Botrytis or gray mold, caused by the fungus Botrytis cinerea, is an important disease impeding raspberry production. In 2005-07 the efficacy of seven organic and/or biorational fungicides plus two cultural controls (in 2006 and 2007) were evaluated for managing Botrytis on ‘Prelude’ and ‘Nova’ red raspberries.
Treatments were determined after consulting with a grower advisory panel. Most treatments did not manage Botrytis better than applying water to the plants (control 1). Applying Captan and Elevate in rotation (control 2) resulted in higher marketable yields and applying Oxidate and Milstop in a tank mixture resulted in lower marketable yields than spraying the plants with water.
Harvested raspberries were stored to determine the effect of the treatments on post harvest disease development. On most evaluation dates disease incidence was not different regardless of treatment. However, when differences were observed, spraying Captan and Elevate in rotation or Endorse resulted in the fewest diseased berries. All other treatments resulted in disease incidence not different than spraying water on the plants.
Two field days on bramble disease management attracting about 100 participants were co-hosted by the Pennsylvania State University, University of Massachusetts, Pennsylvania Association for Sustainable Agriculture, Pennsylvania Certified Organic or Nourse Farms in 2007. An additional field day on disease management and including results from the research part of this project was co-hosted by the Pennsylvania State University, Pennsylvania Association for Sustainable Agriculture and Pennsylvania Certified Organic in 2008. The 2008 field day attracted 55 participants. Lastly, a workshop on bramble disease management attracting about 85 participants was presented at the 2007 Farming for the Future Conference hosted by the Pennsylvania Association for Sustainable Agriculture. A field guide was developed and provided to participants of the field days and workshops. Additionally, the field guide along with instruction for its use was presented at the 2006 Western Pennsylvania Vegetable and Berry Growers Seminar in Butler, PA and at the 2007 Vegetable, Berry and Greenhouse Growers’ Meeting in Mifflinburg, PA reaching about 45 participants. Participants of these events indicated that their knowledge of bramble disease diagnosis and management increased as a result of the presentations. Additionally, the majority of participants adopted diagnosis and/or management strategies presented as determined through a survey.
The objective of this project was to increase grower knowledge and use of preventative tactics for small fruit diseases, and awareness of alternative products for Botrytis management. Organic growers rely primarily on preventative tactics for pest management; however, for some pests, such as Botrytis diseases, preventative management strategies alone are not sufficient for management. For these pests growers turn to alternative chemical options, the efficacy of which is often not established. We approached our objective through a research and education component.
For the research component we evaluated several alternative cultural and chemical options for Botrytis management in a test crop of raspberries. Botrytis was selected as the focus of the research project because it has a widespread negative impact on many crops. Raspberries were selected as a test crop because they are a high-value crop produced by a large number of growers in the NE US. Additionally, since raspberries are extremely susceptible to Botrytis, growers contend with it every year.
For the Extension component of the project, we hosted or co-hosted several activities to increase awareness and use of preventative disease management options for small fruit crops, including those for Botrytis diseases. About 285 growers attended Extension events, with the majority indicating they planned to adopt techniques presented for managing Botrytis. A follow-up survey confirmed the majority of respondents adopted one or more technique(s) presented at the events for managing Botrytis.
Of the 100 growers attending Extension events, 80 will approach disease management on their farms in a more environmentally sustainable way and 50 will have adopted at least one recommended practice one year after Extension events.
Throughout this project 285 growers and industry representatives attended Extension events. One year after the 2007 field day and workshop events, follow-up surveys were administered to the 145 participants. Thirty completed surveys were determined useable. Survey results reveal 29 participants adopted one or more strategies presented at the Extension events for managing Botrytis.
We exceeded our target of 100 growers attending extension events. While we reached the target holding the number of events originally planned, we were invited to co-host additional events on the topic. All 100 growers attending the 2007 workshops indicated they planned to adopt one or more strategies presented for disease management. While we administered 145 surveys by mail (including one follow-up mailing), only 30 completed were useable – less than the 50 we had anticipated. However, 97% or 29 of those who responded had adopted one or more strategies presented for disease management. Even if a much lower percentage of the 285 attendees as a whole adopted any of the strategies presented, it is likely that our goal was reached.
During the 2005-07 growing seasons, six organic/biorational materials, and an additional product in 2007, were evaluated along with two cultural treatments (one in 2006 and one in 2007) for managing Botrytis. An advisory panel of six raspberry growers helped choose treatments from a list they were provided and using criteria they considered important in selecting management tools. These criteria included cost (in terms of both time and money), number or frequency of applications, safety to the environment and humans, compliance with the National Organic Standards, and broadness of expected spectrum of activity.
The following treatments were evaluated. Milstop (BioWorks, Inc., Fairport, NY), approved for organic production, was applied at a rate of 3.75 pounds per acre. Endorse (Arvesta Corp., San Francisco, CA) was applied at a rate of 1.8 pounds per acre. Lime sulfur solution (Miller Chemical and Fertilizer Corp., Hanover, PA) was applied at a spray volume of one percent. Phostrol (Nufarm Americas, Inc., Burr Ridge, IL) was applied at a rate of five pints per acre. Milstop + Oxidate (Biosafe Systems, Glastonbury, CT) tank mixture was used; Milstop was applied at a rate of 3.75 pounds per acre and Oxidate was applied at a spray volume of one percent for the first three applications, and then changed to one-third percent of spray solution volume. Oxidate can be used in organic production and falls into the restricted category, which allows its use when a need is documented. Oxidate + Vigor Cal Phos (Agro-K Corp., Minneapolis, MN) tank mixture was used. Oxidate was applied at a spray volume of one percent for the first three applications, and then changed to one-third percent of spray solution volume corresponding to labeled directions and Vigor Cal Phos was applied at a rate of four quarts per acre. Shemer (AgroGreen Minrav., Ashdod, Israel) + Milstop as a tank mixture was used; Shemer was applied at a rate of 0.2 percent spray solution volume and Milstop was applied at a rate of 0.1 percent spray solution volume. The previous treatment was only evaluated in 2007. All chemical applications rates were based on 2005 manufacturer’s recommendations except for Shemer, which was based on 2007 recommendations.
A cultural treatment was evaluated during the 2006 fruiting season where plots were thinned to six canes per linear foot in August of 2005 and four to five canes per linear foot in March of 2006. The cane thinning treatment was not evaluated during the 2007 growing season because it did not provide any disease control. A “V” trellis cultural control was initiated May 15, 2007 by tying floricanes to a horizontal trellis wire leaving primocanes unrestricted in the inner hedgerow.
Two experimental controls were used. These consisted of applying water at a rate of 50 gal/acre and a standard fungicide rotation of Elevate 50 Water Dispersible Granules (Arvesta Corp., San Francisco, CA) applied at a rate of one and one-half pounds per acre and Captan 50 Wettable Powder (Arvesta Corp., San Francisco, CA) applied at a rate of four pounds per acre.
Botrytis treatments were applied to field plots consisting of ten foot long hedgerows and were arranged in a two (cultivars: ‘Nova’ and ‘Prelude’) X ten (eight treatments and two controls) factorial in a randomized complete block design with four replications. Spray treatments were applied in a volume of water equivalent to 50 gal/acre using a compressed carbon dioxide sprayer operated at 40 psi. Spray equipment was calibrated twice during the growing season. In accordance with current recommendations for conventional fungicides, spray treatments were initiated at 10-15% bloom (early bloom), and then applied two more times at five to seven day intervals during bloom. Treatments were discontinued briefly, and then resumed when harvested berry counts reached 10-15% (early harvest) and continued on five to seven day intervals. These timings corresponded to early, mid and late bloom, and early, mid and late harvest.
Fruit was harvested by hand every Monday, Wednesday and Friday from mid June to late July. Berries were sorted by cultivar into marketable and unmarketable categories with those that were blemished considered unmarketable. Most blemishes were due to insect and mechanical damage. A lesser amount of diseased berries was also observed. Berries were weighed, counted and immediately subjected to post-harvest evaluation.
Fruit were evaluated after harvest in 2006 and 2007 to determine the effect of the treatments on postharvest disease infection. During the 2005 growing season, insufficient yields prevented postharvest analysis. After each harvest, 13 ripe fruit (2006) and 16 ripe fruit (2007) from each treatment plot were placed in 28-celled plastic trays (Gardner’s Candies, Tyrone, PA). When less than 13 fruit (2006) and 16 ripe fruit (2007) were harvested from a treatment plot, fruit from that plot was excluded from postharvest evaluation for that harvest. Trays were then placed in moist chambers. One gallon plastic slider bags (Wegmans private label, Wegmans Food Markets, Inc., State College, PA) lined with 2-layers of industrial hand towels (800 ft roll hand towels model no. 01000, Kimberly Clark, Neehan, WI) that were moistened with water were used as moist chambers. Moist chambers were then placed in storage for three days at room temperature followed by four days at 40 to 45ºF. All berries were infected by four days after harvest but Botrytis was not positively identified until reproductive characteristics developed and could be viewed with an SZ40 Olympus dissecting microscope at 30x.
Numerical data were analyzed with General Linear Model analysis of variance using SAS 9.1.3 (SAS Institute, Cary, N.C.). When differences were detected at P≤0.05, data were subjected to Duncan’s Multiple Range Test.
Conversations and e-mails with our advisory board led to the development of two field days and one workshop in 2007 and presentations at two grower meetings in 2006 and 2007 on bramble disease management including the information we learned from the research trial. An additional field day was held in 2008. The field days were advertised by the Pennsylvania State University, University of Massachusetts and/or Pennsylvania Association for Sustainable Agriculture. The workshop was advertised by the Pennsylvania Association for Sustainable Agriculture and the grower meetings were advertised by Penn State Cooperative Extension.
The general program for each event was a presentation on bramble diseases and management, including results of the research trial, and tips for diagnosing bramble disorders. A 12-page field guide on diagnosing bramble disorders was developed and provided to participants of the field days and workshop. Hand lenses were also provided to participants to assist in diagnosing disorders.
The first field day took place in Rock Springs, PA and was attended by about 50 participants. It was co-hosted by the Pennsylvania State University, Pennsylvania Association for Sustainable Agriculture and Pennsylvania Certified Organic. The program included a plant pathologist, small fruit specialist, sustainable/organic specialist and Master’s student from the Pennsylvania State University and a certification specialist from Pennsylvania Certified Organic.
The second field day took place in South Deerfield, MA and was also attended by about 50 participants. It was co-hosted by Nourse Farms, the Pennsylvania State University and the University of Massachusetts. The program included a plant pathologist from the USDA, Beltsville, MD, a small fruit specialist from the University of Massachusetts and small fruit specialist, sustainable/organic specialist and Master’s student from the Pennsylvania State University.
The third field day took place in Lancaster, PA and was attended by about 55 participants. It was co-hosted by the Pennsylvania State University, Pennsylvania Association for Sustainable Agriculture and Pennsylvania Certified Organic. The program included a small fruit specialist, sustainable/organic specialist and a certification specialist from Pennsylvania Certified Organic.
Additionally, a workshop on bramble disease management attracting about 85 participants was presented at the Farming for the Future Conference in State College, PA hosted by the Pennsylvania Association for Sustainable Agriculture.
The field guide along with instruction for its use was also presented at the Vegetable, Berry and Greenhouse Growers’ Meeting in Mifflinburg, PA and at the Western Pennsylvania Vegetable and Berry Growers Seminar in Butler, PA reaching about 45 participants.
For each year of the trial, no treatment by cultivar interactions for yield were evident.
Marketable yields, unmarketable yields and marketable berry weight were not different regardless of treatment or cultivar in 2005. The planting was two years old in 2005 and substantial yields are not seen until the third year after establishment. This offers an explanation why differences in yield were not seen in 2005 and suggests that a minimum of 3 years of establishment is necessary to obtain useable results.
Marketable and unmarketable yields and the percent berries infected with Botrytis were not affected by treatment in 2006. Applying Captan/Elevate (control 2) resulted in the largest berries at 2.6 grams. Applying water (control 1) resulted in berries that weighed 2.4 grams, which were similar in weight to berries sprayed with Oxidate + Vigor Cal Phos, Lime Sulfur, Phostrol and Endorse or using the cane thinning cultural control. Milstop and Oxidate + Milstop applications resulted in berries smaller than those that received the water sprays (control 1) at 2.2 and 2.1 grams, respectively. ‘Nova’ plots had higher marketable and unmarketable yields and larger berries than ‘Prelude’. Cultivar did not affect the percentage of berries with Botrytis.
In 2006, only marketable berry weight was affected by treatment with Captan/Elevate (control 2) sprays resulting in the largest berries. While not significant, plots sprayed with Captan/Elevate (control 2) had the highest yield and lowest percent berries infected with Botrytis, which might translate to significantly larger berries. Yields in 2006 were increased over 2005, with ‘Nova’ being more productive than ‘Prelude’.
Marketable berry weight and unmarketable yields were not affected by treatment in 2007. Captan/Elevate sprays (control 2) resulted in the largest marketable yields at 5,221 grams/plot. All remaining treatments except Oxidate + Milstop resulted in marketable yields not different than applying water (control 1) at 3,791 grams/plot. Milstop + Oxidate sprays resulted in marketable yields smaller than the water only sprays (control 2) at 2,240 grams/plot, although yields were similar to plots sprayed with Milstop, Lime Sulfur, and Shemer + Milstop.
‘Nova’ produced larger marketable yields than ‘Prelude’. ‘Prelude’ plots had a larger percentage of berries with Botrytis than ‘Nova’. However, marketable berry weight and unmarketable yields were not affected by cultivar.
In 2007, Milstop and Lime Sulfur sprays resulted in a higher percentage of berries with Botrytis compared to the water only treatment. The application of Endorse, Oxidate + Milstop, Oxidate + Vigor Cal Phos, Phostrol, Shemer + Milstop and the “V” trellis cultural control resulted in a similar percent of berries with Botrytis to the water only spray (control 1). Applying Captan/Elevate (control 2) resulted in a lower percentage of berries with Botrytis than did the water only spray (control 1) although similar to plots sprayed with Endorse.
In 2007, plots sprayed with Captan/Elevate (control 2) produced the highest yields. Also, applying Captan/Elevate resulted in the best control of Botrytis. As in 2006, ‘Nova’ was more productive than ‘Prelude’.
Few significant differences in the postharvest evaluations were observed and generally none of the treatments were more effective than the water only control for managing Botrytis. The predominant diseases observed in the postharvest evaluations were Botrytis, blue mold (caused by Penicillum expansum) and rhizopus soft rot (caused by Rhizopus spp). Disease incidence on four consecutive days after the June 30, 2006 and June 25, 2007 harvest was not different regardless of treatment for ‘Prelude’. Disease incidence was not different regardless of treatment for ‘Nova’ one, two, three, and four days after the July 3, 2006 and June 25, 2007 harvest.
Surveys administered to participants of the 2007 field days and workshop indicated that their knowledge of bramble disease diagnosis and management increased as a result of the presentations (average of 3.33 before and 5.27 after the events; 7 point scale – 7 indicating an excellent level of knowledge on bramble diseases and 1 indicating a poor level of knowledge). All participants indicated that they planned on using the field guide for diagnosing bramble disorders, a learned technique to identify diseases, the hand lens provided to identify diseases and other pests and a cultural strategy to manage diseases in the field.
One year after the 2007 field day and workshop events, follow-up surveys were administered to the 145 participants. Thirty completed surveys were determined useable. Survey results revealed that 29 participants adopted one or more strategies presented at the Extension events for managing Botrytis. Strategies adopted included using the Guide for Diagnosing Bramble Problems and the hand lens for diagnosing disorders and using a management technique for the diseases presented. Additionally, 28 of the respondents indicated that they felt better equipped to identify causes of bramble problems on their farms.
Please see Section 4. Materials and Methods.
Additional Project Outcomes
Impacts of Results/Outcomes
Several materials including alternative products and cultural strategies were evaluated for managing Botrytis in a summer-bearing red raspberry crop. None of the materials or cultural treatments were found to be more effective than applying water (control). Growers can save the expense of purchasing these materials for managing Botrytis on raspberries.
Several educational events were held in 2006-08 to present information on diagnosing bramble diseases and managing those diseases using preventative tactics and spray options with softer chemistries. Two hundred eighty five participants attended these events. The majority of participants indicated their knowledge of bramble diseases increased as a result of the events. Ninety-seven percent of respondents to a follow-up survey adopted sustainable strategies for approaching disease management including using a field guide and learned techniques for diagnosing diseases and using a cultural strategy for managing gray mold.
An economic analysis was not preformed as a part of this project. However, based on the above results, growers can avoid using the materials trialed in the research part of this program for managing Botrytis on raspberries and therefore save that expense.
Please see Sections 5. Results and Discussion/Milestones and 6. Impact of Results/Outcomes.
Areas needing additional study
This program successfully evaluated several alternative products and cultural options for managing Botrytis; however, results revealed none were effective for management. This leaves sustainable and organic growers with limited options for managing Botrytis. Further research is needed to evaluate additional sustainable strategies for Botrytis management.