Management & Biological Control Research Unit
USDA-ARS, Arid-Land Agricultural
Steven J. Castle Research Entomologist Arid-Land Agricultural 21881 North Cardon Lane Maricopa, AZ, 85239 (520) 316-6338 (520) 316-6330 FAX
Steven J. Castle
21881 North Cardon Lane
Maricopa, AZ, 85239
(520) 316-6330 FAX
· Ecology and management of agricultural pests
· Arthropod vectors of plant pathogens
· Insecticide resistance monitoring and management
Castle, S. J. 2006. Concentration and management of Bemisia tabaci in melons as a trap crop for cotton. Crop Prot. 25, 574-584.
Prabhaker, N., Castle, S. J., Byrne, F. J., Toscano, N. C., and Henneberry, T. J. 2006. Establishment of baseline susceptibility to various insecticides for glassy-winged sharpshooter, Homalodisca coagulata, by comparative bioassays. J. Econ. Entomol. 99: 141-154.
Castle, S. J., Naranjo, S. N., Bi, J. L., Byrne, F. J., and Toscano, N. C. 2005. Phenology and demography of Homalodisca coagulata in southern
Prabhaker, N., Castle, S. J., Toscano, N. C., and Henneberry, T. J. 2005. Assessment of cross-resistance potential among neonicotinoid insecticides in Bemisia tabaci (Hemiptera: Aleyrodidae). Bull. Entomol. Res. 95, 535-543.
Byers, J. A., and Castle, S. J., 2005. Area-wide models comparing synchronous versus asynchronous treatments for control of dispersing insect pests. J. Econ. Entomol. 98, 1763-1773.
Bi, J. L., Castle, S. J., Byrne, F. J., and Toscano, N. C. 2005. Comparative seasonal nitrogen nutrition fluctuations and population dynamics of the glassy-winged sharpshooter (Homalodisca coagulata) on orange and lemon. J. Chem. Ecol. 31, 2289-2308.
Byrne, F. J., Castle, S. J., Bi, J. L., and Toscano, N. C. 2005. Application of competitive ELISA for the quantification of imidacloprid titers in xylem fluid extracted from grapevines. J. Econ. Entomol. 98: 182-187.
Castle, S. J., Byrne, F. J., Bi, J. L., and Toscano, N. C. 2005. Spatial and temporal distribution of imidacloprid and thiamethoxam in citrus and impact on Homalodisca coagulata populations.
Byrne, F.J., Castle, S.J., Prabhaker, N., and Toscano. N.C. 2003. Biochemical study of resistance to imidacloprid in B-biotype Bemisia tabaci from
Castle, S. J., Toscano, N. C., Prabhaker, N., Henneberry, T. J., and Palumbo, J. C. 2002. Field evaluation of different insecticide use strategies as resistance management and control tactics for Bemisia tabaci (Hemiptera: Aleyrodidae). Bull. Entomol. Res. 92: 449-460.
Henneberry, T. J., and Castle, S. J. 2001. Bemisia:
Toscano, N. C., Prabhaker, N., Castle, S., and Henneberry, T. J. 2001. Inter-regional differences in baseline toxicity of Bemisia argentifolii (Homoptera: Aleyrodidae) to the two insect growth regulators, buprofezin and pyriproxyfen. J. Econ. Entomol. 94: 1538-1546.
Castle, S. J. 2000. Resistance to pesticides. In: Pimentel, D. (Ed.) Encyclopedia of
Ecology and management of agricultural pests
Our laboratory has been involved for many years on the biology and control of the whitefly Bemisia tabaci, a cosmopolitan pest well-known for its monumental outbreaks that have occurred in different parts of the world. The irrigated desert valleys of the southwestern
The essence of the outbreak pyramid is that in circumstances where the bottom two layers are broad with agro-ecological potential, the biotic characteristics inherent in outbreak-prone organisms permit exploitation of the resources in excess of both natural and managed controls. Conceptually, the volume of the management (IPM) layer at the top of the pyramid is much less than the three layers that form the base. In practice, management efforts that are targeted at individual fields, even if they provide superior results, are often eventually overwhelmed by regional population increases of B. tabaci on crop and non-crop vegetation. It is not a failure of management per se to control regional populations of B. tabaci, but rather a function of the combined potential contained within the climate, agriculture and biotic levels of the pyramid that ultimately exceed the capacity of local crop protection.
The challenge for management of B. tabaci in an outbreak-permissive environment such as the
Arthropod vectors of plant pathogens
In addition to being a potentially devastating direct pest of crops, B. tabaci is also a vector of numerous plant viruses that often severely reduce crop yields if infection rates increase early and rapidly. While the practical aspect of plant virus epidemics and the role played by B. tabaci is challenging from an applied perspective, there are also interesting questions concerning the interrelationships of vector, virus and host that are worthy of exploration.
One area of study currently being pursued concerns the effect that virus infection in a plant has on vector performance. Previous work with aphid-borne viruses led to the vector dependency hypothesis which posits that a plant pathogen with greater dependency on a principal vector species will tend to reciprocate the benefit derived from its vector relationship. In contrast, less or non vector-dependent plant pathogens gain less or not at all from vector associations and therefore do little or nothing to benefit the vector-pathogen relationship. Vector-dependent plant pathogens require movement to new hosts that is provided by vector insects, in most cases the only mechanism of dispersal for the pathogen. Reciprocation to the vector can occur through the medium of their mutual host plant. Infection-induced changes in host plant chemistry may actually benefit a vector nutritionally. This concept was first stated over 50 years ago:
“An agent which, through the disease it causes, actually multiplies its own vectors, has an obvious evolutionary advantage over one that does not.”
After demonstrating support for this hypothesis with an aphid-potato virus experimental system (Entomol. Exp. Appl. 69:51-60; Ann. Ent. Soc. Am. 91:661-667), a new system is being tested that consists of B. tabaci as the vector, cotton leaf crumple virus (CLCrV) as the plant pathogen, and cotton as the host plant. Preliminary data suggests that Gossypium hirsutum is less suitable as a host when infected with CLCrV than uninfected. Further study will examine the suitability of G. thurberi, native to the southwestern
Insecticide resistance monitoring and management
Resistance management is a fundamental component of good IPM and is dependent upon continuous monitoring of pest populations to determine resistance levels and, if necessary, make appropriate changes in pesticide use. Current management schemes for B. tabaci are still highly dependent on insecticide treatments in regions of heavy B. tabaci pressure such as the southwestern US, northern
Worldwide, a shift to newer chemistry has been paramount in instituting more effective management for controlling outbreak populations on multiple continents. In particular, systemic application of the neonicotinoid insecticide imidacloprid with its long residual activity has been instrumental in preventing early-season buildups in vegetable crops. Outstanding field efficacy of imidacloprid has been remarkably sustained for over 12 years of intensive, multiple crop use in the southwestern US. However, resistance has occurred in certain locations under heavy B. tabaci pressure such as
Results of systemic uptake bioassays of Bemisia tabaci adults collected at various times of the year in central