Journal of Pest Science最新文献

Studying the efficacy of control methods is paramount to successful management of invasive pests and understanding why some colonies survive is important to improve management practices. Here, the bait Vespex® was used to control invasive wasps across 64 ha of forest in an invaded range near Hanmer Springs, New Zealand. Bait was applied across a standard 50 m by 300 m arrangement and made available for 3 days. Nest mortality rates after 19 days were 29.8%, although nearly all nests were affected with a median overall reduction in nest traffic of 96.5%. The results from logistic regression showed that, all else remaining equal, larger wasp nests, nests further from bait stations, and more isolated nests exhibited lower rates of mortality after baiting. Investigating the change in activity at surviving nests, the results from beta regression suggest that declines in nest traffic were less severe with increasing distance to the nearest bait, but more severe with increasing nest size. These results indicate that while smaller nests are at a higher risk of being killed by the bait, they may not encounter bait as regularly as larger nests. Bait uptake varied considerably across bait stations. Wasp nests were not randomly or uniformly distributed in space, and instead were aggregated across our treatment area, likely due to some aspects of environmental conditions. We suggest further research to be focused on developing an understanding of the drivers of wasp nest development and foraging behaviour, to produce a more flexible baiting procedure that will increase both baiting efficiency and efficacy.

The Asian tiger mosquito Aedes albopictus is one of the most invasive species and an efficient vector of several pathogens. RNA interference (RNAi) has been proposed as an alternative method to control mosquito populations by silencing the expression of genes that are essential for their survival. However, the optimal delivery method for dsRNAs to enhance an optimal RNAi remains elusive and comparative studies are lacking. We have, therefore, compared the efficiency of three non-invasive delivery methods to mosquito larvae: soaking, rehydration and nanoparticle ingestion. Each method was tested separately on four genes predicted to code non-essential proteins (i.e., collagenase-like, kynurenine 3-monooxygenase-like, yellow-like and venom serine protease-like) in order to be able to compare the importance of gene knock-down. All tested methods successfully downregulated mosquito gene expression. However, silencing efficiency strongly varies among methods and genes. Silencing (95.1%) was higher for Kynurenine 3-monooxygenase-like with rehydration and nanoparticle ingestion (61.1%). For the Venom serine protease-like, the most efficient silencing was observed with soaking (74.5%) and rehydration (34%). In contrast, the selected methods are inefficient to silence the other genes. Our findings also indicate that gene copy numbers, transcript sizes and GC content correlate with the silencing efficiency. From our results, rehydration was the most specific and efficient methods to specifically knock-down gene expression in Ae. albopictus larvae. Nevertheless, considering the observed variability of efficiency is gene-dependent, our results also point at the necessity to test and optimize diverse dsRNA delivery approaches to achieve a maximal RNAi efficiency.

Endosymbionts living within insect cells can modify host fitness and could provide new tools for pest control. The endosymbiont Rickettsiella viridis has been transferred experimentally into the green peach aphid, Myzus persicae, a globally important agricultural pest. This Rickettsiella spreads via vertical and horizontal transmission and induces host fitness costs which could potentially suppress pest populations. Endosymbiont prevalence can fluctuate in natural populations, and it is important to identify factors that contribute to their spread or loss. Here, we explore the effects of Rickettsiella infection when aphids are reared on eight different host plants or exposed to thermal, starvation and desiccation stresses. Rickettsiella infection reduced M. persicae fecundity and longevity across all host plants, but the magnitude of costs varied among host plants and generations. Rickettsiella was horizontally transmitted and spread in caged populations at initial ratios of 1:2 Rickettsiella (+): Rickettsiella (−) on all host plants, but with limited long-term persistence under cycling 20–30 °C. We also identified temperature-dependent costs of Rickettsiella infection on heat knockdown time, chill coma recovery, and starvation tolerance. Finally, we present evidence that Rickettsiella infection reduces host activity levels under heat stress. Our results suggest that Rickettsiella infections induce a variety of deleterious effects but with complex environment-dependent interactions. This work helps understand ecological conditions that enhance or limit the spread of these endosymbionts in aphid populations.

The emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is one of the most destructive invasive forest pests in North America, where it has killed hundreds of millions of ash (Fraxinus spp.) trees since its first detection in 2002. Native to Asia, female EAB adults lay their eggs between bark crevices or under loose bark of their host trees. Because of this cryptic egg-laying behavior, field detection of EAB eggs has been extremely difficult, resulting in knowledge gaps of EAB egg-laying behavior. In the present study, I tested the potential use of strips of burlap fabric (0.03 m × 1 m) or polypropylene curling ribbon (0.005 m × 2 m) to induce female EAB adults to lay eggs on the trunks or branches of ash covered with these materials in the field. The burlap trap tested in this study detected more than twice as many EAB eggs (4.9 ± 1.1 eggs per burlap trap) as did the polypropylene ribbon trap (1.9 ± 0.5 eggs per ribbon trap). When the surface area of each trap is standardized to one square meter, however, both burlap fabric and polypropylene ribbon traps are equally effective in inducing female EAB adults to lay eggs onto the covered surface of ash trunks or branches. Potential applications of the oviposition traps for effective detection and control of EAB and other jewel beetles are discussed.

Pyrethroid resistance has become one of the largest obstacles to mosquito control, and Anopheles sinensis is the main malaria vector in China and southeast countries. miRNAs play important roles in many biological processes in insects; however, the diversity and regulation of miRNAs associated with pyrethroid resistance are still little understood at the whole-genome level. This study performed the sequencing and analysis of miRNAs relative to pyrethroid resistance in An. sinensis for the first time, and identified 328 miRNAs, of which 247 are new. A total of 39 miRNAs are identified to be significantly downregulated commonly in all three pyrethroid-resistant populations investigated in comparison to the susceptible strain. There are 7475 genes to be predicted to be targeted by the 39 significantly down-regulated miRNAs, and they were enriched to seven pathways. The regulation of Transferrin by asi-miR-87 was verified using dual-luciferase, and the asi-miR-87 might be involved in P450 pyrethroid detoxification with the affection of iron ion transportation and synthesis through Transferrin. In addition, nine miRNAs were identified to be positively relative to eight genes. This is the first systematic study on the diversity and regulation of miRNAs associated with insecticide resistance at the whole-genome level, and provides an information frame for the understanding of miRNAs and their function in insecticide resistance.

The use of semiochemical-baited traps for detection, monitoring, and sampling bark beetles and woodboring beetles (BBWB) has rapidly increased since the early 2000s. Semiochemical-baited survey traps are used in generic (broad community level) and specific (targeted toward a species or group) surveys to detect nonnative and potentially invasive BBWB, monitor established populations of invasive or damaging native species, and as a tool to survey natural communities for various purposes. Along with expansion in use, much research on ways to improve the efficacy of trapping surveys for the detection of specific pests as well as BBWB in general has been conducted. In this review, we provide information on intrinsic and extrinsic factors and how they influence the efficacy of detecting BBWB in traps. Intrinsic factors, such as trap type and color, and other factors are described, as well as important extrinsic factors such as habitat selection, horizontal and vertical placement, and disturbance. When developing surveys, consideration of these factors should increase the species richness and/or abundance of BBWB captured in traps and increase the probability of detecting nonnative species that may be present. During generic surveys, deploying more than one trap type or color, using an array of lures, and trapping at different vertical and horizontal positions is beneficial and can increase the number of species captured. Specific surveys generally rely on predetermined protocols that provide recommendations on trap type, color, lure, and trap placement.

Many plant parasitic and entomopathogenic nematodes harbor specialized and obligate bacteria as well as viruses. Given their evolutionary persistence, such cryptic species are considered to play effective roles during their host/microbe interactions lifetime, including mutualistic, antagonistic, or yet unknown host effects. To exploit such associations in plant protection, a comprehensive view is needed linking basic evolutionary relationships to applied aspects. This requires identifying the benefit or impact that hosts, acting as pests or biocontrol agents, receive from their endosymbionts. Targeting endosymbionts that are vital for a beneficial nematode or a pest may open novel perspectives for the management of their performance and traits, such as virulence or response to plant defense reactions. Some hypotheses are proposed to develop advanced control strategies through emerging biotechnological approaches.

RNAi-based pesticides have emerged gradually in recent decades and are believed to be the next generation of pesticides. Although resistance to RNA pesticides has been developed and selected in the laboratory in western corn rootworm and Colorado potato beetle, whether RNAi resistance is a general phenomenon in other coleopteran insects and the underlying mechanism of resistance to RNA pesticides are still unclear. Here, we report the development of a highly dsRNA-resistant (> 4110-fold) population (Pv-30R) of Plagiodera versicolora after seven episodes of selection by feeding a laboratory-reared susceptible population (Pv-S) with the leaves of willow plants coated with dsRNA targeting a signal recognition particle protein 54 k (Srp54k) gene. We showed that Pv-30R was cross-resistant to other dsRNAs (dsActin and dsSnap) but susceptible to the Cry3Bb protein from Bacillus thuringiensis, and the resistance was an autosomal and recessive trait. Although no significant differences of the dsRNA stability in the midgut of larvae between Pv-S and Pv-30R were observed, uptake of dsRNA in the midgut tissue of larvae from Pv-30R was disrupted. Overall, these results demonstrate that high levels of resistance to RNA pesticides can developed quickly in P. versicolora in laboratory condition as observed before for other coleopterans, and possibly sharing similar mechanisms of resistance to dsRNA.

In agroecosystems, the efficiency of biocontrol agents could be improved through the artificial selection of specific traits that would enhance their zoophagy level. The aim of this study was to evaluate the impact of artificially selected populations of the omnivorous predatory bug, Nabis americoferus, on the tarnished plant bug, Lygus lineolaris, in organic strawberry crops. Six populations of N. americoferus were selected according to their aggressiveness, three were composed of highly aggressive individuals, whereas the other lines contained docile individuals. The first hypothesis was that, since aggressive predators display a higher attack rate, aggressive lines would exhibit a higher pest control and a better crop protection than docile lines. The second hypothesis was that, when two biocontrol agents species are used conjointly, the presence of at least one docile population would generate a higher synergy between both species. N. americoferus populations were released in an experimental strawberry field, with or without a second intraguild predator, the Anthocorid, Orius insidiosus. Results support the first hypothesis that the aggressive lines generate a better pest control and a better strawberries crop protection than docile lines but only at low pest density. The second hypothesis is neither supported nor rejected since the combination of docile lines and O. insidiosus led to a better pest control at high pest density, but led to a reduced crop protection at low pest density. Our study shows that the artificial selection of aggressiveness has the potential to improve the effectiveness of biocontrol programs.

Rising temperatures due to climate change are predicted to accelerate the life cycle of arthropod herbivores thereby exacerbating pest formation. Notorious pests like spider mites thrive in areas with high temperatures (32–35 °C), and it is predicted that the size and number of such areas will expand in the coming decades. Higher temperatures can directly accelerate population growth, but also indirectly affect them through changes in the plant's defensive mechanisms. Spider mites have been shown to adapt to plant defences, with natural selection favouring defence-suppressing traits. However, it is not known to what extent suppression is affected by rising temperatures and how this might tie into the rate of adaptation and pest damage. In this study, we investigated the effect of two temperatures (25 °C and 32 °C), on the spider mite–tomato interaction, predicting the influence of rising temperatures on favouring defence-adapted mites. We found that all mite strains caused more plant damage at 32 °C, but temperature did not affect the overall patterns of induction and suppression of defence genes. Although fecundity was higher for all strains at 32 °C, juvenile and adult survival was lower, especially for inducer mites. With these data, we parametrized population models for the two strains over three months, indicating that suppressor mites might displace inducers at the higher temperature, either when it is constant or in the form of heat waves. Our models predict that in areas with higher temperatures, defence-suppressing mites are favoured, which will accelerate and consequently spur pest formation.