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The cereal weevil, Sitophilus zeamais is one of the most destructive pests of stored cereals worldwide. Frequent use of fumigants for managing stored-product insects has led to the development of resistance in insects. Essential oils from aromatic plants including the tea oil plant, Melaleuca alternifolia may provide environmentally friendly alternatives to currently used pest control agents. However, little is known about molecular events involved in stored-product insects in response to plant essential oil fumigation. M. alternifolia essential oil was shown to possess the fumigant toxicity against S. zeamais. The constituent, terpinen-4-ol was the most effective compound for fumigant toxicity. M. alternifolia essential oil significantly inhibited the activity of three enzymes in S. zeamais, including two detoxifying enzymes, glutathione S-transferase (GST), and carboxylesterase (CarE), as well as a nerve conduction enzyme, acetylcholinesterase (AChE). Comparative transcriptome analysis of S. zeamais through RNA-Seq identified a total of 3,562 differentially expressed genes (DEGs), of which 2,836 and 726 were up-regulated and down-regulated in response to M. alternifolia essential oil fumigation, respectively. Based on gene ontology (GO) analysis, the majority of DEGs were involved in insecticide detoxification and mitochondrial function. Furthermore, an abundance of DEGs mapped into the metabolism pathway in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database were associated with respiration and metabolism of xenobiotics, including cytochrome P450s, CarEs, GSTs, and ATP-binding cassette transporters (ABC transporters). Some DEGs mapped into the proteasome and phagosome pathway were found to be significantly enriched. These results led us to propose a model of insecticide action that M. alternifolia essential oil likely directly affects the hydrogen carrier to block the electron flow and interfere energy synthesis in mitochondrial respiratory chain. This is the first study to perform a comparative transcriptome analysis of S. zeamais in response to M. alternifolia essential oil fumigation. Our results provide new insights into the insecticidal mechanism of M. alternifolia essential oil fumigation against S. zeamais and eventually contribute to the management of this important agricultural pest.

Insects have mutualistic symbioses with a variety of microorganisms. However, the chemical signals that maintain these insect−microbe relationships are poorly known compared to those from insect−plant symbioses. The spruce bark beetle, Ips typographus, the most destructive forest pest in Europe, has a symbiotic relationship with several fungi that are believed to contribute to its successful invasion of Norway spruce. Here we tested the hypothesis that volatile organic compounds (VOCs) emitted from fungal symbionts could be cues for bark beetles to recognize and distinguish among members of its microbial community. Behavioral experiments with fungi showed that immature adults of I. typographus are attracted to food sources colonized by their fungal symbionts but not to saprophytic fungi and that this attraction is mediated by volatile cues. GC-MS measurements revealed that the symbionts emitted VOCs. Testing the activity of these compounds on beetle antennae using single sensillum recordings showed that beetles detect many fungal volatiles and possess olfactory sensory neurons specialized for these compounds. Finally, synthetic blends of fungal volatiles attracted beetles in olfactometer experiments. These findings indicate that volatile compounds produced by fungi may act as recognition signals for bark beetles to maintain specific microbial communities that might have impact on their fitness.

The red palm weevil Rhynchophorus ferrugineus (Olivier) is an important pest of date palms in many regions of the world. This paper reports the first survey of insecticide resistance in field populations of R. ferrugineus in Pakistan which were collected from seven date palm growing areas across Punjab and Khyber Pakhtunkhwa (KPK) provinces, Pakistan. The resistance was assessed by the diet incorporation method against the formulated commonly used chemical insecticides profenophos, imidacloprid, chlorpyrifos, cypermethrin, deltamethrin, spinosad, lambda-cyhalothrin and a fumigant phosphine. Elevated levels of resistance were recorded for cypermethrin, deltamethrin and phosphine after a long history of insecticide use in Pakistan. Resistance Ratios (RRs) were 63- to 79-fold for phosphine, 16- to 74-fold for cypermethrin, 13- to 58-fold for deltamethrin, 2.6- to 44-fold for profenophos, 3- to 24-fold for chlorpyrifos, 2- to 12-fold for lambda-cyhalothrin and 1- to 10-fold for spinosad compared to a susceptible control line. Resistant R. ferrugineus populations were mainly found in southern Punjab and to some extent in KPK. The populations from Bahawalpur, Vehari, Layyah and Dera Ghazi Khan were most resistant to chemical insecticides, while all populations exhibited high levels of resistance to phosphine. Of the eight agents tested, lower LC50 and LC90 values were recorded for spinosad and lambda-cyhalothrin. These results suggest that spinosad and lambda-cyhalothrin exhibit unique modes of action and given their better environmental profile, these two insecticides could be used in insecticide rotation or assist in phasing out the use of older insecticides. A changed pattern of both insecticides can be used sensibly be recommended without evidence of dose rates and frequencies used.

The red palm weevil (RPW), Rhynchophorus ferrugineus Olivier, is a devastating insect-pest of 29 plants including date palm. It feeds inside the tree bark thus it is difficult to manage using insecticides. Only a few insecticides have been found effective against RPW. Among these insecticide, emamectin benzoate (EMB) is widely used. This insecticide can pose threat human and environmental health as it is used in the form of tree injection. Thus, keeping in view its possible, its sublethal effect on RPW was studied using Age-stage, two sex life table. Life table parameters of the progeny of exposed larvae to LC 10 , LC 25,  and LC 50  of EMB were computed. Statistically higher fecundity (161.12 per female) was observed in control treatment, while less fecundity was observed in LC 50  treatment. Significantly higher values for intrinsic rate of increase ( r ), finite rate of increase ( λ ), and net reproductive rate ( R o ) (0.0376, 1.0383, and 67.13 per day, respectively) were recorded for the control treatment. Contrarily, lower values for  r , R o , and  λ i.e. 0.0318, 23.82, and 1.0324 per day, respectively were recorded in the LC 50  treatment. Decreased population parameters suggest that EMB can be successfully used in for the management of RPW.

The jasmonic acid cascade plays a pivotal role in induced plant resistance to herbivores. There have been a number of investigations into the potential uses of derivatives of this hormone for pest management. Understanding the phenotypic plasticity of plant defense traits interactions in agricultural systems may facilitate the development of novel and improved management practices, which is desirable as management of insects in most agricultural systems is currently heavily reliant on insecticides. The rice water weevil (RWW), Lissorhoptrus oryzophilus Kuschel, is a pest of rice, Oryza sativa, in the southern U.S. and globally. The effects of the jasmonic acid derivative, methyl jasmonate (MJ), on induced defenses to RWW in rice, and the potential costs of MJ-induced resistance to plant growth and fitness, were tested in a series of field and greenhouse trials. It was hypothesized that seed treatments with MJ would reduce densities of larval RWW. A second hypothesis was that MJ seed treatments would alter emergence, biomass accumulation, and yield of rice. The final hypothesis was that induction of plant resistance to the RWW would diminish as the time from seed treatment increased. In order to investigate these hypotheses, RWW densities were determined in greenhouse and field trials. Plant growth was measured in the field by assessing plant emergence, root and shoot biomass, time of heading, and yield (grain mass). Results indicated that MJ seed treatments induced resistance to RWW, although this effect decayed over time. Additionally, there were costs to plant growth and fitness; emergence and heading were delayed and biomass was reduced. Importantly, however, yields on a per-plant were not significantly reduced by MJ treatment. Overall, these results are promising and show the potential for the use of jasmonate elicitors as part of a pest management program in rice.

The problems of the environment and human health related to the use of synthetic and broad-spectrum insecticides have increasingly motivated scientific research on different alternatives and among these, the use of green systems, such as essential oils, have been explored. Several species of the Apiaceae and Asteraceae families, aromatic herbs rich in secondary bioactive metabolites, are used in the industrial field for pharmaceutical, cosmetic, and food purposes. Different essential oils extracted from some species of these families have shown acute toxicity and attractive and/or repellent effects towards different insects. In our work, we investigated the toxic potential of Calendula incana subsp. maritima and Laserpitium siler subsp. siculum essential oils against four insect species, Sitophilus oryzae, Lasioderma serricorne, Necrobia rufipes, and Rhyzoperta dominica, which are common pests of stored products. The composition of both oils, extracted by hydrodistillation from the aerial parts of the two plants, was evaluated by GC×GC-MS. Calendula incana subsp. maritima essential oil was rich in oxygenated sesquiterpenoids, such as cubebol (35.39%), 4-epi-cubebol (22.99%), and cubenol (12.77%), while the Laserpitium siler subsp. siculum essential oil was composed mainly of monoterpene hydrocarbons, such as β-phellandrene (42.16%), limonene (23.87%), and β-terpinene (11.80%). The toxicity Petri dish bioassays indicated that C. maritima oil killed a mean of 65.50% of S. oryzae and 44.00% of R. dominica adults, indicating a higher biocidal activity in comparison with L. siculum oil, while toward the other species, no significant differences in mortality were recorded. Calendula maritima oil could be, then, considered a promising candidate for further tests as an alternative biocide toward S. oryzae and R. dominica. The possibility that the relatively high content of oxygenated sesquiterpenoids in C. maritima essential oil determines its higher biocidal activity is discussed.

Sulfur dioxide (SO2) fumigation was studied in laboratory to determine its potential as an alternative treatment for postharvest control of stored product insects, confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera:Tenebrionidae), and rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae).Three-hour fumigations with 0.1%–2.0% SO2 were conducted against eggs, immature stages, and adults of the 2 insects at 20 °C. Effective control of both insects was achieved. However, there were considerable variations between the 2 insects and among different life stages. Confused flour beetle was more susceptible to SO2 fumigation than rice weevil. Complete control of adults and all life stages of confused flour beetle was achieved in 3-h fumigations with 0.5% and 2.0% SO2, respectively. For rice weevil, 3-h fumigation with 1.5% SO2 resulted in 96.5% adult mortality and the fumigation with 2.0% SO2 resulted in 99.27% mortality of adults and 87.5% mortality of immature stages.Three-hour fumigations with 1% SO2 resulted in <5% egg survival to adults.The study demonstrated high efficacy of SO2 fumigation against the insects and suggested that SO2 fumigation has good potential for postharvest pest control on stored products.

Combining products of natural origin with different mechanisms of action on insect herbivores may provide an alternative among methods of plant protection against pests that are less risky for the environment. The aim of the study was to evaluate the effectiveness of mixtures of Thuja occidentalis L. essential oil and diatomite (EO + DE) compared to each substance separately in reducing economically important pests such as black bean aphid (BBA) Aphis fabae Scop., Colorado potato beetle (CPB) Leptinotarsa decemlineata Say., and pea leaf weevil (PLW) Sitona lineatus L. The effects on mortality (all pests) and foraging intensity (CPB and PLW) were tested. The improvement in effectiveness using a mixture of EO + DE versus single components against BBA was dose- and the developmental stage-dependent. The effect of enhancing CPB foraging inhibition through DE addition was obtained at a concentration of 0.2% EO (both females and males of CPB) and 0.5% EO (males) in no-choice experiments. In choice experiments, mixtures EO + DE with both 0.2% and 0.5% EO concentrations resulted in a significant reduction in CPB foraging. A significant strengthening effect of EO 0.5% through the addition of DE at a dose of 10% against PLW males was observed in the no-choice experiment, while, when the beetles had a choice, the synergistic effect of a mixture of EO 0.5% and DE 10% was also apparent in females. In conclusion, the use of DE mixtures with EO from T. occidentalis appears to be a promising strategy. The results support the idea of not using doses of EO higher than 0.5%.

The integration of essential oils (EOs) with biological control agents offers a promising alternative to synthetic pesticides, though compatibility remains unclear. This study evaluated nutmeg (Myristica fragrans, NM), cinnamon (Cinnamomum verum, CIN), and clove (Syzygium aromaticum, CL) specifically on S. oryzae and L. distinguendus. Olfactory and behavioral responses to whole EOs and major constituents (myristicin, cinnamaldehyde, eugenol) were analyzed using the area preference method (APM) and two-choice behavioral bioassay (TCB), with confirmation by gas chromatography–mass spectrometry (GC-MS). In S. oryzae, APM showed attraction to all three EOs (PI = 0.14 to 0.56). A paradox emerged, however, as single constituents were mostly repellent (eugenol: PI = −0.58 to −0.70; cinnamaldehyde: PI shifted from 0.16 to −0.20), underscoring the complexity of EO mixtures where multiple compounds act jointly rather than individually. In contrast, L. distinguendus strongly avoided CL and CIN in TCB, with fewer than 30% of parasitoids choosing the EO-treated side (χ2 test, p < 0.05). CIN therefore demonstrated selective potential, simultaneously attracting S. oryzae while repelling L. distinguendus. These findings highlight the dual role of EOs as botanical pest control tools, while stressing the need to consider non-target effects before practical application.

The landscape plant, Cinnamomum camphora, is a broad-spectrum insect-repelling tree species, mainly due to a diversity of terpenoids, such as camphor. Despite its formidable chemical defenses, C. camphora is easily attacked and invaded by a monophagous weevil pest, Pagiophloeus tsushimanus. Deciphering the key olfactory signal components regulating host preference could facilitate monitoring and control strategies for this pest. Herein, two host volatiles, camphor and ocimene, induced GC-EAD/EAG reactions in both male and female adult antennae. Correspondingly, Y-tube olfactometer assays showed that the two compounds were attractive to both male and female adults. In field assays, a self-made trap device baited with 5 mg dose d(+)-camphor captured significantly more P. tsushimanus adults than isopropanol solvent controls without sexual bias. The trunk gluing trap device baited with bait can capture adults, but the number was significantly less than that of the self-made trap device and adults often fell after struggling. The cross baffle trap device never trapped adults. Neither ocimene nor isopropanol solvent control captured adults. When used in combination, ocimene did not enhance the attraction of d(+)-camphor to both female and male adults. These results indicate that d(+)-camphor is a key active compound of P. tsushimanus adults for host location. The combination of the host-volatile lure based on d(+)-camphor and the self-made trapping device is promising to monitor and provide an eco-friendly control strategy for this novel pest P. tsushimanus in C. camphora plantations.