Aster Leafhopper Dispersal Casey W. Hoy (state representative to NCR-148) X. Zhou, S. A. Miller, L. R. Nault, L. Beanland Ohio Agricultural Research and Development Center Wooster, OH We have developed a mathematical model of aster yellows epidemiology to explore strategies for managing this important disease of vegetable crops. The model simulates yellows epidemics in fields of lettuce, celery, and carrots. Spatial effects have been included in the simulation model to describe epidemiology in a validation experiment. Interfield movement of leafhoppers initially is being simulated with transition probability matrices. Epidemics are started by immigrating aster leafhoppers, Macrosteles quadrilineatus Forbes, and are influenced by subsequent population dynamics and phytoplasma transmission. Leafhopper movement after arrival in the vegetable growing area influences two critical rates in the epidemiological model: the rate at which uninfected leafhoppers acquire the phytoplasma and the rate at which inoculative leafhoppers transmit the phytoplasma to uninfected plants. Both rates depend on two scales of movement, interplant and interfield. Model predictions indicated that the arrangement of host and nonhost crops could have a significant impact on crop loss from aster yellows. A model validation experiment was conducted during summer of 1997. Treatments were season-long control strategies in one-acre blocks that were divided into 24 plots, 6 plots of each of the following crops: lettuce (susceptible), carrots (susceptible), collards (not susceptible), and sweet corn (not susceptible). A strategy that included cultural controls and reduced insecticide application was compared with the conventional schedule of insecticide applications for aster leafhopper and an untreated check. Colorado Potato Beetle Locomotion and Flight after Bacillus thuringiensis dendotoxin Ingestion (C. W. Hoy, G. P. Head. D. N. Ferro, & A. Alyokhin) Research continues on evaluating the impact of behavioral responses to Bacillus thuringiensis delta endotoxin (Btt) on dispersal of Colorado potato beetle. Locomotion data analysis and estimation of heritability for behavioral response to Btt and its genetic correlation with tolerance is in progress. We have demonstrated dose-dependent effects of Btt on Colorado potato beetle locomotion. Beetles fed transgenic foliage containing lower concentrations of Btt (approximately 5 µg/gm) showed increased frequency of walking during the second hour after ingestion compared with beetles fed standard potato foliage; beetles fed foliage containing higher concentrations (approximately 20 µg/gm) showed decreased frequency. Bibliography: Hoy, C. W., J. A. Wyman, T. T. Vaughn, D. A. East and P. Kaufman. 1996 Food, ground cover and Colorado potato beetle (Say) (Coleoptera: Chrysomelidae) dispersal in late summer. J. Econ. Entomol. 89: 963-969. Murral, D. J., L. R. Nault, C. W. Hoy, L. V. Madden, and S. A. Miller. 1996. Effects of temperature and vector age on transmission of two Ohio strains of the aster yellows phytoplasma by the aster leafhopper (Homoptera: Cicadellidae). J. Econ. Entomol. 89: 1223-1232. Hoy, C. W., G. Head, and F. R. Hall. Spatial heterogeneity and insect adaptation to toxins. Ann. Rev. Entomol. In Press. Head, G., C. W. Hoy, and F. R. Hall. Genetics of response to permethrin in unexposed diamondback moth populations (Lepidoptera: Plutellidae). Ann. Entomol. Soc. Am. In Press. [ 1997 Research Index ]
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Aster Leafhopper Dispersal

Casey W. Hoy (state representative to NCR-148)
X. Zhou, S. A. Miller, L. R. Nault, L. Beanland
Ohio Agricultural Research and Development Center
Wooster, OH

We have developed a mathematical model of aster yellows epidemiology to explore strategies for managing this important disease of vegetable crops. The model simulates yellows epidemics in fields of lettuce, celery, and carrots. Spatial effects have been included in the simulation model to describe epidemiology in a validation experiment. Interfield movement of leafhoppers initially is being simulated with transition probability matrices. Epidemics are started by immigrating aster leafhoppers, Macrosteles quadrilineatus Forbes, and are influenced by subsequent population dynamics and phytoplasma transmission. Leafhopper movement after arrival in the vegetable growing area influences two critical rates in the epidemiological model: the rate at which uninfected leafhoppers acquire the phytoplasma and the rate at which inoculative leafhoppers transmit the phytoplasma to uninfected plants. Both rates depend on two scales of movement, interplant and interfield.

Model predictions indicated that the arrangement of host and nonhost crops could have a significant impact on crop loss from aster yellows. A model validation experiment was conducted during summer of 1997. Treatments were season-long control strategies in one-acre blocks that were divided into 24 plots, 6 plots of each of the following crops: lettuce (susceptible), carrots (susceptible), collards (not susceptible), and sweet corn (not susceptible). A strategy that included cultural controls and reduced insecticide application was compared with the conventional schedule of insecticide applications for aster leafhopper and an untreated check.

Colorado Potato Beetle Locomotion and Flight after Bacillus thuringiensis dendotoxin Ingestion (C. W. Hoy, G. P. Head. D. N. Ferro, & A. Alyokhin)

Research continues on evaluating the impact of behavioral responses to Bacillus thuringiensis delta endotoxin (Btt) on dispersal of Colorado potato beetle. Locomotion data analysis and estimation of heritability for behavioral response to Btt and its genetic correlation with tolerance is in progress. We have demonstrated dose-dependent effects of Btt on Colorado potato beetle locomotion. Beetles fed transgenic foliage containing lower concentrations of Btt (approximately 5 µg/gm) showed increased frequency of walking during the second hour after ingestion compared with beetles fed standard potato foliage; beetles fed foliage containing higher concentrations (approximately 20 µg/gm) showed decreased frequency.

Bibliography:

Hoy, C. W., J. A. Wyman, T. T. Vaughn, D. A. East and P. Kaufman. 1996 Food, ground cover and Colorado potato beetle (Say) (Coleoptera: Chrysomelidae) dispersal in late summer. J. Econ. Entomol. 89: 963-969.

Murral, D. J., L. R. Nault, C. W. Hoy, L. V. Madden, and S. A. Miller. 1996. Effects of temperature and vector age on transmission of two Ohio strains of the aster yellows phytoplasma by the aster leafhopper (Homoptera: Cicadellidae). J. Econ. Entomol. 89: 1223-1232.

Hoy, C. W., G. Head, and F. R. Hall. Spatial heterogeneity and insect adaptation to toxins. Ann. Rev. Entomol. In Press.

Head, G., C. W. Hoy, and F. R. Hall. Genetics of response to permethrin in unexposed diamondback moth populations (Lepidoptera: Plutellidae). Ann. Entomol. Soc. Am. In Press.

[ 1997 Research Index ]