Beetle Mortality Research Articles

Winter mortality of the bark beetle Ips typographus in standing trees and in the ground

Winter mortality of the bark beetle <i>Ips typographus</i> in standing trees and in the ground

An Evaluation of a Winter Mortality Model for the Mountain Pine Beetle

The winter mortality of mountain pine beetle (Dendroctonus ponderosae Hopkins) larvae caused by temperatures below survivable thresholds and sudden decreases in temperature is among the most influential factors limiting population growth. Due to the importance of winter mortality in the demise of mountain pine beetle infestations, a widely used winter mortality model was developed at the Canadian Forest Service and the United States Forest Service. It predicts lethal temperatures and survival probabilities given temperature time series over the winter season. We present a rare and possibly the first peer-reviewed validation of this winter mortality model, wherein we independently tested the model at a new region in Canada by comparing model predictions to the observed lower lethal temperature thresholds and cold-associated mortality. Model predictions were biologically reasonable but slightly biased. Bias was exacerbated by the inaccurate translation of air temperature data from weather stations to temperatures under the bark where larvae develop. The spatial prediction of relative mortality observed across the study area in Banff National Park was poor—likely because the mountainous terrain presents a difficult prediction challenge when under-bark temperatures are not directly observed. Our results will help inform users of model constraints and how to optimize the accuracy of model predictions.

Insecticidal Efficacy of Diatomaceous Earth and Botanical Powders against Pulse Beetle, Callosobruchus analis F. in Stored Mung Bean (Vigna radiata L.)

The pulse beetle is the most damaging insect pest of legumes causing huge economic losses. The experiment was conducted to find out the insecticidal effects of diatomaceous earth (DE) combined with three botanical powders in three different combinations of 25% plant powder with 75% DE, 50% plant powder with 50% DE and 75% plant powder with 25% DE. The results indicated that the least number of adult beetles settled on grains treated with T9 (75% GP + 25% DE and T3 (75% NP + 25% DE) whereas maximum number of adult beetles settled in T4 (25% TP + 75% DE). After 168 hours, all the treatments showed significant mortality (100%) of adult beetles compared to control (43%). All the treatments reduced the number of eggs (3.60 to 6.80 eggs per 20 grains) in comparison to control (17.00). The maximum (28.80) days to adult emergence were documented in T9 whereas; minimum (21.40) days were recorded in untreated grains. Among all the treatments, T9: showed minimum emergence (36.40) of adult beetles whereas; the maximum (125.20) adults emerged in control. The lowest grain damage (5.50%) was observed in T9 as related to the maximum grain damage (28.96%) in the untreated control. The minimum weight loss (3.49%) was recorded in T9. The maximum weight loss (21.08%) was recorded in untreated grains. The use of diatomaceous earth in combination with garlic powder is recommended for the management of pulse beetle under storage conditions.

Effect of Baculovirus oryctes concentration on mortality of Oryctes rhinoceros L.

One of the key plantation crops in Indonesia, particularly in the expanding Riau region, is oil palm (Elaeis guineensis Jacq.). The frequent attacks by Rhinoceros beetles (Oryctes rhinoceros), are the greatest barrier to oil palm development in Riau region. Integrated Pest Management (IPM), which puts an emphasis on ecologically friendly controls one of which uses the entomopathogen Baculovirus oryctes, is the preferred control strategy. This study sought to determine the optimal suspension concentration of Baculovirus oryctes infected larvae on the mortality of the Oryctes rhinoceros beetle. The treatment given was concentration of Baculovirus oryctes suspension of, 0 ml.500 ml−1 water (0 x 106 PIBs.ml−1), 40 ml.500 ml−1 water (6 x 106 PIBs.ml−1), 50 ml.500 ml−1 water (7.6 x 106 PIBs.ml−1), 60 ml.500 ml−1 water (9.3 x 106 PIBs.ml−1) and 70 ml.500 ml−1 water (9.6 x 106 PIBs.ml−1). The results showed that the suspension concentration of 70 ml.500 ml−1 water (9.6 x 106 PIBs/ml) is the best trend concentration because it generates the fastest initial time of death which is 180 hours, lethal time 50 for 288 hours after application and total mortality of 70.83%. The conclusion is that Baculovirus oryctes can be used to kill rhinoceros beetle Oryctes rhinoceros best at a concentration of 70 ml.500 ml−1 water (9.6 x 106 PIBs ml−1).

Assessment of Boll Weevil Susceptibility to Isocycloseram and Ethiprole and Differential Toxicity to Natural Enemies.

Insecticides efficient against the target species while conserving natural enemies in the agroecosystem are required for IPM. With the imminent discontinuation of fipronil, a broad-spectrum insecticide, ethiprole, which belongs to the same group as phenylpyrazole (2B), and isocycloseram, a novel isoxazoline insecticide with distinct mode of action (30), provide options for controlling boll weevil. The susceptibility of the boll weevil, Anthonomus grandis grandis (Boh.), and two natural enemies [Eriopis connexa (Germar) and Bracon vulgaris Ashmead] to these insecticides were studied. Furthermore, the survival and biological traits of the lady beetle, E. connexa, exposed to fipronil, isocycloseram, and ethiprole were assessed. The LC50s values for fipronil, ethiprole, and isocycloseram for A. grandis grandis were 2.71, 0.32, and 0.025mg a.i./L, respectively; 0.86, > 200, and 3.21mg a.i./L for E. connexa; and 2.31, 592.94, and 0.18mg a.i./L for B. vulgaris, respectively. The recommended rates of ethiprole did not cause mortality in adult lady beetles, although fipronil and isocycloseram were highly toxic. Lady beetle larvae and adults survived more than 80% when exposed to dried residues of ethiprole, but less than 10% when exposed to fipronil and isocycloseram. Lady beetle larvae development, reproduction, and predation rates of adults were similar between ethiprole and the control group. Although fipronil and ethiprole belong to the same insecticide group, the difference in toxicity to boll weevils and natural enemies is presented and discussed. Ethiprole was more toxic to boll weevils than to its parasitoid and lady beetle, and isocycloseram was highly toxic to all three species.

Methyl benzoate-related compounds as potential repellents and fumigants for the control of cigarette beetle, Lasioderma serricorne (F.)

The cigarette beetle, Lasioderma serricorne (F.), presents a significant management challenge as a stored product pest. The beetle's increasing resistance to conventional fumigants necessitates the search for alternative solutions to mitigate losses in agro-based industries. Here, we constructed a small molecule compounds library containing twenty-eight methyl benzoate-related compounds (MBCs) and evaluated their repellent and toxic effects against cigarette beetles by Y-tube olfactometer behavioral assays, free-choice box assays and fumigation assays. We found that six MBCs (methyl 3-methoxybenzoate, methyl benzoate, methyl 3-formylbenzoate, methyl 2-aminopyridine-3-carboxylate, methyl 2-aminobenzoate and methyl 4-amino-2-methoxybenzoate) act as repellents for cigarette beetles. Notably, methyl benzoate (MeBA) was effective across a broader range of concentrations (200–4000 ppm) compared to other MBCs. Four compounds (methyl 3-formylbenzoate, methyl 2-aminopyridine-3-carboxylate, methyl 2-aminobenzoate and methyl 4-amino-2-methoxybenzoate) required higher minimum concentrations (500–4000 ppm) than MeBA for repellence, while methyl 3-methoxybenzoate was effective at a concentration (10 ppm) lower than that for MeBA. Mixtures of MeBA with methyl 3-methoxybenzoate and methyl 3-formylbenzoate enhanced the repellent effect against cigarette beetles when compared to MeBA alone. Additionally, exposure to varying concentrations of MeBA, methyl 3-methoxybenzoate, methyl 3-formylbenzoate, and methyl 2-aminobenzoate resulted in 100% mortality of cigarette beetles. Our findings indicate that specific MBCs offer the potential for their use as repellents and fumigants for this problematic stored product pest.

Mortality Pattern of Poecilus cupreus Beetles after Repeated Topical Exposure to Insecticide─Stochastic Death or Individual Tolerance?

The mortality of organisms exposed to toxicants has been attributed to either stochastic processes or individual tolerance (IT), leading to the stochastic death (SD) and IT models. While the IT model follows the principles of natural selection, the relevance of the SD model has been debated. To clarify why the idea of stochastic mortality has found its way into ecotoxicology, we investigated the mortality of Poecilus cupreus (Linnaeus, 1758) beetles from pesticide-treated oilseed rape (OSR) fields and unsprayed meadows, subjected to repeated insecticide treatments. We analyzed the mortality with the Kaplan-Meier estimator and general unified threshold model for survival (GUTS), which integrates SD and IT assumptions. The beetles were exposed three times, ca. monthly, to the same dose of Proteus 110 OD insecticide containing thiacloprid and deltamethrin, commonly used in the OSR fields. Kaplan-Meier analysis showed that the mortality of beetles from meadows was much higher after the first treatment than after the next two, indicating the IT model. Beetles from the OSR displayed approximately constant mortality after the first and second treatments, consistent with the SD model. GUTS analysis did not conclusively identify the better model, with the IT being marginally better for beetles from meadows and the SD better for beetles from OSR fields.

Efficacy of commercially available entomopathogenic nematodes against insect pests of canola in Alberta, Canada.

Certain entomopathogenic nematodes (EPNs) in the families Steinernematidae and Heterorhabditidae are among the most studied biocontrol tools, some of which are commercially available against pest insects. Their use against foliar and subterranean insect pests is largely unexplored in the Canadian Prairies. We conducted a laboratory-based study to produce baseline information on the biocontrol potential of a few commercial EPN species. Percent mortality of flea beetles, diamondback moths (DBMs), lygus, cabbage root maggots, and black cutworms (BCWs) was assessed after 72 hours exposure to Steinernema carpocapsae, S. kraussei, S. feltiae, and Heterorhabditis bacteriophora at varying concentrations (25, 50, 100, and 200 infective juveniles (IJs) per larvae, pupae, or cm2 of soil surface). Irrespective of concentration level, S. carpocapsae and S. kraussei caused significant mortality in DBM and BCW larvae compared with H. bacteriophora.S. kraussei, and S. feltiae were more efficient than S. carpocapsae in controlling root maggot larvae. H. bacteriophora caused zero mortality to root maggots at any concentration. Root maggot pupae were resistant to entry to EPN species tested, likely due to hard outer covering. Compared with root maggot pupae, a moderate level of mortality was observed in DBM pupae, suggesting differential ability of the tested EPNs in killing different life stages of certain pests. All nematode species tested caused low mortality (≤10%) in flea beetle adults. The findings of this investigation form fundamental data essential for carrying out field-based studies on canola and other related crops aimed at control and management of these pest species.

Baseline Susceptibility to a Novel dsRNA-Based Insecticide across US Populations of Colorado Potato Beetle

The Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) is an insect defoliator of the potato, Solanum tuberosum L. This species thrives in agricultural environments because of its flexible and complex life history, as well as its ability to evolve insecticide resistance. As a result, it has become a widely distributed agricultural pest. Ledprona (trade name Calantha) is a recently developed novel double-stranded RNA (dsRNA) insecticide that controls populations of Colorado potato beetle through RNA interference (RNAi). Previous studies have demonstrated the efficacy of ledprona through laboratory, greenhouse, and field studies. Colorado potato beetles from geographically distinct populations are known to vary in their response to insecticides, including experimental compounds based on RNAi. We tested the mortality and foliage consumption of beetles from different areas in the US treated with ledprona and found significant variation in both parameters. The beetles originating from New York were significantly less susceptible to ledprona in leaf disc assays compared to other populations. However, currently there is no evidence of reduced performance of ledprona against that population under field conditions, possibly because intoxicated beetles cannot withstand multiple stressors present in the field. The results of this study confirmed that the ledprona efficacy differs among geographically distinct populations, which may have implications for managing Colorado potato beetles.

Digestive Effect of Aqueous Extract of Nigella sativa Seeds on The Larval and Adult Mortality of The Red Flour Beetle, Tribolium castanium

Digestive Effect of Aqueous Extract of Nigella sativa Seeds on The Larval and Adult Mortality of The Red Flour Beetle, Tribolium castanium

Effectiveness of mahogany seed flour (Swietenia macrophylla) as a bioinsecticide against mortality of Sitophilus zeamais motsch in post-harvest grains

Research has been conducted on the effect of giving Mahogany seed meal (Swietenia macrophylla) on the mortality of the beetle Sitophilus zeamais Motsch. The method used is an experimental method with a complete randomized design consisting of 6 treatments and 4 repeats. The treatment consisted of controls A0 (0%), A1 (2%), A2 (4.8%), A3 (7.4%), A4 (13.0%), and A5 (17.4%). Mahogany seed flour with a concentration in each treatment was mixed with granulated corn to a weight of 50 grams, placed 20 Sitophilus zeamais beetles and observed for 24, 48, 72 and 96 hours. Data were analyzed by anava calculation and BJND test at 24-hour observation, BNT test at 48-hour observation and BNJ test at 72- and 96-hour observations. The concentration of 17.4% gave the greatest beetle mortality effect, namely 75% at 24 hours, 81.25% at 48 hours, 91.25% at 72 hours and 100% at 96 hours from the number of 20 beetles tested. This study also produced KL50 values for mahogany seed flour, namely 11.90% at 24 hours, 10.41% at 48 hours, 8.69% at 72 hours and 7.23% at 96 hours.

Validation of low dosages of γ-radiation and their effect on red beetle mortality, storability characteristics, and nutritional value of sorghum (Sorghum bicolor L. Moench) grain

This research was undertaken to validate the low dosages of γ-radiation of sorghum to examine the efficiency of gamma irradiation doses in quality attributes and storability of sorghum grain. Infested sorghum grains with the red flour beetle at the adult stage were irradiated at 0.25, 0.5, 0.75, 1.0, and 2.0 kGy emitted by 60CO. Subsequently, the mortality rate of the red flour beetle as affected by gamma doses was estimated and the storability characteristics and nutritional value of sorghum grains were measured. Eventually, the Partial Least Squares regression (PLS) analysis was executed to confirm the optimum dose of gamma which eliminate the red flour beetle and enhanced the grain quality. Results provide that the storability characteristics were enhanced after treatments. However, the changes in the germination rate of the grains were not different significantly after radiation. On the other hand, the radiation process enhanced sorghum grins' nutritional quality. Both tannins and phytic acid content dropped significantly and the digestibility and solubility of protein were gradually incremented in the grains. The PLS results indicated that using 1 and 2 kGy reflect the utmost effective dosage for sorghum. It can be concluded that this method is a potent rapid and operative preservation process to the alternate smoking chemical procedure for improving sorghum’s nutritional and functional quality and prolong its shelf life. Possibility of providing effective and rapid quarantine security as an alternative to chemical fumigation protocol to extend shelf life and enhance the nutritional and functional quality of sorghum.

EFFECTIVENESS TESTS OF VEGETABLE INSECTICIDES ESSENTIAL OILS OF MUTMET SEED (Myristica fragrans Houtt.) AND CLOVE FLOWER (Syzygium aromaticum L.) ON RICE BEETLE MORTALITY AND DEVELOPMENT Sitophilus oryzae (Linnaeus, 1763)

This study aims to analyze the inhibition of the development of the F1 generation of rice beetles by nutmeg and clove flower essential oils, and to determine the mortality of rice beetles against nutmeg and clove flower essential oils. The stages of the research started from rearing the rice beetle, preparing test insects, making variations in doses, treatments, and analysis. Two tests were conducted in the study, the first for inhibition of F1 generation activity and the percentage of mortality using the contact method (filter paper). The results showed that nutmeg and clove oil had an effect on the inhibition of the rice beetle F1 generation. Nutmeg oil has the best inhibition power with the percentage of F1 generation inhibition up to 100%. The mortality test using the filter paper method showed that for 48 hours nutmeg essential oil was able to kill rice beetles at all concentrations, namely 5-20% to 100%, while the percentage of 100% mortality was only found in the treatment with clove oil at the highest concentration (20%). The results showed that nutmeg oil showed better results than clove oil for controlling S. oryzae warehouse pests.

Insight into the molecular mechanism of phosphine toxicity provided by functional analysis of cytochrome b5 fatty acid desaturase and dihydrolipoamide dehydrogenase in the red flour beetle, Tribolium castaneum

Phosphine is the dominant chemical used in postharvest pest control. Widespread and highly frequent use of phosphine has been selected for pest insects, including Tribolium castaneum, which is highly resistant. Lipid peroxidation and reactive oxygen species (ROS) are two major factors determining phosphine toxicity; however, the mechanisms of production of these two factors in phosphine toxicity are still unknown. Here, we first determined the time course of phosphine-induced lipid peroxidation and ROS production in T. castaneum. Our results showed that lipid peroxidation occurs before ROS in the process of phosphine toxicity, and fumigated beetles with higher resistance levels were associated with weaker activity on lipid peroxidation and ROS. A significant decline in lipid peroxidation was observed in fumigated individuals after knockdown of cytochrome b5 fatty acid desaturase (Cyt-b5-r) via RNA interference (RNAi), indicating that Cyt-b5-r is critical for triggering phosphine-induced lipid peroxidation. Moreover, significant decreases in both ROS and mortality were detected in fumigated T. castaneum adults fed melatonin for 7 days, an inhibitor of lipid peroxidation. Cyt-b5-r RNAi also inhibited ROS production and mortality in phosphine-treated beetles. Meanwhile, a significant decrease in ROS production (68.4%) was detected in dihydrolipoamide dehydrogenase (DLD) knockdown individuals with phenotypes susceptible to phosphine, suggesting that lipid peroxidation initiates ROS with the expression of DLD. However, a significant increase in ROS (122.1%) was detected in the DLD knockdown beetles with strongly resistant phenotypes, indicating that the DLD-involved pathway may not be the only mechanism of ROS generation in phosphine toxicity and the existence of a moonlighting role in downregulating ROS in strongly resistant T. castaneum.

Survival Time, Mortality Rate, and Feeding Damage of Adult Myllocerus undecimpustulatus undatus (Coleoptera: Curculionidae) Exposed to Biopesticides in Laboratory Bioassays

Survival time, percentage mortality, and feeding behavior were evaluated for adults of the weevil Myllocerus undecimpustulatus undatus Marshall (Coleoptera: Curculionidae) exposed to biopesticides by using a Petri dish plant-based bioassay system. Treatments consisted of three registered entomopathogenic fungal formulations (BotaniGard ES, PFR-97 20% WDG, and Met52 EC) and three biochemical formulations (AzaMax, Entrust, and PyGanic EC); a synthetic chemical insecticide (Sevin SL) and distilled water served as control treatments. Thirty adult M. undecimpustulatus undatus (ten per bioassay cage replicate, three replicates per treatment) were given cocoplum leaves sprayed to the point of runoff with a treatment. Survivorship of weevils was checked daily for 15 days. Five trials (15 total replicates per treatment) were performed. Survival times of weevils in all product treatments were shorter than those of weevils in the water control treatment. Percentages of beetle mortality in the Entrust and BotaniGard treatments were about two-fold higher than in the other treatments. Mean percentages of mycosis for beetles in the BotaniGard, PFR-97, and Met 52 treatments were 90%, 8%, and 5%, respectively. Weevils that consumed BotaniGard-treated leaves caused significantly more leaf damage than weevils that consumed leaves with PFR-97 or Met52. Weevils on leaves treated with Entrust, PyGanic, AzaMax, and Sevin consumed significantly less than those in the fungal and water only treatments. The high mortality rates caused by Entrust and BotaniGard suggest that populations of adult M. undecimpustulatus undatus might be well-managed using these two commercially available biopesticides. Additional testing is needed in the field to corroborate our results obtained under controlled laboratory conditions.

Field Efficacy of Spinetoram for the Management of Coffee Berry Borer (Hypothenemus hampei)

Coffee berry borer (CBB), Hypothenemus hampei, is a damaging insect pest of coffee worldwide. CBB has recently been introduced to Hawaii, so management techniques are still being developed for sustainable and cost-efficient approaches for the effective control of this pest. Field trials were conducted to evaluate the use of spinetoram on CBB infestation and bean damage compared to Beauveria bassiana and an untreated control. Initial CBB infestations were similar, and the treatments resulted in no detectable differences in subsequent new infestations. Damage to the coffee beans was reduced by both spinetoram and B. bassiana compared to controls as the mortality of adult beetles resulting from the treatments prevented them from moving into the bean (C/D position) from the berry (A/B position). The mortality of adult beetles also prevented reproduction, subsequently reducing future CBB populations in the field. When applied to infested berries, spinetoram reduced live beetle populations in the A/B position by 73% and CBBs in the C/D position by 70% compared to the water control, whereas applications of B. bassiana reduced beetles in the C/D position by 37% but had no effect on the live A/B population. An integrated pest management program is recommended for the effective control of CBBs, and the use of spinetoram applications when adult beetles are in the A/B position appears to have potential as another management tool.

Development and Immature Mortality of the Sawtoothed Grain Beetle (Coleoptera: Silvanidae), on Different Sorghum Fractions and Different Temperatures.

Developmental ability of Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae) was examined on six different sorghum milling fractions: Bran, Shorts, Cgrits, Fgrits, Red dogs, Flour, and also on a standard diet of Oat Flakes. For this purpose, a 1-day-old egg was placed in a vial containing 1 g of one of the sorghum fractions and exposed to three temperatures: 25, 30, or 32°C. All vials were checked daily for pupal and adult emergence and mortality of immatures. The developmental time was significantly affected by the type of sorghum fraction. After two weeks, for most of the temperatures examined, the longest developmental times in most cases for both pupation and adult emergence were observed in Flour and Oat flakes. Increasing the temperature from 25 to 30 accelerated the development, while adult emergence time did not differ between 30 and 32°C for all fractions except Flour. Egg mortality ranged from 11 to 78%, while larval and pupal mortality ranged from 0 to 22 and 0 to 45%, respectively for all sorghum fractions and different temperatures tested. Moreover, the mean overall immature mortality occurred at 30°C was 49.2, 39.7, and 65.1% at 25, 30, and 32°C for all the diets examined. The findings of the present work show that O. surinamensis can develop and survive in sorghum milling fractions and that the optimal temperatures for growth enhancement are 30 and 32°C. The temperatures within sorghum milling facilities could support O. surinamensis development on milling fractions if they are not addressed through phytosanitary measures.

Evaluation of the Efficacy of Commercial Plant Extracts of Palazin and Tondxier Against the Red Flour Beetle Tribolium castaneum (Herbest) Under Laboratory Conditions

Al-Fatlawi, N.C.H. and S. Al-Zurfi. 2023. Evaluation of the Efficacy of Commercial Plant Extracts of Palazin and Tondxier Against the Red Flour Beetle Tribolium castaneum (Herbest) Under Laboratory Conditions. Arab Journal of Plant Protection, 41(1): 54-57. https://doi.org/10.22268/AJPP-41.1.054057 The Effect of Tondxier and Palazin plant extracts on the mortality of the flour beetle T. castaneum (Herb) was investigated. Plant extracts were separately tested under laboratory conditions against the beetles using a topical spray. Beetles were sprayed with plant suspensions at different concentrations (1, 2 and 3 ml/L) for both Tondxier and Palazin. Mortality was recorded daily for 15 days while beetles were kept on wheat flour. Both Tondxier and Palazin had an impact on T. castaneum. Commercial Tondxier was more effective than Palazin at the same concentrations tested. Nevertheless, significant differences in the mortality rate at the end of the experiments between second, and 5 th instar larvae and adults treated with Palazin and Tondxier extracts were observed. Second and 5 th instar larvae were more susceptible, and adults were more resistant to Palazin and Tondxier treatments. This study showed that mortality rate increases with increased concentration and length of exposure times. Results obtained suggested that the two plant extracts of Palazin and Tondxier used in this study can be used as potent insect control agents. Keywords: Palazin, Tondxier, Tribolium castaneum, larvae

Fire-caused mortality within tree neighborhoods increases growth of Pinus lambertiana more than growth of Abies concolor

Global increases in large-tree mortality and multiple disturbances such as fire, drought, and pestilence increase the importance of understanding how large-tree growth responds to changes in competitive neighborhoods. We used 34,175 spatially mapped trees within 25.6 ha that burned at low to moderate severity in 2013 to investigate how changes to tree neighborhoods affected growth of 3,652 surviving trees of two species, Abies concolor (white fir) and Pinus lambertiana (sugar pine). Using diameter measurements taken in 2014 and 2019, we estimated post-fire radial growth of each surviving tree. We modeled annual basal area increment as a function of diameter and extracted residuals to yield relative growth rate (RGR). We used a multi-model approach and AIC to compare the species-specific effects on RGR of all post-fire tree mortality within a neighborhood radius versus mortality broken down by cause. To represent density reduction around each surviving tree, we computed crowding metrics for neighborhood radii up to 20 m for all tree mortality combined and for each mortality cause. The best-fit model included terms for density reduction within 10 m of the surviving tree due to 1) fire or mechanical damage and 2) bark beetle mortality, as well as their interactions with species and diameter. Density reduction due to fire or mechanical damage had a positive effect on RGR that was nearly twice as strong for P. lambertiana as A. concolor. Tree diameter interacted with density reduction for just P. lambertiana. Small-diameter (10-cm) P. lambertiana had a fourfold larger increase in basal area increment than large-diameter (60-cm) P. lambertiana as density reduction due to fire or mechanical damage ranged from 0 to 100 %. The strong growth response of medium-diameter P. lambertiana to density reductions could eventually increase the abundance of large-diameter (≥60 cm) P. lambertiana. In conjunction with mortality rates, which were lower for large-diameter P. lambertiana (0.97 %) than A. concolor (3.31 %), this could increase the relative abundance of large-diameter P. lambertiana from 51.2 % in 2020 to 62.6 % by 2050. Changes to competitive neighborhoods can have species-specific effects on large-tree growth, an important consideration for long-term management of fire-prone forests.

Lethal and sublethal effects of synthetic and bioinsecticides toward the invasive ambrosia beetle Xylosandrus compactus.

Exotic ambrosia beetles are emerging widespread pests of several wild and managed trees and shrubs. Xylosandrus compactus (Eichhoff) is one of the most invasive species causing damage to a broad range of host plants. Little information is available on its control, including the impact of insecticides. Bioassays were conducted to evaluate the potential of four bioinsecticides and seven synthetic insecticides in controlling X. compactus. Beetle mortality and sublethal effects on tunneling, cultivation of the mutualist fungus and reproduction were assessed. Concentration-mortality curves were determined for all tested insecticides. Lambda-cyhalothrin was the most toxic insecticide, showing the lowest estimated 90% and 50% lethal concentrations (LC90 and LC50 ), followed by deltamethrin and thiamethoxam. Acetamiprid caused the highest levels of mortality and brood size reduction under extended laboratory conditions. Moreover, acetamiprid, thiamethoxam and lambda-cyhalothrin caused the greatest mortality and, together with deltamethrin, strongly affected progeny occurrence inside infested galleries and beetle brood size. Among the bioinsecticides, pyrethrins significantly affected beetle survival under laboratory conditions, but not brood size in extended laboratory bioassays. Some of the tested insecticides had significant lethal and sublethal effects only when beetles were exposed to fresher residues, highlighting differences in toxicity persistence. This study provides first baseline toxicity data for synthetic insecticides and bioinsecticides with different modes of action and origin toward X. compactus, and the first evidence that several insecticides can cause multiple sublethal effects on this pest. These findings can help in building suitable integrated pest management packages against this pest. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.