The green lacewing Chrysopa formosa as a potential biocontrol agent for managing Spodoptera frugiperda and Spodoptera litura.

Recent advances in biological control of important native and invasive forest pests in China

Predation of mosquitos by odonates in a tropical urban environment: insights from functional response and field mesocosm experiments

Understanding the density-dependent impacts of an invasive predator is integral for predicting potential consequences for prey populations. Functional response experiments are used to assess the rate of prey consumption and a predator’s ability to search for and consume prey at different resource densities. However, results can be highly context-dependent, limiting their extrapolation to natural ecosystems. Here, we examined how simulated habitat complexity, through the addition of substrate in which prey can escape predation, affects the functional response of invasive European green crabs (Carcinus maenas) foraging on two different bivalve species. Green crabs feeding on varnish clams (Nuttallia obscurata) shifted from a Type II hyperbolic functional response in the absence of substrate to density-independent consumption when prey could bury. Green crabs ate few Japanese littleneck clams (Venerupis philippinarum) under all densities, such that no functional response curve of any type could be produced and their total consumption was always density independent. However, the probability of at least one Japanese littleneck clam being consumed increased significantly with initial clam density and crab claw size across all treatments. At mean crab claw size and compared to trials without substrate, the proportion of varnish clams consumed were 4.2 times smaller when substrate was present, but substrate had a negligible effect (1.2 times) on Japanese littlenecks. The proportion of varnish clams consumed increased with crab claw size and were higher across both substrate conditions than the proportion of Japanese littlenecks consumed; however, the proportion of Japanese littleneck clams consumed increased faster with claw size than that of varnish clams. Our results suggest that including environmental features and variation in prey species can influence the density-dependent foraging described by functional response experiments. Incorporating replicable features of the natural environment into functional response experiments is imperative to make more accurate predictions about the impact of invasive predators on prey populations.

Summary Functional and numerical responses are key components in the selection of predators for biological control. We examined the relevance of these responses for predicting the effectiveness of generalist predators, taking into account effects of alternative prey and multiple predators. Our system involved two acarine predators of two prey species on apple. Responses were measured on leaf discs in the laboratory, and predictions assessed on small potted apple trees. In particular, we tested three hypotheses. Hypothesis I: the species with the higher predatory responses will be more effective in limiting prey populations. Neither predator had a consistently higher functional response, which depended on prey stage and species. Amblyseius fallacis had a (approximately two times) higher ovipositional response than Typhlodromus pyri. We therefore hypothesized that A. fallacis would be more effective in controlling prey. No evidence was found to support this hypothesis. Hypothesis II: alternative prey reduce the functional response of predators to target prey. Alternative prey did or did not reduce the functional response to target prey, depending on the predator, stage and species of alternative prey. The only consistent trend for both predators was that the predation of Panonychus ulmi deutonymphs was reduced when Tetranychus urticae was present. Hypothesis III: the predator species with the highest mean ovipositional response will out‐compete the other predator species. The number of predators observed in the mixed predator treatments depended on the prey composition. Although A. fallacis had a higher ovipositional response, it was never more abundant. Intraguild predation probably played a role in determining predator abundance, although prey composition altered intraguild effects. These results highlight the complex nature of predator and prey interactions. Because of these interactions, functional and numerical assays on single predator–single prey systems in simplified laboratory environments do not allow predictions of the growth of mixed populations in realistic habitats, or of the effectiveness of predators as biological control agents in the field.

The invasive tomato spider mite, Tetranychus evansi (Acari: Tetranychidae) is one of the major pests of the solanaceous plants worldwide. The phytoseiid predatory mite Amblyseius swirskii (Acari: Phytoseiidae) is one of the most commonly used predatory mites for augmentative biological control of several important pests in protected crops. Despite its frequent usage in a range of greenhouse crops including tomatoes, several biological characteristics and foraging behaviors of this predator such as functional and numerical responses, have not been studied on T. evansi. In this study, the functional and numerical responses of A. swirskii to four different biological stages (eggs, larvae, protonymphs and deutonymphs) of T. evansi were evaluated under laboratory conditions. The significantly negative P1 values and the type of functional response curves clearly indicate that A. swirskii exhibited a Type II functional response to T. evansi regardless of prey stage. The highest attack rate (α=0.070 h-1) and the shortest handling time (Th=0.426 h) were determined when the predator fed on protonymph and larva, respectively. The highest daily mean number of eggs (1.10±0.10) laid by A. swirskii was obtained at 120 egg density. No significant difference was determined in egg production of the predatory mite among different life stages within the same prey density except 10 prey density. In addition, there was also no difference among prey densities within the same biological stage, except egg stage. According to the results, A. swirskii may not be directly recommended for the biological control of T. evansi on tomato. However, when its inundative release is considered, it may help and improve the success of biological control of T. evansi, especially at early stages of infestations.

Report of an Intracellular Bacterial Symbiont in Noctuidonema guyanense, an Ectoparasitic Nematode of Spodoptera frugiperda

Prey stage preference and functional response of the predatory mite Galendromus flumenis to Oligonychus pratensis

The lifetime functional response and predation rate of Amblyseius swirskii Athias-Henriot on eggs of the two-spotted spider mite, Tetranychus urticae Koch were determined under laboratory conditions using cucumber leaf discs. Densities of 2, 4, 8, 16, 32, 64 and 128 prey were offered to 3, 4, 5, 6, 7, 12, 17, 22 and 27-day-old A. swirskii individuals. Based on the logistic regression, the functional response of twelve-day-old A. swirskii was type III, while the other ages showed type II. The Rogers model was used to estimate searching efficiency (a) and handling time (Th). The longest handling time (1.387±0.315 h) was observed in the protonymphal stage, while the shortest handling time and highest maximum attack rate (T/Th) were estimated at the age of seven-days (0.396±0.057 h and 60.67 prey/day, respectively). In the functional response experiments, results of the highest prey density used (128 eggs) showed that the highest number of prey consumed by A. swirskii individuals aged twelve and seventeen-days old (35.6 and 43.1 eggs, respectively). It is concluded that A. swirskii could be an efficient biological control agent of T. urticae at the middle-age of its life and at higher prey densities.

The rose aphid, Macrosiphum rosivorum (Zhang), is a serious pest of roses in China. Currently, M. rosivorum is managed using almost exclusively with insecticides; therefore, effective, alternative strategies are needed to reduce this dependence on pesticides and the risk of the development of resistance in rose aphids. This study was conducted to evaluate the potential of the seven-spot ladybird, Coccinella septempunctata (L.), as a biological control agent of M. rosivorum in rose production fields. We determined the prey preference of C. septempunctata at constant densities of M. rosivorum for 1st – 4th instar nymphs and for adults. The results showed that Coccinella septempunctata adults had its highest rate of consumption on 4th instars and its lowest rate of consumption on adults among prey life stages. Furthermore, we defined the functional response of predator adults. C. septempunctata adults displayed a type II functional response on all prey stages. The highest attack rate and shortest handling time were for predators fed 1st instar aphids. The proportion of prey consumed by C. septempunctata was higher at lower densities for all stages of rose aphid, implying that C. septempunctata should be released early in an aphid infestation. Our study indicated that C. septempunctata has the potential to be used for control of rose aphids in rose-production fields.

Functional and numerical responses of Stethorus tridens Gordon (Coleoptera: Coccinellidae) preying on Tetranychus bastosi Tuttle, Baker & Sales (Acari: Tetranychidae) on physic nut (Jatropha curcas)

The effect of prey species and the different stages of prey on the predatory efficiency and biology of the phytoseiid mites,Amblyseius gossipi Elbadry andTyphlodromus mangiferus sp. n. was studied. It was found that feeding either predator onTetranychus cucurbitacearum (Sayed) promoted faster development and a higher rate of oviposition than rearing on the twospotted spider mite,T. urticae (Koch). Different stages of both prey species also produced different responses in the biological activities of these predaceous mites.

Assessment of the functional response parameters of Coccinella septempunctata to varying densities of Acyrthosiphon pisum

Understanding of predators functional responses is critical in assessing their efficiency as biological control agents. This study investigates the functional responses of three coccinellid predators Scymnus posticalis Sicard (Coleoptera: Coccinellidae), Platynaspis saundersi Crotch (Coleoptera: Coccinellidae), and Pharoscymnus horni Weise (Coleoptera: Coccinellidae) against varying densities of the prey aphid, Myzus persicae (Hemiptera: Aphididae) under controlled conditions (25 ± 1°C temperature, 70 ± 5% relative humidity and 14 L:10D photoperiod). Predation trials across different prey densities were performed with these adult coccinellid predators. Logistic regression analysis confirmed a Type II functional response for all the three species used in the experiments. Among the three, S. posticalis showed a superior predatory efficiency, with the highest attack rate (a) (0.0994 h-1), shortest handling time (Th) (0.5016 h) and a maximum theoretical predation rate (K) of 48.76 aphids. P. saundersi and P. horni showed lower predatory parameters, positioning S. posticalis as the most efficient predator. These findings underscore S. posticalis as a promising candidate for biological control of M. persicae, with a clear advantage in predation metrics over P. saundersi (a = 0.0876 h-1; Th = 0.5193 h; K = 48.27 aphids) and P. horni (a = 0.0695 h-1; Th = 0.5316 h; K = 47.97 aphids). However, further field validation is essential to assess its real-world efficacy, considering environmental variability and complex ecological interactions.

Ecological traps are threats to organisms, and exist in a range of biological systems. A subset of ecological trap theory is the "ethological trap," whereby behaviors canalized by past natural selection become traps when environments change rapidly. Invasive predators are major threats to imperiled species and their ability to exploit canalized behaviors of naive prey is particularly important for the establishment of the predator and the decline of the native prey. Our study uses ecological theory to demonstrate that invasive predator controls require shifts in management priorities. Total predation rate (i.e., total response) is the product of both the functional response and numerical response of predators to prey. Functional responses are the changes in the rate of prey consumption by individual predators, relative to prey abundance. Numerical responses are the aggregative rates of prey consumption by all predators relative to prey density, which change with predator density via reproduction or migration, in response to changes in prey density. Traditional invasive predator management methods focus on reducing predator populations, and thus manage for numerical responses. These management efforts fail to manage for functional responses, and may not eliminate impacts of highly efficient individual predators. We explore this problem by modeling the impacts of functional and numerical responses of invasive foxes depredating imperiled Australian turtle nests. Foxes exhibit exceptionally efficient functional responses. A single fox can destroy >95% of turtle nests in a nesting area, which eliminates juvenile recruitment. In this case, the ethological trap is the "Arribada" nesting strategy, an emergent behavior whereby most turtles in a population nest simultaneously in the same nesting grounds. Our models show that Arribada nesting events do not oversaturate foxes, and small numbers of foxes depredate all of the nests in a given Arribada. Widely scattering nests may reduce fox predation rates, but the long generation times of turtles combined with their rapid recent decline suggests that evolutionary responses in nesting strategy may be unlikely. Our study demonstrates that reducing populations of highly efficient invasive predators is insufficient for preserving native prey species. Instead, management must reduce individual predator efficiency, independent of reducing predator population size.

Insect parasitoids have been used for the biological control of insect pests through classical importations for the control of invasive phytophagous species, through seasonal or inundative releases for short-term suppression of indigenous or invasive pests, and through conservation of parasitoid activity by the provisioning of resource subsidies and alteration of management practices. In all cases, success in the suppression of a pest is dependent upon the behavioral decisions made by the parasitoid in searching for and parasitizing hosts. For example, in the case of classical biological control, patch choice decisions that maximize parasitoid fitness will tend to increase its regional impact, leading to greater suppression of the pest and success in biological control. In contrast, for augmentative biological control, the goal is to provide local pest suppression and behavior that maximizes fitness might, for example, lead parasitoids to abandon local patches of their hosts before the pest has been suppressed to the desired level. Thus, the behavioral ecology of insect parasitoids is central to the successful implementation of biological control programs. We explore how optimal foraging effects the suppression of global pest densities in a metapopulation context and to what extent the physiological condition and behavioral decisions of foraging parasitoids are likely to influence establishment and impact in classical biological control. In the case of inundative biological control, we discuss the trade-off between optimal foraging behavior and the level of pest suppression at a local scale and consider the use of chemical attractants and arrestants to increase parasitoid activity and patch time allocation. We also discuss the influence of host size and quality, and sex ratio (Wolbachia infection) on parasitoid mass rearing. Finally, the influence of nectar subsidies on parasitoid foraging behavior and host suppression is considered in the context of developing more efficient methods for conservation biological control. 1 Optimal foraging behavior and efficient biological control methods Nick J. Mills and Eric Wajnberg 4 N.J. MILLS AND E. WAJNBERG