Crop injury can occur when an insecticide application predisposes a plant to phytotoxicity from a subsequent foliar herbicide application. However, these products do not normally result in crop injury when applied individually. These interactions are caused by a reduction in the crop’s ability to metabolize these pesticides and/or environmental conditions that result in plant stresses that impact crop growth and development. Typically, pesticide labels provide a warning to growers about these potential interactions and what pesticide product combinations should be avoided. This article discusses herbicide products that can cause crop injury if applied following an at-plant pesticide or applied in a tank mixture with another pesticide.
Weed control in most cropping systems is typically achieved using herbicides. In some cases, crop injury may occur after herbicide applications if environmental conditions are unfavorable for crop growth and development. For example, if conditions are cold and wet following herbicide application, metabolic breakdown of the herbicide within the crop plant will be slowed, resulting in injury to the crop. Insecticides can also interfere with pathways responsible for herbicide metabolism in the plant. For example, applications of malathion insecticide decreased the activity of the p450 enzyme, which is responsible for the breakdown of the herbicide primisulfuron (Beacon®) in corn.1 Other studies have shown similar foliar and root response in corn when an ALS-inhibiting herbicide (e.g., chlorimuron [Classic®], nicosulfuron [Accent®], primisulfuron [Beacon®]) was applied postemergence after an at-plant in-furrow application of terbufos (Counter®).2 In soybean, application of either phorate (Thimet®) or aldicarb (AgLogicTM) insecticides in-furrow at-planting increased plant injury when applied in combination with the herbicide metribuzin (Metribuzin 75DF®) applied preemergence.3,4 The soybean injury observed in this study was on varieties that were normally tolerant to preemergence applications of metribuzin.
Pesticides are often combined or tank-mixed in a single spray application. Similar to the precautions described earlier on postemergence herbicides applied after an at-plant insecticide, tank mixing herbicides with an insecticide for postemergence foliar applications can result in crop damage. Studies have shown that postemergence foliar applications of primisulfuron tank-mixed with an organophosphate (OP) insecticide (e.g., chloripyrifos [Lorsban®]) resulted in foliar injury, plant height reductions, and yield losses in corn.5 In soybean, thifensulfuron (Harmony SG®) herbicide in tank mixes with the OP insecticides, such as malathion or chlorpyrifos, resulted in moderate to severe crop injury ranging from 40 to 82% of the leaf surface. Significant injury was also observed when thifensulfuron was tank mixed and topically applied with a carbamate insecticide, such as methomyl (Lannate®) or carbaryl (Sevin®).6
The herbicides in the HPPD inhibitor (group 27) family are relatively new on the market compared to the ALS-inhibiting herbicides (group 2) described previously. There are several herbicide products available for weed management in corn that contain the active ingredient mesotrione (e.g., Callisto®, Halex GT®, Harness MAX®, Realm Q®, Resicore®, Revulin Q®). Labels for these products specify that postemergence applications of mesotrione should be delayed by a minimum of 45 days following an at-plant application of an OP insecticide (e.g., terbufos). Isoxaflutole (e.g., Balance Flexx®) and tembotrione (e.g., Laudis®) herbicides also contain warnings on use with at-plant and postemergence insecticides. Research has shown that a postemergence application of mesotrione following an at-plant application of terbufos resulted in a crop injury rating of 34%.7 A similar study in Tennessee showed that tembotrione herbicide (group 27) applied postemergence in a tank mixture with chlorpyrifos resulted in a crop injury rating of 56% and reduced yield by over 50%.8 A similar pattern was observed with in-furrow applications of chlorpyrifos followed by an HPPD postemergence herbicide application in corn.8
Guidelines on Using Herbicides with Insecticides
When applying ALS-inhibitor (group 2) or HPPD-inhibitor (group 27) herbicides, observe either the at-plant or tank mix restrictions stated on the label when applying OP or carbamate insecticides. For example, if OP insecticides were applied during crop planting (in-furrow), the herbicide products listed in table 1 are not recommended for postemergence use in-crop until after a specified waiting period. These herbicides listed in table 1 include flumetsulam (SureStart II®, Hornet®), nicosulfuron (Accent®, Revulin Q®, Steadfast Q®), mesotrione (Acuron®, Callisto®, Halex GT®, Harness MAX®, Realm Q®, Resicore®, and Revulin Q®), tembotrione (Laudis®), and rimsulfuron (Realm Q®, Resolve Q®, Steadfast Q®). In addition, tank mixing those herbicides with a foliar OP/carbamate insecticide is not recommended. Applicators should follow the guidelines listed on the label for each product between the herbicide and insecticide applications (table 1).
Table 1. Postemergence (POST) herbicide use precautions following either an at-plant soil organophosphate (OP)/carbamate insecticide or tank mixture with a POST OP/carbamate insecticide. Consult the respective product labels for the most current information.
|Active Ingredient(s)a||Herbicide Product(s)||POST Herbicide Following
At-Plant OP or Carbamate Insecticideb
|POST Herbicide Tank Mix with
POST OP Insecticidec
|ALS-inhibitors (Group 2)|
|flumetsulam||Hornet9, SureStart II10||Do not apply||Do not tank mix, wait 10 d between applications|
|nicosulfuron||Accent11||Do not apply||Do not tank mix|
|nicosulfuron + rimsulfuron||Steadfast Q12||Do not apply||Do not tank mix, wait 7 d before or 3 d after application|
|rimsulfuron + thifensulfuron||Resolve Q13||Do not apply within 45 d of terbufos (Counter®)||Do not tank mix, wait 7 d before or 3 d after application|
|HPPD Inhibitors (Group 27)|
|isoxaflutole||Balance Flexx14||Permitted||Do not tank mix, wait 7 d between applications|
|mesotrione||Acuron15, Callisto16, Halex GT17 Harness MAX18, Resicore19||Do not apply||Do not tank mix, wait 7 d between applications|
|tembotrione||Capreno20, Laudis21||Do not apply||Do not tank mix, wait 7 d between applications|
|mesotrione||Realm Q22, Revulin Q23||Do not apply within 45 d of terbufos||Do not tank mix with an OP, wait 7 d before or 3 d after application|
aThe herbicide active ingredients/products listed in this table have a specific warning concerning the high probability of a negative interaction with an insecticide applied either at-plant preemergence or in a tank mixture postemergence.
bExamples of at-plant OP/carbamate soil insecticides include terbufos (Counter®), aldicarb (AgLogicTM), or phorate (Thimet®)].
cExamples of foliar OP/carbamate insecticides include carbaryl (Sevin®), methomyl (Lannate®), or acephate (Orthene®).
- Potential crop injury can occur if ALS-inhibitor (Group 2) or HPPD-inhibitor (Group 27) herbicides are applied postemergence after an at-plant preemergence application of an OP or carbamate insecticide.
- Caution should be exercised when tank mixing certain herbicide and insecticide products due to potential negative crop response.
- Applicators should always consult and follow pesticide product label guidelines and precautions before planning a weed management program.
- Kreuz K, Fonne-Pfister R. Herbicide-insecticide interaction in maize: malathion inhibits cytochrome p450-dependent primisulfuron metabolism. Pesticide Biochemistry and Physiology. 1992;43:232–240. https://doi.org/10.1016/0048-3575(92)90036-Y.
- Kwon CS, Penner D. The interaction of insecticides with herbicide activity. Weed Technology. 1995;9:119–124.
- Hayes RM, Yeargan KV, Witt WW, Raney HG. Interaction of selected insecticide-herbicide combinations on soybeans (Glycine max). Weed Science. 1979;27:51–54.
- Waldrop DD, Banks PA. Interactions of herbicides with insecticides in soybeans (Glycine max). Weed Science. 1983;31:730–734.
- Biediger DL, Baumann PA, Weaver DN, Chandler JM, Merkle MG. Interactions between primisulfuron and selected soil-applied insecticides in corn (Zea mays). Weed Technology. 1992;6:807–812.
- Ahrens WH. Enhancement of soybean (Glycine max) injury and weed control by thifensulfuron-insecticide mixtures. Weed Technology. 1990;4:524–528.
- Jewett MR, Chomas A, Kells JJ, DiFonzo CD. Corn response to mesotrione as affected by soil insecticide, application method, and rate. Crop Management. 2008;7:1–7. https://doi.org/10.1094/CM-2008-1103-02-RS.
- Steckel LE, Stewart SD, Steckel S. Corn response to POST-applied HPPD inhibitor based premix herbicides with in-furrow and foliar applied insecticides. Weed Technology. 2015;29:18–23.
- AMVAC® Hornet Herbicide: Product label. [accessed 2023 Jan 31] 2020. p. 18. https://www.cdms.net/ldat/ld0AM000.pdf.
- Corteva™ Agriscience. SureStart II Herbicide: Product label. [accessed 2023 Feb 1] 2019. p. 7. https://www.cdms.net/ldat/ldBRC004.pdf.
- Corteva™ Agriscience. Accent® Q Herbicide: Product label. [accessed 2023 Jan 31] 2021. p. 9. https://www.cdms.net/ldat/ld3OS000.pdf.
- Corteva™ Agriscience. Steadfast Q herbicide product label. [accessed 2023 Feb 1] 2021. p. 8. https://www.cdms.net/ldat/ld3OU000.pdf.
- Du Pont™. Resolve® Q Herbicide: Product label. [accessed 2023 Feb 1] 2016. p. 16. https://www.cdms.net/ldat/ld8PT001.pdf.
- Bayer CropScience. Balance Flexx® Herbicide: Product label. [accessed 2023 Jan 31] 2020. p. 21. https://www.cdms.net/ldat/ld8QS019.pdf.
- Syngenta®. Acuron® Herbicide: Product label. [accessed 2023 Jan 31] 2021. p. 23. https://www.cdms.net/ldat/ldC9K007.pdf.
- Syngenta®. Callisto® Herbicide: Product label. [accessed 2023 Jan 31] 2018. p. 40. https://www.cdms.net/ldat/ld56N006.pdf.
- Syngenta®. Halex® GT Herbicide: Product label. [accessed 2023 Jan 31] 2016. p. 22. https://www.cdms.net/ldat/ld8DT001.pdf.
- Bayer CropScience. Harness® MAX Herbicide: Product label. [accessed 2023 Jan 31] 2021. p. 13. https://www.cdms.net/ldat/ld0R1004.pdf.
- Corteva™ Agriscience. Resicore® Herbicide: Product label. [accessed 2023 Feb 1] 2020. p. 10. https://www.cdms.net/ldat/ldCPQ000.pdf.
- Bayer CropScience. Capreno® Herbicide: Product label. [accessed 2023 Jan 31] 2019. p. 33. https://www.cdms.net/ldat/ld90D000.pdf.
- Bayer CropScience. Laudis® Herbicide: Product label. [accessed 2023 Feb 1] 2021. p. 29. https://www.cdms.net/ldat/ld8ET021.pdf.
- Corteva™ Agriscience. Realm® Q Herbicide: Product label. [accessed 2023 Feb 1] 2020. p. 8. https://www.cdms.net/ldat/ld2T9000.pdf.
- Corteva™ Agriscience. Revulin® Q Herbicide: Product label. [accessed 2023 Feb 1] 2021. p. 9. https://www.cdms.net/ldat/ld3OT000.pdf.