Journal of Pest Science最新文献

The olive fruit fly, Bactrocera oleae (Rossi), is a key pest of the olive crop, whose control relies mostly on the use of insecticides. Plant peptides may represent a more environmentally-friendly tool to manage olive fly, due to their recognized role to activate and/or prime plant defence responses against pests. In this work, behavioural experiments (no-choice and two-choice) and analysis of volatile compounds were carried out to evaluate the impact of the exogenous application of the peptide systemin to olive tree on olive fly infestation, and to elucidate its mode of action to prime plant defence. The treatment of olive branches with 10 nM systemin showed to confer protection against olive fly, by reducing significantly the ovipositions (up to 3.0-fold) and the number of infested fruits (up to 2.9-fold) when compared to non-treated branches. This protective effect was even detected in neighbouring non-treated branches, suggesting the ability of systemin to trigger plant-to-plant communication. The deterrent activity of the primed olives was associated with the emission of the volatiles 2-ethyl-1-hexanol, 4-tert-butylcyclohexyl acetate and 1, 2, 3-trimethyl-benzene, which were negatively correlated with oviposition and fly infestation. Systemin has also showed to trigger the biosynthesis of specific volatiles (esters) in olives in response to fly attacks. Overall, the observed protection conferred by systemin against olive fly is likely due to the emission of specific volatiles that can act as a defence and/or as signalling molecules to upregulate the plant defence response. Thus, systemin represents a novel and useful tool to manage olive fruit fly.

Several natural enemies are known as predators of the whitefly Bemisia tabaci, which is one of the most invasive pests worldwide and has developed high resistance to pesticides. However, biological control of this pest on tomato is often difficult because the plant’s glandular trichomes release substances that are toxic to arthropods and hinder the foraging of natural enemies. Therefore, adaptation of natural enemies to this crop is one of the selection criteria for potential biocontrol agents. We collected predatory mites from wild and feral tomato plants and found the species Amblyseius herbicolus and A. tamatavensis. Whereas the latter is known to feed on B. tabaci eggs, we investigated the ability of A. herbicolus to develop and reproduce when feeding on this prey stage, and assessed whether both species can feed and develop on B. tabaci crawlers. To verify the adaptation of these predators to tomato, we assessed their ability to disperse on tomato plants and their establishment on clean tomato plants with pollen as an alternative food. Finally, we evaluated whether the predators were effective in controlling B. tabaci on tomato plants with different pollen dosages as alternative food. We show that both predators fed and reproduced on B. tabaci immatures. A. herbicolus established and dispersed better on tomato plants supplemented with cattail pollen than A. tamatavensis and only A. herbicolus was able to control B. tabaci in two population dynamics experiments. Our results suggest that A. herbicolus is better adapted to tomato than A. tamatavensis and may therefore be a promising biocontrol agent on tomato.

Grapevine leafroll disease (GLD) affects grapevines worldwide. The primary causal agent of GLD is grapevine leafroll-associated virus 3 (GLRaV-3), which spreads to uninfected grapevines via mealybugs and soft-scale insects. Pseudococcus calceolariae (Hemiptera: Pseudococcidae) is a mealybug vector of GLRaV-3 in New Zealand. P. calceolariae also colonizes clovers (Trifolium spp.) growing naturally as vineyard ground cover. Separating mealybug from GLRaV-3 grapevine host could be enhanced by a trap plant: an alternative host attractive to and retentive of the target pest. We evaluated the association between P. calceolariae and ‘Grasslands Huia’ white clover (GHWC). GHWC seed was sown under grapevines in a commercial vineyard (14 × 0.4 ha plots); the control was under-vine herbicide use (7 × 0.4 ha plots, where only few Trifolium spp. plants grew). After 2 years, GHWC cover peaked at 40% mealybug infestation in 2019. From 2018 to 2021, P. calceolariae detection and abundance on GHWC was significantly higher than plants from the control plots. There was no treatment effect for mealybug infestation of grapevine leaves nor of GLRaV-3 incidence, independent of vintage. A glasshouse trial found no transmission of GLRaV-3 by P. calceolariae to any of 256 plants among five clover cultivars tested (Trifolium spp.), including GHWC; mealybug transmitted GLRaV-3 to 35 of 107 Nicotiana benthamiana plants. The results showed that in the 5-year period, added GHWC did not decouple P. calceolariae from the grapevine to reduce GLRaV-3 incidence, but rapid colonization of GHWC by mealybug and the lack of GLRaV-3 transmission to GHWC are encouraging. Further evaluation is needed to assess whether plant biodiversity can benefit a GLRaV-3 ecological management objective.

Tomato plants are attacked by numerous pests and diseases, including the tomato russet mite Aculops lycopersici and powdery mildew, Oidium neolycopersici. Natural enemies of tomato pests are often hindered by the tomato trichomes, while russet mites live under and among these leaf hairs and are therefore protected from these enemies. To find natural enemies that are adapted to tomato and its trichomes, we collected a predatory mite, Amblyseius herbicolus, and an iolinid mite, cf. Homeopronematus anconai sp. nov., from tomato plants in the field. We investigated their potential as biological control agents for pests in this crop. We show that both predators were able to feed and reproduce on russet mites. Subsequently, we show that the iolinid effectively controlled tomato russet mites and powdery mildew on isolated tomato plants, whereas A. herbicolus disappeared from the plants. Altogether, our results show that cf. H. anconai sp. nov. is an efficient biocontrol agent of two key pests on tomato plants. Our results thus contribute to the recent trend of using predators that are effective in controlling both a pest and a pathogen, a promising new strategy for biological crop protection.

Different diversification practices have the potential to reduce pests and therefore pesticide use. Yet, their integration at the agroecosystem level and the evaluation of their multifunctional effects remain limited. Through a two-year field experiment conducted in Germany, we tested whether associating intercropping (faba bean-wheat, followed by breadseed poppy-barley) with pluriannual wildflower strips strengthens the biological regulation of aphid pests and weeds, and enhances cropping system productivity. The contribution of flowering weeds to conservation biological control was also analysed. Aphid but also predator colonization and predation rates on bean and poppy were consistently lower in intercropping compared to sole cropping. Wildflower strips enhanced aphid predation in bean-wheat intercropping, and further reduced aphid colonization at 10 m distance but not at 20 m in poppy-barley intercropping. Weed biomass was consistently reduced in intercropping compared to sole cropping bean and poppy, and did not significantly affect bean and poppy yields in intercropping. The cover of one flowering weed species, Matricaria recutita, was negatively correlated to aphid colonization and positively correlated to predation rate. Matricaria recutita flowers were also visited more often by predatory hoverflies in plots adjacent to wildflower strips. Finally, land equivalent ratio was consistently higher than 1, and the highest in bean-wheat intercropping associated to wildflower strips. The study demonstrates the benefits of associating wildflower strips to intercropping to strengthen biological control and cropping system productivity. Flowering weeds, maintained at an acceptable level through intercropping, turn out to be relevant functional biodiversity in interacting with wildflower strips for conservation biological control.

This study investigated the infestation of tomato plants by the plant-parasitic nematode, M. incognita, and its accurate detection by plant electrophysiology (PE). Dedicated tests were done on whole plants to record electrophysiological signals from nematode infested and uninfested plants and to establish a trained model indicating nematode-induced stress. Monitoring nematode-induced stress by PE confirmed the results obtained by assessing root galls and quantifying xylem sap 3 to 4 weeks after infestation. The machine learning model captured the stress intensities and the time course of plant damage caused by nematodes. Stress caused by second-stage juveniles (J2) infestation appeared 3 to 5 days after infestation (DAI), whereas stress caused by egg infestation was detected 5 to 7 days later (10–13 DAI). For the first time, the real-time effectiveness of nematicides was recorded in further tests. Nematode infested plants treated preventatively with cyclobutrifluram (TYMIRIUM® technology) showed a delayed and short (about 3 days) period of low stress intensity, whereas infested but untreated plants showed a period of maximum stress for about 12 days. In addition, depending on the type of application (preventative or curative), different modes of biological activity of IRAC group N-2 and N-3 nematicides (fluopyram, abamectin) could be captured by PE signalling. PE offers a new way of monitoring plant health in real time, which is particularly valuable for accessing ‘invisible’ pests, such as plant-parasitic nematodes in the soil.

Climate change leads to more frequent droughts that may alter multitrophic networks in agroecosystems by changing bottom-up and top-down effects on herbivorous insects. Yet, how bottom-up effects of drought alter tritrophic interactions remains poorly understood. This study investigated two intensities of drought stress in the tritrophic system consisting of sugar beet (Beta vulgaris), an aphid (Aphis fabae), and its parasitoid (Aphidius colemani). We thoroughly investigated each trophic level, examining the performance of plants, pest insects, and parasitoids, as well as the attraction of parasitoids to herbivore-induced plant volatiles (HIPVs). Drought stress negatively affected plant growth but benefited A. fabae, leading to faster development and a higher reproduction rate. Drought-stressed plants also emitted less plant volatiles, which resulted in reduced attraction of A. colemani to aphid-infested plants. Drought indirectly affected parasitoid performance, as evidenced by lower emergence rates and production of fewer females, although mummification rates were higher on drought-stressed plants. Reduced parasitoid attraction and performance on drought-stressed plants may exert lower top-down pressure on aphid populations. Combined with increased aphid performance, this may facilitate aphid outbreaks, which could further weaken drought-stressed plants. Our findings highlight the need to study multiple trophic levels and emphasize the importance of incorporating HIPVs and parasitoid attraction when assessing combined abiotic and biotic stresses in crops.

The ecotoxicological consequences of synthetic pesticides have encouraged stakeholders to search for eco-friendly pest control tools, like essential oils (EOs). Nano-delivery systems (nanoparticles and nano-emulsions) seem ideal for developing EO-based biopesticides, although production processes should be standardized and implemented. In this study, nano-emulsions loaded with a high amount of Allium sativum L. EO (15%) were developed using different mixed bottom-up/top-down processes. Garlic EO was chemically analyzed by gas chromatography-mass spectrometry (GC-MS) and formulations were physically characterized using Dynamic Light Scattering (DLS) apparatus. The insecticidal activity against Planococcus citri Risso (Hemiptera: Pseudococcidae) and selectivity toward Apis mellifera L. (Hymenoptera: Apidae) worker bees was evaluated. Garlic EO was mainly composed of sulphur components (96.3%), with diallyl disulphide and diallyl trisulphide as the most abundant compounds (37.26% and 28.15%, respectively). Top-down processes could produce stable nano-emulsions with droplet size in the nanometric range (< 200nm) and good polydispersity index (PDI < 0.2). In contrast, the bottom-up emulsion was unstable, and its droplet size was around 500nm after 24 hours. High-energy emulsification processes significantly increased the residual toxicity of garlic EO against 3rd instar P. citri nymphs, whereas the developed formulations were harmless to A. mellifera workers in topical application. This study confirmed that the production process significantly affected the physical properties and efficacy against target pests. The lack of adverse impact on honeybees denotated the potential of these formulations as bioinsecticides in organic and/or IPM programs, although further extended ecotoxicological studies are necessary.

Lygus lineolaris Palisot de Beauvois (Hemiptera: Miridae) is the primary insect pest of strawberry in eastern and central North America. Strategies to minimize L. lineolaris colonization of strawberry at bloom and peak fruit susceptibility without impacting pollinator health must be developed. To this end, we examined the potential of alfalfa perimeter strips to reduce L. lineolaris populations in June-bearing strawberry fields. Over a three-year experiment, L. lineolaris densities and beneficial arthropod abundance were monitored in commercial strawberry fields with and without alfalfa perimeter strips. Alfalfa perimeter strips were found to concentrate L. lineolaris populations and led to a 36% reduction in L. lineolaris densities in adjacent strawberry plots compared to controls. When a protein immunomark-capture experiment was conducted to examine the extent of movement between the alfalfa strips and adjacent strawberry plots, it was determined that approximately three times as many L. lineolaris migrated from strawberry to alfalfa than vice versa. Moreover, adult females were overrepresented among immigrants to alfalfa, suggesting that alfalfa may be a preferred oviposition site for L. lineolaris. While the presence of alfalfa perimeter strips increased beneficial arthropod abundance and diversity in experimental plots overall, these increases were limited to the alfalfa itself, with little spillover into adjacent strawberry plots. These data suggest that preferential utilization of alfalfa by L. lineolaris underlies the observed population reductions and that alfalfa acts as a trap crop in June-bearing strawberries.

Endosymbiosis is very common between bacteria and insects, and it has been deeply studied for over a century on model insects such as Bactrocera oleae, the key pest of the olives. It was demonstrated that “Candidatus Erwinia dacicola” is the main component of its midgut bacterial communities, acting a fundamental role in the fly’s nutrition process and thus on its fitness. In this study, Trichoderma secondary metabolites have been used to treat olive fruit fly in order to alter the “Ca. Erwinia dacicola” titer and to assess the subsequent effects on its host. The selected metabolites, 6-pentyl-α-pyrone and harzianic acid, directly affect the insect’s fitness also on the subsequent generation, but not always in a concentration-dependent manner. Aside from the direct effects, the treatments also showed a modification of the bacterial titer. Therefore, real-time qPCRs were carried out on wild individual flies highlighting natural variations of the symbiont presence and activity during the seasons. The data obtained suggest that bioactive fungal metabolites can be formulated for direct or indirect control strategies of B. oleae in integrated pest management programs.