By: Bonnie L. Grant, Certified Urban Agriculturist
Herbicide plant damage can arise in a variety of forms. It is usually the result of unintentional contact with chemicals from spray drift or contact with vapor. Recognizing accidental herbicide injury may be difficult as the symptoms can mimic other plant conditions. Know the classic signs and learn how to treat plants accidentally sprayed with herbicide.
The type of injury can be determined by the time symptoms begin to show. Problems that appear right after new plants begin to germinate are often the result of carry-over from previous applications, high rates of application, shallow planting and even poor timing.
Herbicide plant damage that appears on mature plants may be due to drift, misapplication, high temperatures or humidity, incorrect treatment and tank contamination. The home gardener will usually notice accidental herbicide injury on mature plants due to misapplication and timing.
The signs of injury will depend on the type of herbicide which contacted the plant. Post-emergence broadleaf herbicides are responsible for most injuries. These result in twisted leaves, cupped foliage, narrower new leaves, and roots that appear on the surface in annual plants. On ornamental grasses, these products cause yellowing and die back.
Pre-emergence controls are not as dangerous and herbicides that are applied systemically rarely result in problems unless they are over-applied. The exceptions are herbicides that have amine salt, which allows the chemical to liquefy and travel more easily through soil.
Non-selective herbicides will cause accidental herbicide injury in many instances and these controls must be applied according to directions and with caution. Symptoms of herbicide injuries from these products include yellowing in leaves, die back and general ill health in plants that might have been exposed. In some cases, fixing herbicide spray drift is possible if it is caught early enough.
Contact non-selective herbicide injury is usually most evident in the leaves. A foliar method is used for application, which increases chances of drift. Plants accidentally exposed should have affected leaves pruned off to prevent the spread of the herbicide deep into the plant. It may also help to water the plant thoroughly to dilute the chemicals. If left untreated, the plant will eventually die.
Plants exposed to other chemical formulas may survive if you give them superior care for the next year. Keep the plant watered properly, fertilize in spring and prevent competition from weeds. If no other factors, such as disease or insects, are affecting your plant, then your leafy friend may outlive you.
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Cleaning up persistent weeds in the garden may require the use of a nonspecific herbicide, such as Roundup. While you're careful, accidents happen and if an overspray gets on your hydrangea, you'll have to act quickly to prevent the active ingredient in Roundup, glyphosate, from damaging the plant. Hydrangeas (Hydrangea spp.) are medium to large shrubs, hardy in U.S. Department of Agriculture plant hardiness zones 4 through 9.
High winds, blowing dust and low humidity can damage the leaves and stems on tomato plants. Injury is similar and is often confused with drift damage from phenoxy-type herbicides (Fig. 6). Heat and low moisture can cause the edges of the tomato leaves to die back, then twist and curl.
Hot dry weather may also cause a symptom called physiological leaf roll. This is a self defense response, where leaves and leaflets curl slightly to prevent further water loss (Fig. 7). Mild leaf roll generally does not lower yields or quality, though severe symptoms may cause flowers to drop and fewer fruit to set.
These symptoms may look like damage from other causes, but if wind damage is the only problem, plant health will generally normalize once weather conditions improve.
Kelsey Deckert, Horticulturist, Morton/Burleigh Counties
July 6, 2020
Herbicide Injury on Plants
Are the leaves on your tomato plants curling up tightly? Are you seeing cupping of leaves on trees? If you are seeing these symptoms or distorted/deformed leaves of plants, you most likely are seeing the effects of herbicide injury.
Herbicide injury, especially on garden plants, have been very prevalent the past couple weeks in this area. Many homeowners want to achieve the perfect, weed-free, manicured lawns. In doing so there may be accidental drift onto garden plants or trees. Tomatoes and potatoes are very sensitive to herbicide injury are typically are the ones first noticed with issues in a garden.
I often hear I didn’t spray for any weeds. If that is the case there are other sources that can contribute to herbicide injury. Other sources could be grass clippings used as a mulch from a lawn that has been sprayed, neighbors or farmers spraying nearby, compost, manure, and even animals that have tracked on an area that has been sprayed can bring herbicide into a garden.
Unfortunately, there isn’t anything that can be done with plants that have herbicide injury. Trees can tolerate an accidental spraying. Garden plants should be discarded.
For more information, contact:
Kelsey Deckert, Extension Agent - Horticulture
Burleigh/Morton County Extension (701) 221-6865 or (701) 667-3340
Have you noticed your tree, or trees, going into an unreasonable state of decline or seem to be stunted? Do you notice leaf curling or leaves that look cupped? Perhaps leaves are discolored or have brown dead spots? Your trees could be victims of herbicide damage. Even if you keep an organic landscape, your neighbors may not. If your neighbors have used an herbicide or weed & feed on their property, your trees could be collateral damage. It’s always good to talk with neighbors about what treatments they apply to their property that can affect yours.
Some herbicides are selective some aren’t. Selective herbicides are formulated to kill specific plants. Non-selective herbicides will damage or kill any vegetation they come in contact with. If herbicides are not applied properly and under the right conditions, your trees or landscape can fall victim to a neighbor’s herbicide treatment. Applying herbicides on a windy day can result in the chemicals drifting onto your property. Or, if they are applied on an exceedingly warm dry day, the chemicals can become volatile (vaporize into the air through evaporation). For example, if your neighbor has been using Roundup regularly to kill weeds near your trees, it could drift or become volatile, causing damage to your plants when it comes in contact with their leaves.
Weed & Feed products are a common silent killer of trees. Many contain the chemical atrazine, which shuts down the sugar making process of susceptible plants. One absorbed, the plant can no longer feed itself. For small weeds, the kill happens quickly. Large trees can often tolerate one application of such a project and have time to flush it from their systems before permanent damage is done. However, that depends on the time the product is applied and how often. They’re often applied in spring, which is the worst time for your trees. Atrazine will most hurt your trees as they are pushing out their new spring growth. While a large mature tree can tolerate one application of such a product annually, more applications can lead to the tree’s death. So, if your neighbor is putting down weed & feed and it comes in contact with your tree’s roots, you could have a serious problem.
Diagnosing herbicide damage on trees can be very tricky. Often, symptoms may appear similar to other pest or disease issues. An experienced arborist will look for many different factors to determine if your tree was damaged by herbicides.
There are a variety of herbicides that could negatively affect your trees. Here are a few of the most common ones.
Phenoxy herbicides: This includes products that contain 2,4-D. They cause curling of stems and leaves. After abnormal growth, leaves will appear chlorotic (yellowing) and necrotic (browning). Affects broadleaf plants.
Paraquat: Causes burning and necrosis on plants that they come in contact with. If spray drift is minor, affected plants may only be spotted with necrotic tissue on their leaves. Affects many types of vegetation.
Glyphosate is the main ingredient in Round-up and Kleen-up. When applied it causes yellowing, wilting, and browning of the leaves with death being the eventual outcome. Some trees or large shrubs, when sprayed, may not show injury until the following season, but will then appear stunted and chlorotic. Glyphosate is a non-selective herbicide that can damage your trees when it comes in contact with foliage through drift or evaporation.
Atrazine, Simazine and others are applied as weed & feed products or directly to the soil around driveways, fences and sidewalks to stop weeds. They move very slowly through the soil and can be absorbed by your tree’s roots. Symptoms of damage sometimes may not show up for a year. You’ll notice a slight yellowing and chlorosis around the margins and veins of the leaves. Healing from this type of herbicide damage can take years.
If you are trying to reduce the use of chemicals in your life, the landscape is a great place to start. Ready to be more eco-friendly for your family, pets and the environment? Give us a call to learn about our year-round fertilization SEASONS Program. We can also have the soil tested in your landscape so we’ll know exactly what your trees and plants need to thrive.
Categories: Conservation, Organics
Tags: Conservation, Dallas, Organics, Preservation, Roots, Urban Trees
Posted: December 1, 2014
Here is a summary of herbicide injury scenarios in soybeans (glyphosate tolerant), white beans, kidney beans and adzuki beans showcased at the South West Crop Diagnostic Days in Ridgetown on July 6th and 7th, 2011.
From left to right: soybeans, white beans, kidney beans, adzuki beans
Sandea (halosulfuron) is currently not registered in Ontario. Above is a post-emergent application of the 70 g ai/ha rate of Sandea, which represents an overlap rate (2X) of the product. Note that soybeans and adzuki beans are significantly affected (or perhaps dead is a better description). The white and kidney beans on the other hand are slightly stunted. The intended use of this product will be in certain market classes of edible beans (clearly not adzuki beans), and most likely applied prior to crop emergence. Sandea is a sulfonylurea herbicide (group 2) and the soybeans best show the characteristic reddish/brown veins on the underside of leaf tissue, along with stunting (see below).
sulfonylurea (group 2) injury in soybean, note the reddish/brown leaf veins.
Scenario 2: Broadstrike RC (flumetsulam) applied postemergence
From left to right: adzuki beans, kidney beans, white beans, soybeans
This scenario illustrates two significant points. The first is that Broadstrike RC is not registered in edible beans at all and for good reason as edible beans are extremely sensitive to most sulfonylurea herbicide when applied postemergence. In scenario 1, you’ll recall that we saw the typical “group 2” injury that caused brownish/red veins on the underside of leaves. Other common “group 2” herbicide injury symptoms include yellowing and distortion of leaf tissue along with stunting.
Yellowing and stunting of white beans typically caused by post emergent "group 2" herbicides
Secondly, Broadstrike RC should only be applied to soybeans prior to their emergence. This application was mistakenly made at the unifoliate stage. Although the soybeans will not die, there was a significant amount of leaf distortion and yellowing.
Injury caused by Broadstrike RC applied to emerged soybeans, an off-label application causing significant leaf distortion and yellowing.
Scenario 3: Valtera + Dual II Magnum applied prior to bean emergence
From left to right: soybean, white bean, kidney bean, adzuki bean
In this scenario Valtera (flumioxazin – group 14) + Dual II Magnum (s-metolachlor/benoxacor – group 15) was applied at an overlap rate (2X field rate). Edible beans are quite sensitive to flumioxazin so it is not surprising to see the level of crop injury shown above. Both herbicides are registered for use in soybeans when applied prior to emergence. However combining these two products in a tank-mix dramatically increases the potential for Valtera injury (see below). There are several other factors that increase the potential for severe flumioxazin injury and were discussed in a previous post.
Severe crop injury as a result of water ponding after an application of Valtera
Scenario 4: The cumulative affect of mixing herbicides from the same chemical group
From left to right: adzuki beans, kidney beans, white beans and soybeans
Eragon (saflufenacil – group 14) was tank-mixed with Valtera (flumixoazin – group 14) and applied at the field overlap rate (2X field rate) prior to bean emergence. Then at the first trifoliate stage, Reflex (fomesafen – group 14) was applied. This scenario illustrates how we can compromise a plant’s ability to metabolize a specific mode of action by over-whelming it with multiple herbicides that all affective the same site of action. Although, in this case we targeted group 14 herbicides, the impact to the crop would be similar had we combined 3 “group 2” herbicides. Simply put, a plant can only handle so much. Below is another example of severe “group 14” herbicide injury.
The combination of applying Eragon + Valtera prior to crop emergence and Reflex post crop emergence lead to severe group 14 injury as the plant could not adequately metabolize all that was thrown its way.
Scenario 5: I can’t keep these co-packs straight!
The number of combination or “co-packs” in glyphosate tolerant crops is pretty overwhelming, and they all seem to have similar names (and oddly all starting with the letter “G”). The image below illustrates a mistake where a corn herbicide co-pack of glyphosate + Elim (rimsulfuron – group 2) was inadvertently sprayed on soybeans. The below image shows perfectly the injury symptoms of stunting, yellowing and reddish/brown veins that one will see with severe sulfonylurea injury in soybean.
Stunting, yellowing and reddish/brown leaf veins from severe "group 2" herbicide injury, in this instance caused by mistakenly applying rimsulfuron, a corn herbicide.
Scenario 6: By sure to follow application instructions on the label.
The below image is a perfect depiction of hormonal herbicide injury on soybeans, particularly when the herbicide has been applied to the soil prior to crop emergence.
Typical leaf distortion as the result of 2,4-D applied prior to soybean emergence but ignoring the 7-10 day pre-plant interval.
In the United States, a glyphosate + 2,4-D Ester application made 7 days prior to soybean planting is a pretty standard treatment in both “Roundup Ready” and non-GMO soybeans. The potential to see the crop injury shown in the image above depends largely on 3 factors. The first and most important is the interval between herbicide application and soybean planting. In the U.S. a minimum interval of 7 days is required. The second factor is 2,4-D formulation as the Ester formulations do not persist in the soil as long as the amine formulations and therefore Ester formulations should always be used. Lastly, the higher the rate, the greater the risk. In Ontario, research conducted by the University of Guelph has shown acceptable soybean tolerance to pre-plant applications of 2,4-D Ester (660 g/L) at 400 mL/ac. In this scenario all three factors were ignored and injury occurred.
Scenario 7: Do NOT apply Eragon to emerged soybeans!
Eragon (saflufenacil – group 14) is a fast acting herbicide that is quite effective on annual broadleaf plants and is only registered for use on soybeans and corn when applied prior to crop emergence. Therefore it is logical that if you were to apply it to emerged beans that severe crop injury occurs (see below). This also applied to Valtera (flumixazin – group 14) and Guardian Plus (glyphosate + Classic + Valtera). It should also be noted that edible beans are extremely sensitive to saflufenacil even when applied prior to crop emergence.
Severe injury as a result of Eragon (saflufenacil) being applied after soybean emergence, a non-registered application timing.
Scenario 8: If the crop is up and you still want to use your preemergence herbicide, think again!
Just because a herbicide can be applied before and after crop emergence in one crop (e.g. corn) does not mean the same applies in soybeans and edible beans. Below is a picture of Dual II Magnum injury to soybeans when applied at the unifoliate stage. Note the two different types of injury symptoms. The speckling of the unifoliate leaves most likely caused by the “emulsified concentrate” product forumlation and the other is the “draw-string” leaf distortion of the soybean leaflets caused by the herbicides active ingredient (metolachlor).
"Draw string" leaf distortion caused by metolachlor and speckling of the unifoiate leaves casued by the "emulsified concentrate" formulation of Dual II Magnum.
Scenario 9: Cumulative stress
The photo below shows off-target drift by a “bleaching” herbicide, in this case Callisto (mesotrione – group 27) onto white beans.
The virbant white/yellowing of leaf tissue caused by off-target Callisto drift.
Drift injury is sometimes made worse when certain herbicides are applied to the crop after the drift event occurs and has been documented in the literature. In this particular case, the in-crop application of Basagran (bentazon) that occurred 3 days after application, dramatically increased the severity of bleaching injury. In the photo below, although the entire plot received an off-target drift of Callisto, only the front part of the plot received the in-crop application of Basagran. The injury is less severe where Basagran was not applied.
Off-target callisto drift made worse when basagran was applied 2 days later but to only the front half of the plot area