the green tip bud stage in Spring 2012, urea application and leaf-chopping sanitation were discussed and documented for the commercial and university orchard sites.

Under the guidance of UMASS scientists, the 1st scab spray was delayed in apple blocks until the pink bud stage in Spring 2012 at 6 commercial sites in MA, CT, VT, and southwest NH. Scab incidence was assessed in foliage in June and in fruit in Sept. and was found to be comparable to grower control blocks that received a standard fungicide program. In all cases, injury was kept well below the economic level. At 2 of the sites (Walpole, NH and Saxton’s River, VT) there were infection periods before the pink bud stage. At the UMASS research farm, test plot fungicide applications were delayed successfully until the pink bud stage, but were unsuccessful when pushed further to the bloom stage. A significant infection period occurred between the 2 dates and too much unprotected green tissue was infected. At the UNH research farm, test plot fungicide applications were successfully delayed to the petal fall bud stage after 3 infection periods had occurred in 1 trial and until the pink bud stage in another trial. As in MA and ME, scab incidence was assessed in foliage in June and in fruit in September. At the UME research farm, test plot fungicide applications were successfully delayed to the pink and to the bloom bud stages. Powdery mildew was also assessed and was not found to be higher in plots that had delayed fungicide programs.

In most of the research sites in 2012, there were no infection periods before the pink bud stage. For this reason, the UNH trial pushed one of the treatments to petal fall (by which time 3 infection periods had occurred). Because of the very early spring in 2012 with unusually dry weather between the green tip and pink bud stages the scab management alternatives did not get a rigorous challenge. Traditionally, apple growers in New England start spraying for scab at green tip. If they were not calculating their infection periods carefully in 2012, they might have applied 2 or more unnecessary applications before the pink bud stage. Growers in this study, however, had the benefit of access to weather-based decision support tools (NEWA and/or Orchard Radar) and training from project scientists on how to use these tools. This part of the study benefitted all. As we were adjusting to the erratic and unusual weather patterns we realized that the scab ascospore maturation model was not accurately predicting the beginning or end of primary scab season. This finding spurred research within the project to test and improve the model.

In fall, 2012, another round of PAD assessments were performed, many with the growers, to prepare for the 2013 season. Three additional orchards were added to the study in MA. Sanitation strategies were planned with all growers.

2013: Under the guidance of UMass scientists, the 1st scab spray was delayed in apple blocks until the pink bud stage in Spring 2013 at 5 sites in MA, CT, VT, and southwest NH. Test blocks also received urea applications and leaf chopping. These sites had low enough levels of scab infestation to pass a PAD assessment in Fall 2012. Scab incidence was assessed in foliage in June and in fruit in Sept. and was found to be comparable to grower control blocks that received a standard fungicide program. In all cases, injury was kept below the economic injury level. There was no rainfall between the green tip and pink bud stages and therefore no infection periods. Because of this, the differences between test blocks and control blocks were fewer than expected. However, 4 of the growers who delayed their 1st sprays until the pink bud stage and started spraying their control blocks earlier and averaged 9 days of delay between the test blocks and the control blocks. At 6 additional sites, where blocks of apple trees failed the PAD in Fall 2012, the sanitation part of the study was performed. Test blocks received urea applications and leaf chopping. Control blocks received no urea and less leaf chopping. Fungicides were not delayed: rather a full protectant spray program was used from the green tip bud stage on. At 2 of the sites, there was less scab in the test blocks compared to the control blocks. At 4 sites the amounts were not different. PAD assessments were done at all sites and a few new sites in Fall 2013 to prepare for the 2014 season.

At the UNH research farm, sprays in 4 blocks of apples trees were delayed until full bloom, sprays in 3 blocks were delayed until tight cluster, and 4 blocks (controls) were given a standard protectant program starting at green tip. All blocks received urea and flail leaf chopping in the fall of 2012. The bloom sprays were delayed 35 days and the tight cluster sprays were delayed 10 days as compared to the control blocks. There was 1 infection period prior to bloom. In 2 of the comparisons, there was more fruit scab in the trees that were delayed until bloom than in the controls. In the other 2, the amount of scab was not different. UNH scientists also worked with 5 commercial growers. One of them delayed successfully until late pink and had no scab on leaves in July or on fruit in September. Three growers performed the sanitation strategies, after failing the PAD in Fall 2012. Levels of scab were low in July and September and all 3 passed the PAD in September.

At the UME research farm, 3 blocks of apples trees were delayed until bloom (a delay of 11 days), 3 were delayed until tight or open cluster (a delay of 5 days), and 3 (controls) were sprayed from green tip on (no delay). In 8 of the 9 blocks, the amount of scab was very low in the PADs each year, the July leaf counts, and the September fruit counts. Scab management was very successful and there were no differences among treatments. In the 9th block, there was 4.2% fruit scab in the section that was delayed until bloom, 0.8% in the section delayed until open cluster, and 0% in the control. UME scientists also worked with 3 commercial growers. These all had very low PAD counts going into the study. Each had a delayed block (delayed 20 days) and a control block. All 3 had very low amounts of scab in leaves and fruit in delayed blocks as well as control blocks (no differences). All 3 also passed the PAD assessments in Fall 2013.

In most of the research sites in 2013, there were no infection periods before the pink bud stage. For this reason, the UNH and UME scientists pushed one of the treatments at some of the sites to a “delay until full bloom 1st spray”. One infection period occurred between pink and bloom. UMass growers were not willing to change the protocol and wait that long. This was reasonable as a similar dry spell in Spring 2012 resulted in a massive infection period at bloom and some scab problems. For both 2012 and 2013, the scab management alternative strategies of this study did not get challenged as vigorously as planned in this study. In an average year, there would be 2-3 infection periods before the pink bud stage.

Growers in this study had the benefit of access to weather-based decision support tools (NEWA and/or Orchard Radar) and training from project scientists on how to use these tools. All of the growers routinely checked for scab forecasting from one of these sources and many have weather stations directly linked to NEWA. To make the information more accurate and site-specific, this project worked in all 3 states to improve the scab ascospore maturation model. This includes new methods for spore-trapping and maturation assessment during primary scab season and adjustments for dry periods. We need to more accurately predict the beginning and end of scab season.

2014: Spray application records have been collected from all cooperating growers in the study for 2014. Pesticide usage was compared between experimental treatments and their controls.

 Under the guidance of UMass scientists, 15 sites in MA, CT, VT, and southwest NH were evaluated for fall leaf scab infestation in Oct. 2013. Nine of them had low enough levels of scab to pass the PAD test and qualified for the delayed 1st scab spray strategy for Spring 2014. The average number of days the blocks were delayed as compared to the “Control” plots was 9.4 days. At the time of that 1st scab spray, the average % maturity of the scab ascospores was 20%. Due to the delays, less fungicide was used in the “Test” plots: 5.5 dosage equivalents (DE) of fungicide as compared to 6.6 in the “Control” plots. “Test” plots also received urea applications and maximum leaf chopping while “Control” plots received minimal leaf chopping. Scab incidence was assessed in foliage in June 2014 and in fruit in Sept. and was found to be comparable to grower control blocks that received a standard fungicide program. In 7 of the 9 sites, injury was kept below the economic injury level. For 1 of the exceptions, the higher amount of fruit scab (12% incidence) was caused by the use of very low fungicide rates and by waiting too long to make the 1st application. The other high incidence of scab (8%) was probably caused by proximity to an abandoned orchard. At 5 additional sites, where blocks of apple trees failed the PAD in Fall 2012, the sanitation part of the study was performed. Test blocks received urea applications and maximum leaf chopping. We defined maximum leaf chopping as at least 2 passes with a flail or a rotary mower (and minimum as one pass). Many growers also added leaf-sweeping, leaf-raking and/or flexible arms that could get close to tree trunks to their maximum sanitation practices. Control blocks received no urea and less leaf chopping. Fungicides were not delayed: rather a full protectant spray program was used from the green tip bud stage on. At 4 of the sites, there was very little scab in the leaves in June or in fruit in September in either of the plots. At the 5th site there was little scab in June, but a moderate amount appeared in the fruit in September. In both the Delayed and the Sanitation-only trials, plots ranged in size from 1 to 5 acres. Most plots were assessed for leaf scab in Fall 2014 (PADs were performed). Most growers indicated plans to continue with urea applications, leaf chopping, and delays after the end of the study. This is a indication of the positive impact of the project.

 At 4 commercial sites in NH, 1 “Test” plot of apples was delayed until Pink or until 2 infection periods had passed. At the time of that 1st scab spray, the average % maturity of the scab ascospores was 21%. The fungicide dosage equivalents (DE) in the “Test” plots was 3.62 versus 4.12 in the “Control”. All “Test” plots received maximum leaf chopping. Some received urea applications as well. The “Control” plots had minimum leaf chopping and no urea. The 3 other sites did not delay the 1st spray in the “Test” plots, but did reduce the overall number of sprays. The average DE in the “Test” plots was 4.6 versus 7.4 in the “Controls”. A savings of 2.8 fungicide full-rate applications was achieved. Scab levels were never higher in the “Test” plots (leaves or fruit) than they were in the “Controls” and were always well below 1 % incidence. All plots were assessed for leaf scab in Fall 2014, and all passed the PAD. All growers indicated plans to continue with urea applications, leaf chopping, and delays where possible, even after the end of the project.

At 4 commercial sites in ME, all “Test” plots of apples were delayed until Pink or until 2 or more infection periods had passed. The average number of days that the 1st spray was delayed was 9.8. At the time of that 1st scab spray, the average % maturity of the scab ascospores was 38%. The average fungicide dosage equivalents (DE) in the “Test” plots were 4.9 versus 6.12 in the “Control”. A savings of 1.2 fungicide full-rate applications was achieved. Scab levels were kept very low in all plots except for 1 “Control” plot, which had a fruit scab incidence of 5 %. All “Test” plots were assessed for leaf scab in Fall 2014, and all passed the PAD. All growers indicated plans to continue with urea applications, leaf chopping, and delays where possible after the end of the study.

Growers participating in this study have had the benefit of access to weather-based decision support tools (NEWA or Skybit, or AgRadar) and training from project scientists on how to use these tools. Project scientists have purchased weather stations and annual contracts with NEWA. They have also purchased Skybit data for farms that did not have on-site weather stations. Glen Koehler at UME, a key scientist in this study, provided AgRadar for the sites that had Skybit data. All of the growers routinely monitored scab forecasting from one of these sources and many had weather stations directly linked to NEWA. To make the information more accurate and site-specific, this project continued to work in all 3 states to improve the scab ascospore maturation models. This included new methods and equipment for spore-trapping and maturation assessment during primary scab season (designed by Bill MacHardy at UNH). UMass scientists have also been performing replicated spray trials to compare the advantages and disadvantages of using two data sources (RainWise weather stations and Skybit) with 4 analytical tools (NEWA, Skybit, AgRadar, and RIMpro) to time scab spray applications (see Publications).

Participation Summary

Education

Educational approach:

2012: Two workshops/advisory meetings, one in MA (Oct.) (18 attendees) and one in ME (Aug.) (70 attendees), were held in 2012 to train groups of apple growers in scab management alternatives (SMA). The trainings included developing reduced fungicide and sanitation strategies, demonstrations of potential ascospore dose assessments (PAD), and use of decision support tools (NEWA, AgRadar). William MacHardy, Daniel Cooley, Glen Koehler, and Renae Moran were speakers/leaders in ME. Daniel Cooley, Arthur Tuttle, and Jon Clements were speakers/leaders in MA. In July 2012, the delayed fungicide program research plots at UMass were toured and discussed at the annual summer fruit grower’s meeting (~100 attendees). The concepts and strategies pertaining to scab management alternatives (SMA) were also presented at 9 grower twilight meetings during April-June (approx. 30 attendees each). The project was also discussed at the Winter 2013 meeting of the Maine State Pomological Society. (60 attendees).

The New England Apple Scab Control Practices Survey: A survey was conducted in May-July 2012 to learn about current apple scab management in commercial apple orchards within New England. 507 growers were invited to take the survey and 115 responded. A report was written by Renae Moran and was web-published at http://extension.umass.edu/fruitadvisor and at comparable websites in ME and NH. In summary, growers reported use of at least one sanitation measure on 41% of acres, but only 15% of growers were doing a fall scab PAD index. The primary reasons for not doing a fall scab PAD were lack of time (37%) and lack of training (36%). Seventy nine percent of growers reported routine start of scab fungicide protection at Green Tip or Half inch Green bud stages, but 75% would consider delaying fungicide use with additional demonstration of effectiveness of delay strategy and training in methods that reduce scab risk such as sanitation and measuring the scab risk with a PAD index.

2013: Groups of apple growers were educated in scab management alternatives (SMA) at two grower meetings in 2013, one in MA (Oct.) (45 attendees) and one in ME (Aug.) (~40 attendees). The sessions included the delayed 1st spray strategy, sanitation strategies, reduced-risk fungicides, potential ascospore dose assessments (PAD), and use of decision support tools (NEWA and AgRadar). William MacHardy was the featured speaker in ME. Arthur Tuttle spoke in MA. The concepts and strategies pertaining to scab management alternatives (SMA) were also presented at 5 grower twilight meetings, and at the eIPM Stakeholder’s Meeting at Ward’s Berry Farm by UMass project scientists during April-June 2013. (approx. 30 attendees each). UME scientists presented project ideas, strategies, and results at the Maine Agricultural Trades Show (Jan.), at the Pre-season Tree Fruit Meeting (Mar.), and at the UME Highmoor Farm Summer Tour (July), the Great Maine Apple Day (Oct.), the NH Risk Management Meeting (Nov.), and at a Pesticide Applicator Training Session (Nov.). UNH scientists presented project ideas, strategies and results at 2 additional twilight meetings (April and June) and a grower seminar in late fall. In all 3 states, project scientists worked with cooperating growers and their staff to train them in scab management alternatives. These alternatives were also discussed in spring issues of Healthy Fruit (http://extension.umass.edu/fruitadvisor), J. Clements, editor and in the Maine Tree Fruit Newsletter.

2014: Groups of apple growers were educated in scab management alternatives (SMA) in 6 grower meetings in NH and MA. (attendees averaged 41). Topics included the delayed 1st spray strategy, sanitation strategies, reduced-risk fungicides, potential ascospore dose assessments (PAD), and use of decision support tools. The concepts and strategies pertaining to SMA were also presented at 5 additional grower twilight meetings in MA and RI, and at the UMass eIPM Stakeholder’s Meeting (February, Grafton, MA) by UMass project scientists (attendees averaged 30). In all 3 states, project scientists worked with cooperating growers and their staff to train them in scab management alternatives.

We worked closely with 22 growers to implement and adopt advanced scab management alternatives via replicated trials. Several other growers participated in scab management activities in a less formal manner. These activities were also discussed in April-June issues of Healthy Fruit (http://extension.umass.edu/fruitadvisor), J. Clements, editor, in the Maine Tree Fruit Newsletter, and in the April-July issues of the New Hampshire Integrated Pest Management Newsletter (http://nhipm.wordpress.com). Frequent updates on apple scab ascospore maturity lab and field tests were published in these newsletters.

The New England Apple Scab Control Practices Survey: The survey that was conducted in May-July 2012 to learn about the state of apple scab management in commercial apple orchards within New England (published in Fall 2013 in Fruit Notes 78(4): 9-11 (http://extension.umass.edu/fruitadvisor) was followed-up with an end-of-project survey in April-July 2014. Both surveys were designed and analyzed by Renae Moran at UME. The results highlight impacts of the study. We obtained the following results from 77 responding growers.

• Sanitation, an approach to disease control implementing sweeping/raking/mowing/chopping and/or urea spraying, is practiced by 74% of surveyed growers in northern New England, an increase of 7% over the last two years. The proportion of acres in which sanitation was used increased by 23%.

• Scab indexing, a method to predict disease and to reduce the use of fungicide (includes the PAD or potential ascospore dose evaluations), is practiced by 24% of growers, an increase of 9% over the last two years. 

• In 2014, 28% of the responding apple growers reduced fungicide use on all or part of their apple acreage by using sanitation, measuring the scab index or by growing resistant varieties.

Websites

http://ag.umass.edu/fruit  The home site for “Healthy Fruit” which published scab management updates from late March through June each year.  Also for Fruit Notes, the New England Tree Fruit Management Guide, fact sheets pertaining to apple scab management, and information related to weather data, weather stations, and decision support systems (DSS) for apple growers.  Also known as UMass fruitadvisor.

https://extension.umaine.edu/ipm/ag-radar-background/ag-radar-apple-sites AgRadar. Glen Koehler’s decision support systems (DSS) were used regularly by growers in all 3 states. Of particular relevance to this study were the apple scab models.

http://newa.cornell.edu Network for Environment and Weather Applications Network (NEWA). Led by Juliet Carroll. 22 weather stations maintained in MA by Cooley, Tuttle, and Clements; 46 weather stations in MA linked to NEWA. Growers in all states involved in the project used the decision support systems (DSS) regularly. Of particular relevance to this study were the apple scab models.

Publications

2012-2015. Clements, J., ed. Healthy Fruit. Newsletter published weekly, March to October and as needed for alerts year-round, 23 issues/year. Included pest alerts, meeting announcements, fact sheets and updates to the New England Tree Fruit Management Guide. https://umassfruitadvisor/publications/healthy-fruit

2012-2015. New Hampshire Integrated Pest Management Newsletter: 2012-2016. Published weekly during growing season. Each year during the project there were frequent updates on apple scab management. For example, in 2014 see July 2– Volume 10 No. 5, May 28 – Volume X No. 4, May 13 – Volume X No. 3, and April 22 – Volume X No. 2. http://nhipm.wordpress.com/

2012-2015. Green, T., M. Rozyne, A. Tuttle, J. Carroll, J. Clements K. Leahy and D. R. Cooley. Eco-apple protocol and grower self-assessment. Working document for 2012 growing season – version 9.0   IPM Institute of North America, Inc., Madison, WI. 38 pp. (Revised annually).

2012-2015. Cooley, D. R. Development of more sustainable disease management tactics for apple production in the Northeast. MAS 00407. Expt. Sta. Hatch Rept. http://www.reeis.usda.gov/web/crisprojectpages/225216.html (10/1/2010 – 9/30/2015). 3 pp.

  1. Cooley, D., A. Tuttle, and J. Clements. University of Massachusetts Extension Fruit IPM Report for 2012. Fruit Notes, Vol. 77(4): 16-17. http://umassfruitnotes.com/v78n4/a3.pdf
  1. Clements, J. and D. Cooley. A Comparison Of Two Sources Of Environmental Data And Three Model Outputs For Primary Apple Scab In 2012 At The UMass Cold Spring Orchard. Fruit Notes 78(2): 4-11. (http://umassfruitnotes.com/v78n2/a2.pdf)
  1. Moran, Renae, G. Koehler, C. Smith, G. Hamilton, W. MacHardy, L. Berkett, H. Faubert, M. Concklin, A. Tuttle, J. Clements, and D. Cooley. Survey of New England Apple Growers On Using Sanitation and Delaying Early-season Fungicide Applications. Fruit Notes, Vol. 78, No. 4. Pages 9-11. http://umassfruitnotes.com/v78n4/a2.pdf
  1. Cooley, D.R., A. Tuttle, S. Villani, K. Cox, G. Koehler, T. Green, and P. Werts. Increasing fungicide use in New England apples. Fruit Notes 78 (Fall): 1-6. (http://umassfruitnotes.com/v78n4/a1.pdf)
  1. Cooley, D.R., A. Tuttle, J. Clements, S. Schloemann, and E. Garofalo. University of Massachusetts Fruit IPM Report 2014. Horticultural News 94 (Fall): 5-8. (http://www.horticulturalnews.org/94-4/a2.pdf)
  1. Cooley, Daniel, A. Tuttle, J. Clements, and S. Schloemann. Massachusetts Fruit IPM Report for 2013 Growing Season. Fruit Notes, Vol. 79, No. 1. Pages 7-9. http://umassfruitnotes.com/v79n1/a2.pdf
  1. Cooley, D. R. and J. Clements. Preliminary evaluation of four decision support systems for management of apple scab in the northeastern U.S. Phytopathology 105 (Suppl. 1):S1.6.
  1. Garofalo, E., D.R. Cooley, J.M. Clements and A.F. Tuttle. Discrepancies Between Direct Observation of Apple Scab Ascospore Maturation and Disease Model Forecasts in the 2014 and 2015 Growing Seasons.  Fruit Notes 81(2) 7-18. (http://umassfruitnotes.com/v81n2/a2.pdf)
  1. Moran, R. et al. The New England Apple Scab Control Practices Survey. Fruit Notes 81(1): 1-6. (http://umassfruitnotes.com/v81n1/a1.pdf)

Seminars

  1. Koehler, G. Tree Fruits – IPM Strategies to Reduce Risk – Risk Management Seminar: Apple Pest Problem Scenarios and What Growers Should Plan to Do Based on the Scenario. UNHCE – Hillsborough County Office Meeting Room, Goffstown, NH. Nov. 9.

Presentations

  1. Cooley, D.R. and J. Clements. Observations on utility of multiple disease forecasting models from an Extension perspective. The Midwest Weather Working Group, North Central IPM Center, at American Phytopathological Soc. Annual Mtg, Austin TX. Aug. 9. 28 attendees.
  1. Clements, J., and D. Cooley. Some observation on using multiple disease forecasting models during the 2013 growing season from an Extension perspective. The New York, New England, Canadian Pest Management Conference/Northeast IPM Tree Fruit Working Group Meeting. October 22-23, Burlington, Vermont. 49 attendees.
    http://www.northeastipm.org/neipm/assets/File/TFWG-Massachusetts.pdf
  1. Clements, J. and D. Cooley. Some observation on using multiple disease forecasting models during the 2013 growing season from an Extension perspective. The 2013 Great Lakes Fruit Workers Meeting, November 12-15, Bowmanville, Ontario, Canada. 40 attendees. http://greatlakesfruitworkers.weebly.com/2013-glfw-meeting-archive.html
  1. Cooley, D.R. Reducing Fungicide Applications against Apple Scab Using Sanitation and Potential Ascospore Dose. 75th Annual New York, New England & Canadian Fruit Pest Management Workshop, Burlington VT. 63 attendees.
  1. Broders, K. Tree Fruit Disease Research at UNH. New Hampshire Fruit Growers Annual Meeting. Concord, NH. March 20, 2014.
  1. Clements, J. A Comparison of Weather Models for Fruit Growers. Vermont Tree Fruit Growers’ Assoc. 118th Annual Meeting. February 13. Middlebury, VT. 60 attendees.
  1. Cooley, D.R. and J. Clements. Decision Support Systems for Apple Scab Management. The Midwest Weather Working Group, Annual Meeting, Minneapolis, MN. Aug. 8, 2014. 25 attendees.
  1. Smith, C. Apple Scab. Tree Fruit Twilight Meeting. Currier Orchard. Merrimack, NH. April 23.
  1. Smith, C. Apple Scab. Tree Fruit Twilight Meeting. Surowiec Farm. Sanbornton, NH. June18.
  1. Smith, C. and K. Broders. Apple Scab Project at UNH Woodman Farm and Apple Disease Research. New Hampshire Tree Fruit Meeting. New Hampshire Agricultural Experiment Station (NHAES). UNH – Woodman Farm, Durham, NH. July 16.
  1. Cooley, D.R. and J.M. Clements. Decision Support Systems Evaluation in Massachusetts. Invited presentation. National Weather Work Group, Aug. 5-7, Ventura, CA. 23 attendees.
  1. Garofalo, E.W. and Cooley, D.R. Discrepancies Between Observed Ascospore Maturity and Model Predictions in the 2014 and 2015 Apple Scab Seasons. 77th Annual New York, New England & Canadian Fruit Pest Management Workshop, Burlington VT, 65 attendees.
  1. Cooley, D.R. Tactics for Apple Scab Management. Southwest Michigan Horticulture Days, Mendel Center, Lake Michigan College, Benton Harbor, MI, 4 Feb. 40 attendees. sanitation-for-apple-scab-management
  1. Cooley, D.R. Sanitation: Stack the Deck Against Scab; New Technology in Apple Scab and Fire Blight Management. Henry Wallace Center, FDR Memorial Library, Hyde Park, NY, 3 March 2016, 70 attendees.

Additional Project Outcomes

Project outcomes:

Impacts of Results/Outcomes

The most significant impacts of the project were those experienced by the 22 apple growers who participated directly in the research demonstration trials, many for 2 years and some for all 3 years. Impacts for these growers were greatly increased understanding of the disease and how to manage it, reduction in worry, in many cases reduction of 1 or 2 sprays in the spring, shifts to cultural control (sanitation), and better management of fungicide resistance problems. Many of these growers assessed overwintering scab inoculum incidence with us, all performed the sanitation strategies between leaf fall of each year and green tip the following springs, and all did the tasks involved in maintaining delayed 1st spray or sanitation-only blocks of apple trees through the growing seasons.

They also became expert at using the decision support tools available to them on NEWA or AgRadar regarding scab management and became advanced IPM practitioners. There were several growers in each state who heard about the project at twilight meetings and grower workshops and asked for help managing scab. Many of them had too much scab to qualify for the delayed 1st spray strategy, and did not have blocks of trees officially in the trials. However, after working with us on sanitation and decision support systems they all reduced their scab problems.

As will be discussed in the Farmer Adoption section, most growers directly involved in the study and the research scientists in all 3 states asserted that they would be continuing the relevant practices in future years. A much larger group of growers and extension scientists were exposed to the study and it’s practices at workshops, grower meetings, field walks, and through publications (see Publications/Outreach for details). It is harder to assess impacts on these groups, but the end-of-project survey attempted to do this (see Publications).

Economic Analysis

During the course of the project we engaged the growers in discussions of the relative costs and benefits of most of the scab management alternative strategies. For example, the cost of doing leaf-chopping in a block of apple trees is about the same ($10.00/acre) as the cost of a scab spray (although there is a wide range of costs among the many scab fungicides). When you factor in the added benefit of improving your management of resistance to a fungicide by eliminating a spray or 2, it is no wonder that sanitation practices increased during the study. Spraying urea is more costly ($60.00/acre) and although very effective, was adopted to a lesser extent. The cost of doing a PAD count in a 1 acre block = the cost of the grower’s or another person’s time for about 15 minutes if the block is fairly clean. Two acres would be about 20 min. If you eliminate a spray in the spring, you save the cost of the fungicide, the time to do the spray, the fuel, the wear and tear on the equipment, the soil compaction, and the possible deleterious effects on the eco-system. We did not have economists involved in the study, but growers are adept at this kind of analysis. For them, it’s a combination of the bottom line and managing risk.

 

 

Farmer Adoption

At the end of the original study (apple harvest 2014), the 22 growers who were actively participating in the project were asked if they were planning to continue with some or all of the scab management strategies that they had been employing. Twenty-one said yes, the 22nd said maybe. We decided to keep track of what they did over the next 9 months as a way of documenting grower adoption. At 16 of the farms (possibly more), potential ascospore dose (PAD) assessments were done in fall 2014. At 13 of these sites, the scab level was low enough to qualify the trees for delays in spraying the following spring. At 16 of the sites, leaves were chopped (mostly with flail) and at 7 sites urea was applied between leaf fall 2014 and green tip 2015. The 1st spray in the spring was delayed by at least a week in seven out of the 13 blocks that qualified for this action. All growers reported good scab control and all reported extensive use of decision support systems (DSS) (either on NEWA or AgRadar). Most of the growers attributed their success to increased sanitation, increased knowledge of scab management, better use of DDS, contact with University and Extension scientists, and Extension publications.

Assessment of Project Approach and Areas of Further Study:

Areas needing additional study

At the beginning of the study many apple growers in New England were just beginning to use decision support systems (DSS) like those available on the NEWA website, AgRadar, or Skybit. Four years later, the number with expertise in these systems is much greater. University and Extension scientists need to keep up with this and help growers evaluate the usefulness of these systems and their updates and improvements. A 4rth system, RIMpro, is now available. It is more complicated and perhaps more powerful and useful. There is a need to use it, evaluate it, and help growers use it. There is also a need to help growers who want to grow apples organically use these systems and manage scab more effectively. During the course of this study, work was done in all 3 states to better understand apple scab spore maturation in the spring and the effects of long dry periods and abnormal weather patterns. This work is on-going. Results will be used to improve the scab models on the DSSs. Also, as climate change becomes more pronounced, and we have more erratic weather patterns (higher and lower temperatures, more and less rainfall, more severe storms) it becomes more important to study the effects of these phenomena on agricultural systems.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.