Neonicotinoid Insecticides for Ornamentals The Good, Bad and Ugly Catharine Mannion University of Florida, IFAS Tropical Research and Education Center
Neonicotinoids Insecticides • Acetamiprid • Use of these insecticides has grown • Clothianidin considerably since the • Dinotefuran forerunner of the group (imidacloprid) was first • Imidacloprid introduced in the early • Thiamethoxam 1990’s • Nitempyram • Seven neonicotinoid insecticides • Thiacloprid
Neonicotinoid Insecticides What do We Know • Systemic • Effective against sucking insects but also some chewing insects • Rates tend to be lower than traditional insecticides • Labeled as “Warning” or “Caution” • IRAC Mode of Action – 4A
Neonicotinoid Insecticides What do We Know • Act on the insect central nervous system • Mode of action is similar to that of nicotine • Both nicotine and neonicotinoids act on an acetylcholine receptor; but neonicotinoids act on a unique receptor in insects making it less toxic to mammals which is unlike nicotine which is more selectively toxic to mammals
SPECIFICITY OF NEONICOTINOIDS FOR α 4 β 2 NICOTINIC RECEPTORS IC* 50 nM Selectivity Neonicotinoid Ratio Insect Vertebrate Acetamiprid 8.3 700 84 Clothianidin 2.2 3,500 1,591 Dinotefuran 900 >100,000 >111 Imidacloprid 4.6 2,600 565 Nicotine 4000 7 0.002 *Concentration of neonicotinoid or nicotine that produces 50% inhibition of the nicotinic receptor (Tomizawa and Casida, 2005)
What are the Variables Associated with Successful Applications? Growing Type of Plant Environment (container, field, greenhouse, landscape, etc) Target Pest(s) Application Method ( foliar, drench broadcast, injection, etc) Ecological Considerations (runoff, leaching, non-targets)
What are the Variables Associated with Successful Applications?
Speed of Uptake and Persistence • Target pest • Acid dissociation differences constant (pK a ) • Half ‐ life of the • Octanol ‐ Water insecticide (in soil Coefficient and water) (Log P or Log K ow ) • UV stability • Water solubility • Light intensity • Soil adsorption • Transpiration rate
UV Stability of Neonicotinoids Slide Credit: Presentation by C. Sclar, Longwood Gardens Data obtained from published EPA registration documents (R. Fletcher)
pK a and Log P (Log K ow ) Values for Neonicotinoids Neonicotinoid Acid Dissociation (AI) Constant Log P Acetamiprid 0.7 0.8 Clothianidin 11.1 0.7 Dinotefuran 12.6 ‐ 0.64 Imidacloprid “weak base” 0.57 Thiamethoxam n/a ‐ 0.13 Slide Credit: C. Sclar; F. Byrne
Relative Water Solubility of Neonicotinoids Slide information courtesy C. Sclar. Longwood Gardens
Summary of Characteristics Neonicotinoid pK a Log P K oc Water A.I. (Log K ow ) Sol. Acetamiprid Low High Med. High Clothianidin High High Med. Low Dinotefuran High Low Low Very High Imidacloprid None? High High Low Thiamethoxam None Low Med. High Slide information courtesy C. Sclar. Longwood Gardens
Some Generalizations… Neonicotinoid Relative Speed Relative Rate A.I. of Uptake of Persistence Acetamiprid Fast Short – Mod. Clothianidin Slow (?) Mod. – Long Dinotefuran Fast Short – Mod (?) Imidacloprid Slow (?) Long Thiamethoxam Med(?) – Short – Mod. (?) Fast Slide information courtesy C. Sclar. Longwood Gardens
Acetamiprid • Trade name: Tristar 30SG (Caution) • For use on ornamental and flowering plants grown outdoors and in greenhouses, shadehouses and lathhouses • Not for homeowner use • Application: Foliar only
Clothianidin • Arena 50WDG; – Turfgrass, sod farms, landscape ornamentals, interiorscapes, and non ‐ bearing fruit and nut trees in the landscape – Drench, broadcast, foliar • Aloft G or SC – contains clothianidin and bifenthrin – Turf and landscape ornamentals around residential, institutional, public, commercial, and industrial buildings, parks, recreational areas, athletic fields and sod farms (specific labels for golf courses) – Drench, broadcast, foliar
Dinotefuran • Safari 20 SG; 2G • For greenhouse, nursery, interiorscapes and outdoor landscapes • Application – foliar, broadcast, soil drench, soil injection, micro ‐ irrigation, drip irrigation, overhead irrigation, ebb and flood, trunk spray
Imidacloprid • Merit 75WP; 75WSP, 2F, 0.5G – Commercial and residential landscapes and interiorscapes – Foliar and soil applications • Marathon II, 60 WP, G – Greenhouses, nurseries and interiorscapes – Foliar and soil applications • CoreTect – Landscapes, interiorscapes, forested areas – Soil application
Imidacloprid • Discus – Field and container nurseries – Combined with a pyrethroid (cyfluthrin) – Foliar, soil injection, soil drench • Allectus SC – Turfgrass and landscape of residential lawns, commercial, industrial, institutional, and recreational areas (Not golf courses or sod farms) – Combined with a pyrethroid (bifenthrin) – Foliar, broadcast, drench, soil injection,
Thiamethoxam • Flagship 25 WG – Greenhouses, lath and shadehouses, containers, field nurseries – Foliar, broadcast, drench, chemigation, • Meridian 25WG; 0.33G – Turfgrasses on golf courses, residential lawns, commercial grounds, parks, playgrounds, athletic fields and sold farms and ornamentals plants in residential and commercial landscapes, parks, golf courses and interiorscapes – Foliar, broadcast, drench, soil injection
Methods of Application There are numerous options on how to apply the neonicotinoids; • Take advantage of the different methods • Take advantage of the different formulations • Fit the method of application for the site • The site and method needs to be on the label • Consider the methods that gets the needed result with the least negative impact on the environment/non ‐ targets
Ornamental Pest Management with Neonicotinoids Key ornamental pests – Scales – Mealybugs – Whiteflies – Thrips
Ornamental Pest Management with Neonicotinoids Examples from South Florida 1. Differences in efficacy 4. Avoiding unnecessary applications – Cycad aulacaspis scale – Ficus thrips – Asian citrus psyllid 5. Soil versus drench 2. Differences due to host – Ficus whitefly stage 6. Insecticide rate – Diaprepes root weevil – Ficus whitefly 3. Difference due to host plant – Lobate lac scale
1. Examples of Differences due to Efficacy • Cycad aulacaspis scale – Dinotefuran and acetamiprid were more efficacious than imidacloprid • Asian citrus psyllid – As foliar sprays, two neonicotinoid products that also contained a pyrethroid and (Discus and Allectus) and thiamethoxam (Flagship) provided longer control than others testes – Not much differences among products used as a drench – Longer control with drenches versus foliar application
Management of Cycad Aulacaspis Scale in Florida • Pest of numerous cycads • Fronds eventually become brown and desiccated; ultimately causing plant death
• Oils Pesticide – Ultra fine horticultural Oil Options – Oganocide • Insect growth regulators – Distance • Foliar insecticides – Orthene – Malathion – Safari – TriStar • Soil insecticides – Safari
Management of Cycad Aulacaspis Scale
Control Merit ‐ drench Distance ‐ foliar Dimethoate ‐ foliar Merit ‐ foliar Organocide Dimethoate ‐ drench
Management of Cycad Aulacaspis Scale 100 80 Percent Mortality 60 40 20 0 0 6 12 18 25 32 Days After Application Control Allect Merit (drench) Merit (foliar) Discus Merit (foliar+drench)
Management of Asian Citrus Psyllid ( Diaphorina citri ) on Orange Jasmine • Vectors citrus greening disease • Pest of citrus and closely related plants
2 nd spray application
Percent Mortality of Asian Citrus Psyllid on Orange Jasmine 100 90 control 80 70 Flag 4oz 60 Flag 6oz 50 40 Flag 8oz 30 Flag drench 4oz 20 Flag drench 10 8oz 0 2 dat 5 dat 8 dat 12 dat 15 dat 19 day 22 day 29 day 38day 45 day 53 day 59 day 68 day 74 day
2. Examples of Differences Due to Stage of Insect • Diaprepes root weevil – Differences in efficacy of medium (5 ‐ 6 th instar) larvae among 3 products (imidacloprid, imidacloprid + cyfluthrin, and dinotefuran; however, with larger larvae (9 th instar), no difference – One neonicotinoid (dinotefuran) provided control of adults when applied as a drench
Management of Diaprepes Root Weevil in Florida • Major pest of citrus, sugarcane, ornamentals, root crops • Regulatory risk – all stages are commonly spread on infested plant material
Recovered Live Diaprepes Root Weevil Larvae (5 ‐ 6 th instar)
Recovered Live Diaprepes Root Weevil Larvae (9 th instar)
Percent Adult Mortality after Feeding on Foliage from Plants Treated with Insecticides
3. Examples of Differences Due to Stage of Insect • Lobate lac scale – efficacy between two neonicotinoids was different on two host plants
Management of Lobate Lac Scale in Florida • A pest on more than 300 tropical and subtropical fruits and ornamentals • Causes branch dieback and sometimes plant death
Management of Lobate Lac Scale in Florida Evaluated 8 weeks after 1 st application Drench application Foliar application UF/IFAS
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