Neonicotinoid Insecticides for Ornamentals The Good, Bad and Ugly Catharine Mannion University of Florida, IFAS Tropical Research and Education Center

Neonicotinoids Insecticides Use of these insecticides has grown considerably since the forerunner of the group (imidacloprid) was first introduced in the early 1990’s Seven neonicotinoid insecticides Acetamiprid Clothianidin Dinotefuran Imidacloprid Thiamethoxam Nitempyram 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 α4β2 NICOTINIC RECEPTORS Neonicotinoid IC* 50 nMSelectivity Ratio InsectVertebrate Acetamiprid Clothianidin2.23,5001,591 Dinotefuran900>100,000>111 Imidacloprid4.62, Nicotine *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? Type of Plant Ecological Considerations (runoff, leaching, non-targets) Growing Environment (container, field, greenhouse, landscape, etc) Application Method ( foliar, drench broadcast, injection, etc) Target Pest(s)

What are the Variables Associated with Successful Applications? How fast will it work? How long will it last?

Speed of Uptake and Persistence Target pest differences Half-life of the insecticide (in soil and water) UV stability Light intensity Transpiration rate Acid dissociation constant (pK a ) Octanol-Water Coefficient (Log P or Log K ow ) Water solubility Soil adsorption

UV Stability of Neonicotinoids Data obtained from published EPA registration documents (R. Fletcher) Slide Credit: Presentation by C. Sclar, Longwood Gardens

pK a and Log P (Log K ow ) Values for Neonicotinoids Neonicotinoid (AI) Acid Dissociation ConstantLog P Acetamiprid Clothianidin Dinotefuran Imidacloprid“weak base”0.57 Thiamethoxamn/a-0.13 Slide Credit: C. Sclar; F. Byrne

Relative Water Solubility of Neonicotinoids Clothianidin Imidacloprid Acetamiprid Dinotefuran Thiamethoxam Slide information courtesy C. Sclar. Longwood Gardens

Summary of Characteristics Neonicotinoid A.I. pK a Log P (Log K ow ) K oc Water Sol. AcetamipridLowHighMed.High ClothianidinHigh Med.Low DinotefuranHighLow Very High ImidaclopridNone?High Low ThiamethoxamNoneLowMed.High Slide information courtesy C. Sclar. Longwood Gardens

Some Generalizations… Neonicotinoid A.I. Relative Speed of Uptake Relative Rate of Persistence AcetamipridFastShort – Mod. ClothianidinSlow (?)Mod. – Long DinotefuranFastShort – Mod (?) ImidaclopridSlow (?)Long ThiamethoxamMed(?) – Fast Short – Mod. (?) 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 – Cycad aulacaspis scale – Asian citrus psyllid 2.Differences due to host stage – Diaprepes root weevil 3.Difference due to host plant – Lobate lac scale 4.Avoiding unnecessary applications – Ficus thrips 5.Soil versus drench – Ficus whitefly 6.Insecticide rate – Ficus whitefly

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

Pesticide Options Oils –Ultra fine horticultural Oil –Oganocide Insect growth regulators –Distance Foliar insecticides –Orthene –Malathion –Safari –TriStar Soil insecticides –Safari

Management of Cycad Aulacaspis Scale

Control Merit-drench Merit-foliar Organocide Distance -foliar Dimethoate-drench Dimethoate-foliar

Management of Cycad Aulacaspis Scale

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

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 Drench applicationFoliar application Evaluated 8 weeks after 1 st application UF/IFAS

4. Example of a Comparison with a Non- neonicotinoid and Avoiding Unnecessary Applications Ficus thrips – No differences among products when populations were low; – Similar efficacy with a non-neonicotinoid insecticide

Ficus Thrips (Gynaikothrips uzeli) Photos: UF/IFAS MREC First noted in 2003 due to heavy damage on Ficus benjamina in south Florida Feeding causes sunken, reddish spots on leaves. Leaves tend to curl and fold inward.

5. Examples of Differences Due Method of Application Ficus whitefly – Soil applications provided longer control

Management of Ficus Whitefly (Singhiella simplex) in Florida New continental record Causes severe leaf drop; branch dieback

Ficus Whitefly “Panic situation” Continuing to spread in the landscape and nurseries Management – Nursery Established whitefly program Management – Landscape – Homeowner (over-the-counter products) – Commercial applicators – High potential for overuse – Potential for disruption of natural enemies

Control of Ficus Whitefly

Soil and Foliar Applications

6. Example of Differences Due Rate of Application In this situation, there were no differences in the two products tested or in the rate that was used of each product

Exotic Soft Scale (Hemiptera: Coccidae) 2008 – Reported from Monroe County on croton Continues to spread and now found in several southern Florida Counties New to science; it is has been described as a new genus and species Hosts – Numerous ornamental and fruit host ; many native plants in Florida Photo: H. Glenn, UF/IFAS

Control of Croton Scale

Ornamental Pest Management with Neonicotinoids Very useful, important group of compounds No, they do not always work Consider the differences among the different ai’s, formulations, and methods of application and use to your advantage Recognizing – When, where and how to use them – Recognizing “added” benefits – Manage the “popularity” of these products – Recognizing situations for overuse or misuse

Pest Alerts –University of Florida ( –DOACS ( pest-alert.html) Web Resources

Catharine Mannion Research and Extension Specialist Ornamental Entomology University of Florida, IFAS Tropical Research and Education Center SW 280 th Street Homestead, FL