Predicting predation efficiency of biocontrol agents: linking behavior of individuals and population dynamics (original) (raw)
Related papers
Modelling Population Dynamics of Aphids and Their Natural Enemies
Aphid Biodiversity under Environmental Change, 2010
Aphids are serious pests of many agricultural crops. Therefore, a good understanding of their population dynamics is vitally important for crop protection. There have been several attempts were made to forecast the abundance of aphids and develop expert systems to help farmers optimize prophylactic measures and minimize their costs. The advisory systems, however, did not receive general acceptance and disappointingly few forecasting systems are in use. The failure of models to predict aphid population dynamics for practical purposes is due to the extremely wild oscillations in aphid numbers caused by intrinsic (size, fecundity, mortality, migration rate) and external factors (weather, especially temperature). As a consequence, the predictions are unlikely to be robust enough for reliable forecasting, mainly because they depend on the course of weather during the season, which cannot be predicted. Here we present a critical review of existing models of aphid population dynamics, examine biological assumptions that are incorporated in the models and present one of the latest models of aphid metapopulation dynamics. We conclude that natural enemies are unlikely to affect aphid population dynamics late in the season, but may have an effect very early in the season, when aphid colonies are still small and predators might be able to reduce the numbers of these colonies. Empirical verification of this is still very weak, however, and further experiments on this aspect of predator prey dynamics should be undertaken.
1995
A model was developed to estimate the effect of predation by Episyrphus balteatus larvae on aphid populations in fields of winter wheat. Feeding rate of syrphid larvae was estimated from experiments in field cages using a Holling type-III function. During larval development, syrphids consumed a maximum of 396 aphids, which is only half the potential feeding rate reported from laboratory experiments. The lower consumption rate in the field may be attributed to the additional time required by the predators to find prey. Isoclines derived from the model were used to estimate the abundance of syrphid larvae necessary to prevent further pest increases
PAST AND FUTURE MODELS OF PREDATOR-PREY POPULATION DYNAMICS: THE IMPORTANCE OF GENERATION TIME RATIO
Mathematical models of predator-prey population dynamics are widely used for predicting the effect of predators as biological control agents, but the assumptions of the models are more relevant to parasite-host systems. Predator-prey systems, at least in insects, substantially differ from what is assumed by these models. The main differences are: (i) Juveniles and adults have to be considered as two different entities, as the former stay within a patch and do not reproduce, while the latter move between patches of prey where they reproduce. (ii) Because of their high mobility, food availability is likely to be less restrictive for adults than juveniles, which are confined to one patch. Therefore, a functional response to prey abundance may not be important for adults. (iii) Egg and larval cannibalism are common in insect predators. Therefore, the quality of patches of prey for their larvae determines the reproductive strategy of adult predators more than the availability of food for the adults. Here we develop a new model, based on the above considerations, which is suitable for modelling these interactions. We show that selection should favour mechanisms that enable predators to avoid reproducing in patches with insufficient prey and those already occupied by predators.
Annals of Applied Biology, 1999
We tested in a field experiment two hypotheses for why polyphagous predators aggregate at concentrations of aphids: 1) because they are attracted directly to aphids as prey, or 2) because they are attracted to alternative prey that aggregate around the honeydew produced by aphids. Small plots were established in the field with two experimental treatments, aphid addition and honey spraying, and a watersprayed control, each replicated 10 times. Arthropods were recorded by pitfall traps and sticky traps in each plot. Diptera were significantly more abundant in the honey plots. Of the predators, Agonum dorsule, "All carabids" and Philonthus sp. were most ,abundant in the honey plots; Tuchyporus spp. and carabid and staphylinid larvae were most abunda;t-in the aphid addition plots. It is suggested that these results reflect differences among the predators in their ability to tolerate and utilise aphids as food.
The quality of aphids as food for generalist predators: implications for natural control of aphids
European Journal of Entomology, 2005
The paper reviews existing data on the food quality of cereal aphids for generalist predators. Data are presented for spiders, harvestmen, carabid and staphylinid beetles, cockroaches, ants and one species of bird. All results agree that cereal aphids are low-quality food compared to alternative prey types (in most studies fruit flies). This is associated both with a low consumption capacity for aphids and a low utilization efficiency of the aphid food. A pure aphid diet allows full juvenile development in only a few species. Aphids as part of mixed diets can have negative, neutral or positive effects, which depends on the quality of the remaining diet. The low consumption capacity for aphids is due to the development of a specific feeding aversion. Genetic variation in the ability to tolerate aphids has been documented, indicating that predators may be able to adapt to a higher proportion of aphids in the diet in areas where outbreaks are frequent. A consequence of these findings is that predator populations rely on alternative prey (e.g. Collembola and Diptera) for maintenance and reproduction, and are probably unable to benefit nutritionally from an aphid outbreak. The low food quality of aphids to generalist predators explains why generalist and specialist predators have widely different roles in aphid biocontrol, but does not rule out that under some conditions the generalists may be able to inhibit aphid population growth sufficiently to prevent an outbreak, as field experiments have indicated. Simulation modelling shows that a low consumption capacity for aphids has little influence on the ability to prevent aphid population increase at low aphid immigration rates, but a great influence at high aphid immigration rates. Modelling also indicates that there may be an optimal availability of high-quality alternative prey that maximizes the impact of generalist predators on aphid population growth.
Dynamics of food-prey-predator systems and agricultural practices
Crop fields are complex systems where the basic crop interacts with species that feed from it, and are, in turn, depredated or parasited by other species. These relations create a dynamic system with several counterintuitive behaviours. On the other hand agricultural practices based on pesticide application have been subject to debate and the economic benefits of chemical pesticides and their externalities are questioned , Tjomhom1998, Widawsky 1998. This paper presents a food-prey-predator model of an agricultural system. The singular dynamics of this system and the effects of pesticide application on it are studied. There are many examples of agricultural plagues subject to predation, each one having its particular dynamics, but the model presented in this paper is a general one that aims to capture the most general features of pests dynamics. The results show that the prey-predator dynamics is an important fact to take into account if pesticides are applied, the effects of several agricultural practices concerning pesticide application and the development of pesticide resistances are investigated. Food-prey model. The simplest model developed is the food-prey model (figure 1). The food is harvested every season. Growth rates, carrying capacity and food per prey parameters can only be chosen within a restricted set, otherwise the prey would extinct (figure 2).
Entomologia Experimentalis et Applicata, 2006
Ecologists may wish to evaluate the potential for predators to suppress prey populations through the costs of induced defensive behaviors as well as through consumption. In this paper, we measure the ratio of non-consumptive, defense-inducing encounters relative to consumptive encounters (henceforth the 'disturbed : consumed ratio') for two species of aphids and propose that these disturbed : consumed ratios can help evaluate the potential for behaviorally mediated prey suppression. For the pea aphid, Acyrthosiphon pisum (Harris) (Homoptera: Aphididae), the ratio of induced disturbances to consumption events was high, 30 : 1. For the cotton aphid, Aphis gossypii (Glover) (Homoptera: Aphididae), the ratio of induced disturbances to consumption events was low, approximately 1 : 14.
Biocontrol, 2004
Generalist predators are potential controlagents of aphids in cereal fields. Becauseaphids are low-quality prey for most generalistpredators, the availability of alternativehigh-quality prey may influence theinteractions between aphids and their predatorsby reducing the predation rate due to loweredpreference for aphids. We analysed this bytesting the ability of six generalist predators(the spiders Erigone atra (Bl.), Clubiona lutescens (Westr.)/reclusaO.P.-C., Pachygnatha degeeri Sundevall,Pardosa prativaga (L.Koch), the carabidbeetle Bembidion lampros (Herbst), andthe harvestman Oligolophus tridens (C.L.Koch)) to suppress Rhopalosiphum padi(Linné) populations in the presence orabsence of alternative prey types (fruit fliesDrosophila melanogaster (Meigen) or thecollembolan Tomocerus bidentatus(Folsom)). Experiments of 10 days duration werecarried out in a microcosm set-up. Withoutalternative prey all predators except B.lampros were able to reduce aphid populationdevelopment significantly relative topredator-free controls. The harvest spider O. tridens was the most efficient predator(<90% reduction). Presence of alternativeprey (fruit flies) had a significant negativeeffect on aphid limitation by P. prativagaand a weak positive effect in B. lampros, but did not influence the ability to reduce aphids in E. atra, Clubiona, P. degeeri and O. tridens. In addition, 24-hours' consumption experiments with adult P. degeeri and subadult C. lutescens/reclusa, using R. padi and D. melanogaster as prey types, showed markedly lower consumption rates of aphid than of fruit fly prey. The microcosm arrangement is a simple way to partly simulate the habitat complexity of an agricultural field under laboratory conditions and proved to be a useful tool for investigating complex predator-prey interactions.