Peter C Ellsworth

Peter C Ellsworth

Professor, Entomology
Professor, Entomology / Insect Science - GIDP
Specialist, Entomology
Specialist, BIO5
Primary Department
Department Affiliations
Contact
(520) 374-6225

Work Summary

Peter Ellsworth is working to develop science-based solutions for integrated pest management through applied ecological investigations and organized outreach programs of Cooperative Extension, with principal focus on cotton; Integrated whitefly, Lygus, and pink bollworm management in cotton.

Research Interest

Peter Ellsworth, PhD, has broad interests in insect-crop interactions and applied insect ecology with particular emphasis on those aspects, which may be exploited for sound ecological and economical pest management. His responsibilities are to develop science-based solutions for integrated pest management through applied ecological investigations and organized outreach programs of Cooperative Extension, with principal focus on Bemisia tabaci, Lygus hesperus and Pectinophora gossypiella in the cotton agroecosystem, other field crops, and new crops as well as in cross-commodity interactions. In addition, Dr. Ellsworth is interested in insect phenology, diapause, insect-water relations, predictive modeling, pest biology, sampling, thresholds, and damage dynamics.As Director of the multi-disciplinary Arizona Pest Management Center, Dr. Ellsworth helps manage the institution's NIFA Extension IPM grant, serves as the state's federal IPM Coordinator and Pesticide Coordinator, and oversees and helps organize teams of research and extension faculty for the betterment of the science and application of IPM in Arizona.

Publications

Crowder, D., Ellsworth, P., Naranjo, S., Tabashnik, B., & Carriere, Y. (2013). Modeling resistance to juvenile hormone analogs: linking evolution, ecology, and management. In Juvenile Hormones and Juvenoids: Modeling Biological Effects and Environmental Fate. ed Devillers J.

CRC Press, Boca Raton

Crowder, D. W., Ellsworth, P. C., Tabashnik, B. E., & Carriére, Y. (2008). Effects of operational and environmental factors on evolution of resistance to pyriproxyfen in the sweetpotato whitefly (Hemiptera: Aleyrodidae). Environmental entomology, 37(6).

Pyriproxyfen has been an important insecticide used as part of an integrated pest management (IPM) program for the sweetpotato whitefly, Bemisia tabaci (Gennadius) (B biotype), in Arizona cotton. We used a simulation model to examine the effects of pyriproxyfen concentration, insecticide action thresholds, crop diversity, planting date, and pyriproxyfen decay on evolution of resistance to pyriproxyfen in B. tabaci. In the model, pyriproxyfen use was restricted to cotton with a limit of one application per season. Other model parameters were based on data from laboratory and field experiments. Whitefly population densities and the number of insecticide applications per year increased as resistance evolved. Resistance evolved slowest with a low pyriproxyfen concentration. Lower action thresholds for pyriproxyfen and higher action thresholds for insecticides other than pyriproxyfen also slowed the evolution of resistance. However, lower action thresholds for pyriproxyfen resulted in more insecticide sprays per year with a high pyriproxyfen concentration. Resistance to pyriproxyfen evolved fastest in cotton-intensive regions and slowest in multicrop regions. In regions with noncotton crops, increasing immigration to cotton slowed resistance. Resistance evolved faster with earlier planting dates, although fewer insecticide sprays were needed compared with fields planted later in the year. Faster rates of pyriproxyfen decay slowed resistance. In some cases, strategies that delayed resistance were effective from an IPM perspective. However, some strategies that delayed resistance resulted in higher population densities. Results suggest that modification of operational and environmental factors, which can be controlled by growers, could prolong the efficacy of pyriproxyfen.

Carriere, Y., Ellers-Kirk, C., Harthfield, K., Larocque, G., Degain, B., Dutilleul, P., Dennehy, T., Marsh, S., Crowder, D., Li, X., Ellsworth, P., Naranjo, S., Palumbo, J., Fournier, A., Antilla, L., & Tabashnik, B. (2012). Spatial Prediction of Insecticide Resistance Provides Support for the Refuge Strategy. PNAS.

doi: 10.1073/pnas.1117851109

Ellsworth, P. C. (1998). Whitefly management in Arizona: looking at the whole system. Proceedings of the 1998 beltwide cotton conferences, San Diego, CA, USA, January 5-9 1999, 65-68.

Abstract:

Whiteflies remain a threat to production of cotton in Arizona. Looking at a series of commercial-scale trials, levels last season were delayed compared to previous years, but at higher densities than in 1995, an outbreak year. Efforts must be expended to optimize insect growth regulator (IGR) use and integrate these tactics with other aspects of crop and pest management. Broad spectrum insecticide use prior to treatment for whiteflies with IGRs alters the ecology of the system. Whitefly densities consistently increased after disruption with a Lygus insecticide relative to Lygus-untreated areas. While Lygus control is a production imperative, guidelines are presented for minimizing the impact of this disruption. The modes of action for the two IGRs differ substantially and result in subtle changes in population age structure and dynamics. The consequences of these changes impact natural enemies and should be noted by producers when selecting an IGR or monitoring populations after treatment. Re-treatment after initial IGR sprays depends on many factors. While apparently simular levels of suppression are possible when only one IGR is used, regimes using both available IGRs resulted in the fewest number of damaging large nymphs late in the season, just prior to defoliation. Conventional insecticides rotated according to pre-IGR introduction guidelines ('95IRM') also suppressed populations significantly and comparably to IGR regimes until late in the season. Then whitefly densities rose aggressively just prior to defoliation and pyrethroid susceptibility was significantly reduced in the 95IRM regime. Full adoption of IGR-based technology along with 'Bt' cotton allows growers to better manage whiteflies with fewer disruptions which can lead to secondary pest outbreaks, pest resurgence, and insecticide resistance.

Asiimwe, P., Ellsworth, P. C., & Naranjo, S. E. (2016). Natural enemy impacts on Bemisia tabaci (MEAM1) dominate plant quality effects in the cotton system. ECOLOGICAL ENTOMOLOGY, 41(5), 642-652.