A Review of Survey Results Regarding Auxin Herbicides and Vineyard Damage: Grape Grower Feedback
Background
Herbicide drift, the unintentional movement of herbicide particles or vapors from the target area to off-target areas, can impact grape growers' profitability. While auxin herbicides effectively control certain weeds, they require caution when applied. The adoption of no-till farming and auxin herbicide-resistant crops, has increased the use of 2,4-D and dicamba, increasing the risk of herbicide drift damage to off-target cropping systems.
The awareness of pesticide applicators regarding herbicide drift damage to grapevines is vital in minimizing off-target movement and potential harm. Applicators can take preventive measures to reduce the risks associated with auxin herbicide drift, such as following precautional practices while spraying (e.g., nozzle type, boom height, drift-reducing adjuvants) and considering wind velocity and temperature when spraying their crops. We surveyed grape growers and pesticide applicators to explore the current impact and understanding of herbicide drift in vineyards in Pennsylvania and surrounding states. We also sought to understand the awareness and perceptions of herbicide applicators about the possible detrimental effects of herbicide drift on grapevines and how to prevent these cases from happening; we will present the results from these survey questions in a forthcoming extension article.
Approach
We were granted permission to adapt a survey developed and deployed by Ohio State University Extension and developed as part of the resources of the North Central IPM Center (Brown 2022). Our online survey was conducted from April to June 2023. The survey deployment was limited to the Penn State Extension email distribution lists and newsletters, which target growers based on their area of interest(e.g., row crop, commercial landscape, turfgrass management, grape production, etc.). Because of IRB requirements, survey respondents were not required to complete all the questions, and IP addresses were not collected. Where indicated, we removed answers from outside of Pennsylvania and the greater Mid-Atlantic region. Respondents indicated the producer group(s) they identify with grape grower, agronomic crop farmer, right of way/roadside/woodland manager, commercial landscape manager, commercial pesticide applicator, and pastureland manager.
Grape grower results
One hundred grape growers responded to the survey. However, 32 were non-commercial grape growers and they were excluded. After data cleanup, 63 grape grower responses were further analyzed, although not every respondent answered every question in the survey. Of these 63 grape growers: (1) 51 were from Pennsylvania; (2) one indicated to also be a commercial pesticide applicator; and (3) 15 also managed other crops and pastureland. The average vineyard size of the 63 grape grower respondents was 11 acres, with a median of nine acres.
Grape growers in our survey were concerned about auxin/PGR herbicide drift. A total of 54% percent of respondents indicated that they are extremely and moderately concerned about herbicide drift (Figure 1).
Figure 1.
In addition, there was an even split in level of concern regarding herbicide drift of the last seven years: the same number of grape growers (48%) stated their level of concern about auxin/PGR herbicide drift has increased or remained unchanged, while only 5% answered that their level of concern has decreased.
Figure 2.
Grape growers have several options to manage the risk of herbicide drift damage in their vineyards. Table 1 represents different strategies adopted by grape growers to manage herbicide drift risk. Most respondents (57%) proactively approached neighboring herbicide applicators to discuss drift concerns, 38% used Field Watch or a similar registry for sensitive crops, and 35% attended a workshop about managing herbicide drift risks.
| Actions | % |
|---|---|
| Approached a neighboring herbicide applicator preemptively with herbicide drift concerns | 57% |
| Used Field Watch or a similar registry for sensitive crops | 38% |
| Attended a workshop about managing herbicide drift risks | 35% |
| Sought information on herbicide drift damage symptoms, testing labs, or steps for reporting | 25% |
| None | 19% |
| Planted a buffer zone or tree line to provide protection from drift | 6% |
| Changed or moved crops due to drift concerns | 3% |
Although particle (droplet) drift can cause unintentional herbicide damage, it’s not the sole causal mechanism for which herbicide damage can occur. Twenty-eight growers in the survey indicated that they presumed injury came from herbicide volatilization (not particle drift, but drift of vapors through volatilization), and seven growers indicated that they experienced herbicide damage from contaminated sprayer equipment.
Scouting
Frequent scouting of vineyards for diseases, pests, and abiotic stress is recommended throughout the growing season. When asked how often the respondents scout (walking vineyard rows and looking closely into canopies) their vineyard, most respondents reported that they scout weekly to several times per week, which the authors believe is an appropriate frequency for commercial grape production.
Figure 3.
While a significant majority (61%) of respondents indicated that they are “moderate to very confident” in identifying damage caused by auxin/PGR herbicide drift, there are still 21% who only feel somewhat confident and 18% who lack confidence. This suggests a potential need for further educational efforts about identification and of herbicide drift damage symptoms in vineyards.
Figure 4.
Herbicide drift damage
We asked survey respondents which herbicides they suspect to cause grapevine damage due to off-target herbicide movement from other land managers. We know from a previous question asked to applicators and land managers (other than grape growers) (n=144) that the most used auxin/PGR herbicides are 2,4-D (79%), followed by Dicamba (66%), Triclopyr (63%) and Clopyralid (41%). Grape growers (n=46) suspect most of the damage is caused by 2,4-D, Dicamba, followed by unknown herbicides. 2,4-D can cause off-target herbicide damage, the potential risk for which is greatly dependent on the formulation (Sysnoskie et al. 2015); grower perceptions seem to parallel current understanding. Thus, if in fact, 2,4-D is causing the most “herbicide drift cases,” it is possible that the “ester” formulation remains a popular herbicide choice, as this formulation has been found to increase the risk of off-target damage relative to amine and choline versions (Sysnoskie et al. 2015). In the ‘other’ category, metribuzin and glyphosate were listed.
| HerbicideHerbicide | % (n=46) |
|---|---|
| 2,4-D | 65% |
| Dicamba | 33% |
| Unknown | 28% |
| Other | 15% |
| Triclopyr | 13% |
When asked about the off-target source of drifted herbicides, most respondents suspect row crop fields (65%), followed by lawn or landscaping (26%). In the ‘others’ category, respondents added the following locations to be considered sources of herbicide drift: railroad, sod farm, and electric powerline maintenance/weed control.
| Suspected off-target source | % (n=43) |
|---|---|
| Row crop field in production | 65% |
| Lawn or landscape (home or business) | 26% |
| Other | 26% |
| Unknown | 17% |
| Meadow, pasture, or fallow area | 15% |
| Roadside weed control | 11% |
Costs incurred related to herbicide drift are highly variable, depending on the damage, and can be related to:
- Tissue testing
- Labor hours spent on the investigation, filing complaints, etc.
- Consulting fees
- Loss in grape sales
- Permanent vine damage/replacement costs
- Lawyer costs
The overall damage caused by herbicide drift to vineyard operations can be hard to assess, especially in retrospect. We asked grape growers to estimate the annual average loss of total grape production due to herbicide drift over the last seven years. Of the 51 respondents, 27% reported a loss of less than 5%, 18% reported a loss of 6-10%, 6% reported a loss of 11-25%, and 10% of respondents reported a loss of more than 25%. The remainder reported no loss or were not sure (33%).
Many growers are forced to act when they suspect herbicide drift symptoms in their vineyards. The table below shows grape grower actions in response to vineyard herbicide drift damage (actual or suspected).
| Answer | % (n=51)* |
|---|---|
| I approached a neighboring herbicide applicator with concerns about a specific drift event | 65% |
| I took photos of possible herbicide damage | 55% |
| I contacted my viticulture extension personnel | 35% |
| I signed up for Field Watch or a similar crop registry for sensitive crops for the first time | 31% |
| I contacted an herbicide or crop specialist for advice or diagnosis regarding herbicide drift | 29% |
| None of these | 24% |
| I collected samples myself for herbicide residue testing | 12% |
| I paid for private testing for herbicide residues | 10% |
| I contacted a lawyer regarding herbicide drift | 10% |
| Other | 8% |
| I changed the variety and/or field location to avoid future damage or loss (or plan to do so in the future) | 6% |
| I was forced to break a sales agreement | 2% |
* total percentages exceed 100% due to the select-all-that-apply style of the question.
Concerning costs associated with tissue testing for herbicide residue presence - costs ranged from $400 to $1,200. For advice regarding herbicide drift, expenses for consulting fees ranged from $1,000 to $2,700. Only five of 55 grape growers talked to an insurance agent about adding a chemical drift liability endorsement.
Growers also shared the following experiences, reported below as quotes, which show, in some cases, that communication can be effective at stopping drift damage occurrence:
• 2019 was our only economic loss due to herbicide damage, and lost over $75K in grapes sales.
• The cost of sending my annual letter. Since starting to do this, we have not seen any more damage.
• loss of downstream revenue from lost wine production
• Herbicide drift for years. Began plotting damage only then determined a neighbor us spraying 2,4 D. I called farm/land owner, farm land renter, and commercial applicator promising to bring a lawsuit against them for damages if we experienced another cycle of damage. They changed practices, after which we have not been damaged by drift.
Only 11 (20%) of survey respondents who answered questions about herbicide drift complaints (n=56) filed an herbicide drift complaint with the Department of Agriculture in their respective state. None of the respondents took legal action. Twenty-nine respondents indicated that their respective state’s herbicide complaint procedure was not helpful in recovering damages. None of the 34 respondents who answered the question about receiving compensation for herbicide damage in the past seven years indicated that they were compensated.
The most important sources for grape growers to receive information for management, identification, or other advice related to drift issues are extension services, other growers, and grower associations (Table 5).
| Sources | Have not used | Used but not helpful | Used and was helpful | Responses |
|---|---|---|---|---|
| Grower association or advocacy group | 59% | 4% | 37% | 46 |
| Ag retail business (spray applicators) | 71% | 13% | 16% | 45 |
| Another grower/farmer | 38% | 10% | 52% | 48 |
| State agency (e.g., state department of agriculture or state chemist’s office) | 71% | 6% | 23% | 48 |
| Chemical company rep, hotline, or website | 76% | 9% | 15% | 46 |
| County or state extension service | 33% | 2% | 65% | 48 |
| Private crop consultant | 80% | 2% | 18% | 44 |
| Lawyer | 88% | 5% | 7% | 42 |
Conclusion
Herbicide drift can be an issue, particularly for sensitive crops such as grapevines, which have been determined to have an extreme sensitivity based on visual damage symptoms relative to other crops (Culpepper et al. 2018). Herbicides will continue to be used to manage unwanted weeds across several management systems near vineyards. The key to managing the amount of herbicide drift cases is education and communication – from both the applicators as well as the vineyard owner/manager. Penn State Extension and other land grant extension institutions can help with technical advice and education. However, communication with neighbors is important to mitigate future herbicide drift incidents.
Resources and further reading
- Pennsylvania Department of Agriculture
- Bureau of Plant Industry
- PAPlants
- Herbicide Drift and Drift Related Damage
- Burndown Herbicides, Drift, and Vineyards
- Pennsylvania Agricultural Mediation Program Page at Penn State Ag Law
- Herbicide Injury and the Problem of Spray Drift
References
Brown C. 2022. Survey results resources. Herbicide Drift Risk Management for Specialty Crops. The Ohio State University. September 2, 2022.
Culpepper S, Smith J, and J Prostko. 2018. Dicamba and 2,4-D Visual Sensitivity Scale for Georgia in 2018. University of Georgia Extension.
Sosnoskie LM, Culpepper AS, Braxton LB, and JS Richburg. 2015. Evaluating the Volatility of Three Formulations of 2,4-D When Applied in the Field. Weed Technology 29: 177-184.
This data and article is possible due to funding from the Pennsylvania Liquor Control Board and support from the Pennsylvania Wine Marketing and Research Program. The authors are grateful for the funding and support.
