Bt Susceptibility and Oviposition Preferences of Fall Armyworm (Lepidotera: Noctuidae) Host Strains

Bt Susceptibility and Oviposition Preferences of Fall Armyworm (Lepidotera: Noctuidae) Host Strains David A. Ingber and Charles E. Mason University of Delaware, Department of Entomology and Wildlife Ecology

Fall armyworm (Spodoptera frugiperda Smith) (Lepidoptera: Noctuidae)

Fall Armyworm University of Wisconsin Jeff Gore

Fall Armyworm University of Wisconsin Jeff Gore Bt management Cry1Ab Cry1Ac Cry1F

Host Strains Corn and Rice strains (Pashley 1986) Matt Bertone

Host Strains Corn and Rice strains (Pashley 1986) Corn strain Larger grasses Rice strain Smaller grasses Fidelities are not absolute Corn Bermuda grass

Host Strains Corn and Rice strains (Pashley 1986) Corn strain Larger grasses Rice strain Smaller grasses Fidelities are not absolute Differentiation Wing morphometrics Cañas-Hoyos et al. 2014

Host Strains Corn and Rice strains (Pashley 1986) Corn strain Larger grasses Rice strain Smaller grasses Fidelities are not absolute Differentiation Wing morphometrics Genetic and molecular techniques Cañas-Hoyos et al. 2014 Pashley 1986; Nagoshi et al. 2006

Host Strains Feeding Preferences Mate selection preferences Tolerance to conventional insecticides Pheromone composition Oviposition preferences Tolerance to Bt toxins Pashley et al. 1987, Pashley et al. 1992, Adamczyk et al. 1997, Whitford et al. 1988, Groot et al. 2010, Meagher et al. 2011, Vélasquez-Vélez et al. 2011, Ríos-Díez et al. 2012

Host Strains Feeding Preferences Mate selection preferences Tolerance to conventional insecticides Pheromone composition Oviposition preferences Tolerance to Bt toxins Pashley et al. 1987, Pashley et al. 1992, Adamczyk et al. 1997, Whitford et al. 1988, Groot et al. 2010, Meagher et al. 2011, Vélasquez-Vélez et al. 2011, Ríos-Díez et al. 2012

Objective & Hypotheses

Objective & Hypotheses Objective Compare the Bt susceptibility and oviposition preferences of corn and rice strain fall armyworm. Diet-based bioassays Greenhouse experiments

Objective & Hypotheses Objective Compare the Bt susceptibility and oviposition preferences of corn and rice strain fall armyworm. Hypotheses H 1 : Rice strain fall armyworm will be more susceptible to Bt toxins than corn strain. H 2 : Host strains will prefer to oviposit on plant species that they are more commonly associated with.

Insects USDA-ARS, Gainesville, FL Google

Insects USDA-ARS, Gainesville, FL Rice Strain (ARS-R) Collected from pasture grass Duval County Likely never exposed to Bt Google

Insects USDA-ARS, Gainesville, FL Rice Strain (ARS-R) Collected from pasture grass Duval County Likely never exposed to Bt Corn Strain (ARS-C) Collected from sweet corn Hendry County Possible Bt exposure Google

Insects USDA-ARS, Gainesville, FL Rice Strain (ARS-R) Collected from pasture grass Duval County Likely never exposed to Bt Corn Strain (ARS-C) Collected from sweet corn Hendry County Possible Bt exposure Control Corn Strain (FR-C) Frontier Agricultural Sciences Continuous culture since 1998, ~300 generations Never exposed to Bt Diet-Based Bioassays only Google

Diet-based Bioassays Proteins tested Cry1Ab Cry1Ac Cry1F Storer et al. 2010 Ríos-Díez et al. 2012

Diet-based Bioassays

Cry1Ab

Cry1Ab LC 50 : 1341.0 ng/cm 2 95% FL: 785.8 to 2555.0 µg/cm 2

Cry1Ac

Cry1Ac LC 50 : 472.6 ng/cm 2 95% FL: 21.0 to 861.3 µg/cm 2 LC 50 : 927.4 ng/cm 2 95% FL: 552.3 to 1207.0 µg/cm 2

Cry1F

Cry1F LC 50 : 211.3 ng/cm 2 95% FL: 158.7 to 264.4 µg/cm 2 LC 50 : 565.0 ng/cm 2 95% FL: 409.6 to 696.6 µg/cm 2 LC 50 : 544.7 ng/cm 2 95% FL: 409.9 to 654.4 µg/cm 2

Oviposition Experiments

Oviposition Experiments Corn Cotton Rice Bermuda grass (BG)

No-Choice Oviposition Corn Cotton Rice Bermuda grass (BG)

No-Choice Oviposition Corn Cotton Rice Bermuda grass (BG)

No-Choice Oviposition One-Way ANOVA ARS-C: d.f. 3,39, F = 2.05, P = 0.1248 ARS-R: d.f. 3,39, F = 2.82, P = 0.0524 P = 0.0524

No-Choice Oviposition One-Way ANOVA ARS-C: d.f. 3,39, F = 2.05, P = 0.1248 ARS-R: d.f. 3,39, F = 2.82, P = 0.0524 P = 0.0524

Two-Choice Oviposition

Two-Choice Oviposition Corn / Rice Corn / Cotton Corn / BG Rice / BG Rice / Cotton BG / Cotton

Corn Strain (ARS-C) Comparison Corn / Rice Corn / BG Corn / Cotton Rice / BG Rice / Cotton BG / Cotton Egg masses 8 / 2 15 / 1 14 / 2 2 / 1 4 / 4 3 / 3 Goodness of fit: P = 0.1094 0.0005 0.0042 1.0000 1.0000 1.0000

Corn Strain (ARS-C) Comparison Corn / Rice Corn / BG Corn / Cotton Rice / BG Rice / Cotton BG / Cotton Egg masses 8 / 2 15 / 1 14 / 2 2 / 1 4 / 4 3 / 3 Goodness of fit: P = 0.1094 0.0005 0.0042 1.0000 1.0000 1.0000

Corn Strain (ARS-C) Comparison Corn / Rice Corn / BG Corn / Cotton Rice / BG Rice / Cotton BG / Cotton Egg masses 8 / 2 15 / 1 14 / 2 2 / 1 4 / 4 3 / 3 Goodness of fit: P = 0.1094 0.0005 0.0042 1.0000 1.0000 1.0000 Csiszár and Tsunády 1984 McDonald et al. 1999

Rice Strain (ARS-R) Comparison Corn / Rice Corn / BG Corn / Cotton Rice / BG Rice / Cotton BG / Cotton Egg masses 6 / 1 1 / 6 9 / 0 3 / 2 3 / 0 2 / 0 Goodness of fit: P = 0.1250 0.1250 0.0039 1.0000 0.2500 0.5000

Rice Strain (ARS-R) Comparison Corn / Rice Corn / BG Corn / Cotton Rice / BG Rice / Cotton BG / Cotton Egg masses 6 / 1 1 / 6 9 / 0 3 / 2 3 / 0 2 / 0 Goodness of fit: P = 0.1250 0.1250 0.0039 1.0000 0.2500 0.5000 Csiszár and Tsunády 1984 McDonald et al. 1999

Objective & Hypotheses

Objective & Hypotheses Objective Compare the Bt susceptibility and oviposition preferences of corn and rice strain fall armyworm. Hypotheses H 1 : Rice strain fall armyworm will be more susceptible to Bt toxins than corn strain. H 2 : Host strains will prefer to oviposit on plant species that they are more commonly associated with.

Results Summary Diet-based Bioassays Bt protein Susceptibility Cry1Ab Rice strain > Corn strain Cry1Ac Inconclusive Cry1F Rice strain > Corn strain Greenhouse Experiments Host strain Experiment Host preferences Corn strain No-choice None Two-choice Corn Rice strain No-choice Rice and BG Two-choice Corn, Rice, and BG

Results Summary Diet-based Bioassays Bt protein Susceptibility Cry1Ab Rice strain > Corn strain Cry1Ac Inconclusive Cry1F Rice strain > Corn strain H 1 : Generally supported Greenhouse Experiments Host strain Experiment Host preferences Corn strain No-choice None Two-choice Corn Rice strain No-choice Rice and BG Two-choice Corn, Rice, and BG

Results Summary Diet-based Bioassays Bt protein Susceptibility Cry1Ab Rice strain > Corn strain Cry1Ac Inconclusive Cry1F Rice strain > Corn strain H 1 : Generally supported Greenhouse Experiments Host strain Experiment Host preferences Corn strain No-choice None Two-choice Corn Rice strain No-choice Rice and BG Two-choice Corn, Rice, and BG H 2 : Inconclusive

Results Summary Diet-based Bioassays Bt protein Susceptibility Cry1Ab Rice strain > Corn strain Cry1Ac Inconclusive Cry1F Rice strain > Corn strain H 1 : Generally supported Greenhouse Experiments Host strain Experiment Host preferences Corn strain No-choice None Two-choice Corn Rice strain No-choice Rice and BG Two-choice Corn, Rice, and BG H 2 : Inconclusive

Discussion

Discussion Mixed populations

Discussion Mixed populations Bt

Discussion Mixed populations More Tolerant Bt

Discussion Regional resistance managment Reproduced from Pashley 1988 with added collection locations from Adamczyk et al. 1997, Prowell et al. 2004, Nagoshi et al. 2006, and Ríos-Díez et al. 2012.

Current Research Diet-based bioassays Additional rice strain population (DuPont-Pioneer) Oviposition studies Compare damaged and undamaged corn plants

More Studies are Needed Past study Bt Insecticides Oviposition Pitre et al. 1983 Pashley et al. 1987 Whitford et al. 1988 Adamczyk et al. 1997 Siebert et al. 2008 Virla et al. 2008 Meagher et al. 2011 Ríos-Díez and Saldamando-Benjumea 2011 Ríos-Díez et al. 2012

Dissertation committee Dr. Charles Mason Dr. Lindsey Flexner Dr. Charles Bartlett Dr. Greg Shriver Dr. John McDonald Lab members Holly Walker Kelsey Fisher William Cissel Acknowledgements U.Del. MTA team Dr. Cordell Overby Sean Hayes Wendy Jordan General advice Dr. Ana Vélez Bruce Lang Michael Vella Insect suppliers USDA-ARS, Gainesville, FL Dr. Robert Meagher Amy Rowley Material suppliers DuPont-Pioneer Monsanto Company Dow AgroSciences Frontier Agricultural Sciences All photos used in this presentation that were not taken by the authors have been attributed to their photographer or institute of origin with the exception of the photos presented on slides three and four which were left unattributed in order to maintain presentation coherence. This research was supported by DuPont-Pioneer, and by the USDA National Institute of Food and Agriculture Grant no. 2015-31100-06010 authorized under the Hatch Act. This project contributes regionally to the NC246 Project: Ecology and Management of Arthropods in Corn.

Questions?

Colony Rearing

Bt Toxins tested Cry1Ab Cry1Ac Cry1F Serial dilutions Initial: 2000 ng/cm 2 Dilutions 1500 ng/cm 2, 1100 ng/cm 2, 800 ng/cm 2, 500 ng/cm 2, 250 ng/cm 2, 62.5 ng/cm 2 Control: 0 ng/cm 2 Serial Dilutions Storer et al. 2010 Ríos-Díez et al. 2012

Negative Controls One-way ANOVA Prop. Survival: d.f. 2,47, F = 2.77, P = 0.0731 Mean Weight: d.f. 2,47, F = 64033, P < 0.0001

No-Choice Oviposition One-Way ANOVA ARS-C: d.f. 3,56, F = 0.94, P = 0.4273 ARS-R: d.f. 3,44, F = 0.19, P = 0.9015

Two-Choice Oviposition Téllez-Rodriguez et al. 2014

Two-Choice Oviposition Diet-based Bioassays Bt protein Susceptibility Cry1Ab Rice strain > Corn strain Cry1Ac Inconclusive Cry1F Rice strain > Corn strain Greenhouse Experiments Host strain Experiment Host preferences Corn strain No-choice None Two-choice Corn Rice strain No-choice Rice and BG Two-choice Corn, Rice, and BG Téllez-Rodriguez et al. 2014

Two-Choice Oviposition Diet-based Bioassays Bt protein Susceptibility Cry1Ab Rice strain > Corn strain Cry1Ac Inconclusive Cry1F Rice strain > Corn strain Greenhouse Experiments Host strain Experiment Host preferences Corn strain No-choice None Two-choice Corn Rice strain No-choice Corn, Rice, and BG Two-choice Corn, Rice, and BG Téllez-Rodriguez et al. 2014