Soil-dwelling Pests Research Articles

Trap crops enhance the control efficacy of Metarhizium brunneum against a soil-dwelling pest

Soil-dwelling insect pests may cause considerable damage to crops worldwide, and their belowground lifestyle makes them hard to control. Amongst the most promising control agents for subterranean pests are soilborne entomopathogenic fungi (EPF) such as Metarhizium brunneum. Albeit EPF can be highly pathogenic to their target pest species under laboratory conditions, their efficacy in the field is often limited due to adverse environmental conditions. Here, we test for the first time if the efficacy of EPF can be improved when they are augmented with trap crops. In a field experiment, the M. brunneum strain ART2825 was combined with a trap crops mixture of six plant species and evaluated for its control effect of wireworms (Coleoptera: Elateridae). When both were combined in the main crop, potato damage was lowered on average by 42.5% and wireworm abundance by 50.8%. Single application of trap crops or EPF lowered damage/pest abundance only by 29.9%/15.89% and 34.7%/4.77%, respectively. Importantly, the strength of the synergistic pest control effect between trap crops and EPF increased disproportionately with increasing wireworm abundance. However, DNA-based gut content analysis showed that wireworms’ feeding preferences were not shifting toward the trap crops. Our findings demonstrate that combining trap crops with EPF improves the efficacy of the latter and leads to a synergistic control effect which magnifies with increasing wireworm abundance. Hence, the synergistic effect of EPF and trap crops might be a promising control strategy for soil-dwelling pests in general and significantly improve our abilities to manage soil pests environmentally friendly.

The application of entomopathogenic nematode modified microbial communities within nesting mounds of the red imported fire ants, Solenopsis invicta

Entomopathogenic microorganisms (e.g., fungi, bacteria, nematodes) have been widely used in biological control of soil-dwelling pests, including the red imported fire ant (RIFA), Solenopsis invicta, a notorious invasive pest worldwide. The application of large amounts of entomopathogenic microorganisms to soil may affect the indigenous soil microbial communities. However, reports about the effect of entomopathogenic nematodes (EPN) on soil microbial communities are very few. In this study, the effects of EPN on RIFA populations and microbial communities in mounds were investigated. Our results showed that the application of the EPN Steinernema carpocapsae. All strain on mounds efficaciously suppressed RIFA worker populations, without forming significantly more satellite mounds compared with the control treatment. The application of EPN did not impact the bacterial and fungal diversity in soils derived from the RIFA mounds. However, it slightly altered the taxonomic make-up of the bacterial communities, but significantly altered the taxonomic composition of fungal communities at the phylum, family, and genus levels. The abundances of some beneficial bacteria and fungi, such as Streptomyces, decreased, while those of plant and animal pathogenic bacteria and fungi, dramatically increased, after EPN treatment. On the other hand, the abundances of some entomopathogenic fungi, such as Fusicolla, Clonostachys, and Mortierella, increased. Redundancy analysis or canonical correspondence analysis revealed a positive correlation between the efficacious EPN control and the presence of the insect-resistant bacteria, Sinomonas, as well as entomopathogenic fungi Fusicolla and Mortierella. This suggests that the interactions between EPN and entomopathogenic fungi may play a role in the biological control of RIFA. Our discoveries shed light on the interactions among EPN, RIFA, and soil microbial communities, and emphasize a possible mutualistic relationship between EPN and entomopathogenic fungi in the biological control of RIFA.

Occurrence and management of two emerging soil-dwelling pests ravaging cabbage and onions in Kenya

Cabbage and Onion production in sub-Saharan Africa face numerous pest constraints that needs to be overcome to feed the rapidly growing population. This study aimed to establish the occurrence, incidence, and severity of soil-dwelling pests of cabbage and onions, and current management practices in five Counties of Kenya. Our findings revealed that most farmers grew hybrid vegetables on a small scale, which were highly dominated by various pest species (Delia platura, Maladera sp., and Agriotes sp. for cabbage and Atherigona orientalis and Urophorus humeralis for onion. The occurrence, incidence and severity of the various pest species on both crops varied considerably. Over 95% of the farmers relied on synthetic insecticides, which were applied weekly or bimonthly with limited success. Our findings demonstrate that invasive and polyphagous A. orientalis and D. platura were the most devastating pests of onion and cabbage without effective control options. Therefore, effective, sustainable, and affordable management strategies are required to control the spread of these pests to other crops in the region.

Functional response of two soil-dwelling predatory mites, Macrocheles mammifer (Berlese) (Acari: Macrochelidae), and Stratiolaelaps scimitus (Womersley) (Acari: Laelapidae), on thrips Megalurothrips usitatus (Bagnall) (Thysanoptera: Thripidae)

Megalurothrips usitatus (Bagnall) (Thysanoptera: Thripidae), commonly known as the Asian bean thrips, is a destructive pest of leguminous crops, causing significant damage and economic losses. In the present study, the functional responses and predation rates of two predatory mites Macrocheles mammifer Berlese (Macrochelidae) and Stratiolaelaps scimitus (Womersley) (Laelapidae) on M. usitatus pupae were evaluated. The former was discovered in a cowpea Vigna unguiculata (Linn.) Walp. field of southern China, while the latter is commonly used as a biological control agent for soil-dwelling pests. Both M. mammifer and S. scimitus females consumed more M. usitatus than protonymphs, and the predation rate of the adult stage of M. mammifer was found to be significantly higher than that of S. scimitus. Likewise, logistic regression analysis revealed that both predators exhibited a type II functional response. Females of M. mammifer and S. scimitus displayed a higher attack rate and shorter handling time (T<sub>h</sub>) compared to conspecific protonymphs when preying on pupae of M. usitatus. Female M. mammifer recorded the highest attack rate (a) of 4.028, closely followed by female S. scimitus at 3.994. The protonymph of M. mammifer had an attack rate of 2.651, while the protonymph of S. scimitus displayed the lowest rate of 1.402. Female M. mammifer exhibited the shortest handling time (0.089), indicating superior prey-handling ability. Overall, the predatory mites M. mammifer and S. scimitus demonstrated considerable promise for managing M. usitatus, with M. mammifer displaying higher efficacy than S. scimitus.

CARBOFURAN INTOXICATION IN MALES, ALSO CALLED CAT KILLER PILLS

Carbofuran is a frequently used insecticide, acaricide, and nematicide that is used in the field of agriculture all around the world. Presently, carbofuran is commonly used in malicious poisoning. It is among the class of insecticides that are used to eradicate soil-dwelling pests from crops. Approximately 20,000 tonnes of this product is used annually. As effective as it is in controlling insects, it has notorious side effects on humans and is now introduced as "Cat Killer Pills." A 26-year-old male, a healthy student of 12th standard, presented with a suicidal attempt with this 'Cat Killer Pill.' 6 hours after ingestion, he experienced weakness, fatigue, sweating, breathing difficulties, and disorientation. He was initially treated at another hospital, where he was intubated due to a suppressed respiratory system. Upon presentation, he was intubated. He was treated with Atropine and Pralidoxime, which helped in his cure. The results of this study suggest that in addition to the cholinolytic effects of atropine, Pralidoxime may prevent and antagonize the acute toxicity of carbofuran by reactivating cholinesterase and rapid elimination of carbofuran.

Field application of encapsulated entomopathogenic nematodes using a precision planter

The use of entomopathogenic nematodes (EPNs) as a biological control agent in agriculture has shown efficacy against various soil-dwelling pests. Despite its potential, high production costs and inconsistent field efficiency remain significant challenges. Although EPNs can be applied using irrigation systems and spraying equipment, optimized applications are required. This study aimed to evaluate the feasibility of applying EPNs in gelatin capsules and planting with a precision planter. It was hypothesized that this method would lead to more controlled and uniform EPN application. The effects of EPN encapsulation on dispersal and field persistence in the soil were also investigated. Larval mortality for capsule applications was between 53 and 67% under field conditions, with no statistical difference compared to the drip irrigation applications. Dispersal trials were carried out using custom steel olfactometers, and capsule application did not have any adverse effects on the dispersal of infective juveniles for 24, 48 and 72 h. Persistence trials revealed no significant differences between the capsule and control groups, with a maximum persistence of 50 days. The results suggest that the capsule technique could be a promising option for large-scale EPN applications, and further optimization may lead to improved results.

Role of neonicotinoid preparations for spike grain crop seedlings protection against click beetle and Frit fly larvae in Belarus

Recently, in winter and spring grain crops for pre-sowing seed treatment among the assortment of insecticides the preparations of insecticidal and insectofungicidal action based on neonicotinoids: acetamiprid, imidacloprid, clothianidin and thiamethoxam have been widely used. At the current stage of chemical method development of plant protection against harmful arthropods, neonicotinoids are rapidly developing and promising group of neurotoxic insecticides and having a fundamentally different mechanism of action on insects – they inhibit nicotine-acetylcholine receptors. Pre-sowing seed material treatment with insecticides protects the sown seeds, hypocotyls and aboveground plant organs against soil and intrastem pests. It is revealed that during the growing seasons of 2019–2021 in the experimental field, economically significant phytophages are lined click beetle (Agriotes lineatus L.) and Frit flies of autumn and spring generations (Oscinella spp.), indicating the study of their larvae number and harmfulness and measures allowing to control the vital activity of insects in agrocenoses conditions. Plants damaged by them lag behind in growth and die. Improving the range of effective preparations with different active substances used by the method of pre-sowing treatment of grain crop seeds to protect plants during germination against phytophages is an obligatory link in the technology of crops cultivation and one of the factors of their number effective control, what has determined the relevance of the choice of our research topic. Pre-sowing winter and spring cereals seed treatment with neonicotinoid preparations based on imidacloprid (Coyote, SC, Sidoprid, FSC, Tabu, WSC), acetamiprid (Leatrin, SC, Bagrets Plus, SC, Vershina Plus, SC) and thiamethoxam (Questor Forte, SC) have provided plant seedlings high protection against click beetle and Frit fly larvae damage. The results of studies conducted in 2019–2021 have shown that the effectiveness of preparations have varied by years depending on weather conditions and pests number before sowing and at seedlings stage. The indicators of winter grain crops plant damage reduction by wireworms have made 78,8–91,1 %, Frit flies 60,0–85,0 %, spring cereals – 80,0–91,6 % and 80,7–91,1 %, respectively. Through years of research the insecticides for seed treatment have helped to increase the stored grain yield of cereal crops, on the average, from 0,7 to 6,2 cwt/ha, or 1,0–13,5 %. The data obtained will serve as a basis for justifying protective measures to reduce the number and harmfulness of soil-dwelling and terrestrial pests in order to improve the phytosanitary situation in the agrocenoses of cereals.

Entomocomplex of onions in the Right-Bank Forest-Steppe of Ukraine

Goal. To monitor the phytosanitary condition of onion crops in the Right-Bank Forest-Steppe of Ukraine and to establish the species composition of dominant pests.
 Methods. The research was carried out in accordance with the generally accepted methodological recommendations in entomology.
 Results. As a result of long-term monitoring of onion crops, 12 species of phytophages from the ranks of Coleoptera — 46.2%, Lepidoptera — 23.1%, Diptera — 15.4%, Thysanoptera — 10.4%, Orthoptera — 5.0% and others. In the phase of leaf development (main shoot) (ВВСН 1—19) the most harmful are soil-dwelling pests: larvae of Agriotes sputator L. and Agriotes lineatus L.; larvae of the Melolontha melolontha L., the Melolontha hippocastani F), the Amphimallon solstitialis L.; Scotia segetum Schiff. and Gryllotalpa gryllotalpa L. In the phase of the beginning of thickening of the base of the leaves — bulb formation (ВВСН 41—43) phytophages dominate: onion fly (Delia antique Mg.), onion trips (Trips tabaci Lind.), Ceuthorrhynchus jakovlevi Schulzer.
 Conclusions. It was studied that with the number of soil pests 1.5—2.8 specimens/m2, plant damage is 24.6—28.3%, which is the reason for the liquefaction of crop density. It has been established that significant damage to onion crops is caused by the onion fly (Delia antique Mg.), the period of harmfulness of which lasts throughout the growing season. During the years of research, the flight of the phytophagous adult took place in the third decade of April — first decade of May, at the sum of active CAT temperatures (> 5°C) = 104—131°С. Mass flight of the pest was observed in the II—III decades of May, at an average daily air temperature of 12.8—17.4°C.

Comparative Nanopore Sequencing-Based Evaluation of the Midgut Microbiota of the Summer Chafer (Amphimallon solstitiale L.) Associated with Possible Resistance to Entomopathogenic Nematodes.

Root-feeding Amphimallon solstitiale larvae and certain other scarab beetles are the main soil-dwelling pests found in Europe, while entomopathogenic nematodes (EPN) have been used as a biocontrol agent against these species. Our study provides the first detailed characterization of the bacterial community of the midgut in wild A. solstitiale larvae, based on the nanopore sequencing of the 16S rRNA gene. In the whole dataset, we detected 2586 different genera and 11,641 species, with only 83 diverse bacterial genera shared by all studied individuals, which may represent members of the core midgut microbiota of A. solstitiale larvae. Subsequently, we compared the midgut microbiota of EPN-resistant and T0 (prior to EPN exposure) individuals, hypothesizing that resistance to this parasitic infection may be linked to the altered gut community. Compared to the control, the resistant insect microbiota demonstrated lower Shannon and Evenness indices and significant differences in the community structure. Our studies confirmed that the gut microbiota alternation is associated with resistant insects; however, there are many processes involved that can affect the bacterial community. Further research on the role of gut microbiota in insect-parasitic nematode interaction may ultimately lead to the improvement of biological control strategies in insect pest management.

The lure of hidden death: development of an attract-and-kill strategy against Agriotes obscurus (Coleoptera: Elateridae) combining semiochemicals and entomopathogenic nematodes

Wireworms are polyphagous soil-dwelling pests that are hard to control. Attract-and-kill strategies, combining attractive semiochemicals with biocontrol agents, have great promise to control insect pests. We hypothesized that the combination of plant semiochemicals and entomopathogenic nematodes (EPNs) in an attract-and-kill system could greatly enhance the nematodes' efficiency against wireworms. We evaluated the potential of alginate beads loaded with plant extracts and EPNs to control Agriotes obscurus. We tested the efficiency to kill wireworms or to reduce their feeding activity when combining potato tuber extracts as attractants with any of seven different EPN populations. While a direct application of EPNs on wireworms did not reduce the feeding activity nor increased their mortality, the combination of attractants and EPNs encapsulated in alginate beads resulted in attraction and consumption of the EPNs and caused up to 50% wireworm mortality with the EPN species Steinernema carpocapsae. Beads with EPNs caused a significant reduction of the wireworms' feeding activity. This study shows that wireworms feeding on EPN-containing beads have their feeding activity and survival negatively affected. Considering their long developmental time and the survival capability of EPNs in the soil, implementing this attract-and-kill system in the field might be a suitable strategy for the long-term management of wireworms.

Evaluation of 13-Tetradecenyl Acetate Pheromone for Melanotus communis (Coleoptera: Elateridae) Detection in North Carolina Row Crop Agroecosystems.

Melanotus communis Gyllenhal (Coleoptera: Elateridae) larvae are a common soil-dwelling pest of many crops, including sweet potato, grains, and tobacco. Although many studies have focused on the larval stage of this pest, the seasonal activity and ecology of the adults (click beetles) are not well understood. The overarching goal of this study was to relate M. communis adult activity to host crops in the North Carolina row-crop agroecosystem. To do this, we conducted a two-year study documenting male M. communis activity, using a recently identified sex attractant pheromone, 13-tetradecenyl acetate. This project was divided into two parts: 1) a pheromone assessment study testing the efficacy and specificity of 13-tetradecenyl acetate, and two analogs, 13-tetradecenyl butyrate and 13-tetradecenyl hexanoate, and 2) a landscape survey using traps baited with 13-tetradecenyl acetate. Results of the efficacy study showed that 13-tetradecenyl acetate was the most effective M. communis lure when compared to non-baited control traps or traps baited with the two homologs. The landscape study documented a strong association between M. communis catch and the adjacent crop type. We found that adult M. communis abundance was greatest near corn, followed by sweet potato, and then cotton. Analysis of activity over time found that the peak activity occurred during July. Overall, this project demonstrates the usefulness of pheromone-baited traps in providing new information about M. communis activity.

Dominant egg surface bacteria of Holotrichia oblita (Coleoptera: Scarabaeidae) inhibit the multiplication of Bacillus thuringiensis and Beauveria bassiana

Holotrichia oblita (Coleoptera: Scarabaeidae) and some other scarab beetles are the main soil-dwelling pests in China. Bacillus thuringiensis (Bt) and Beauveria bassiana (Bb) are entomopathogens that have been used as biocontrol agents of various pests. However, scarab larvae especially H. oblita exhibited strong adaptability to these pathogens. Compared to other scarabs, H. oblita could form a specific soil egg case (SEC) structure surrounding its eggs, and young larvae complete the initial development process inside this structure. In this study, we investigated the role of SEC structure and microorganisms from SEC and egg surface in pathogen adaptability. 16S rRNA gene analysis revealed low bacterial richness and high community unevenness in egg surface, with Proteobacteria, Firmicutes, Bacteroidetes and Fusobacteria dominating. In terms of OTUs composition analysis, the data show that the egg surface contains a large number of unique bacteria, indicating that the egg bacterial community may be derived from maternal transmission. Furthermore, we found that all culturable bacteria isolated from egg surface possessed antimicrobial activity against both Bt and Bb. The Pseudomonas bacteria with a significantly higher abundance in egg surface showed strong Bt- and Bb antagonistic ability. In conclusion, this study demonstrated a unique and antimicrobial bacterial community of H. oblita egg surface, which may contribute to its adaptability. Furthermore, the specific SEC structure surrounding the H. oblita eggs will provide a stable microenvironment for the eggs and egg surface bacteria, which probably provides more advantages for H. oblita adaptation ability.

Efficacy assessment of entomopathogenic nematodes native to Morocco against the white grubs Rhizotrogus obesus Lucas and Geotrogus olcesii Fairmaire (Coleoptera: Scarabaeidae)

The white grubs Rhizotrogus obesus Lucas and Geotrogus olcesii Fairmaire (Coleoptera: Scarabaeidae) are two of the most problematic soil-dwelling pests of some annual crops in Morocco, where they may become a target for entomopathogenic nematodes (EPN). In this study, fourteen EPN strains reported from different fields in Morocco were investigated for their efficacy against both scarab species, under laboratory and greenhouse conditions. In laboratory experiments, seven strains of Heterorhabditis bacteriophora (HB-MOR2, HB-MOR6, HB-MOR1, HB-MOR5, HB-MOR7, HB-MOR4, and HB-MOR8) and one strain of Steinernema feltiae (SF-MOR10), provided remarkable efficacy against R. obesus (38–73% of mortalities). The EPN strains of Steinernema sp.2 (Sfg-MOR12), H. bacteriophora (HB-MOR4), Steinernema sp.1 (Sfg-MOR11), and H. bacteriophora (HB-MOR1) caused mortality rates ranging from 53 to 68% against G. olcesii. In greenhouse experiments where chlorpyrifos-ethyl was used as a positive control, larval mortality of R. obesus caused by both strains of H. bacteriophora, HB-MOR6 (81%) and HB-MOR2 (75%), was higher than that obtained by chlorpyrifos-ethyl (73%). The mortality rate in G. olcesii caused by Steinernema sp.2 (Sfg-MOR12) (77%) was the same as for chlorpyrifos-ethyl treatment (74%). Therefore, it can be concluded that EPN can constitute a promising biological alternative for the sustainable control of R. obesus and G. olcesii.

A knowledge-based approach to designing control strategies for agricultural pests

Chemical control of insect pests remains vital to agricultural productivity, but limited mechanistic understanding of the interactions between crop, pest and chemical control agent have restricted our capacity to respond to challenges such as the emergence of resistance and demands for tighter environmental regulation. Formulating effective control strategies that integrate chemical and non-chemical management for soil-dwelling pests is particularly problematic owing to the complexity of the soil-root-pest system and the variability that occurs between sites and between seasons. Here, we present a new concept, termed COMPASS, that integrates ecological knowledge on pest development and behaviour together with crop physiology and mechanistic understanding of chemical distribution and toxic action within the rhizosphere. The concept is tested using a two-dimensional systems model (COMPASS-Rootworm) that simulates root damage in maize from the corn rootworm Diabrotica spp. We evaluate COMPASS-Rootworm using 119 field trials that investigated the efficacy of insecticidal products and placement strategies at four sites in the USA over a period of ten years. Simulated root damage is consistent with measurements for 109 field trials. Moreover, we disentangle factors influencing root damage and pest control, including pest pressure, weather, insecticide distribution, and temporality between the emergence of crop roots and pests. The model can inform integrated pest management, optimize pest control strategies to reduce environmental burdens from pesticides, and improve the efficiency of insecticide development.

Impacts of neonicotinoid seed treatments on soil-dwelling pest populations and agronomic parameters in corn and soybean in Quebec (Canada).

Agricultural soil pests, including wireworms (Coleoptera: Elateridae), are managed primarily with pesticides applied directly to seeds before sowing. Seeds coated with neonicotinoids have been used widely in Quebec (Canada) for several years. To assess the agronomic and economic value of neonicotinoid seed treatments in soybeans and corn in Quebec, trials were conducted from 2012 to 2016 in 84 fields across seven regions in Quebec. We evaluated the effect of neonicotinoid seed treatments on soil pest densities, crop damage and yield. The results showed that 92.6% of corn fields and 69.0% of soybean fields had less than 1 wireworm per bait trap. However, no significant differences in plant stand or yield were observed between treated and untreated corn or soybeans during the study. This study shows that neonicotinoid seed treatments in field crops in Quebec are useful in less than 5% of cases, given the very low level of pest-associated pressure and damage, and that they should not be used prophylactically. Integrated pest management (IPM) strategies need to be developed for soil insect pests to offer effective alternative solutions to producers.

Efficacy of entomopathogenic nematodes against the sugarbeet wireworm, Limonius californicus (Mannerheim) (Coleoptera: Elateridae)

Wireworms, the larval stage of click beetles (Coleoptera: Elateridae), are economically important soil-dwelling pests that attack many field crops worldwide. Wireworms have become a serious threat to spring wheat in the Northern Great Plains because of lack of effective control measures, creating a need for alternative control methods such as biological control with entomopathogenic nematodes (EPNs). A laboratory bioassay was used to test ten EPN strains and identify infective EPN strains against the sugarbeet wireworm, Limonius californicus (Mannerheim) (Coleoptera: Elateridae). Steinernema carpocapsae (Weiser) (All and Cxrd strains) and S. riobrave Cabanillas, Poinar, and Raulston (355 and 7–12 strains) killed 60–70% of L. californicus larvae in four weeks when applied at 700 Infective juveniles (IJs) (25 IJs/cm2), 1400 IJs (50 IJs/cm2), 2800 IJs (100 IJs/cm2), and 5600 IJs (200 IJs/cm2) per larva in the laboratory. Also, Heterorhabditis bacteriophora (Poinar) VS strain and Steinernema rarum (Doucet) 17c + e strain caused 50–60% mortality to L. californicus larvae after four weeks when applied at 5600 IJs/larva. However, regardless of the concentration applied, the penetration rate of infective juveniles into the host did not exceed 33%. In shade house trials, S. riobrave and S. carpocapsae strains caused 34–56% L. californicus mortality after four weeks with 50 and 56% mortality caused by S. carpocapsae All and S. riobrave 355 strain, respectively when applied at the rate of 80,000 IJs/pot. These results suggest that S. carpocapsae and S. riobrave may have significant potential for protecting spring wheat crops from L. californicus.

The complete mitochondrial genome of click beetle Agrypnus sp. (Coleoptera: Elateridae) and phylogenetic analysis

Larvae of click beetles are the most important soil-dwelling agricultural pests and are abundant throughout the world. Agrypnus sp. belongs to the subfamily Agrypninae of Elateridae. Here, we sequenced and annotated the complete mitochondrial genome (mitogenome) of Agrypnus sp., the new representative of the mitogenome of the subfamily. This mitogenome was 16,056 bp long and encoded 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), and two ribosomal RNA unit genes (rRNAs). Gene order was conserved and identical to most other previously sequenced Elateridae. The nucleotide composition biases towards A and T, which together made up 70.8% of the entirety. Phylogenetic analysis based on 13 PCGs sequences showed that Agrypnus sp. got together with the same subfamily species Pyrophorus divergens, Pyrearinus termitilluminans, Ignelater luminosus, and Hapsodrilus ignifer with high support value.

Interactive effects of temperature and time on cold tolerance and spring predation in overwintering soil predatory mites (Gaeolaelaps aculeifer Canestrini)

Soil living mites have large potential as biocontrol agents against soil-dwelling pests, but little is known about their ecological and ecophysiological responses to cold. We investigated the interactive effects of acclimation temperature and time on cold tolerance in the laelapid mite Gaeolaelaps aculeifer Canestrini after exposure to 5, 10, 15, or 20 °C for 1, 4, or 8 days. Another group of mites were subjected to simulated winter by gradually lowering the temperature from 20 to 0.8 °C during three months, while measuring tolerance to −2 and −5 °C as well as supercooling point and melt onset temperature of body fluids at start (20 °C; “summer”), at 5 °C (“autumn”), and at 0.8 °C (“winter”). A third group was kept at constant 10 °C as a constant mild cold comparison. We found a strong interaction between exposure temperature and time on cold tolerance, with rapid cold hardening after 24 h at 5 °C but increasing cold acclimation at 10 °C. During simulated winter, tolerance to −2 °C was high after two months at 4.1 °C, but then decreased to intermediate levels after another month at 0.8 °C. The supercooling point did not change over the simulated winter, but melt onset temperature was lowered after 0.8 °C exposure. Mites preyed and reproduced readily following simulated winter, but at lower rates than if kept at constant 10 °C. Our study indicates that G. aculeifer can overwinter following release, and suggests that cold storage is advantageous before inoculative release in early spring.

Bazı inorganik gübrelerin entomopatojen nematodlar (Steinernema feltiae Tur-S3 ve Heterorhabditis bacteriophora HBH) üzerine etkileri

Entomopathogenic nematodes (EPNs) are used effectively in biological control because of their virulence against soil dwelling pests, long-term efficacy and harmlessness to the environment. EPNs spend most of their life in the soil and have host- finding behavior. They can be affected by agricultural activities such as fertilization, tillage and irrigation. The objective of this study was to determine the direct effects of inorganic fertilizers on EPNs. For this purpose, 6 inorganic fertilizers used extensively in agriculture and two species of EPN (Steinernema feltiae Tur-S3 and Heterorhabditis bacteriophora HBH) were selected for the study. They were exposed to 1 gr/l, 5 gr/l and 10 gr/l fertilizer doses under laboratory conditions and checked for mortality for 10 days. Steinernema feltiae (Tur-S3) was more resistant to inorganic fertilizers than H. bacteriophora HBH, and DAP, NPK and NP had more adverse effects than the other fertilizers on both strains.

Entomopathogenic nematode performance against Popillia japonica (Coleoptera: Scarabaeidae) in school athletic turf: Effects of traffic and soil properties

Entomopathogenic nematodes (EPNs) have potential as an alternate means of controlling soil-dwelling pests in settings such as school athletic fields, where use of chemical pesticides is often restricted or prohibited. Athletic fields are also unique among turfgrass systems, as their distinct pattern of foot traffic can result in compaction and other soil properties varying across different areas of the field, potentially causing variability in EPN performance even within a single field, as many abiotic and biotic soil properties are known to influence EPN efficacy. We tested the efficacy of the EPNs Steinernema feltiae and Heterorhabditis bacteriophora against third-instar grubs of the Japanese beetle Popillia japonica in high-traffic and low-traffic areas of two soccer fields in New York State, one grown atop loam soil and the other atop loamy sand. Efficacy was low in the loam soil but modest for both species in the loamy sand, though the only significant increase over controls occurred in S. feltiae-inoculated plots within low traffic areas in 2016. Non-metric multidimensional scaling revealed positive associations between efficacy of both EPN species and soil sand content, suggesting that sandy soils are most optimal for curative applications against turfgrass pests. Soil biotic factors, such as microarthropod abundance, were not found to have an effect on EPNs. These results will aid turfgrass managers by improving knowledge of the conditions required for effective use of EPNs.