Use of pre-emergence (soil applied) and post-emergence (burndown) herbicides are standard practice for maintaining early season weed control in most apple orchards in the Northeastern United States. There is good evidence to show that maintaining a weed free strip from May through July improves both tree growth and yield (Breth 2014). Standard herbicide applications are typically made to achieve full coverage of the weeded strip, which can result in herbicide contacting the tree trunk. While single-season studies have shown no significant impact of glyphosate or other post-emergence herbicide use over the course of a single season (Breth & Tee 2013), others have reported long term effects on tree health from repeated use of glyphosate, glufosinate, or paraquat (the most commonly used post-emergent materials). For example, glufosinate injury has been implicated in the death of the cambium layer in the year following the application (Majek 2014). Similarly, glyphosate use has been correlated with decreased winter hardiness and increased Botryosphaeria canker infections (Rosenberger et al 2013), and in some instances with decreased trunk diameter (Chandran 2015).
There are a number of practices a grower can use to reduce herbicide contact to the tree trunks within the orchard.
One way to prevent tree damage is to carefully follow herbicide label directions, including all warnings and mitigation practices intended to reduce the risk of crop injury. Herbicide labels frequently specify minimum tree age requirements and caution against contact with green plant tissue, including immature bark and root suckers. Systemic herbicides such as glyphosate or 2,4-D should also not be applied immediately after cutting suckers, as the freshly cut stems can readily absorb the product.
Pre-emergence herbicide applications made during tree dormancy can reduce trunk injury risk in the long term, by suppressing weed emergence and thereby decreasing the need for post-emergence applications. Pre-emergence herbicides should be selected based on the weed species present within the field you are planning to treat. It is often helpful to tank mix pre-emergence herbicides to extend the range of species controlled. To help choose your herbicides, you can review Cornell's herbicide efficacy table at the following link: https://enych.cce.cornell.edu/submission.php?id=984&crumb=crops|crops|apples|crop*38
We cannot overstate the importance of good sprayer calibration. The risk for trunk injury increases as herbicide concentrations increase. The risk of tree injury can therefore be reduced by ensuring the sprayer is properly calibrated with even spray distribution.
The use of a shielded boom can also minimize herbicide contact with the trunk. Shielded sprayers will also minimize bounce-back from bare soil that sometimes allows a haze of small droplets to drift upward into the canopy. When making herbicide applications with any boom sprayer, keep the pressure as low as possible (no more than 30 psi) to minimize small droplets generation. If that is not feasible, use air-induction nozzles.
Many existing herbicide boom sprayers can likely be retrofitted with a shield or hood, but a few companies manufacture shielded sprayers that may be worth considering. Some companies include:
- MiCRON: https://www.micronweedmanagement.com/en/spray-dome
- Eastern Manufacturing: https://easternmfg.ca/herbicide-sprayer/
Weather at the time of application is also an important consideration. Previous studies (Rosenberger 2014) have cautioned that the risk for trunk damage increases when herbicide applications are made during or just prior to periods of drought stress. Herbicide physical drift and vaporization is more likely to occur on hot, windy days with low humidity, when spray droplets evaporate more quickly and are easily carried by the wind.
Even when best management practices are followed, there is still a risk of herbicides reaching the trees. Growers can use various physical barrier materials to further reduce herbicide contact with trunks, such as painting with latex, Tyvek or milk carton guards, grow tubes, or short pieces of drainage pipe (Mitchem, 2017). From 2021 to 2023, we evaluated the effectiveness of Tyvek sheets used as trunk guards as part of an ARDP-funded project. In an August 2021 trial, half of the trees at each of two field sites (one in Western and one in Eastern New York) were protected by a 10x10 inch sheet of Tyvek stapled around the base of the trunk, while the other half were not (serving as a control). Then, eight strips of water sensitive paper were attached to trunks of ten trees each at each field site. The water sensitive strips were placed vertically from 0-3, 3-6, 6-9, and 9-12 inches above the soil line, on both the east (facing towards the sprayer) and south (facing within the tree row) sides of the trunks. On the trees with Tyvek tree guards, water sensitive strips were attached under the guards. Herbicides were applied with the cooperating growers’ standard herbicide boom sprayers. All strips were then collected, fixed to a sheet of paper, and scanned. ImageJ was utilized to assess percent coverage of strips.
Tyvek trunk guards greatly reduced herbicide deposition on tree trunks at both study sites. In eastern NY, deposition decreased from 7.54% on unguarded trunks to 0.06% on guarded trunks, representing a 99% reduction (P = 0.008). Similarly, in western NY, deposition decreased from 26.76% on unguarded trunks to 0.56% on guarded trunks, a 98% reduction (P = 0.0125).
Herbicide Deposition Reduction by Tyvek Trunk Guards | ||||
Site | Deposition with Guard | Deposition without Guard | Reduction in Trunk Spray Deposition Provided by Guard | P-value |
Eastern NY | 0.06% | 7.54% | 99% | 0.008 |
Western NY | 0.56% | 26.76% | 98% | 0.0125 |
Despite the reduction in herbicide deposition, we did not observe differences in tree growth or health from the use of trunk guards during the three-year study. We did observe more woolly apple aphids under the guards in Western NY.
In a follow-up study, we evaluated several methods for protecting trunks in newly planted orchards in eastern and western New York. Treatments included wrapping trunks with Tyvek sheets, painting trunks with white latex paint, or leaving trunks unprotected as a control. The orchards were managed using the host farms’ conventional herbicide programs. Tree growth, survival, and canker incidence have been monitored from spring 2022 through fall 2025.
To date, we have not observed differences in tree growth among treatments. However, in the eastern New York site we observed a higher incidence of cankers in the unprotected control trees (43%) compared with trees protected with Tyvek guards (25%) or white latex paint (11%), although these differences were not statistically significant.
Similar studies have been conducted in other regions of the United States. Hill et al. (2013) found latex paint reduced stunting from glufosinate in newly planted hazelnut trees compared to unshielded trees. Painted trees exhibited greater trunk growth and approximately 50% less trunk damage compared to unshielded trees. Trunk guards provided even greater protection but reduced wood density and increased bark sensitivity to sunburn and chemical injury upon removal. These findings suggest that guards should remain in place until trees are well established, or that several weeks should be allowed between guard removal and subsequent herbicide applications to allow the bark to harden.
Walter and Lightle (2018) compared different lengths of time between removing trunk guards and applying latex paint before spraying. They found that painting green almond trunks immediately after carton guard removal provided little protection against trunk damage from glyphosate and glufosinate applications in California. Painted trees had similar or greater trunk damage and canopy stress than unpainted trees that were allowed to harden off for nine weeks prior to herbicide application. Trees that still had cartons attached had lower stress than unpainted or painted tress. The authors concluded that cartons provide the best protection in young trees, but if removed as trees mature, growers should wait more than nine weeks before any subsequent herbicide application to allow bark to harden properly.
Emerging Technology
More advanced technologies, such as vision-guided spraying systems, may allow growers to reduce the amount of herbicide applied in orchards and further lower the risk of crop injury. An IR-4 project conducted by Lynn Sosnoskie and Thierry Besançon evaluated the WEED-IT spray system, which uses optical sensors to detect chlorophyll (the green pigment found in plants’ leaves and young bark) and activate nozzles only where vegetation is present, rather than spraying continuously across the entire field. While this technology has been tested in grapes and blueberries, it could be adapted to orchards. This technology will be most effective when combined with a good dormant pre-emergence herbicide program, as lower weed pressure reduces the frequency of nozzle activation events and, consequently, the cumulative risk of herbicide contact with trunks.
In summary, carefully follow herbicide label directions, including all crop protection warnings. Make good use of pre-emergence herbicides during tree dormancy to reduce your starting weed pressure so as to be less reliant on burndown herbicides later in the season. Ensure your sprayer is properly calibrated and functioning correctly to minimize the risk of tree damage. While labor intensive, applying physical barriers around the trees, like white latex paint, milk cartons, or Tyvek guards, can further reduce herbicide deposition. Shielded or hooded sprayers can reduce herbicide contact with the trunks further, and vision-guided spray systems may allow growers to apply fewer post-emergence herbicides to their orchards. As with any IPM program, combining multiple tactics provides the greatest risk reduction.
References
Besançon T. 2021. About the safe use of glufosinate and glyphosate herbicides in apple and peach orchards. Rutgers Cooperative Extension Pest and Plant Advisory. 29 Jun 2021.
Breth DI, Tee E. 2013. New findings in weed control in young apple orchards. New York Fruit Quarterly. 21(4):13–18.
Breth DI. 2014. Critical weed control requirements in high density apple orchards. New York Fruit Quarterly. 22(4):5–9.
Chandran RS. 2015. Effect of glyphosate application rates, timings, and formulations on apple trees. International Journal of Tropical Agriculture. 33(2 Pt III):1329–1330.
Hill RJ, King DR, Moretti ML. 2023. The prevention of herbicide injury to hazelnut trunks [Internet]. WSU Small Grains; [accessed 2026 Feb 10]. Available from: https://smallgrains.wsu.edu/weeders-of-the-west/2023/01/26/protecting-h…
Majek B. 2014. Glufosinate products, sold as Rely 280, expand as generic products enter the market. Rutgers Cooperative Extension Pest and Plant Advisory. 27 Jun 2014.
Mitchem WE. 2017. Weed management considerations for peach orchards [Internet]. Raleigh (NC): North Carolina State University Cooperative Extension; [accessed 2026 Feb 9]. Available from: https://peaches.ces.ncsu.edu/wp-content/uploads/2017/02/weedmanagement…
Osipitan OA, Yildiz-Kutman B, Watkins S, Brown PH, Hanson BD. 2020. Impacts of repeated glyphosate use on growth of orchard crops. Weed Technology. 34(6):888–896.
Rosenberger D, Watkins C, Miranda-Sazo M, Kahlke C, Fargione M, Nock J, Rugh A. 2013. Effects of glyphosate on apple tree health. New York Fruit Quarterly. 21(4):23–27.
Rosenberger D. 2014. Apple summer diseases, herbicide problems, and irrigation [Internet]. Highland (NY): Tree Fruit Diseases: Observations and Archives; [accessed 2026 Feb 10] Available from: https://blogs.cornell.edu/plantpathhvl/2014/06/30/apple-summer-diseases…
Walter D, Lightle D. 2019. Can trunk paint mitigate herbicide damage in young almond trees? [Internet]. Davis (CA): University of California Agriculture and Natural Resources; [accessed 2026 Feb 10] Available from: https://ucanr.edu/blog/uc-weed-science-weed-control-management-ecology-…