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SWD Impacts 2014

To advance our understanding of the ongoing effects of spotted wing drosophila in host crops, we have produced impact statements for the 2012 and 2013 growing seasons. Our 2012 Impact Statement was developed by surveying entomologists throughout the eastern United States about their state-level observations, and our 2013 Impact Statement summarized the results of a national stakeholder survey. To determine the effects of SWD during the 2014 growing season, we again conducted a national survey of stakeholders, using the same form as during 2013. Surveys were made available online and at grower meetings. Surveys at grower meetings were conducted from January 9 through March 8 2015. The online questionnaire was made available at the eFly SWD Working Group website and emailed as a link to grower email lists, grower organizations, and cooperative extension agents. Online responses were collected from December 11 2014 through February 13 2015.

A total of 436 individuals responded to the survey; 144 respondents completed paper copies at grower meetings and 292 filled out the survey online.

Respondent geographic diversity

Survey respondents were from at least 31 different states (Figure 1); four respondents declined to provide their location.

Figure 1. Number of respondents by state, combined online and paper surveys. Four respondents declined to provide state information.

Figure 1. Number of respondents by state, combined online and paper surveys. Four respondents declined to provide state information.

In addition to representing 31 states, responses were widely distributed geographically (Figure 2). The largest number of responses came from southern states (42.8%), followed by western (24.4%), Northeast (17%), and Midwestern (14.6) states.

Figure 2. Regional distribution of responses. Regions corresponded to those use by Regional IPM Centers (http://www.ipmcenters.org/).

Figure 2. Regional distribution of responses. Regions corresponded to those used by Regional IPM Centers (http://www.ipmcenters.org/).

Demographic information in addition to state was collected from respondents to the online survey, and of those, 56.5% were conventional fruit growers, 13.5% were organic fruit growers, 9% were extension agents or specialists, 2.9% were crop consultants, 4.8% were homeowners, and 13.5% were engaged in other activities or did not provide demographic information. Demographic information beyond state was not collected on paper surveys as all respondents were growers.

Crops grown

In contrast to 2013, the majority of respondents (52%) grew only one SWD host crop, although a large number of respondents still grower than two host crops (Figure 3).

Figure 3. Number of SWD host crops grown per respondent.

Figure 3. Number of SWD host crops grown per respondent.

The majority of respondents grew blueberries, followed by strawberries, raspberries, blackberries, grapes, and cherries (Table 1). Respondents represented a substantial portion of US blueberry, blackberry, and raspberry acreage.

Table 1. Spotted wing drosophila host crops grown by respondents.

Crop Number of respondents growing crop Total acres represented Percentage of total US acres*
Blueberries 284 17234 21%
Blackberries 134 1573 11%
Raspberries 139 1347 8%
Strawberries 144 1921 3%
Cherries 86 2853 2%
Grapes 128 2748 0%

*Acreage totals by crop were from the 2014 USDA NASS Noncitrus Fruits and Nuts Summary (blueberries, raspberries, strawberries, cherries, grapes) or 2012 Census of Agriculture (blackberries).

Crop level impacts

The average, minimum and maximum reported percentage loss across all responses for each crop was calculated (Tables 2-7). In addition, average loss by crop was calculated for each state with more than two total responses and compared to the value of each crop within a state. Crop values for each reporting state were obtained either from the 2014 USDA NASS Noncitrus Fruit and Nut Preliminary Summary, January 2015 when available, or estimated based on reported acreage in 2012 Census of Agriculture and reported crop value and yield per acre from the 2014 USDA NASS Noncitrus Fruit and Nut Preliminary Summary.

Potential crop losses were also calculated based on the total value of a crop within reporting states with greater than three respondents and the average percentage loss observed across all states. In the case of blueberries, blackberries, raspberries, cherries, and grapes potential losses were higher than observed losses. However in the observed losses for strawberries was higher than averaged potential loss, due to particularly high loss percentages in some states (Table 5).

When totaled across all crops, the estimated crop loss due to SWD experienced in the crops and states represented in our survey was $133,309,400. The potential national crop loss due to SWD based on 2014 average damage is $1,276,992,028.

Table 2. Estimate crop loss due to SWD in blueberries, 2014.

Crop Number of Responses Average percentage crop loss Minimum observed loss Maximum observed loss
Blueberry  289 13% 0% 100%
Value of potential national crop loss $105,091,444
State Number of Responses Average percentage crop loss 2014 estimated value Estimated 2014 crop value lost
AR 22 5% $619,000 $30,950
CT* 8 14% $4,410,158 $617,422
GA 85 3% $109,800,000 $3,294,000
IN 6 17% $2,780,000 $472,600
MA* 3 2% $7,891,325 $157,827
MD* 5 6% $1,398,592 $83,916
MI 14 19% $114,320,000 $21,720,800
MO* 3 17% $1,980,488 $336,683
NC 41 5% $72,181,000 $3,609,050
NJ 12 2% $79,181,000 $1,589,260
NY 24 16% $4,208,000 $673,280
OH* 5 3% $3,889,515 $116,685
OR 6 5% $106,692,000 $5,334,600
PA* 8 11% $10,545,592 $1,160,015
RI* 6 24% $1,398,592 $335,662
VA* 19 7% $4,318,280 $302,280
WI* 6 2% $3,909,932 $78,199
Estimated observed loss across reporting states $39,913,277
Potential total loss across reporting states $68,874,711
*Values calculated based on reported acreage in 2012 Census of Agriculture and crop value ($1.71/lb) and yield estimates (5970 lb/acre) from 2014 USDA NASS Noncitrus Fruit and Nut Preliminary Summary.

Table 3. Estimated crop loss in blackberries due to SWD, 2014.

Crop Number of Responses Average percentage crop loss Minimum observed loss Maximum observed loss
Blackberry  131 27% 0% 100%
Value of potential national crop loss* $67,626,444
State* Number of Responses Average percentage crop loss 2014 estimated value Estimated 2014 crop value lost
AR 20 13% $8,831,616 $1,148,110
CT 4 35% $404,782 $141,674
GA 11 4% $10,487,544 $419,502
IL 3 67% $2,171,106 $1,454,641
IN 7 34% $2,820,000 $450,412
MD 6 13% $827,964 $107,635
NC 20 32% $7,451,676 $2,384,536
NY 13 10% $4,084,622 $408,462
OH 4 46% $6,476,518 $2,979,198
PA 6 23% $2,704,682 $622,077
VA 13 17% $4,949,385 $841,395
WI 3 2% $883,162 $17,663
Estimated observed loss across reporting states $10,975,307
Potential total loss across reporting states $13,661,406
*Values calculated based on reported acreage in 2012 Census of Agriculture and crop value ($2.11/lb) and yield estimates (8720 lb/acre) from 2014 USDA NASS Noncitrus Fruit and Nut Preliminary Summary. Eastern yield estimates in research trials range from 18,000 to 20,000 lb/acre, so values are likely conservative.

Table 4. Estimated crop loss in raspberries due to SWD, 2014.

Crop Number of Responses Average percentage crop loss Minimum observed loss Maximum observed loss
Raspberry  130 41% 0% 100%
Value of potential national crop loss $159,303,450
State* Number of Responses Average percentage crop loss 2014 estimated value Estimated 2014 crop value lost
AR 5 1.30% $543,767 $7,069
CT 7 38% $1,798,613 $683,473
IN 9 48% $1,380,331 $662,559
MD 5 63% $1,254,846 $790,553
MI 3 17% $12,318,405 $2,094,129
MN 4 74% $1,181,793 $874,527
MO 3 63% $648,337 $408,452
NC 12 48% $1,443,073 $692,675
NJ 5 0% $1,777,699 $0
NY 23 30% $14,326,159 $4,297,848
OH 3 38% $8,386,554 $3,186,891
PA 9 38% $5,855,948 $2,225,260
VA 12 36% $2,300,551 $828,198
WI 12 16% $5,249,439 $839,910
Estimated observed loss across reporting states $17,591,544
Potential total loss across reporting states $23,970,859
* Values calculated based on reported acreage in 2012 Census of Agriculture and crop value ($2.05/lb fresh) and yield estimates (10,020 lb/acre) from 2014 USDA NASS Noncitrus Fruit and Nut Preliminary Summary.

Table 5. Estimated crop loss in strawberries due to SWD, 2014.

Crop Number of Responses Average percentage crop loss Minimum observed loss Maximum observed loss
Strawberry 133 6% 0% 55%
Value of potential national crop loss $171,925,920
State Number of Responses Average percentage crop loss 2014 estimated value Estimated 2014 crop value lost
AL* 3 3% $2,052,764 $61,583
AR* 8 26% $818,507 $212,812
CT* 6 0% $3,676,787 $0
GA* 10 2% $1,818,905 $36,378
IL* 3 0% $4,118,521 $0
IN* 7 2% $3,702,771 $74,055
MD* 5 0% $2,858,279 $0
MN* 4 55% $7,730,346 $4,251,690
MO* 3 0% $2,546,467 $0
NC 16 1% $23,490,000 $234,080
NJ* 6 3% $3,650,802 $109,524
NY 21 3% $6,880,000 $225,600
OH 3 0% $4,200,000 $0
PA 4 4% $6,888,000 $211,200
SC* 3 0% $5,794,512 $0
VA* 9 0% $3,767,732 $0
WI 15 1% $5,738,000 $64,350
Estimated observed loss across reporting states $5,481,273
Potential total loss across reporting states $5,319,204
* Values calculated based on reported acreage in 2012 Census of Agriculture and crop value ($156.74/cwt fresh) and yield estimates (82.89 cwt/acre) from 2014 USDA NASS Noncitrus Fruit and Nut Preliminary Summary.

Table 6. Estimated crop loss in cherries due to SWD, 2014.

Crop Number of Responses Average percentage crop loss Minimum observed loss Maximum observed loss
Cherry 81 9% 0% 100%
Value of potential national crop loss $82,037,970
State Number of Responses Average percentage crop loss 2014 estimated value Estimated 2014 crop value lost
MD* 4 24% $6,805,024.00 $1,633,206
MI 4 0% $98,739,000 $0.00
NC* 6 1% $1,597,742 $15,977.42
NY 10 0% $1,073,000 $0
OR 24 10% $79,168,000 $7,916,800
VA* 10 1% $4,682,131 $46,821
WA 3 3% $515,930,000 $15,477,900
WI 3 3% $1,885,000.00 $140,490
Estimated observed loss across reporting states $48,834,766
Potential total loss across reporting states $70,088,261
* Values calculated based on reported acreage in 2012 Census of Agriculture and crop value ($1.01/lb, sweet cherries; $0.48/lb tart cherries) and yield estimates (98200 lb/acre sweet; 2280 lb/acre tart) from 2014 USDA NASS Noncitrus Fruit and Nut Preliminary Summary.

Table 7. Estimated crop loss in grapes due to SWD, 2014.

Crop Number of Responses Average percentage crop loss Minimum observed loss Maximum observed loss
Grapes 122 12% 0% 100%
Value of potential national crop loss $691,006,800
State Number of Responses Average percentage crop loss 2014 estimated value Estimated 2014 crop value lost
AR* 5 2% $4,011,984 $80,240
CT* 6 3% $2,986,699 $89,601
GA* 3 7% $10,815,640 $757,095
IN* 12 20% $3,438,047 $687,609
MD* 4 20% $3,794,668 $758,934
NC 23 1% $933,000 $9,330
NY 8 4% $5,070,000 $160,240
OR 6 5% $118,320,000 $5,916,000
VA 27 15% $12,784,000 $1,917,600
WI* 11 3% $4,552,487 $136,575
Estimated observed loss across reporting states $10,513,233
Potential total loss across reporting states $19,877,103
* Values calculated based on reported acreage in 2012 Census of Agriculture and crop value ($0.38/lb) and yield estimates (14800 lb/acre) from 2014 USDA NASS Noncitrus Fruit and Nut Preliminary Summary.

We further compared the effect of farm size on reported crop loss across all reporting growers (Tables 8-13). In general, small farms experienced higher crop loss than larger farmers across, and small farms were also more likely to experience 100% crop loss due to SWD than were larger farms. At least one blueberry, blackberry, or raspberry grower reported 100% crop loss, but no strawberry, cherry, or grape growers reported total crop loss. This suggests that SWD damage may be more severe in blueberries, blackberries, and raspberries than in the other reported crops.

Table 8. Reported percentage crop loss in blueberries by farm size.

Very large farms (>100 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
47 7% 0% 100%
Large farms (50-100 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
18 4% 0% 100%
Medium farms (11-50 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
44 17% 0% 100%
Small farms (1-10 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
110 12% 0% 100%
Very small farms (<1 acre)
Number of responses Average loss Minimum observed loss Maximum observed loss
61 19% 0% 90%

Table 9. Reported percentage crop loss in blackberries by farm size.

Very large farms (>100 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
1 2% 2% 2%
Large farms (50-100 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
5 50% 1% 75%
Medium farms (11-50 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
14 17% 0% 100%
Small farms (1-10 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
35 18% 0% 100%
Very small farms (<1 acre)
Number of responses Average loss Minimum observed loss Maximum observed loss
79 34% 0% 100%

Table 10. Reported percentage crop loss in raspberries by farm size.

Large farms (50-100 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
4 31% 0% 100%
Medium farms (11-50 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
7 52% 10% 80%
Small farms (1-10 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
47 32% 0% 100%
Very small farms (<1 acre)
Number of responses Average loss Minimum observed loss Maximum observed loss
74 47% 0% 100%

Table 11. Reported percentage crop loss in strawberries by farm size.

Very large farms (>100 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
3 7% 0% 10%
Large farms (50-100 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
2 5% 5% 5%
Medium farms (11-50 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
17 10% 0% 60%
Small farms (1-10 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
68 3% 0% 75%
Very small farms (<1 acre)
Number of responses Average loss Minimum observed loss Maximum observed loss
54 8% 0% 100%

Table 12. Reported percentage crop loss in cherries by farm size.

Very large farms (>100 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
19 21% 0% 100%
Large farms (50-100 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
5 5% 0% 10%
Medium farms (11-50 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
9 1% 0% 2%
Small farms (1-10 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
20 1% 0% 5%
Very small farms (<1 acre)
Number of responses Average loss Minimum observed loss Maximum observed loss
33 6% 0% 70%

Table 13. Reported percentage crop loss in grapes by farm size.

Very large farms (>100 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
4 15% 10% 20%
Large farms (50-100 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
7 14% 0% 30%
Medium farms (11-50 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
30 9% 0% 50%
Small farms (1-10 acres)
Number of responses Average loss Minimum observed loss Maximum observed loss
46 16% 0% 100%
Very small farms (<1 acre)
Number of responses Average loss Minimum observed loss Maximum observed loss
41 6% 0% 80%

Table 14. Input increases associated with spotted wing drosophila summarized by crop. Note that growers were asked about input increases across their entire farm, not for individual crops. Categories with fewer than two responses are indicated by -.

Number of responses by crop Number of respondents indicating increased pesticide use Reported percentage of increase/additional cost per acre Average reported cost increase per acre for pesticide use ($/acre) Number of respondents with increased labor costs Average percentage of labor increase
All respondents (436) 287 106% $183 192 26%
Respondents only growing blueberries (122) 90 76% $104 59 23%
All respondents growing blueberries (276) 180 201% $139 139 65%
Respondents only growing blackberries (7) 7 89% $                      190 4 48%
All respondents growing blackberries (131) 81 90% $325 62 21%
Respondents only growing raspberries (4) 1
All respondents growing raspberries (135) 79 186% $348 69 25%
Respondents only growing strawberries (12) 4 94% $138 2 18%
All respondents growing strawberries (145) 81 262% $293 67 19%
Respondents growing only cherries (22) 17 39% $122 7 6%
All respondents growing cherries (84) 58 249% $286 38 13%
Respondents growing only grapes (38) 17 66% $138 6 33%
All respondents growing grapes (76) 76 87% $125 56 5%

Respondents comments

Respondents were also given the opportunity to include comments.  Frequent comments expressed a desire for better insecticides but also for ways to reduce the amount of insecticide needed, through improved materials, better application methods, or non-chemical controls.  Several commenters indicated that damage on their farm was less severe in 2014 than in 2013, but they also indicated that they have reduced losses as compared to previous years through increasing pesticide use and labor, as reflected in the responses summarized in Table 14.

Comparison to previous year impacts

More stakeholders completed the 2014 impact assessment survey than in the previous year, 436 compared to 249. This high response rate underscores the continued significance of SWD for berry and tree fruit growers.

Despite some grower comments that SWD losses were lower in 2014 than in 2013, the average percentage crop loss reported increased for all host crops (Table 15).

Table 15. Average crop loss reported in 2013 and 2014 impact assessment surveys.

Crop 2013 2014
Blueberries 4.7% 13%
Blackberries 12% 27%
Raspberries 16.3% 41%
Strawberries 3.6% 6%
Cherries 3.1% 9%
Grapes 2% 12%

Written By

Photo of Dr. Hannah BurrackDr. Hannah BurrackAssoc. Professor and Extension Specialist (Berry, Tobacco and Specialty Crops) (919) 513-4344 hannah_burrack@ncsu.eduEntomology and Plant Pathology - NC State University
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