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Project Director(s): Glen C. Rains, Ashfaq Sial Ahmad
Project Title: Evaluation of Sanitation as an IPM tool for SWD Control in Blueberry
Problem and Justification:
Fruit production in the US has recently been challenged with a new invasive insect pest, spotted
wing drosophila (SWD), Drosophila suzukii Matsumura (Diptera: Drosophilidae). The SWD, a
native of Eastern and Southeastern Asia (1), is a devastating pest of small and stone fruits. Since
it’s first detection in California in 2008 (2, 3), the SWD has spread throughout the United States
(4) causing significant losses in crop yield and quality, and risk of even more profound damage.
The SWD is highly polyphagous insect (5, 6) and presents a major threat to soft- and thinskinned fruit crops including blueberries, caneberries (blackberries and raspberries), cherries,
strawberries, peaches, and grapes worldwide. SWD larvae have also been observed feeding on
other wild and cultivated hosts including pears, persimmons, figs, loquat, currents, mulberry,
buckthorn, and dogwood (5).
Based on descriptions of SWD biology, SWD adults mate within 1-2d of emerging. Females
can lay more than 600 eggs in their lifetime, usually 1-3 eggs per fruit. Eggs are inserted just
under the skin of fruit, but paired respiratory filaments are left projecting from fruit, which allow
the number of eggs to be assessed microscopically. Eggs develop in 1-3d, larvae in 5-7d, and
pupae in 3-15d. Therefore, under optimal conditions of about 20 °C, one generation can
complete development in about 8 -10 d leading to 15 generations per year (7). Because of this
short generation time, SWD populations can increase to potentially devastating levels rather
quickly. Estimates of 100-fold population increase every 2 wk are plausible. Actual loss statistics
have been more difficult to generate, however, potential losses due to damage caused by SWD in
fruit crops in the United States have been estimated at $850-900 million annually (8, 9).
Georgia is among the top three blueberry producing states in the US (NASS 2012). Blueberries
are the number one fruit crop in Georgia with an annual farm gate value of $250 million (10) and
economic impact of $1 billion on the state economy (A. A. Sial, Pers. Comm. with Georgia
Blueberry Growers Association). Since its first introduction in Georgia in 2010, SWD
infestations have led to 15-20% loss of blueberry crop annually (A. A. Sial, Pers. Comm. with
Georgia Blueberry Growers Association). Blueberries produced in the Southeastern states are
primarily marketed as fresh fruit in the US as well as export markets. The fresh fruit marketers
have zero tolerance for SWD infestation. Detection of a single larva in fruit samples can result in
rejection of the entire shipment.
It can be difficult to determine if fruit are infested by SWD at harvest because they often appear
otherwise sound. Unfortunately, currently available traps and baits are useful for determining fly
presence only, but are not reliable predictors of fly density and fruit infestation risk. While this
aspect of SWD monitoring is actively being investigated (11, 12), SWD management is currently
achieved primarily through preventative insecticide applications (2, 13-15). The number of
insecticides available is limited to those with SWD activity and sufficiently short preharvest
intervals (≤3 days) to allow their use on frequently picked crops such as blueberries. The most
effective insecticides available for use against SWD are primarily broad-spectrum chemicals
including organophosphates, pyrethroids, and spinosyns (13-16), the use of which is further
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complicated by annual application restrictions, preharvest intervals, and trade related issues with
residue tolerances.
In order to meet the zero tolerance policy for SWD mandated by the marketers, growers have to
make calendar-day weekly insecticide applications, which are reapplied if feasible in the event of
rain, resulting in as many as twice weekly applications as a preventive measure. In general, fruit
growers are reluctant to apply broad-spectrum pesticides due to residues and associated health
and environmental concerns. Additionally, the insecticides are quite expensive and frequent
application of insecticides significantly increases the cost of production leading to lower profits
for growers. Furthermore, repeated applications with similar broad-spectrum materials could lead
to resistance development in SWD rather quickly, compromising the useful life span of these
products, and threatening the sustainability of SWD management programs.
It is therefore critical to improve currently practiced management programs based solely on
prophylactic insecticide applications and develop more sustainable practices to manage SWD in
commercial fruit crops by incorporating non-chemical management tactics including cultural
control as part of the integrated pest management (IPM) programs. Crop hygiene and sanitation
is one of the most commonly used cultural practices to manage fruit fly populations because
fallen, damaged, and over-ripe fruit in the orchards serve as a source of attraction for fruit flies
and also provides suitable habitat for breeding and larval development. Studies with other fruit
fly species have revealed that significantly higher proportion of the fruit on the ground was
infested with Fijian fruit fly (Bactocera passiflorae) as compared with that on the tree at a
similar stage of maturity (17).
In the context of fruit fly IPM, sanitation refers to destruction of all fallen and unwanted fruit
from the orchard to ensure that larvae do not survive to pupate in the ground, and later emerge as
adult flies. This tactic can help prevent fruit fly egg and larval (maggot) development in infested
fruit and deny female adult flies a suitable oviposition site which significantly reduces the fly
population in the orchards. A large-scale area-wide destruction of fallen fruit in the orchards
resulted in successful control of the Chinese citrus fruit fly (B. minax) in China (17).
General fruit fly control recommendations include field sanitation. Sanitation usually entails
removal of the fallen fruit by hand which are covered or sealed in plastic and set in the Sun to
solarize and kill the eggs and developing larvae. Sanitation is extremely labor intensive and the
overall benefit has not been quantified for growers to invest the time and effort.
Blueberry producers currently need to optimize time and money spent towards control of SWD.
While there are many recommended practices for control, some are labor intensive, expensive
and unproven. In addition, as stated earlier, constant use of pesticides also bring about the
development of resistance and problems associated with pesticide residue and minimum reentry
periods during harvest. As such, the development of sanitation mechanization procedures and
determination of effectiveness on controlling SWD would be benefit to growers by developing a
procedure that reduces pesticide applications. Packinghouse owners would potentially benefit by
reducing the necessary sampling, sorting, freezing and other additional steps due to the reduced
infestation of fruit. There will also be a potential benefit to marketers and exporters with a
reduced risk of exceeding maximum residue level (MRL) due to the reduction in pesticide use.
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Objectives:
The goal of this project was to use a blueberry field sanitizer to eliminate larvae from fallen fruit
by rupturing the skin of the fruit on the ground. This was accomplished by mounting a leaf
blower on the front of a tractor to move fallen blueberries from between the rows to the row
middles (alleys) and developing a roller with modified surface to break open the skins and
disrupt the development of the SWD eggs and larvae. To reach this specific goal we completed
the following objectives:
1. Developed the field sanitizer for fallen blueberries
2. Evaluated the field sanitation of blueberry crop using sanitizer.
3. Analyzed and disseminated field test results to stakeholders
4. Assessed stakeholders view of sanitation before and after disseminating results.
Results:
1. Develop field sanitizer for fallen blueberries
The field sanitizer consisted of two components: blower and roller. The prototype blower was
selected and designed to move fallen fruit from between the bushes in the row to the row middle
where they will be rolled over to kill or disrupt the development of the eggs and larvae inside the
berries. Each component was developed as follows.
a. Blower
A gas-powered backpack blower (Echo PB-770T) was purchased and modified for mounting to
the front of a Ford 2610 tractor (Figure 1). The blower selected could move 756 cfm at an
average of 196 mph at full speed. The force of the air from the blower and the angle and shape of
the tube had a significant effect on the effectiveness in moving blueberries from between the
rows. An adjustable arm was designed to mount on the front of the tractor and hold the end of the
blower nozzle. It can be raised/lowered and extended/retracted to improve movement of
blueberries between the bushes.
Figure 1 Blower mounted to front of Tractor
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The trigger mechanism was changed so that blower speed could be adjusted from the tractor seat.
The end of the blower was modified to increase the vertical air pressure to cover more of the
variable terrain (Figure 2). A GoPro Silver video camera was also mounted as shown to record
the blower action in the field.
Figure 2. Modified end of blower tube and GoPro Camera.
b. Roller Design
A 36” poly roller packer with 18” dia. was purchased from Agri-supply Co. in Tifton, GA. The
roller was filled with water and pulled behind the tractor. To improve the blueberry skin
disruption, a covering was attached as an outer skin of the smooth roller. Several different
attachments were examined as potential “skins”, each purchased from American Floormats
(Figure 3a). The final covering was the “Nautilus Pool Mat” and is shown attached to the roller
in Figure 3b. The weight of the roller was adjusted by adding water to the hollow roller. Weight
was tested in the range of 200 to 400 lbs. The attachment to the tractor was modified so that the
roller rotated with the terrain of the row middles.
Figure 3 a) Selected materials for roller covering.
b) Selected covering on roller.
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The weight of the roller is important to rupture of the fruit skin. However, the ground condition
may also be important. If the ground is soft, the roller may push the blueberries into the ground
without damaging the fruit. Over all soil types and weights, the heavier the roller the better the
ability to disrupt the skin covering of blueberries placed on a test area in Tifton. Data was
collected and plotted, however, a computer virus erased the data. We also tested the roller with
and without covering. Without a covering the roller is smooth. The material chosen in figure 3b
was the best for creating creases and pressure on the berries to allow the type of action needed to
disrupt SWD development. Figure 4 is a picture of the entire system.
Figure 4 Rear and front view of sanitizer/blower on tractor
2. Evaluate Field Sanitation of Blueberry Crop using Sanitizer.
Field testing of the sanitizer was conducted at the University of Georgia Blueberry Research
Farm in Alma, GA. The field tests were conducted to evaluate sanitation as a useful method to
help control SWD and to evaluate the sanitizer as a useful tool in sanitation.
a. Sanitation Treatments/Preparation
SWD traps were built, sanitizer tested in tractor, and plots prepared for testing the sanitizer
during the Summer 2014 blueberry harvest. The field treatments consisted of the matrix of tests
shown in Table 1 for rabbiteye blueberry varieties.
Table 1: Treatments and number of reps per treatment in Rabbiteye plots
Sanitation
Only
Sanitation
+ Spray
½ Sanitation +
½ Spray
Spray
Only
No
Treatment
Treatment #
1
2
3
4
5
Reps
3
3
3
3
3
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Figure 5 Field layout for treatments, black lines are blueberry rows. 5 treatments x 3 reps.
The spray treatments were with Mustang max applied at 40 GPA and 4 oz/acre of active
ingredient. Each test treatment had 3 replicates, each rep covering 4 rows of blueberries, 75 feet
long. Data was collected from sanitation of the inner 2 rows (alley 2, fig. 5) in each repetition.
The sanitizer was used to blow berries from alley 1 and 3 into alley 2. The blower was then
turned off as the sanitizer traveled down alley 2 to have the roller sanitize the berries in the row
middle of the alley. Sanitation treatments were conducted on a weekly basis for all plots, except
the ½ sanitation + ½ spray treatment. These treatments were sanitized once every 2 weeks and
sprayed in the alternating weeks.
b. Data Collection
Data for each rep of each treatment were collected as follows. Each treatment was evaluated by
three methods. First, traps were placed in the center of one rep of each treatment. Traps consisted
of 32 oz. cups with 10-12 holes (3/16” of an inch) 1” below the top of the cup containing ½” of
trap mix. These traps were collected weekly and replaced with fresh bait. Trap contents were
identified with 15x hand microscope in the lab. Also, for each treatment, 500 fallen berries were
collected weekly and put in growth chambers for 2 weeks. Number of emerging flies were
counted and used to compare treatments. Lastly, blueberries were counted in 10 foot segment
between bushes in the rows where they were inaccessible to the tractor tire or roller. These
counts were taken before and after running the blower/roller combination at 3 mph through the
field as shown in Figure 6. The berries were counted on the left and right side of the alley. This
resulted in an assessment of how effectively the blower moved berries from between the bushes.
Berries were not collected in those treatments (4 and 5) that were not sanitized.
c. Data Presentation
Sanitation data was presented to the Annual Georgia Blueberry Growers meeting in Alma, GA
and the SWD OREI Planning Meeting in Atlanta. A pre- and post- presentation survey was
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handed out and growers asked to fill out two short questionnaires before and after the meeting
presentation on our sanitation study (Appendix A).
3. Analyze field test results
a. Trap Data
Due to the amount of spraying at the UGA Blue Berry Research Farm, there were very few SWD
found in the traps even in the untreated plots (Treatment 4). Only during harvest were there any
collected and then only in small numbers as shown in Table 2.
Table 2 – Adult SWD found in traps. Samples taken once per week within rep 2 of each
treatment.
Date
Plot re Rep-Treatment
Male
Female
6/5/2014
2--1
0
0
2--2
2
0
2--3
1
0
2--4
0
0
2--5
1
0
6/12/2014
2--1
0
0
2--2
0
0
2--3
1
0
2--4
1
1
2--5
1
0
6/19/2014
2--1
1
0
2--2
0
0
2--3
0
1
2--4
0
1
2--5
0
1
6/26/2014
2--1
0
0
2--2
0
0
2--3
0
1
2--4
1
3
2--5
1
2
7/3/2014
2--1
2
7
2--2
3
4
2--3
0
5
2--4
2
1
2--5
3
2
Fallen blueberries collected and incubated for 2 weeks did not show any emergent flies for all 5
weeks of data tested. This somewhat correlated with the lack of SWD found in traps.
Subsequently, we were not able to assess if the sanitation mechanism made a difference in SWD
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populations. There were none there to begin with. However, we were able to assess the ability of
the blower to move blueberries from between the blueberry bushes so that they could be
accessed by the roller. The tables below show the week by week movement of the berries. The
columns show the number of berries between the trees before and after running the blower.
Therefore, the fewer the berries after, the more berries were moved by the blower.
b. Moving Berries with Blower
Berries were counted in each treatment before and after running the blower for each week of the
test. We ran the blower every other week on the ½ sanitation + ½ sprayer treatment. Week 1 did
not have any berries on the ground for treatment 5, so collection began there on week 3. Results
are report by rep-treatment (such as 2-1 is rep 2 treatment 1) as shown in Figure 4.
Week 1
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Week 2
Week 3
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Week 4
Week 5
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Five Week Total
The average percent of berries moved from between the blueberry bushes to where the
roller and/or tire could roll over them was 47% for the left and right side of the bushes.
The challenges moving forward are:
1. The area around the bushes must be kept clean and void of weeds. Any weeds in the row
with the blueberry bushes prevent them from moving to the alley.
2. Some blueberries also get blown into the base of the blueberry bushes, where they get
stuck. The direction and number of tubes blowing the blueberries should be modified to
blow blueberries away from the bushes when they get into the base of the bushes.
3. To sanitize blueberries closer to the base of the blueberry bushes, the roller should be
moved to the outside of the tractor wheel, providing a width of the roller plus the tractor
wheel for rolling over blueberries. The figure below is a top view of lego model showing
the roller outside the tractor wheel, where it would be next to the base of blueberry
bushes, closer to blueberries for sanitation.
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Presentation to Growers
Sanitation data was presented to the Annual Georgia Blueberry Growers meeting and the organic
blueberry growers meeting. A pre- and post- presentation survey was handed out and growers
asked to fill out two short questionnaires, one before and one after the meeting (Appendix A).
The first question tracked the respondent’s level of how important they thought sanitation was
before and after the presentation. It also asked if they knew what it was before and after the
meeting. There were 129 pre-survey respondents, but only 93 post-survey respondents. Whether
this had an overall effect on each of the questions is unknown. While there appeared to be only 3
respondents after the meeting that did not know what sanitation was, compared to 39 before, the
rest of the results are mixed. The grower responses before and after the sanitation presentation
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are relatively unchanged from 1 through 6, which would be somewhat a lack of importance, the
results before and after are relatively unchanged. There was a marked increase in response of
importance at the 7-8 level, but then there were actually fewer people post-presentation who
believed it was of a higher level of importance (9-10). A follow-up question from the pre-survey
revealed that 78% of growers responding had never used sanitation methods. Those that had used
sanitation methods reported equipment cleaning and weed control as their sanitation methods.
The second post-test question asked if the growers knowledge of sanitations was increased, 1,
being very little and 10 being significantly. These results were very encouraging as shown in the
bar chart. Over 60% rated their increased knowledge of sanitation as 8 or greater.
Fifty-five percent of growers that responded were more likely to try adding sanitation to their
SWD program and about that same percentage would pay at least $500.00 to implement the
sanitation system presented and developed for this project. However, 19% were not willing to
spend any money on sanitation.
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Literature Cited:
1. Lee, J. C., D. J. Bruck, H. Curry, D. Edwards, D. R. Haviland, R. A. Van Steenwyk, B. M.
Yorgey. 2011. The susceptibility of small fruits and cherries to the spotted wing drosophila,
Drosophila suzukii. Pest Manag. Sci. 67, 1358e1367.
2. Walsh, D. B., M. P. Bolda, R. E. Goodhue, A. J. Dreves, J. Lee, D. J. Bruck, V. M. Walton, S. D.
O’Neal, F. G. Zalom. 2011. Drosophila suzukii (Diptera: Drosophilidae): invasive pest of
ripening soft fruit expanding its geographic range and damage potential. J. Int. Pest Manage. 2,
1e7. http://dx.doi.org/10.1603/IPM10010.
3. Hauser, M. 2011. A historic account of the invasion of Drosophila suzukii (Matsumura)(Diptera:
Drosophilidae) in the continental United States, with remarks on their identification. Pest Manag.
Sci. 67, 1352e1357.
4. Burrack, H. J., J. P. Smith, D. G. Pfeiffer, G. Koeher and J. LaForest. 2012. Using volunteer
based networks to track Drosophila suzukii an invasive pest of fruit crops. J. Integrated Pest
Management 3(4): B1B5.
5. Cini, A., C. Ioriatti, Anfora, G. 2012. A review of the invasion of Drosophila suzukii in Europe
and a draft research agenda for integrated pest management. Bull. Insectol. 65, 149e160.
6. Burrack, H. J., G. E. Fernandez, T. Spivey, D. A. Kraus. 2013. Variation in selection and
utilization of host crops in the field and laboratory by Drosophila suzukii Matsumara (Diptera:
Drosophilidae), an invasive frugivore. Pest Manag. Sci. http://dx.doi.org/10.1002/ps.03489.
7. Kanzawa, T. 1939. Studies on Drosophila suzukii Mats (in Japanese).Yamanashi Agricultural
Experimental Station, Kofu, Japan.
8. Bolda, M. P., R. E. Goodhue, F. G. Zalom. 2010. Spotted wing drosophila: potential economic
impact of a newly established pest. Agric. Resour. Econ. Update Univ. Calif. Giannini Found.
Agric. Econ. 13, 5e8.
9. Goodhue, R. E., M. Bolda, D. Farnsworth, J. C. Williams, F. G. Zalom. 2011. Spotted wing
drosophila infestation of California strawberries and raspberries: economic analysis of potential
revenue losses and control costs. Pest Manag. Sci. 67, 1396e1402.
10. Wolfe, K. and T. Shepherd. 2011 Georgia Farm Gate Value Report. The University of Georgia,
Center for Agribusiness and Economic Development, College of Agricultural and Environmental
Sciences. Athens, GA: 2012.
11. Lee, J. C., L. D. Barrantes, E. H. Beers, H. J. Burrack, A. J. Dreves, L. J. Gut, K. A. Hamby, D.
R. Haviland, R. Isaacs, A. R. Nielson, T. Richardson, C. R. Rodriguez-Saona, P. W. Shearer, C.
A. Stanley, D. B. Walsh, V. M. Walton, F. G. Zalom, D. J. Bruck. 2013. Improving trap design
for monitoring Drosophila suzukii (Diptera: Drosophilidae). Environ. Entomol. (in press).
12. Landolt P. J., T. Adams, H. Rogg. 2011. Trapping spotted wing drosophila, Drosophila suzukii
(Matsumura) (Diptera: Drosophilidae), with combinations of vinegar and wine, and acetic acid
and ethanol. J. Appl. Entomol. doi:10.1111/j.1439-0418.2011.01646.x.
13. Bruck, D. J., M. Bolda, L. Tanigoshi, J. Klick, J. Kleiber, J. DeFrancesco, B. Gerdeman, H.
Spitler. 2011. Laboratory and field comparisons of insecticides to reduce infestation of
Drosophila suzukii in berry crops. Pest Manag. Sci. 67, 1375e1385.
14. Beers, E. H., R. A. Van Steenwyk, P. W. Shearer, W. W. Coates, J. A. Grant. 2011. Developing
Drosophila suzukii management programs for sweet cherry in the western United States. Pest
Manag. Sci. 67, 1386e1395.
15. Haviland, D. and E. H. Beers. 2012. Chemical control programs for Drosophila suzukii that
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comply with international limitations on pesticide residues for exported sweet cherries. Journal
of Integrated Pest Management Vol. 3, Issue 2.
http://esa.publisher.ingentaconnect.com/content/esa/jipm/2012/00000003/
16. Timmeren, S. V. and R. Isaacs. 2013. Control of spotted wing drosophila, Drosophila suzukii, by
specific insecticides and by conventional and organic crop protection programs. Crop Protection
54, 126-133.
17. Allwood, A. J., A. Leblanc, E. T. Vueti, E. Bull. 2001. Fruit fly control methods for the Pacific
Island countries and territories. Pest Advisory Leaflet, Secretariat of the Pacific Community.
Plant Protection Service, 40.
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APPENDIX A – Survey, Pre and Post
Pre-Meeting Blueberry Workshop Survey – scale of 1-10. 1 equal not important and 10 equals
very important. For each answer circle your best response or fill in the blank
1. How important would you rate sanitation as a control measure for SWD in Blueberries?
If you do not know what sanitation is, circle 0.
0
1
2
3
4
5
6
7
8
9
10
2. Have you used sanitation to control SWD or other pests in the past?
Yes
No
If yes, what pest and what sanitation method did you use?
Pest__________
Sanitation Method ____________________________________
_____________________________________________________________________
3. How important is SWD control to you for blueberry production?
1
2
3
4
5
6
7
8
9
10
4. How many acres of blueberries do you produce? (fill-in blank)
Highbush _____ Rabbiteye ____ High Density ____
5. What strategies do you employ to control SWD? Circle all that apply
Aerial Spraying
Ground Spraying
Cultivar Selection
Scouting
Others _________________________________________________
Traps
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Post-Meeting Blueberry Workshop Survey – scale of 1-10. 1 equal not important or not likely
and 10 equals very important or very likely. For each answer circle your best response
1. How important would you rate sanitation as a control measure for SWD in Blueberries?
If you do not know what sanitation is, circle 0.
0
1
2
3
4
5
6
7
8
9
10
2. Did the presentation increase you understanding of sanitation for SWD control?
1
2
3
4
5
6
7
8
9
10
3. How likely are you to implement sanitation procedures as described in this
presentation?
1
2
3
4
5
6
7
8
9
10
4. How much would you be willing to spend as a one-time expense to utilize sanitation as
described at the meeting to help control SWD?
$0
$100-$200
$200-$500
$500-$1000
$1000-$2500.00
5. Do you believe, based on the presentation, that adding sanitation to your SWD control
strategy would reduce pesticide applications?
Yes
No