Journal of Pest Science最新文献

Studies using nonhost plant odors to deter insect pests and protect host plants have reported mixed results. Moreover, how adjacent nonhost plants affect the ability of insect herbivores to locate hosts is unclear. We examined the effects of location of two nonhost rosemary plants (Rosmarinus officinalis) relative to a host peanut plant (Arachis hypogaea) under fixed wind direction on the host-finding ability (number of eggs laid) of Spodoptera exigua. We then correlated the effects with the degree of odor mixing between the host and nonhost plants. Subsequently, we investigated whether row orientation affects the ability of insects to find hosts. The degree of odor mixing between host and nonhost plants was greater when the rosemary plants were upwind and downwind than when they were crosswind from the peanut plants. Closer plant spacing resulted in more odor mixing. The number of eggs laid on peanut plants was reduced when the degree of odor mixing was high. When rosemary plants were replaced with odorless plastic plants, the odorless plants upwind and downwind from the peanut plant were also associated with fewer eggs laid. In the field, significantly fewer eggs were laid on peanut plants when the row orientation was perpendicular to the prevailing wind direction. Nonhost rosemary plant location relative to the host plant significantly affected the host-finding ability of S. exigua by influencing the degree of odor mixing between host and nonhost plants and by physical barrier effects of nonhost plants. Our results may provide insights for future pest management strategies.

In this study, we hypothesized that Crotalaria juncea (L., Fabaceae), particularly due to its content of the pyrrolizidine alkaloid monocrotaline, would affect the development, fecundity, and longevity of Diabrotica speciosa (Germar) Coleoptera: Chrysomelidae). We initially assessed the effects of C. juncea plants and their various parts (leaves, stems, and roots) on the insect. Newly hatched larvae were inoculated in containers with (i) popcorn plants (Zea mays L. var everta); (ii) C. juncea plants; (iii) popcorn plants associated with C. juncea; and (iv) popcorn plants with portions of leaves, stems, and roots (mulch) of C. juncea (25 ± 2 °C, 60 ± 10% RH, and a 14-h photoperiod). The larvae were kept in these conditions until adult emergence, after which the adults were provided with common bean leaflets. The presence of C. juncea during the larval stage influenced the biological parameters of D. speciosa. We observed 100% larval mortality when exposed to isolated C. juncea plants, and a decrease in immature survival and adult longevity when C. juncea was associated with popcorn. In a subsequent trial, we investigated the effects of crude organic extracts of C. juncea on the same biological parameters. Newly hatched larvae were placed on popcorn plants with roots treated with extracts from different parts of C. juncea (aerial parts, roots, and entire plants) and using various solvents (hexane, dichloromethane, and methanol) as extractors. Plants with roots treated with root extracts of C. juncea exhibited lower survival rates during the immature stage, as well as reduced fecundity and egg viability. This indicates that allelochemicals from C. juncea have a detrimental impact on the development, fecundity, and viability of D. speciosa eggs. Chemical analysis of the C. juncea extracts revealed that monocrotaline, while present in various plant parts, is not the sole component responsible for the observed effects on the insects.

The Japanese beetle (Popillia japonica) is an invasive scarab beetle originating from Japan. In the European Union, it is listed as a priority quarantine pest. Currently, it is mainly controlled using synthetic insecticides. Here, we tested an environmentally friendly control alternative. We investigated whether Japanese beetle adults can be used as vectors to autodisseminate lethal doses of the European native entomopathogenic fungus Metarhizium brunneum ART 212 within adult populations. Additionally, we tested whether infested females could carry conidia into the soil environment during oviposition, increasing neonate larval mortality. We showed that inoculated adults can indeed transmit the fungal conidia horizontally for up to two days, significantly reducing the survival of both donor and recipient beetles in same-sex and opposite-sex couples. Furthermore, horizontal transmission among adults was verified under semi-field conditions. Another set of laboratory tests showed that beetles carried the inoculum to their oviposition sites, where larval survival was reduced at high concentrations (≥ 1.11 × 10⁵ conidia/g substrate). However, the release of inoculated beetles in semi-field cages resulted in soil fungal concentrations more than ten times lower, failing to provide larval control. Thus, carriage of M. brunneum ART 212 into the soil by female vectors does not seem to provide control of larvae outside the laboratory setup. However, our results suggest that lethal conidial doses can be autodisseminated among the more susceptible adults. This may be the basis for an environmentally friendly control strategy against invasive Japanese beetle adults, applicable in both agricultural and non-agricultural areas.

The vast majority of historical biological control introductions have not resulted in documented negative effects on non-target species. However, in some cases, an absence of evidence of harm could be due to insufficient evidence of absence: That is, data specifically gathered to show that non-target species are not affected by the released biological control agent. The parasitoid fly Istocheta aldrichi (Mesnil) (Diptera: Tachinidae) was introduced to North America a century ago as a biological control agent targeting the invasive Japanese beetle, Popillia japonica Newman (Coleoptera: Scarabaeidae). Despite its longstanding and widespread establishment, the host specificity of I. aldrichi remains underexplored due to a lack of dedicated post-release monitoring. Leveraging crowdsourced data from iNaturalist.org, we investigated potential non-target parasitism among scarab beetles observed within the current geographic range of I. aldrichi. The taxonomic accuracy of iNaturalist identifications was evaluated and curated. Our analysis of > 21,000 observations of non-target scarabs photographed within the geographic range of I. aldrichi suggests that I. aldrichi is highly specific to P. japonica. Candidate parasitoid eggs resembling those of I. aldrichi were extremely rare on non-target species, representing less than 0.001% of all observations and not exceeding 1.3% of observations for any individual non-target species. These findings provide evidence that the incidence of non-target attacks by I. aldrichi is likely negligible, at least with respect to the scarab species commonly observed on iNaturalist. They also show the potential for crowdsourced data to complement traditional methods assessing whether non-target ecological impacts may have resulted from past biological control introductions.

Plants can acquire an enhanced resistance against pathogen by application of natural or artificial compounds. Application of these compounds results in earlier, faster and/or stronger responses of plant to the subsequent pathogen attacks, a process called chemical priming. Beta-aminobutyric acid (BABA) is recognized for its inducing and priming ability to enhance plant resistance against a broad spectrum of pathogens. However, BABA potential to induce and prime pepper plant (Capsicum annuum) resistance against the invasively polyphagous MEAM1 whitefly remains understudied. In the present study, we sprayed pepper plants with 20 mM BABA to assess its defense responses, as well as the host preference and performance of MEAM1. We found that MEAM1 showed a substantial preference for settling and laying eggs and a significantly higher performance on untreated plants in comparison with those treated with BABA. Compared with the control plants, BABA-treated pepper plants significantly increased the contents of total phenols and flavonoids, which coincided with the increased expression of the genes in the phenylpropanoid pathway. These results suggest that induced resistance of pepper by BABA application reduced MEAM1 host preference and performance. Furthermore, MEAM1 infestation on BABA-treated pepper plants significantly increased the contents of total phenols and flavonoids, and their expression of the genes in the phenylpropanoid biosynthesis pathway. Collectively, our findings suggest that BABA is a potent chemical inducer and priming agent, capable of bolstering pepper resistance against MEAM1. The resistance mechanism is partly due to the activation of the salicylic acid (SA) signaling and the phenylpropanoid metabolic pathways.

Prey sharing in predatory mammals and birds has been shown to reduce fights for food between predators, increase predation efficacy, and safeguard food availability by reciprocal sharing, providing immediate and delayed benefits for the sharers. However, little is known about the incidence of prey sharing in arthropods and the implications for biological control have been mostly overlooked. In this study, the feeding behavior of two aphid predators, Micromus angulatus and Chrysoperla carnea, was investigated to assess the incidence of prey sharing and its possible consequences for biological control of aphids. A video-recording setup was used to investigate the feeding behavior of the predators at various predator/prey ratios. Different numbers of predatory larvae were placed into arenas containing five Myzus persicae subsp. nicotianae. The behavior of the predators was recorded for four hours and the number of prey killed was scored. Our results indicate that prey sharing is a density-dependent behavior, increasing at higher predator/prey ratios. Larvae of M. angulatus performed prey sharing seven times more often than C. carnea and accepted higher numbers of predators sharing a single aphid. Interestingly, a positive correlation between the number of prey-sharing events and the number of aphids killed by the predators was found, suggesting that prey sharing could increase the kill rate of the predators. Additionally, the presence of conspecific larvae enhanced the predation success of M. angulatus. Our findings indicate that prey sharing is an adaptive behavior that could improve the foraging efficacy and kill rate of arthropod predators.

Principal active ingredients used in chemical control tactics after harvest are pyrethroids, including for long-lasting insecticide-incorporated netting (LLIN). However, pyrethroid resistance by stored product insects has become widespread. Thus, the aim of our study was to evaluate whether a synergist, piperonyl butoxide (PBO), could rescue efficacy of alpha-cypermethrin LLIN against a field strain and pyrethroid-resistant strain of maize weevil, Sitophilus zeamais (Motschulsky) in the laboratory. Adult S. zeamais were first exposed to the vials treated with PBO or acetone (solvent control) for 1 h or 3 h, then exposed to either alpha-cypermethrin LLIN or control netting for 1 h or 3 h. Immediate mortality was recorded directly after exposure, as well as delayed mortality at 24, 48, 72, and 168 h later with adult conditions recorded as alive, affected, or dead. At 1-h exposure, the addition of PBO significantly reduced the percentage of field strain S. zeamais adults alive by 7–42% after subsequently exposed to LLIN compared to the control, but PBO did not significantly affect the percentage of alive pyrethroid-resistant adults. After a 3-h exposure, there were significantly fewer field strain (by 24–47%) and pyrethroid-resistant (by 13–36%) individuals alive when exposed to PBO compared to the control. PBO elicited quicker mortality for the pyrethroid-resistant strain. We confirmed in a separate assay that our susceptible laboratory strain was more susceptible than our field and pyrethroid-resistant strain of S. zeamais. Our results suggest that the addition of a synergist to LLIN formulations may improve efficacy against stored product insects and support resistance management.

The pepper weevil, Anthonomus eugenii, is a subtropical pest of pepper plants that appears to be expanding its geographic range as evidenced by its increasing occurrence and persistence in field and greenhouse pepper crops in temperate areas. Here, we investigated the cold tolerance of A. eugenii and its potential for winter survival in temperate areas by comparing non-acclimated (24 °C) and cold acclimated (10 °C) adults and larvae for their cold tolerance strategy, supercooling points, and lower lethal thermal limits. Acclimated larvae were treated with silver iodide to assess their survival in the presence of an ice nucleator. Survival of non-acclimated adults was measured following exposure to 0 °C for an extended period. We also tested whether non-acclimated adults and larvae could survive winter at three outdoor sites in southwestern Ontario (agricultural field, adjacent to unheated building, and inside an unheated building). Adults and larvae died at freezing and even pre-freezing temperatures. Acclimation improved adult cold tolerance, decreasing the LT₅₀ by 3 °C, with half of the non-acclimated adults surviving around 6 days at 0 °C. External inoculation increased larval supercooling points (SCPs), but did not improve cold tolerance. In winter field studies, survival was evident only in the first month, but no insect survived afterwards at any of the overwintering sites. We conclude that A. eugenii is chill-susceptible, and winter temperatures will restrict outdoor establishment in temperate areas, but that high winter temperatures in empty greenhouses encourage indoor establishment.

Guava production in India faces significant challenges due to the invasion of the root-knot nematode Meloidogyne enterolobii. Biological control using metabolite-producing Streptomyces spp. offers a better alternative to synthetic nematicides for managing nematode populations in soil and roots. The native Streptomyces rochei isolated from nematode suppressive guava rhizosphere demonstrated complete inhibition of M. enterolobii egg hatching (100%) and juvenile mortality (100%) compared to other native species. Further, secondary metabolites produced by S. rochei were profiled using gas chromatography/mass spectrometry (GC/MS) analysis and molecular docking experiments were carried out with the key protein Me col-1 (collagen gene) of M. enterolobii. Notably, bioactive compounds of S. rochei such as oxymatrine, melezitose, 2(3H)-furanone, 5-hexyldihydro, 2-nonadecanone 2, and cyclohexane exhibited nematicidal activities. Among them, oxymatrine (− 6.7 kcal/mol), melezitose (− 6.5 kcal/mol), and 2(3H)-furanone (−4.4 kcal/mol) showcased the highest binding affinity against Me col-1. A glasshouse experiment was conducted to study the nematode suppressive effect of cell-free culture filtrate extracts of S. rochei GA, Streptomyces spp. GHS-3 and GHRS-5 on guava seedlings inoculated with M. enterolobii. Guava plants treated with S. rochei GA suppressed M. enterolobii parasitism with a 79.1% reduction in the number of egg masses, and promoted plant growth by 75%. This study highlights the nematotoxic potential of biomolecules produced by S. rochei GA as a promising alternative to synthetic nematicides for the management of M. enterolobii.