Journal of Pest Science最新文献

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.

Floral resources such as nectar are essential for increasing survival and population growth of synovigenic parasitic wasps in agroecosystems. Although the bottom-up effect of cadmium (Cd) has been identified as a major ecological force influencing multitrophic interactions of synovigenic parasitoids, information on the direct effects of Cd-contaminated floral resources on the fitness of natural enemies which might impact their fitness and effectiveness are still lacking. In this study, we assessed the performance of three commonly used Trichogramma species exposed to Cd-contaminated sucrose solutions. Female survival, longevity, the female/male adult proportion, and F₁ emergence rate of T. japonicum were not affected by Cd concentrations. However, a decline in the survival rate of females, their longevity, and female/male adult proportion were observed for T. dendrolimi at high Cd concentration. No significant differences in female/male adult proporation and longevity of T. ostriniae were found at wide Cd concentration ranges. Our results suggest that Cd-contaminated nectar resources can negatively affect performance of some Trichogramma spp., indicating Cd contamination in nectar would directly reduce the potential value of these species in IPM programs. These results not only increase our understanding of interspecific variations in synovigeny of Trichogramma, but also suggest that releases of T. japonicum and T. ostriniae rather than T. dendrolimi should be considered at Cd-contaminated sites.

The pivotal role of gut microbiota in maintaining the insect host’s well-being has been extensive researched. Here, our research objective was to determine the microbes in the gut of larvae of the potato tuberworm (Phthorimaea operculella) and to investigate the role they play in the host development, metabolism, gut structure integrity and immune deficiency (Imd). Shotgun metagenomics sequencing from specimens collected in major potato-producing regions in China, and principal coordinate analysis revealed that the geographic location explained much of the variance in bacterial composition, but Enterococcus mundtii was dominant in all samples. KEGG analysis demonstrated that carbohydrate metabolism was the major function of the P. operculella’s gut microbiome. Subsequently, with the use of artificial diet supplemented with antibiotics, the gut microbes were removed, especially the bacteria of the Enterococcus genus were significantly decreased. Typically, insects fed with antibiotics showed a lower carbohydrate metabolism, survival rate, longer developmental period and poorer fecundity. Metabolomics analysis also confirmed that the antibiotics treatment had a striking impact on the metabolic profile in the gut, especially for starch degradation. In addition, the gut homeostasis with its microbiota composition, metabolism and gut structure was damaged in the antibiotics-treated insects. In summary, our data provide evidence that a complex interaction exists between the microbiome of the gut and the metabolism and structure integrity of the host insect, which is essential for its growth and development. These findings enhance our comprehension of the microbiota's function in insects and facilitate the advancement of environmentally friendly management strategies for this pest.

The Melaleuca genus has insecticidal activity against agricultural pests. In particular, Melaleuca rhaphiophylla essential oil (MREO) showed high toxicity against some stored product weevils in a short period. Therefore, the present study aimed to evaluate the sublethal dose and the effect on biochemical markers of MREO and its emulsion (MREM) against Sitophilus zeamais and Sitophilus oryzae. The emulsion was prepared by combining hydroxypropyl methylcellulose (HPMC) (2 wt%) with MREO to concentrations of 39.18 and 25.61 μL of substance L⁻¹ of air for S. zeamais and S. oryzae, respectively. The insecticidal activity of both MREO and MREM was evaluated by the fumigation method, followed by the determination of Glutathione S-Transferase (GST), esterase-α, esterase-β, superoxide dismutase (SOD), acetylcholinesterase (AChE) activities, and lipid peroxidation (LPO). The MREO caused a mortality rate above 25%, with an increase of AChE and LPO for both species, there was altered esterase-α for S. zeamais and inhibition of GST, esterase-α, esterase-β and SOD activity for S. oryzae. Meanwhile, the MREM caused a mortality rate of less than 1.5%, with an increase in GST, SOD, and LPO enzymes for both species, and an increase in the enzymatic activity of esterase-α for S. oryzae. Therefore, we concluded that MREO demonstrated higher insecticidal activity, while MREM caused continuous toxicity at fragmented doses caused by emulsion exposure, stimulating detoxification and resistance mechanisms.

The increasing spread and destructiveness of the honeydew moth, Cryptoblabes gnidiella (Lepidoptera: Pyralidae: Phycitinae), requires an effective pest management approach, in which the application of insecticides is based on the presence and abundance of the insect in the vineyard. Pest monitoring, however, is challenging because of the difficulties in identifying eggs and larvae. Forecasting models, particularly physiologically based demographic models (PBDMs), are helpful tools in the management of several agricultural insect pests. No PBDMs of note are available for C. gnidiella to date. Herein, we adapted a PBDM for Lobesia botrana to C. gnidiella by using literature data on insect developmental rates to fit temperature-dependent equations, and we validated the model by using independent data consisting of weekly male catches in pheromone traps placed in 16 wine-growing areas of Central and Southern Italy, between 2014 and 2022. Comparison of model predictions versus trap data of adults provided R² = 0.922, CRM (coefficient of residual mass, a measure of the model tendency to overestimate or underestimate the observed values) = 0.223, and CCC (the concordance correlation coefficient) = 0.924. Goodness-of-fit results showed that the model was capable of correctly predicting C. gnidiella flights, with a little tendency to underestimate real observations. Overall, our results make the model quite realistic and potentially useful to support insect monitoring activities and decision-making in crop protection, at least in the contexts in which the model was validated. Further validations should be carried out to test the model ability to also predict the presence of C. gnidiella juvenile stages.

Plants employ different defensive strategies to limit or avoid nematode attacks, including the recruitment of beneficial microorganisms that can support plants by enhancing their defence mechanisms. We investigated the effect of the two nematode egg parasitising fungi, Niesslia gamsii and Polydomus karssenii, on nematode suppression on tomato using greenhouse experiments. Their potential against Meloidogyne hapla was evaluated by analysing direct parasitism and the expression of plant defence-related genes, through quantitative reverse transcriptase PCR. Niesslia gamsii and P. karssenii were originally isolated from naturally infested eggs of the cereal cyst nematode Heterodera filipjevi, and their nematode pathogenicity was proven through Koch’s postulates. Fungal treatments with N. gamsii and P. karssenii reduced by 32–31% M. hapla egg numbers per root system, respectively. Both treatments also significantly lowered the nematode reproduction rate (Rf value) when compared to the control. Both fungi affected the nematode root invasion by limiting penetration of M. hapla second-stage juveniles (J2) into tomato roots, 3 and 7 days after inoculation. The results showed a substantial effect of both fungi on inducing defence responses in tomato plants towards M. hapla. Pre-treatment with N. gamsii and P. karssenii led to the expression of different marker genes associated with pathogen response pathways, including salicylic and jasmonic acid/ethylene-regulated defensive. These findings suggest that N. gamsii and P. karssenii could prime the plant host for enhanced defence upon nematode attack.