Pest Control Strategies Research Articles

Natural Products: Are They Efficient Alternatives against the Stored Grain Pest Sitophilus zeamais?

Cereal crops strongly contribute with the world economy and because of this the reduction of their productivity may lead to irreparable economic consequences worldwide. The maize weevil Sitophilus zeamais is the main pest of maize in the field or during processing, storage and commercialization of grains, also attacking processed food. The population control of S. zeamais uses a restrict panel of synthetic insecticides which are associated with environmental contamination, selection of resistant individuals and toxicity to non-target organisms, including humans and other animals. This scenario has stimulated the search for new insecticides and plant metabolites stand out because of their high degree of biodegradability and more selective toxicity. This work provides a review of the effect of plant compounds on S. zeamais to encourage the use of these ingredients in more ecofriendly strategies for pest control. Plant insecticides can exert their toxicity by ingestion, contact and/or fumigation resulting in damage to the development, survival and reproductive potential of S. zeamais, or may present food deterrent activity, which protects the substrates from the attack by the insects. The data reviewed contribute to consolidate the use of natural products in control of S. zeamais.

Genetic differentiation in pesticide resistance between urban and rural populations of a nontarget freshwater keystone interactor, Daphnia magna.

There is growing evidence that urbanization drives adaptive evolution in response to thermal gradients. One such example is documented in the water flea Daphnia magna. However, organisms residing in urban lentic ecosystems are increasingly exposed to chemical pollutants such as pesticides through run‐off and aerial transportation. The extent to which urbanization drives the evolution of pesticide resistance in aquatic organisms and whether this is impacted by warming and thermal adaptation remains limitedly studied. We performed a common garden rearing experiment using multiple clonal lineages originating from five replicated urban and rural D. magna populations, in which we implemented an acute toxicity test exposing neonates (<24h) to either a solvent control or the organophosphate pesticide chlorpyrifos. Pesticide exposures were performed at two temperatures (20°C vs. 24°C) to test for temperature‐associated differences in urbanization‐driven evolved pesticide resistance. We identified a strong overall effect of pesticide exposure on Daphnia survival probability (−72.8 percentage points). However, urban Daphnia genotypes showed higher survival probabilities compared to rural ones in the presence of chlorpyrifos (+29.7 percentage points). Our experiment did not reveal strong temperature x pesticide or temperature x pesticide x urbanization background effects on survival probability. The here observed evolution of resistance to an organophosphate pesticide is a first indication Daphnia likely also adapts to pesticide pollution in urban areas. Increased pesticide resistance could facilitate their population persistence in urban ponds, and feed back to ecosystem functions, such as top‐down control of algae. In addition, adaptive evolution of nontarget organisms to pest control strategies and occupational pesticide use may modulate how pesticide applications affect genetic and species diversity in urban areas.

Herbivore-induced volatiles influence moth preference by increasing the β-Ocimene emission of neighbouring tea plants.

Herbivore-induced plant volatiles prime neighbouring plants to respond more strongly to subsequent attacks. However, the key volatiles that trigger this state and their priming mechanisms remain largely unknown. The tea geometrid Ectropis obliqua is one of the most devastating leaf-feeding pests of tea plants. Here, plant-plant communication experiments demonstrated that volatiles emitted from tea plants infested by E. obliqua larvae triggered neighbouring plants to release volatiles that repel E. obliqua adult, especially mated females. Volatile analyses revealed that the quantity of eight volatiles increased dramatically when plants were exposed to volatiles emitted by infested tea plants, including (Z)-3-hexenol, linalool, α-farnesene, β-Ocimene and (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT). The results of behavioural bioassays demonstrated that β-Ocimene strongly repelled mated E. obliqua females. Individual volatile compound exposure experiments revealed that (Z)-3-hexenol, linalool, α-farnesene and DMNT triggered the emission of β-Ocimene from tea plants. Chemical inhibition experiments demonstrated that the emission of β-Ocimene induced by (Z)-3-hexenol, linalool, α-farnesene and DMNT were dependent on Ca2+ and JA signalling. These findings help us to understand how E. obliqua moths respond to volatiles emitted from tea plants and provide new insight into volatile-mediated plant-plant interactions. They have potential significance for the development of novel insect and pest control strategies in crops.

Determining relevant traits for selecting landrace accessions of Phaseolus lunatus L. for insect resistance.

Plant-insect interactions are a determining factor for sustainable crop production. Although plants can resist or tolerate herbivorous insects to varying degrees, even with the use of pesticides, insects can reduce plant net productivity by as much as 20%, so sustainable strategies for pest control with less dependence on chemicals are needed. Selecting plants with optimal resistance and photosynthetic traits can help minimize damage and maintain productivity. Here, 27 landrace accessions of lima beans, Phaseolus lunatus L., from the Yucatan Peninsula were evaluated in the field for morphological resistance traits, photosynthetic characteristics, insect damage and seed yield. Variation was found in physical leaf traits (number, area, and dry mass of leaves; trichome density, specific leaf thickness and hardness) and in physiological traits (photosynthetic rate, stomatal conductance, intercellular carbon, water-use efficiency, and transpiration). Five accessions (JMC1325, JMC1288, JMC1339, JMC1208 and JMC1264) had the lowest index for cumulative damage with the highest seed yield, although RDA analysis uncovered two accessions (JMC1339, JMC1288) with strong positive association of seed yield and the cumulative damage index with leaf production, specific leaf area (SLA) and total leaf area. Leaf traits, including SLA and total leaf area are important drivers for optimizing seed yield. This study identified 12 important morphological and physiological leaf traits for selecting landrace accessions of P. lunatus for high yields (regardless of damage level) to achieve sustainable, environmentally safe crop production.

The \u03b22Tubulin, Rad50-ATPase and enolase cis-regulatory regions mediate male germline expression in Tribolium castaneum

Genetics-based pest management processes, including the sterile insect technique, are an effective method for the control of some pest insects. However, current SIT methods are not directly transferable to many important pest insect species due to the lack of genetic sexing strains. Genome editing is revolutionizing the way we conduct genetics in insects, including in Tribolium castaneum, an important genetic model and agricultural pest. We identified orthologues of β2Tubulin, Rad50-ATPase and enolase in T. castaneum. Using RT-PCR, we confirmed that these genes are predominantly expressed in the testis. PiggyBac-based transformation of T. castaneum cis-regulatory regions derived from Tc-β2t, Tc-rad50 or Tc-eno resulted in EGFP expression specifically in the T. castaneum testis. Additionally, we determined that each of these regulatory regions regulates EGFP expression in different cell types of the male gonad. Cis-regulatory regions from Tc-β2t produced EGFP expression throughout spermatogenesis and also in mature sperms; Tc-rad50 resulted in expression only in the haploid spermatid, while Tc-eno expressed EGFP in late spermatogenesis. In summary, the regulatory cis-regions characterized in this study are not only suited to study male gonadal function but could be used for development of transgenic sexing strains that produce one sex in pest control strategies.

A highly-contiguous genome assembly of the Eurasian spruce bark beetle, Ips typographus, provides insight into a major forest pest

Conifer-feeding bark beetles are important herbivores and decomposers in forest ecosystems. These species complete their life cycle in nutritionally poor substrates and some can kill enormous numbers of trees during population outbreaks. The Eurasian spruce bark beetle (Ips typographus) can destroy >100 million m3 of spruce in a single year. We report a 236.8 Mb I. typographus genome assembly using PacBio long-read sequencing. The final phased assembly has a contig N50 of 6.65 Mb in 272 contigs and is predicted to contain 23,923 protein-coding genes. We reveal expanded gene families associated with plant cell wall degradation, including pectinases, aspartyl proteases, and glycosyl hydrolases. This genome sequence from the genus Ips provides timely resources to address questions about the evolutionary biology of the true weevils (Curculionidae), one of the most species-rich animal families. In forests of today, increasingly stressed by global warming, this draft genome may assist in developing pest control strategies to mitigate outbreaks.

Climate Change and Major Pests of Mediterranean Olive Orchards: Are We Ready to Face the Global Heating?

Simple SummaryThe phenomenon of climate change affects the entire world, especially the most vulnerable areas such as the Mediterranean. Since the olive growing is one of the main economic sources for the Mediterranean countries, investigations on olive pests under global heating are necessary. Nowadays, knowledge on the topic is scarce, and nothing is known about the effects of climate change on olive pest parasitoids and predators. This information could be fundamental to understand the phenomena of pest outbreaks that are spreading in the Mediterranean olive orchards. The use of prevention tools (e.g., monitoring, prediction models) may help in controlling olive pests under a climate change scenario.Evidence of the impact of climate change on natural and agroecosystems is nowadays established worldwide, especially in the Mediterranean Basin, an area known to be very susceptible to heatwaves and drought. Olea europaea is one of the main income sources for the Mediterranean agroeconomy, and it is considered a sensitive indicator of the climate change degree because of the tight relationship between its biology and temperature trend. Despite the economic importance of the olive, few studies are nowadays available concerning the consequences that global heating may have on its major pests. Among the climatic parameters, temperature is the key one influencing the relation between the olive tree and its most threatening parasites, including Bactrocera oleae and Prays oleae. Therefore, several prediction models are based on this climatic parameter (e.g., cumulative degree day models). Even if the use of models could be a promising tool to improve pest control strategies and to safeguard the Mediterranean olive patrimony, they are not currently available for most O. europaea pests, and they have to be used considering their limits. This work stresses the lack of knowledge about the biology and the ethology of olive pests under a climate change scenario, inviting the scientific community to focus on the topic.

Biology, parasitoid complex and potential distribution of saxaul's dominant defoliators, Teia dubia (Lepidoptera: Lymantriidae).

Natural enemies that impact pest populations must be understood in order to build integrated pest control strategies and to understand the most important aspects affecting pest dynamics. Haloxylon ammodendron (C. A. Mey.) Bunge is an important perennial plant species extensively used in sand stabilization and wind prevention in arid areas. This study aimed to determine the main defoliators that damage H. ammodendron and the parasitoid complex associated with them. Twelve species of defoliators were found in Northern Xinjiang, and Teia dubia (Tauscher) (Lepidoptera: Lymantriidae), Scrobipalpa sp. (Lepidoptera: Gelechiidae), and Eucharia festiva Hüfnagel (Lepidoptera: Arctiidae) were the dominant pests. T. dubia is the predominant defoliator with three generations a year. Northwest China, Central Asia, and the Mediterranean region are potentially suitable habitats for T. dubia in the world, while Xinjiang is the primary distribution area in China. Parasitoids belonging to seven species and four families were reared from the larvae of T. dubia, they were all endoparasitoids and koinobiont. Cotesia sp. (Hymenoptera: Braconidae) is the dominant parasitoid and prefer to parasitic in the 3rd-5th instar larvae. The present study provides the basis for understanding the species composition and natural enemies of lepidopteran defoliators. It will be an effective tool for the integrated pest management programs of H. ammodendron forest.

Genome and transcriptome analysis of the beet armyworm Spodoptera exigua reveals targets for pest control.

The genus Spodoptera (Lepidoptera: Noctuidae) includes some of the most infamous insect pests of cultivated plants including Spodoptera frugiperda, Spodoptera litura, and Spodoptera exigua. To effectively develop targeted pest control strategies for diverse Spodoptera species, genomic resources are highly desired. To this aim, we provide the genome assembly and developmental transcriptome comprising all major life stages of S. exigua, the beet armyworm. Spodoptera exigua is a polyphagous herbivore that can feed on > 130 host plants, including several economically important crops. The 419 Mb beet armyworm genome was sequenced from a female S. exigua pupa. Using a hybrid genome sequencing approach (Nanopore long-read data and Illumina short read), a high-quality genome assembly was achieved (N50 = 1.1 Mb). An official gene set (18,477 transcripts) was generated by automatic annotation and by using transcriptomic RNA-seq datasets of 18 S. exigua samples as supporting evidence. In-depth analyses of developmental stage-specific expression combined with gene tree analyses of identified homologous genes across Lepidoptera genomes revealed four potential genes of interest (three of them Spodoptera-specific) upregulated during first- and third-instar larval stages for targeted pest-outbreak management. The beet armyworm genome sequence and developmental transcriptome covering all major developmental stages provide critical insights into the biology of this devastating polyphagous insect pest species worldwide. In addition, comparative genomic analyses across Lepidoptera significantly advance our knowledge to further control other invasive Spodoptera species and reveals potential lineage-specific target genes for pest control strategies.

Efficacy of entomophatogenic fungi Beauveria bassiana and Cordyceps sp against Crocidolomia pavonana (FABR.) Lepidoptera: Pyralidae) as possible pest management strategy on pepper multi-cropping plantation

Black and white pepper have been considered as the most important perennial crops in some regions of Indonesia yet it took about 3-5 years before the plant start producing. One of the possible approaches to maintain the income of the farmer in the perennial plantation is multi-cropping with high-value annual crops, such as vegetables. However, many pests of vegetables already showed resistance to the common synthetic pesticide applied on the black pepper plant. Thus, it is necessary to apply another strategy for pest control, by applying entomopathogenic fungi. In this study, bioassays and field efficacy of two local isolates of entomopathogenic fungi (Beauveria bassiana and Cordyceps sp.) against one of the most insecticide-resistant pests, larvae of Crocidolomia pavonana (Fabr.) was conducted. In this study, exposure to 1 x 104 conidia mL−1 to 1 x 107 conidia mL−1 resulted in mean larval mortalities from 23.33 to 100% in two days. The probit analysis showed that the LC50 of B. bassiana was estimated at 4.26 x 104 conidia mL−1 which significantly more toxic than Cordyceps sp. (1.57 x 105 conidia mL−1) although the lethal time was similar. From the field tests, cabbage was sprayed with suspension contained 107 conidia mL−1. Means percent of mortality for all treatments was more than 75% and significantly higher (P < 0.05) than the control (tween 80). Conidia of Cordyceps sp. in palm oil cooking oil offered the most promising result against the C. pavonana.

60Co-γ Radiation Alters Developmental Stages of Zeugodacus cucurbitae (Diptera: Tephritidae) Through Apoptosis Pathways Gene Expression.

Radiation is considered as a promising insect pest control strategy for minimizing postharvest yield losses. Among various techniques, irradiation is a method of choice as it induces lethal biochemical or molecular changes that cause a downstream cascade of abrupt physiological abnormalities at the cellular level. In this study, we evaluated the effect of 60Co-γ radiation on various developmental stages of Zeugodacus cucurbitae Coquillett and subsequent carry-over effects on the progeny. For this purpose, we treated eggs with 30- and 50-Gy radiation doses of 60Co-γ. We found that radiation significantly affected cellular antioxidants, insect morphology, and gene expression profiles. Our results indicate that in response to various doses of irradiation reactive oxygen species, catalase, peroxidase, and superoxide dismutase activities were increased along with a significant increase in the malondialdehyde (MDA) content. We observed higher mortality rates during the pupal stage of the insects that hatched from irradiated eggs (50 Gy). Furthermore, the life span of the adults was reduced in response to 50 Gy radiation. The negative effects carried over to the next generation were marked by significantly lower fecundity in the F1 generation of the irradiation groups as compared to control. The radiation induced morphological abnormalities at the pupal, as well as the adult, stages. Furthermore, variations in the gene expression following irradiation are discussed. Taken together, our results signify the utility of 60Co-γ radiation for fruit fly postharvest management.

Studying the Activity of Neuropeptides and Other Regulators of the Excretory System in the Adult Mosquito.

Studies of insect physiology, particularly in those species that are vectors of pathogens causing disease in humans and other vertebrates, provide the foundation to develop novel strategies for pest control. Here, a series of methods are described that are routinely utilized to determine the functional roles of neuropeptides and other neuronal factors (i.e., biogenic amines) on the excretory system of the mosquito, Aedes aegypti. The Malpighian tubules (MTs), responsible for primary urine formation, can continue functioning for hours when removed from the mosquito, allowing for fluid secretion measurements following hormone treatments. As such, the Ramsay assay is a useful technique to measure secretion rates from isolated MTs. Ion-selective microelectrodes (ISME) can sequentially be used to measure ion concentrations (i.e., Na+ and K+) in the secreted fluid. This assay allows for the measurement of several MTs at a given time, determining the effects of various hormones and drugs. The Scanning Ion-selective Electrode Technique uses ISME to measure voltage representative of ionic activity in the unstirred layer adjacent to the surface of ion transporting organs to determine transepithelial transport of ions in near real time. This method can be used to understand the role of hormones and other regulators on ion absorption or secretion across epithelia. Hindgut contraction assays are also a useful tool to characterize myoactive neuropeptides, that may enhance or reduce the ability of this organ to remove excess fluid and waste. Collectively, these methods provide insight into how the excretory system is regulated in adult mosquitoes. This is important because functional coordination of the excretory organs is crucial in overcoming challenges such as desiccation stress after eclosion and before finding a suitable vertebrate host to obtain a bloodmeal.

Non-smooth ecological systems with a switching threshold depending on the pest density and its rate of change

Non-smooth Filippov systems may be used to provide natural description and characterize ecosystems with threshold control strategies. One common control strategy is the economic threshold (ET) often seen in integrated pest management. Recently switching systems consisting of free and controlled subsystems and guided by the threshold ET were developed and investigated. The key hypothesis in these systems is to consider only the pest density against a certain threshold value to construct the switching condition. This means that the rapid or saturated growth of pest population was not taken into account. Practical pest control strategies depend not only on the number of pests, but also on the growth rate of pests. This paper examines a new switching system guided by weighting the pest number and its growth rate as the threshold level. Theoretical analyses reveal that the proposed threshold strategy results in nonlinear sliding curve with complex sliding mode dynamics including multiple sliding segments and pseudo-equilibrium, confirmed by the sliding segment bifurcations. Moreover, the local and global sliding bifurcations clarify the fact that variations of ET and the new threshold control strategy not only lead to rich sliding dynamics such as various sliding periodic solutions, but also have important consequences on pest control.

Efficacy of food-based attractants for monitoring Drosophila suzukii (Diptera: Drosophilidae) in berry crops

Spotted-Wing Drosophila (SWD), Drosophila suzukii Matsumura is an invasive fruit fly pest of soft-skinned fruits that causes serious economic losses in the berry growing areas of central Mexico. Effective attractants are necessary to detect its presence, to monitor populations where established, and to explore new strategies for pest control. The capture of D. suzukii in four food-based attractants was compared with apple cider vinegar (ACV) as the reference attractant in blackberry, raspberry, and blueberry crops. An active yeast-based lure, Fly Buster Powder®, resulted the most effective attractant capturing SWD flies in blackberry and blueberry. However, this attractant was similar to SuzukiiTrap® Max Captures, ACV and Pherocon® SWD, but less effective than a two-component attractant (2C trap) in raspberry. The specificity of attractants was variable among crops and experiments but Fly Buster Powder® tends to be highly selective in the capture of SWD with up to 70% of D. suzukii from all drosophilids captured. Fly Buster Powder® and 2C trap attractants were more effective trapping D. suzukii when aged for 7 days than when aged for 1 or 15 days. The specificity of both yeast-based attractants was significantly reduced when aged for 15 days than when aged for 1 or 7 days.

Gene drive strategies of pest control in agricultural systems: Challenges and opportunities.

Recent advances in gene‐editing technologies have opened new avenues for genetic pest control strategies, in particular around the use of gene drives to suppress or modify pest populations. Significant uncertainty, however, surrounds the applicability of these strategies to novel target species, their efficacy in natural populations and their eventual safety and acceptability as control methods. In this article, we identify issues associated with the potential use of gene drives in agricultural systems, to control pests and diseases that impose a significant cost to agriculture around the world. We first review the need for innovative approaches and provide an overview of the most relevant biological and ecological traits of agricultural pests that could impact the outcome of gene drive approaches. We then describe the specific challenges associated with using gene drives in agricultural systems, as well as the opportunities that these environments may offer, focusing in particular on the advantages of high‐threshold gene drives. Overall, we aim to provide a comprehensive view of the potential opportunities and the remaining uncertainties around the use of gene drives in agricultural systems.

Plant Lectins as Insecticidal Agents Against Cotton Leafworm Spodoptera littoralisand Their Potential Applications in Crop Protection

Background: The production of insecticidal proteins is one of the greatest vital direct defense responses in plants against the attack by phytophagous insects. One particular class of the entomotoxic proteins present in many plant species is lectins that is used against a wide range of important insects. Aim: The insecticidal activity of two lectins from seeds of white kidney bean (Phaseolus vulgaris) and soybean (Glycine max) on the growth, development and survival of the cotton leafworm, Spodoptera littoralis Boisd. (Lepidoptera: Noctuidae) was studied. Methods: Lectin products were isolated and purified using ammonium sulfate precipitation. Insecticidal activity, growth-inhibitory and physiological effects on the differential haemocyte count of lectin products were evaluated against S. littoralis. In vivo effects of lectin products on some S. littoralis enzymes were also determined. Results: Lectin contents in 250 g seeds were 700 and 500 mg in soybean and white kidney bean, respectively. The total protein concentrations were 160-163 and 118-120 mg/mL in soybean and white kidney bean, respectively. The insecticidal activity of lectin products exerted a strong effect on the larval weight gain and the reduction of the weight reached to 75.25%. Furthermore, the other developmental stages of pupation and adult formation were also affected. An elongated larval duration was noticed since larval duration was 24.8 days compared with control (12.0 days). Complete pupation (100%) was recorded in the control; however, a significant decrease in pupation was found to be 54.0% in treated larvae. Lectin products increased the average number of 123.9 haemocytes (123.9) compared to the control (94.4 haemocytes/field). In addition, lectin products inhibited the activity of total proteases, α-amylase, GST and total esterases. Conclusion: It can be concluded that the lectins have high potential in pest control strategies based on their activity towards the cotton leafworm, S. littoralis. These findings suggest that lectin products are interesting tools for integrated pest management in important agriculture crops.

Volatiles from host plant brinjal attract the brinjal Fruit and Shoot Borer -Leucinodes orbonalis Guenee

• Entire volatile profile of brinjal plant reported first time. • Brinjal plant volatiles contain 100 different chemical constituents. • Host plant volatiles play a major role in the attraction of insect pest. • Attractant effects of brinjal host plant volatiles to BFSB leads to the development of an effective insect pest control strategy. Brinjal Fruit and Shoot Borer- Leucinodes orbonalis Guenee is a major insect pest on brinjal- Solanum melongena worldwide. An effective strategy used in developing pest controlling agents is the synergism between insect pheromones and host plant volatiles, which can increase the attraction of insect pest. The present study was aimed at investigating the chemical constituents and attractant effects of the volatiles extracted from different parts of the host plant brinjal on the behavior of adult L. orbonalis . Bioassay using Y-shaped olfactometer revealed that the one-day old virgin female, gravid female and male insects respond positively to the host plant volatiles extracted from fruits, leaves and shoots but not to that of flowers. It was shown that the gravid females were significantly attracted to all three volatiles (p < 0.05). Bioassay using X-shaped olfactometer identified that all three types of insects highly preferred the volatiles from fruits (p < 0.05). Gas chromatography-mass spectrometry analysis of volatiles indicated that brinjal plant produces volatile secondary metabolites, which include 2,2′-(Ethane-1,2-diylbis(oxy))bis(ethane-2,1-diyl) dibenzoate (12.11%), 3,7-dimethylocta-1,6-dien-3-ol (22.38%), Benzyl alcohol (22.9%) and Benzyl alcohol (27.06%) as major constituents from fruits, shoots, leaves and flowers respectively. Responses of insects to the volatiles from host plant in the absence of visual cues direct us to focus on the importance of host plant volatiles to locate the plant. Results of this study emphasize the major role that host plant volatiles play in the attraction of insect pests towards the plant.

Dynamics of Microbial Communities across the Life Stages of Nilaparvata lugens (Stål)

Understanding the composition of microorganismal communities hosted by insect pests is an important prerequisite for revealing their functions and developing new pest control strategies. Although studies of the structure of the microbiome of Nilaparvata lugens have been published, little is known about the dynamic changes in this microbiome across different developmental stages, and an understanding of the core microbiota is still lacking. In this study, we investigated the dynamic changes in bacteria and fungi in different developmental stages of N. lugens using high-throughput sequencing technology. We observed that the microbial diversity in eggs and mated adults was higher than that in nymphs and unmated adults. We also observed a notable strong correlation between fungal and bacterial α-diversity, which suggests that fungi and bacteria are closely linked and may perform functions collaboratively during the whole developmental period. Arsenophonus and Hirsutella were the predominant bacterial and fungal taxa, respectively. Bacteria were more conserved than fungi during the transmission of the microbiota between developmental stages. Compared with that in the nymph and unmated adult stages of N. lugens, the correlation between bacterial and fungal communities in the mated adult and egg stages was stronger. Moreover, the core microbiota across all developmental stages in N. lugens was identified, and there were more bacterial genera than fungal genera; notably, the core microbiota of eggs, nymphs, and mated and unmated adults showed distinctive functional enrichment. These findings highlight the potential value of further exploring microbial functions during different developmental stages and developing new pest management strategies.

Principles and Methods of Counteracting Harmful Salmon–Arthropod Interactions in Salmon Farming: Addressing Possibilities, Limitations, and Future Options

The arthropod salmon louse (Lepeophtheirus salmonis) is a major threat to Atlantic salmon aquaculture and wild salmonids. Essentially like in monoculture, very high concentrations of susceptible hosts may result in high reproduction and severe production of waves of pests. Pest management is crucial both for fish health and protection of wild fish populations from aquaculture influence. Various methods have been utilized to control salmon lice infestations, such as pesticide use, physical treatments, construction modifications, fallowing, breeding, vaccination, and biological control. Most of the methods are partially successful, but none completely fulfills the necessary pest control strategy. Like in agriculture, lice/pest management is an arms race, but the marine environment makes it even more difficult to precisely hit the target pest and avoid unintended negative effects on general wildlife. In this study, we provide an overview of the methods and principles of salmon lice management and address current possibilities and limitations. We also highlight the potential of emerging strategies and enabling technologies, like genome editing, RNA interference, and machine learning, in arthropod management in aquaculture.

Laboratory bioassay of six pesticides, an entomopathogenic fungus, and a botanical pesticide on two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae)

The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) is a serious pest that infests different agricultural crops in Bangladesh. The application of different types of pesticides (botanical and chemical) with various modes of action and bio-pesticides was used for the first time to develop sustainable pest control strategies against spider mites. In this study, the effects of six chemical insecticides viz. abamectin, bifenthrin, bifenazate, etoxazole, hexythiazox, and spinosad, and entomopathogenic fungus Beauveria bassiana and botanical neem oil were evaluated against adult and egg stages of T. urticae under laboratory conditions. Treated mites were kept in controlled conditions at 25 ± 1 ℃, 60–70% RH and a photoperiod of 16:8 h (L: D). The LC50 values of all chemicals [for adults, abamectin (0.51 ml/L), bifenthrin (3.26 ml/L), bifenazate (3.82 ml/L), hexythiazox (3.27 ml/L) and spinosad (3.83 ml/L); for eggs, abamectin (0.56 ml/L), bifenthrin (3.48 ml/L), bifenazate (26.81 ml/L), hexythiazox (4.18 ml/L) and spinosad (18.28 ml/L)] suggest that they were effective against eggs and adult females of the T. urticae. Etoxazole (LC50 = 3.99 ml/L) is recommended against egg stage. The neem oil was found to be moderately effective (for adult, LC50 = 1.26%; for egg, LC50 = 1.77%) against eggs and adult females of T. urticae. The B. bassiana was also found to be effective against eggs and adult females of T. urticae. Finally, it could be concluded that all chemicals used in this study are effective for the management of two spotted spider mite but the entomopathogenic fungus B. bassiana and botanical neem oil were promising alternatives for successful management of T. urticae in IPM programs.