Models of Populations: Demography, Population Genetics, Geographic Spread, and Management.

Both LeConte and Smith and Lawrence are among the most damaging insects impacting corn in North America. has also invaded Europe and has become an important pest in that region. Computer models have become an important tool for understanding the impact and spread of these important pests.

Blended Refuge and Insect Resistance Management for Insecticidal Corn.

In this review, we evaluate the intentional mixing or blending of insecticidal seed with refuge seed for managing resistance by insects to insecticidal corn (Zea mays). We first describe the pest biology and farming practices that will contribute to weighing trade-offs between using block refuges and blended refuges. Case studies are presented to demonstrate how the trade-offs will differ in different systems.

Natural enemies delay insect resistance to Bt crops.

We investigated whether development of resistance to a Bt crop in the presence of a natural enemy would be slower than without the natural enemy and whether biological control, in conjunction with a Bt crop, could effectively suppress the pest population. Additionally, we investigated whether insecticide-sprayed refuges of non-Bt crops would delay or accelerate resistance to the Bt crop. We used a system of Bt broccoli expressing Cry1Ac, a population of the pest Plutella xylostella with a low frequency of individuals resistant to Cry1Ac and the insecticide spinosad, and a natural enemy, Coleomegilla maculata, to conduct experiments over multiple generations.

Insect resistance management for stored product pests: a case study of cowpea weevil (Coleoptera: Bruchidae).

The cowpea weevil, Callosobruchus maculatus F. (Coleoptera: Bruchidae), can cause up to 100% yield loss of stored cowpea seeds in a few months in West Africa. Genes expressing toxins delaying insect maturation (MDTs) are available for genetic engineering.

Modeling a western corn rootworm, Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae), maturation delay and resistance evolution in Bt corn.

Background: Emergence delay and female-skewed sex ratios among adults of Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) from Bt corn have been reported in field studies. The authors used a simulation model to study the effect of a maturation delay and a female-skewed sex ratio for D. v.

Modeling the integration of parasitoid, insecticide, and transgenic insecticidal crop for the long-term control of an insect pest.

The tools of insect pest management include host plant resistance, biological control, and insecticides and how they are integrated will influence the durability of each. We created a detailed model of the population dynamics and population genetics of the diamondback moth, Plutella xylostella L., and its parasitoid, Diadegma insulare (Cresson), to study long-term pest management in broccoli Brassica oleracea L.

Putting the brakes on a cycle: bottom-up effects damp cycle amplitude.

Pest population density oscillations have a profound effect on agroecosystem functioning, particularly when pests cycle with epidemic persistence. Here, we ask whether landscape-level manipulations can be used to restrict the cycle amplitude of the European corn borer moth [Ostrinia nubilalis (Hübner)], an economically important maize pest. We analysed time series from Minnesota (1963-2009) and Wisconsin (1964-2009) to quantify the extent of regime change in the US Corn Belt where rates of transgenic Bt maize adoption varied.

Western corn rootworm (Coleoptera: Chrysomelidae) dispersal and adaptation to single-toxin transgenic corn deployed with block or blended refuge.

A simulation model of the temporal and spatial dynamics and population genetics of western corn rootworm, Diabrotica virgifera virgifera LeConte, was created to evaluate the use of block refuges and seed blends in the management of resistance to transgenic insecticidal corn (Zea mays L.). This Bt corn expresses one transgenic corn event, DAS-59122-7, that produces a binary insecticidal protein toxin (Cry34Ab1/Cry35Ab1) and provides host-plant resistance.

Seeds of change: corn seed mixtures for resistance management and integrated pest management.

The use of mixtures of transgenic insecticidal seed and nontransgenic seed to provide an in-field refuge for susceptible insects in insect-resistance-management (IRM) plans has been considered for at least two decades. However, the U.S.

Modeling evolution of Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae) to transgenic corn with two insecticidal traits.

A simulation model of the population dynamics and genetics of western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), was created to evaluate the use of refuges in the management of resistance to transgenic insecticidal corn, Zea mays L., expressing one or two toxin traits. Hypothetical scenarios and a case study of a corn hybrid pyramided with existing toxins are simulated.

Density-dependent and density-independent mortality of the western corn rootworm: impact on dose calculations of rootworm-resistant Bt corn.

The percentage of viable eggs of the western corn rootworm, Diabrotica virgifera virgifera LeConte, which survived to the adult stage was evaluated for the effect of egg density in 2005 and 2007 in central Missouri. In 2005, each plot was 2.44 by 3.

Microarray analysis yields candidate markers for rotation resistance in the western corn rootworm beetle, Diabrotica virgifera virgifera.

As pest species may evolve resistance to chemical controls, they may also evolve resistance to cultural control methods. Yearly rotation of corn (Zea mays) with another crop interrupts the life cycle of the western corn rootworm beetle (Diabrotica virgifera virgifera, Coleoptera: Chrysomelidae), but behavioral resistance to crop rotation is now a major problem in the Midwest of the USA. Resistant adult females exhibit reduced fidelity to corn as a host and lay their eggs in the soil of both corn and soybean (Glycine max) fields.

Evolutionary analysis of herbivorous insects in natural and agricultural environments.

Herbivorous insects offer a remarkable example of the biological diversity that formed the foundation for Darwin's theory of evolution by natural selection. The ability of insects to evolve resistance rapidly to insecticides and host-plant resistance present a continual challenge for pest management. This paper considers the manner in which genetic constraints, host-plant availability and trade-offs affect the evolution of herbivorous insects in natural and agricultural environments, and the extent to which lessons learned from studying natural systems may be applied to improve insect resistance management in agricultural systems.

Finding the economics in economic entomology.

To recommend new pest management tactics and strategies to farmers and policy makers, economic entomologists must evaluate the economics of biologically reasonable approaches. We collected data to determine how frequently these economic evaluations occur. We discovered from our survey of entomological journals representing the discipline of economic entomology that < 1% of research papers published since 1972 include economic evaluations of pest management tactics.

Planting transgenic insecticidal corn based on economic thresholds: consequences for integrated pest management and insect resistance management.

A simulation model of the western corn rootworm, Diabrotica virgifera virgifera LeConte, was used to investigate whether sampling and economic thresholds can improve integrated pest management (IPM) and insect resistance management (IRM) when transgenic insecticidal crops are used for insect pest management. When transgenic corn killed at least 80% of susceptible larvae, the calculated economic threshold increased linearly as the proportion of susceptible beetles surviving the toxin increased. The use of economic thresholds slightly slowed the evolution of resistance to transgenic insecticidal crops.

Definitions of pathogenicity and virulence in invertebrate pathology.

Accurate definition and usage of terminology are critical to effective communication in science. In a recently published article, the clarity and consistency of the terms pathogenicity and virulence as used in invertebrate pathology were called into question, and a revision of these terms was proposed. Our objective was to examine definitions of pathogenicity and virulence and their use in invertebrate pathology, and respond to this article.

"Active" refuges can inhibit the evolution of resistance in insects towards transgenic insect-resistant plants.

Negative cross-resistance (NCR) toxins that hitherto have not been thought to have practical uses may indeed be useful in the management of resistance alleles. Practical applications of NCR for pest management have been limited (i) by the scarcity of high toxicity NCR toxins among pesticides, (ii) by the lack of systematic methodologies to discover and develop such toxins, as well as (iii) by the lack of deployment tactics that would make NCR attractive. Here we present the concept that NCR toxins can improve the effectiveness of refuges in delaying the evolution of resistance by herbivorous insect pests to transgenic host plants containing insecticidal toxins.