Asian Pears, an alternative crop for Northeast fruit growers - Developing a Plant Growth Regulator Thinning Program to Ensure Profitability

Final Report for ONE08-090

Project Type: Partnership
Funds awarded in 2008: $9,997.00
Projected End Date: 12/31/2010
Region: Northeast
State: New Jersey
Project Leader:
Daniel Ward
Rutgers University
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Project Information

Summary:

The move to diversified marketing and diversified crop mixes is important to the survival of fruit growers in the Northeastern U.S. Fruit growers have developed an interest in producing Asian pears due to market demand. Asian pears are a favorite commodity of the large Asian population in NJ and the Northeast, having gone mainstream though the marketing efforts of the larger chain stores.

Asian pear fruit marketability and price received is largely determined by fruit size. Asian pears must be thinned annually to achieve optimum fruit size and avoid alternate bearing. Prior to 2008 most Asian pear fruit thinning was done exclusively by hand. Labor costs for hand thinning ranged from $3,000-$10,000 dollars per acre to obtain premium fruit.

Previous attempts at utilizing plant Growth Regulators for chemical thinning of Asian pears have met with limited success.

Our work indicates that a labeled cytokinin plant growth regulator, MaxCel®(6-benzyladenine), is an effective thinner for Asian pears. With two years of significant test results with MaxCel in Northern New Jersey, on several Asian pear cultivars, we have an economically viable treatment to recommend to Asian pear growers in the mid Atlantic region when used at the full label rate for pears. MaxCel significantly reduced hand-thinning costs. Grower adoption and successful use of MaxCel on Asian pears across New Jersey has confirmed the efficacy of MaxCel for Asian pears. At the $125-$193/Acre cost of MaxCel (200ppm rate/1 gallon), NJ growers, when surveyed, have been able to reduce their hand thinning labor costs by 50-66% per acre. If growers reduce their hand labor costs by 50% with MaxCel, that is a $460,350 dollars savings, 66% would be $607,660 annually to New Jersey farmers. If we extrapolate to 50% of the Mid Atlantic-New England acreage or 500 acres, Asian pear growers are saving over 3 million dollars annually in hand thinning labor costs.

Introduction:

The move to diversified marketing and diversified product mixes is important to the survival of fruit growers in the Northeastern U.S. Urbanization and development pressures are forcing growers to utilize a combination of direct market sales, including roadside stands, pick-your-own and tailgate marketing at farmer’s markets. Fruit growers have had to diversify not only their direct marketing mix but, also continue to consider new high value crops addressing changing demographics and resulting potential markets. Fruit growers have developed an interest in producing Asian pears due to increased market demand. As Asian pears, (Pyrus Pyrifolia, Pyrus Ussuriensis) have become more popular in New Jersey and the New York metropolitan area due to changing demographics, more growers are planting acreage of Asian pears.

Most cultivars of Asian pears bloom heavily every year. Asian pears must be thinned annually to achieve optimum fruit size and avoid alternate bearing. Asian pear fruit quality and price is largely determined by fruit size. Large fruit are highly desired and bring excellent market price. Small fruit is difficult to sell and command much lower prices. The most common method of controlling fruit size and crop load up until 2008 had been hand thinning. Hand thinning is very labor intensive and expensive. The vagaries of labor availability and inconsistent thinning from tree to tree also create management problems. The cost to hand thin ranges between 1-4 person-hours per tree at approximately 300-500 trees per acre, depending on the size of the tree. H2A labor rates are currently $10.23 per hour. This translates to labor cost of $3,000 to $8000 per acre per year to obtain premium size fruit.

None had been found to date that would accomplish this goal adequately.

Asian pear growers urgently need an affordable effective fruit thinner if they are to retain profitability and continue to adopt the cultivation of this crop. Relative efficacy, safety of plant growth regulators (PGR’s) as thinners, relative sensitivity of cultivars, appropriate timing of application and appropriate rates of application are all unknown for Asian pears. Previous attempts at PGR thinning of Asian pear have met with limited success. Extensive work had been done looking for a plant growth regulator (PGR) or combinations of PGR’s that would chemical thin an adequate amount of fruit off. The material that held some promise was Accel, a 6Ba material combined with GA. This product, Accel by Abbot Laboratories, was the precursor product to MaxCel. Both Prunty & Marini and McArtney & Wells found Accel to reduce fruit set on Asian pear by 40-70%. MaxCel by Valent included pears on the label. The MaxCel Pear Tech bulletin (2007-Max-8003 MaxCel Pear Tech Bulletin.pdf) gave details and data for use with Bosc and Bartlett European type pears but no mention of Asian pears. Based on this preliminary work we felt that MaxCel may hold promise for thinning Asian pears.

Literature Review

Prunty and Marini (2000) used Accel, Ethrel (ethephon), NAA and Carbaryl on ‘Shinko’ and ‘Hosui’ when the average fruit diameter was 9 mm. Fruit set was reduced by 40 to 70 % with Accel at 84 ppm and ethephon at 678 ppm. NAA and Carbaryl were less effective. Accel at 0-105 ppm and ethephon at 0-678 ppm treatments reduced fruit set linearly with increasing concentration on ‘Shinko’. In both years ‘Shinko’ was easier to thin than ‘Hosui’.

Regina M. Prunity, Richard P. Marini, 2000. Chemical-thinning Asian Pears. HortScience June 2000 35:438
http://hortsci.ashspublications.org/content/35/3/438.2.short

McArtney and Wells found that Fruit set was reduced on Shinko and Housi Asian pear 40 to 70% by Accel at 84 ppm and ethephon at 678 ppm, but NAA at 8 ppm and carbaryl were less effective. In 1999, Accel was applied at a range of 0 to 105 ppm and ethephon was applied at a range of 0 to 678 ppm. All treatments contained carbaryl and oil. Fruit set/100 flower clusters declined linearly with increasing ethephon concentration on ‘Shinko’, but was not tested on ‘Hosui’. Fruit/100 blossom clusters declined linearly with increasing Accel concentration on ‘Shinko’. On ‘Hosui’ Accel reduced fruit set by more than 40%, but treatments did not differ significantly (5% level) from the control. In both years ‘Shinko’ was easier to thin than ‘Hosui’.

McArtney, Steven J. and Wells, Gilbert H. 1995. ‘Chemical thinning of Asian and European pear with ethephon and NAA’. New Zealand Journal of Crop and Horticultural Science, 23: 1, 73 — 84 http://www.informaworld.com/smpp/title~content=t918982744

Project Objectives:

Our objective is to develop a recommendation for fruit thinning for Asian pears using labeled Plant Growth Regulators (PGR’s). Growing Asian pears will be significantly more efficient requiring much less labor with the development of effective, economical PGR fruit thinners. This will help to ensure the economic viability of fruit growers in the Northeast.

Cooperators

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  • Bob Clark
  • Winfred Cowgill
  • Ging Lee

Research

Materials and methods:
2007 North Jersey Trial

A study was initiated in a mature commercial orchard, bearing ‘Hosui’ trees in northern New Jersey in 2007. Two rates of MaxCel® (200 and 250 ppm) were applied in 100 GPA of water at 80 PSI with a handgun application utilizing a Spraying Systems Company AA43 GunJet (Spraying Systems, Wheaton, IL). The sprayer was a custom manufactured machine consisting of a 110 gallon tank, utilizing a PTO driven Teel Pro Series Roller Pump Model Number 2P058. Regulade at 8 ounces per 50 gallons was used as a surfactant and included in the spray material. Treatments were applied when the largest fruit were 12 mm in diameter (14 May 2007). The two concentrations and an untreated control were arranged in a randomized complete block design blocked on crop load. The experiment was conducted in eight blocks and single trees served as experimental units.

Response to treatment was evaluated by marking and measuring the diameter of three limbs per tree. The blossom clusters (9 May 2007) and fruit (13 June 2007) were counted on each limb. Follow-up hand thinning was performed on all trees 18 June 2007. Teams of thinners were assigned to blocks and the time required to thin each tree recorded. The circumference of all the fruit on the three limbs was measured using an electronic fruit size measure (GÜSS Inc. Strand, South Africa) (n=244-277) near the time of harvest (28 August 2007). A hailstorm (16 August 2007) near the time of harvest damaged fruit too severely to obtain yield data.

Fruit counts were used to calculate fruit set per 100 blossom clusters. Crop load was expressed as fruit per cm2 of limb cross-sectional area (LCSA). Time required for hand-thinning was expressed as minutes for one person to thin a tree. Fruit size was converted from circumference to diameter for presentation. A mixed effects analysis of variance was performed on each of these responses using the SAS System (SAS Institute Inc, Cary, NC 27513). Pairwise comparison of means was performed using the LSD test.

Thinning trials were conducted at two commercial Asian pear orchards, one in Northern (Pittstown Fruit Farm) and one in Southern (Chestnut Run Farm) New Jersey. Each orchard was considered a separate experiment conducted in a randomized complete block design. During bloom in 2008 flower cluster counts and limb circumference were recorded on two flagged limbs per tree. Trees were then blocked by flower cluster density and treatments applied using commercial orchard equipment and conventional spray methods. All spray applications included Regulaid as a surfactant and MaxCel as the thinning agent. Spray application timing was be based on crop development and applications were made when largest fruit averaged 10-12 mm in diameter. Response to treatment was assessed by counting fruit set after spray application and calculating fruit set per cm2 of limb cross-sectional area. Final crop load adjustment was performed as needed by hand thinning. Time required for final crop load adjustment was recorded and combined with estimates of thinning cost to calculate total cost of thinning for treated and untreated trees. Return bloom was assessed by counting flower cluster density in the year following treatment. Fruit set, final crop load, thinning time per tree, and mean fruit size were analyzed using analysis of variance (using the MIXED procedure of the SAS System) to test for treatment effects and estimate magnitude of thinning effects.

2008 Concentration Trial

In 2008 spray applications of MaxCel at 0, 200, or 250 ppm were applied at 12 mm average fruit diameter to ‘Hosui’ (in 2007) and ‘Kosui’ trees in Northern New Jersey and at 0, 50, 100, 150, 200, and 250 ppm to ‘Hosui’(in 2008), ‘Shinko’, and ‘Yoinashi’ trees in Southern New Jersey. Treatments were applied in 100 GPA of water at 80 PSI with a handgun sprayer. Response to treatment was evaluated by marking and measuring the diameter of three limbs per tree. Response to treatment was evaluated by marking and measuring the diameter of three limbs per tree. The blossom clusters and fruit were counted on each limb. Follow-up hand thinning was performed on all trees 18 June 2008. Teams of thinners were assigned to blocks and the time required to thin each tree recorded. The circumference of all the fruit on the three limbs was measured using an electronic fruit size measure (GÜSS Inc. Strand, South Africa) (n=244-277) near the time of harvest (28 August 2007). A hailstorm (16 August 2007) near the time of harvest damaged fruit too severely to obtain yield data.

Fruit counts were used to calculate fruit set per 100 blossom clusters. Crop load was expressed as fruit per cm2 of limb cross-sectional area (LCSA). Time required for hand-thinning was expressed as minutes for one person to thin a tree. Fruit size was converted from circumference to diameter for presentation. A mixed effects analysis of variance was performed on each of these responses using the SAS System (SAS Institute Inc, Cary, NC 27513). Pairwise comparison of means was performed using the LSD test.

Research results and discussion:
2007 North Jersey Trial

Fruit set and crop load were both reduced by MaxCel® (P=0.0124 and P=0.0029 respectively) (Table 1). Both concentrations of MaxCel® reduced fruit set but, 200 ppm was not different from 250 ppm (P=0.7220). Crop load was also reduced by both concentrations but, again, 200 ppm was not different from 250 ppm (P=0.4510). Thinning effect was not enhanced by the higher concentration suggesting that other factors, such as initial crop load, weather conditions, or antecedent carbohydrate status of the trees limit the response to MaxCel®.

Hand thinning was required to adjust crop levels in all trees. Even when the MaxCel® treatments removed many fruit, the distribution of fruit required hand adjustment. Time required for hand thinning was reduced by MaxCel® (P=0.0007) (Table 1). Time required for hand thinning was reduced from 30 to 15 minutes per tree in trees treated with 250 ppm (P=0.0002). The 200 ppm concentration reduced thinning time below that of control trees (P=0.0553) but, not as much as the 250 ppm concentration (P=0.0103).

A hailstorm severely damaged the fruit approximately ten days before anticipated harvest. This prevented the collection of yield data. At the time of the hail damage, the fruit had attained most of their size potential so, fruit diameters measured after the hailstorm likely reflect the treatment differences that would have occurred at harvest time. Fruit diameter was increased by MaxCel® (P=0.0270) (Table 1). Both 200 ppm and 250 ppm of MaxCel® increased fruit diameter (P=0.0611 and P=0.0095 respectively) but, 200 ppm was not different from 250 ppm (P=0.3228).

The timing of application was effective for achieving thinning. Effects of thinning on crop value and costs of thinning need to be determined as well to permit quantitative analysis of the costs and benefits of chemical thinning with MaxCel®.

2008 New Jersey Trials

Our field results are encouraging. Briefly, in both experiments in Northern New Jersey (2007-2008) 200 and 250 ppm the cytokinin formulation(MaxCel) reduced fruit set significantly but, 200 ppm was not different from 250 ppm (Fig 1).

Time required for hand thinning was significantly reduced in the experiments in Northern New Jersey in ‘Hosui’ trees treated with 250 ppm and in ‘Kosui’ trees treated with either 200 or 250 ppm (Fig 2). Our evidence indicates that cytokinins (MaxCel) can be an effective thinner for some Asian pears.

Concentration Experiment South Jersey

In 2008 spray applications of MaxCel at 0, 200, or 250 ppm were applied at 12 mm average fruit diameter to ‘Hosui’ (in 2007) and ‘Kosui’ trees in Northern New Jersey and at 0, 50, 100, 150, 200, and 250 ppm to ‘Hosui’(in 2008), ‘Shinko’, and ‘Yoinashi’ trees in Southern New Jersey. Treatments were applied in 100 GPA of water at 80 PSI with a handgun sprayer. In both experiments in Northern New Jersey the 200 and 250 ppm treatments reduced fruit set significantly but, 200 ppm was not different from 250 ppm. Table 1. In Southern New Jersey, where crop load was much less, significant thinning was only obtained with 250 ppm and only in one cultivar (‘Yoinashi’) Table 2. Time required for follow-up hand thinning to adjust crop levels was significantly decreased only in the experiments in Northern New Jersey. Time required for hand thinning was significantly reduced in ‘Hosui’ trees treated with 250 ppm and in ‘Kosui’ trees treated with either 200 or 250 ppm. Table 3. Kosui fruit size, as average fruit weight, was significantly increased at the 200 ppm rate (full label rate).

MaxCel can be an effective a chemical thinner for Asian pears.

Research conclusions:

Asian pear growers have expressed high levels of interest in this technology as a means to increase their profitability. Some participants have used the thinning agent in trees not being used for our experiments. Our work has stimulated some New Jersey growers to begin using the thinner on other cultivars of Asian pears being grown in the region.

Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary:

Education/outreach description:
Outreach

Asian Pear Website

A Rutgers Asian pear website that will include all of our project data is under construction at our NJ Sustaining Farms Website http://njsustainingfarms.rutgers.edu/ and
http://njsustainingfarms.rutgers.edu/asianpear.html

Preliminary results from 2007 were reported at the North East Plant Growth Regulator Meeting in Wilkes-Barre, PA in March 2008. This is a working group of over 45 industry, University and private consultants working with Plant Growth Regulators. Presentations were made at the Northeast Regional Meeting of the American Society for Horticultural Science (ASHS) in New Brunswick, NJ in January 2008, and at the Annual Conference of the ASHS in Orlando FL in July 2008. Additional results including the 2008 experiments were reported at North East Plant Growth Regulator Meeting in Wilkes-Barre, PA in March 2009 and at the Annual Conference of the ASHS in St. Louis, MO in July 2009. Presentation was made at the Great Lakes Fruit Workers Conference, Fishkill, NY. This annual conference trains extension workers from Cornell, Michigan State Univ., Ontario, Quebec, NJ and UMASS. Two integrative talks (one in English and one in a Spanish language session) were presented to growers at the Mid-Atlantic Fruit and Vegetable Growers Conference in Hershey, PA in February 2010. This grower conference and trade show attracts over 950 growers from NJ, PA, MD, DE, VA and 6 other states. Presentations were made at the Rutgers Cooperative Extension North Jersey Fruit meeting in 2008 in Broadway, NJ and at the Rutgers Cooperative Extension South Jersey Fruit meeting in Clayton, NJ in 2010. Additional presentations were made at the April RCE first Twilight Fruit meeting at the Rutgers Snyder Farm in 2008, 2009, and 2011 as part of the chemical thinning updates at these meetings. A web based Horticultural Talk on Demand of Dr Wards presentation ‘Chemical Fruit Thinning of Asian Pears’ at the 2009 Annual Conference of the ASHS in St. Louis, MO is available at http://www.ashs.org/db/horttalks/detail.lasso?id=764

Publications

Cowgill, Win, D. Ward, R. Magron, N. Vincent, T. Gianfagna, S. Solner-Figler, Chemical Fruit Thinning of Asian Pears Using Cytokinin, 2008. HortScience June 2008 vol. 43 no. 3 590-600 http://hortsci.ashspublications.org/content/43/3/590.full

Chemical Fruit Thinning of Asian Pears With Cytokinin (MaxCel). 2009. Prodeedings of International Great Lakes Fruit Workers Conference- Great Lake Fruit Workers Conference, Fishkill, New York www.hrt.msu.edu/glfw/GLFW_2009_Abstracts/2009_25.pdf

Daniel L. Ward,* Winfred Cowgill, Neil Vincent, Rebecca Magron, 2009. Thomas Gianfagna, Cytokinin for Chemical Fruit Thinning of Asian Pears. HortScience http://www.ashs.org/db/horttalks/detail.lasso?id=764

Daniel Ward, Win Cowgill, Neil Vincent, Rebecca Magron, Tom Gianfagna. 2008. Chemical fruit thinning of Asian Pears Using Cytokinin. HortScience. 43(4): 1294-1295.

Majek, B.A., Cowgill, W.P., Jr. 1999. “Weed Control in Asian Pears”. Rutgers Agricultural Research and Extension Center Field Crop, Vegetable and Fruit Weed Control, 1999 Research Results 275-282

Project Outcomes

Project outcomes:

One of the difficulties in looking at the economics of Asian pear production is the lack of any meaning full data on their production in NJ and the USA. According to the USDA National Agricultural Statistics Service, NJ Field Office Director, the most recent agricultural statistics data on pears would be the 2007 Ag census data. However Asian pear (phone conversation, 2/9/12) statistics were not collected or reported separately, they were lumped in with European pears. With no systematic official data collected, we have gathered meaningful numbers by informally surveying our extension colleagues in Pennsylvania and New York and summarizing our on farm knowledge of New Jersey growers. We estimate there are approximately 200 acres of Asian pears in New Jersey, over 500 acres in Pennsylvania, 300 in New York and several hundred more in Maryland and New England with an expanding market potential.

Hand thinning is the largest direct cost of Asian pear production. The cost to hand thin ranges between 1-4 person-hours per tree, at approximately 300 -500 trees per acre, depending on the size and age of the tree. H2A labor rates are currently $10.23 per hour. This translates to labor cost of $3,000 to $8000 per acre per year to obtain premium size fruit.

The economics are that MaxCel has consistently performed well on Asian pears in NJ. Efficacy is dependant on the temperature and timing of the application, spray coverage and other factors. However based on our research and surveying the results of our growers who have adopted its use the reduction in hand thinning is 50 to 66 % on an annual basis.

If we take an average tree density of 300 trees per acre, x an average of 2 person hours per tree, that equals 600 hours per acre. Assuming 200 acres of Asian pears in NJ and 75% use MaxCel, 150 acres remain. Our federal H2A labor is $10.23 per hour x 600 Hours = $6, 138 per acre x 150 acres = $920,700 thinning costs in just NJ. If growers reduce this labor and cost by 50% with MaxCel that is a $460,350 dollars savings, 66% would be $607,662.

It should be noted that H2A labor actually costs much more as the grower has to cover the significant takes, provide roundtrip transportation toe country of origin and provide housing at no cost. It is probably closer to $16-18 per hour.

If we extrapolate to the 1000 acres we know of above in the Northeast and look at just 50% of the acreage or 500 acres the numbers look like this: 500 x $6,138/Acre =over 3 million dollars in savings to our Northeast Asian pear growers annually.

Farmer Adoption

The majority of our Asian pear farmers in New Jersey have whole-heartedly adopted the use of MaxCel for thinning their crops. The reduction of their thinning labor costs by ½ to 2/3 is significant. Since MaxCel was already labeled for European pears and apples, it is readily available in the market. This has helped us keep our fruit growers sustainable by providing the tools they need to produce a new tree fruit crop in their business that is highly profitable if marketed correctly.

Assessment of Project Approach and Areas of Further Study:

Areas needing additional study

Further evaluation on the numerous Asian pear cultivars would be on top of the list. Not all cultivars of Asian pear respond exactly the same. Evaluations of other PGR combinations and surfactants may further enhance the efficacy of MaxCel in chemical thinning of Asian pears as they have done in apples. Ninety five percent of apple acreage is chemically thinned so there is room to improve on Asian pear acreage.

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.