Conditions Affecting Herbicide Control of Grasses
Candice Prince
Aquatic Weed Control Short Course 2018
Grasses and Varying Environments
• Many problematic grasses are able to tolerate a wide variety of environmental conditions
Environment and Herbicide Efficacy
• Environmental conditions prior to, during, and after herbicide application affect efficacy• Direct: absorption and translocation
• Indirect: growth and physiology
From Tao et al. 2016
Factors affecting herbicide efficacy
• Leaf traits affect how much herbicide is taken up by plants
• Cuticle width
• Leaf number and size
• Leaf angle From Tao et al. 2016
Benjamin Cummings
Ben Himme
Factors affecting herbicide efficacy
• Plants that are not actively growing may see limited translocation ofsystemic herbicides
• Photosynthetic rate
Brian Hazell
Factors affecting herbicide efficacy
• Biomass can affect management success in rhizomatous species
• Root to shoot ratios
• Regrowth potential
Delaware Invasive Species Council
Jailisse Knowles
Chis Evans, Bugwood.org
Effects of Flooding
• Tolerance varies with species
• ↓ leaf area
• ↓ photosynthesis (can recover in flood tolerant species)
• May initially limit number of leaves exposed to herbicide applications
Flooding
• Flooded conditions may limit herbicide efficacy in torpedograss (Quincy et al. 2018)
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Flooding
• Flooded conditions may limit herbicide efficacy in torpedograss• Translocation issue?
Greg MacDonald
Effects of Drought
•Upright leaf angle
•↓ photosynthesis, growth
•↓ leaf area, leaf number
•↑ leaf cuticle thickness• Composition of cuticle can
change →more hydrophobic
Ben Himme
Benjamin Cummings
Drought
• Water-stress has decreased efficacy of ACCase-inhibiting herbicides for certain grass species (Pereira 2010, Pereira et al. 2011)
• Goosegrass• Plantain signalgrass
John D. Byrd, Bugwood.org
Effects of Salinity
• Tolerance varies with species
• ↓ photosynthesis, growth
• ↓ leaf area, leaf number
• ↑ leaf thickness
• ↑ root:shoot ratios
Jailisse Knowles
From Tao et al. 2016
Salinity
• Salinity decreased efficacy of glyphosate and imazapyr in torpedograss, not in phragmites (more salt tolerant) (Prince et al. 2018)
Saline (15 ppt) Freshwater (0.7 ppt)
Torpedograss treated with glyphosate (4 lb. a.i./A)
Effects of Light
• High light:• ↑ photosynthesis
• ↑ leaf thickness and cuticle development
• Low light:• ↓ leaf thickness
• ↑ leaf area
• ↓ leaf number
• ↓ photosynthesis
• ↓ root:shoot ratios
Jailisse Knowles
From Tao et al. 2016
Light
• Shade has been shown to increase injury by contact herbicides (Mellendorf et al. 2015, Thompson and Nissen 2002)
•Higher light intensity may increase injury by systemic herbicides (Varanasi et al. 2016)
Effects of High Temperature
•↑ cuticle permeability
•↓ photosynthesis
•↓ biomass
•↓ leaf area
Brian Hazell
Ben Himme
Temperature
• Mixed effects, species dependent
• Increased effects in some grasses (johnsongrass, bermudagrass) → increased absorption of herbicide (Jordan 1977; McWhorter and Azlin 1978)
• Decreased effects in others (large crabgrass, green foxtail), → greater metabolism, volatilization of herbicides, or other changes (Smeda and Putnam 1990; Johnson and Young 2002)
Effects of CO2
• ↑ leaf thickness
• ↑ photosynthesis (C3 species)
• ↑ root:shoot ratios
Jailisse Knowles
Ben Himme
Current Climate Conditions
Climate Change Conditions
Hei
ght
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)Climate Change
• Increased temperature and atmospheric [CO2] may reduce herbicide efficacy in certain grasses, like phragmites (Prince et al. 2017)
Take-Away:
• Consider the environmental conditions when planning, try to apply when growing conditions are ideal
• Flooding→may decrease efficacy
• Drought→may decrease efficacy
• Salinity→may decrease efficacy
• Light→ depends on herbicide (contact vs. systemic)
• Temperature→ depends on species
References• Johnson, B.C., Young, B.G. 2002. Influence of temperature and relative humidity on the foliar activity of mesotrione.
Weed Science, 50:157-161
• Jordan, T. N. 1977. Effects of temperature and relative humidity on the toxicity of glyphosate to bermudagrass (Cynodondactylon). Weed Science, 25: 448-451.
• McWhorter, C. G., Azlin, W. R. . 1978. Effects of environment on the toxicity of glyphosate to johnsongrass (Sorghum halepense) and soybeans (Glycine max). Weed Science, 26: 605-608
• Mellendorf, T.G., Young, J.M., Matthews, J.L., Young, B.G. 2015. Influence of application variables on the foliar efficacy ofsaflufenacil on horseweed (Conyza canadensis). Weed Science, 63:578-586
• Pereira, M.R.R., 2010. Efeito de herbicidas sobre plantas de Brachiaria plantaginea submetidasa estresse hı´drico. Planta Daninha, 28: 1047–1058
• Pereira, M.R.R., Souza, G.S.F., Martins, D., Melhoranc¸a Filho, A.L., Klar, A.E., 2011. Respostas de plantas de Eleusine indica sob diferentes condic¸o˜es hı´dricas a herbicidas inibidores da ACCase. Planta Daninha, 29: 397–404
• Prince, C.M., MacDonald, G.E., Erickson, J.E. 2017. Phragmites australis management in Florida under climate change conditions. Presentation for the Florida Weed Science Society Annual Meeting. Haines City, Fl.
• Prince, C.M., MacDonald, G.E. 2018. Effects of salinity on herbicide efficacy for two grass species. Presentation for the Florida Weed Science Society Annual Meeting. Haines City, Fl.
• Quincy, K., Enloe, S., Netherland, M. 2018. The influence of water depth on herbicide efficacy for torpedograss (Panicum repens). Presentation for the Florida Weed Science Society Annual Meeting. Haines City, Fl.
• Smeda, R.J., Putnam, A.R. 1990. Influence of temperature, rainfall, grass species, and growth stage on efficacy of fluazifop. Weed Technology, 4:349-355
• Thompson, W.M., Nissen, S.J. 2002. Influence of shade and irrigation on the response of corn (Zea mays), soybean (Glycine max), and wheat (Triticum aestivum) to carfentrazone-ethyl. Weed Technology, 16: 314-318
• Varanasi, A., Prasad, P.V.V., Jugulam, M. 2016. Impact of climate change factors on weeds and herbicide efficacy. Advances in Agronomy, 15: 107-146