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PubMed2004

State-dependent impulsive models of integrated pest management (IPM) strategies and their dynamic consequences.

A state-dependent impulsive model is proposed for integrated pest management (IPM). IPM involves combining biological, mechanical, and chemical tactics to reduce pest numbers to tolerable levels after a pest population has reached its economic threshold (ET). The complete expression of an orbitally asymptotically stable periodic solution to the model with a maximum value no larger than the given ET is presented, the existence of which implies that pests can be controlled at or below their ET levels. We also prove that there is no periodic solution with order larger than or equal to three, except for one special case, by using the properties of the LambertW function and Poincare map. Moreover, we show that the existence of an order two periodic solution implies the existence of an order one periodic solution. Various positive invariant sets and attractors of this impulsive semi-dynamical system are described and discussed. In particular, several horseshoe-like attractors, whose interiors can simultaneously contain stable order 1 periodic solutions and order 2 periodic solutions, are found and the interior structure of the horseshoe-like attractors is discussed. Finally, the largest invariant set and the sufficient conditions which guarantee the global orbital and asymptotic stability of the order 1 periodic solution in the meaningful domain for the system are given using the Lyapunov function. Our results show that, in theory, a pest can be controlled such that its population size is no larger than its ET by applying effects impulsively once, twice, or at most, a finite number of times, or according to a periodic regime. Moreover, our theoretical work suggests how IPM strategies could be used to alter the levels of the ET in the farmers' favour.

Animals↗
PubMed2002

Potential for the use of elicitors of plant resistance in arthropod management programs.

Plants protect themselves from arthropod herbivores both directly, by expressing biochemical and morphological traits that interfere with herbivore development or behavior, and indirectly, by facilitating the action of natural enemies of herbivores. These direct and indirect resistance mechanisms are not always expressed at maximal levels by plants, but rather can be induced to higher levels by a variety of stimuli, most notably prior herbivory. The recent discovery of chemical elicitors of induced responses has led to interest in manipulating the inducible responses of plants for crop protection. Applications of elicitors of induced responses made at appropriate times during the growing season of a crop have the potential of activating both direct and indirect mechanisms of plant resistance and thereby simultaneously augmenting host-plant resistance and biological control. This strategy may serve as an important component of a multifaceted, ecologically-based pest management program and is unlikely to precipitate the rapid evolution of countermeasures by target pests. However, this strategy will not be appropriate in all crops or against all arthropod pests. The conditions under which the use of an elicitor is likely to be successful are discussed, and examples of the successful use of elicitors are reviewed.

Agriculture↗
PubMed2007

Efficacy of strips coated with Metarhizium anisopliae for control of Varroa destructor (Acari: Varroidae) in honey bee colonies in Texas and Florida.

Strips coated with conidia of Metarhizium anisopliae (Metschinkoff; Deuteromycetes: Hyphomycetes) to control the parasitic mite, Varroa destructor (Anderson and Trueman) in colonies of honey bees, Apis mellifera (Hymenoptera: Apidae) were compared against the miticide, tau-fluvalinate (Apistan) in field trials in Texas and Florida (USA). Apistan and the fungal treatments resulted in successful control of mite populations in both locations. At the end of the 42-day period of the experiment in Texas, the number of mites per bee was reduced by 69-fold in bee hives treated with Apistan and 25-fold in hives treated with the fungus; however mite infestations increased by 1.3-fold in the control bee hives. Similarly, the number of mites in sealed brood was 13-fold and 3.6-fold higher in the control bee hives than in those treated with Apistan and with the fungus, respectively. Like the miticide Apistan, the fungal treatments provided a significant reduction of mite populations at the end of the experimental period. The data from the broodless colonies treated with the fungus indicated that optimum mite control could be achieved when no brood is being produced, or when brood production is low, such as in the early spring or late fall. In established colonies in Florida, honey bee colony development did not increase under either Apistan or fungal treatments at the end of the experimental period, suggesting that other factors (queen health, food source, food availability) play some major role in the growth of bee colonies. Overall, microbial control of Varroa mites with fungal pathogens could be a useful component of an integrated pest management program for the honey bee industry.

Animals↗
PubMed2006

The compatibility of a nucleopolyhedrosis virus control with resistance management for Bacillus thuringiensis: co-infection and cross-resistance studies with the diamondback moth, Plutella xylostella.

The use of genetically modified crops expressing Bacillus thuringiensis (Bt) toxins can lead to the reduction in application of broad-spectrum pesticides and an increased opportunity for supplementary biological control. Bt microbial sprays are also used by organic growers or as part of integrated pest management programs that rely on the use of natural enemies. In both applications the evolution of resistance to Bt toxins is a potential problem. Natural enemies (pathogens or insects) acting in combination with toxins can accelerate or decelerate the evolution of resistance to Bt. In the present study we investigated whether the use of a nucleopolyhedrovirus (AcMNPV) could potentially affect the evolution of resistance to the Bt toxin Cry1Ac in Plutella xylostella. At low toxin doses there was evidence for antagonistic interactions between AcMNPV and Cry1Ac resistant and susceptible insects. However, this antagonism was much stronger and more widespread for susceptible larvae; interactions were generally not distinguishable from additive for resistant larvae. Selection for resistance to Cry1Ac in two populations of P. xylostella with differing resistance mechanisms did not produce any correlated changes in resistance to AcMNPV. Stronger antagonistic interactions between Bt and AcMNPV on susceptible rather than resistant larvae can decrease the relative fitness between Bt-resistant and susceptible larvae. These interactions and the lack of cross-resistance between virus and toxin suggest that the use of NPV is compatible with resistance management to Bt products.

Animals↗
PubMed2002

Lethal and sublethal effects of a granulovirus on the tomato moth Lacanobia oleracea.

A Scottish isolate of Lacanobia oleracea granulovirus (LoGV) was tested against larvae from a laboratory colony of L. oleracea (Lepidoptera: Noctuidae) using the peroral bioassay technique. The median lethal doses ranged from 10(1.38) occlusion bodies in first instar larvae to 10(7.45) in fifth instars. Sublethal effects on development and reproduction were observed among the survivors of virus challenge. Larvae dosed as first and second instars had faster developmental rates, and those dosed as fourth and sixth instars had reduced larval and pupal weights, compared to their respective controls. There was a 15% reduction in the number of eggs laid by adults that developed from infected larvae, but no reduction in egg viability. The F(1) generation did not show significantly greater mortality than controls, suggesting a lack of transovarial transmission. The significance of these results in terms of pest management of the tomato moth is discussed.

Animals↗
PubMed2001

Sex-biased dispersal and a density-independent mating system in the Australian brushtail possum, as revealed by minisatellite DNA profiling.

Natal dispersal can have important effects on mammal population structure and dynamics following a local population crash. Such dispersal is of practical importance when applied to the control of pest species because dispersal may significantly, and undesirably, reduce the population recovery time following a control operation. The relative dispersal rate of the sexes is also critical because that too will affect the rate of population increase. Here, we describe a field experiment in which we reduce the density of two populations of the Australian brushtail possum, and use genetic similarity, as estimated by minisatellite DNA profiles, to investigate dispersal in the original (undisturbed) and recovering populations. Our results show that the genetic similarity within the undisturbed populations was lower between males than between females. Conversely, the genetic similarities between males and females in the two recovering populations were not significantly different, while relatedness among males was significantly higher in the recovering populations when compared with those in the pre-removal populations. These data indicate two important characteristics of dispersal in possums: (i) that dispersal in established populations is sex biased towards males; and (ii) that within the first 3 years following population control, 'the vacuum effect', whereby individuals from areas adjacent to a control area expand their home range and invade the depopulated area, is the most important factor in the re-colonization process for possums. We found no evidence that the mating system, which is polygynous, varied when the density was markedly reduced. These results indicate that drastic reductions in population density by conventional control will not affect the rate of spread of biological control agents that rely on sexual transmission for dissemination.

Animals↗
PubMed2006

Effects of hydrophilic and hydrophobic kaolin-based particle films on pea aphid (Homoptera: Aphididae) and its entomopathogen Pandora neoaphidis (Entomophthorales: Entomophthoraceae).

Hydrophobic and hydrophilic kaolin-based particle films are effective for control of insect pests in certain agricultural crops. How these products interact with potential biological control agents is not well documented. This study was conducted to evaluate the effects of the hydrophobic (M96-018) and hydrophilic (Surround WP) kaolin-based particle films (Engelhard Corporation, Iselin, NJ) on pea aphid, Acyrthosiphon pisum (Harris), on peas (Pisum spp.), and on the fungal aphid pathogen Pandora neoaphidis (Remaudière and Hennebert) Humber. Over two field seasons (2001 and 2002) in northern Idaho, applications of M96-018 significantly reduced the rate of pea aphid increase on pea, but Surround WP, tested only in 2001, did not reduce aphid population growth rate. Neither particle film treatment was as effective as a standard application of esfenvalerate (DuPont Asana). In the laboratory, particle films suppressed pea aphid populations by up to 30%. M96-018 seemed to have some repellent activity based on aphid distributions after treating plants. When applied along with P. neoaphidis conidia, M96-018 but not Surround WP caused higher percentage of infection mortality of pea aphids by P. neoaphidis than occurred on controls treated only with P. neoaphidis conidia. P. neoaphidis conidia deposited on glass slides coated with M96-018, produced more germ tubes and secondary conidia than those deposited on untreated glass slides or slides treated with Surround WP. This result suggests that greater infection of pea aphids on plants treated with M96-018 is in part a result of a direct enhancement of fungal germination by the particle film.

Analysis of Variance↗
PubMed2000

The potential for antitick plants as components of an integrated tick control strategy.

Extracts from various African plants have been shown to possess strong acaricidal and/or tick repellent properties. Some of the plant extracts are capable of reducing tick feeding, molting, fecundity, and viability of eggs. Pasture grasses capable of repelling, trapping, and killing ticks have also been reported. These grasses possess hairs (trichomes) that retard ticks from climbing to the top of the grasses in order to attach themselves to passing animals. Furthermore, some grass species, such as Stylosanthes, produce viscous fluids that poison and kill ticks. Results obtained with antitick plants are presented in this paper and feasibility of using them in an integrated tick control strategy is discussed.

Africa↗
PubMed1996

Efficiency of Altosid (S-methoprene) liquid larvicide formulated on Biodac (granular carrier) against spring Aedes species in flooded woodlots.

Exposure of spring Aedes larvae to Altosid Liquid Larvicide formulated on the granular carrier Biodac under field conditions was evaluated. Both aerial and hand-applied treatments were monitored. Mosquitoes collected from aerially treated sites (9 kg/ha) showed an average 80% mortality. In hand-treated sites excellent control was achieved at label rates of 11.3-14.7 kg/ha (10-13 lb/acre); at dosages less than recommended rates, control was unsatisfactory.

Aedes↗
PubMed1976

The yellow mongoose (Cynictis penicillata) as a latent focus of rabies in South Africa.

The role of C. penicillata as a latent focus of rabies in South Africa is discussed. A description of the colony life, feeding and breeding habits and the relationship of the Yellow Mongoose to the Suricate Meerkat and Ground Squirrel is given. Observations on the epidemiology and symptomatology of rabies in the Yellow Mongoose are reported and various methods of control are suggested.

Animals↗