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Article

Summer Cafe: In Vitro Case Study of Biological Repellents Against the Large Pine Weevil

by
Ilze Matisone
1,
Kristaps Ozoliņš
1,
Roberts Matisons
1,*,
Mārtiņš Spāde
1,
Uldis Grīnfelds
1 and
Rinalds Trukšs
2
1
Latvian State Forest Research Institute (LSFRI) Silava, Rigas Street 111, LV2169 Salaspils, Latvia
2
Jifteco Ltd., Gustava Zemgala Street 74, LV1039 Riga, Latvia
*
Author to whom correspondence should be addressed.
Forests 2025, 16(7), 1139; https://doi.org/10.3390/f16071139
Submission received: 21 May 2025 / Revised: 1 July 2025 / Accepted: 9 July 2025 / Published: 10 July 2025
(This article belongs to the Section Forest Health)
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Abstract

Growing environmental concerns have led to the search for alternative biological repellents against the large pine weevil Hylobius abietis L., Europe’s most important coniferous forest regeneration pest. A laboratory study was carried out to assess the effectiveness (damage intensity) of six combinations of a novel biological repellent, consisting of plant-based oils, beeswax, calcium carbonate, vanillin, pine bark extractives, terpentine, abrasive particles, solvent, and a viscosity agent, in comparison with commercially available repellent Norfort LDW 115. The application complexity of the repellents, their persistence on seedlings, and the extent of H. abietis damage were evaluated. The five alternative repellents had higher protection compared to the control repellent, highlighting the potential for new alternative repellents. The base (without additives) repellent provided the highest protection, indicating a redundancy of admixtures. A mixed cumulative link model, employed to estimate differences between the repellents, estimated 85% undamaged and none significantly damaged saplings in the case of the base repellent. However, the consistency and hence persistence of certain repellents on plantlets would benefit from improvements; further field studies are needed to upscale the test of the stability and efficiency of high levels in real environments under different H. abietis population pressures.

1. Introduction

As the climate changes, shifts in the relationship between forest pests, their natural enemies, and the food base occur [1]. Extended growing seasons and higher temperatures may enhance the reproductive potential of phytophagous insects and lead to higher abundances, hence more intense feeding damage to host plants [2,3]. Furthermore, increasing climate extremes can boost forest pest development/outbreaks, increasing biotic risks for forest regeneration [2,4].
Scots pine Pinus sylvestris (L.) is one of the most common and economically important tree species in boreal and hemiboreal forests in Europe [5]. Although the areas replanted with pine have decreased in the Baltics in recent years, it remains one of the three (birch, pine, and spruce) most preferred species [5,6]. The reduction of pine-covered areas in recent years has been primarily related to increasing biotic risks, which threaten the success and sustainability of forest restoration after clear-cutting [7,8].
The large pine weevil Hylobius abietis (L.) is one of the most destructive and economically important forest regeneration pests that kills high proportions of one- to three-year-old conifer seedlings/saplings, particularly in post-clear-cut stands across Europe [4]. The beetle damages seedlings/saplings of all native coniferous species and some species of deciduous trees, while preferring Scots pine [9,10]. The adult weevils cause feeding damage on the stem bark of conifer seedlings/saplings, frequently filling them by girdling near the stem base [4]. Additionally, the beetles feed on the phloem and buds, disturbing further development of the seedlings/saplings [8].
Extending vegetation periods with prolonged drought periods in warm summers [11,12] are favourable for the large pine weevil [13], hence the risks of outbreaks in the hemiboreal zone of Europe are increasing [14,15,16]. Such risks are related to boosted development of the beetle [12,17] and extension of the feeding period [18,19].
Although H. abietis is present in conifer forests throughout Europe, its abundance and the risk for outbreak vary considerably between locations and are related to the availability of suitable substrate (fresh stump) for breeding [20]. Current management strategies in Northern Europe (retention forestry) support a constantly high population of H. abietis [20,21,22,23]. Without countermeasures, seedling/sapling mortality is mostly high, reaching 100% [23,24].
Despite the environmental and health concerns and issues [25,26,27], insecticide treatment of the seedlings before explanting is a common and efficient method [28,29,30]. The restrictions of chemical protection of seedlings highlight the necessity for alternatives to conventional insecticides, such as coatings and repellents for physical protection [31,32,33]. The current protection methods and their utility against H. abietis damage have been recently reviewed by Lalík et al. (2021) [8]. Regarding mechanical protection, waxing has successfully protected 65%–90% of seedlings for up to three seasons. Sand coating of seedlings during two years demonstrated similar levels of protection as insecticides but was only applicable for containerised seedlings in nurseries. Glueing protected approximately 50% of seedlings, yet it was less successful than waxing; however, this method was still in the testing stage.
To reduce planting expenses, increase protection effectiveness to specific regions, and reduce the risk of pests getting acclimated to frequently applied repellents, the development of novel substances is necessary [28]. Extensive experimental testing of efficiency and environmental effects is needed to assess their upscaling potential and widescale applicability [28,34]. In this regard, natural and biodegradable substances might become superior under increasing demand for closer-to-nature forestry [8]. Plant-based oils, pine bark extractives, beeswax, calcium carbonate, and strong scents (e.g., vanillin) have been proposed as biological, widely available, inexpensive substances, which in proper combination can be highly adhesive, persistent, and odorous [8,35], thus repulsive to the large pine weevil.
Current alternative repellents on the market are water-based solutions containing acrylates, which are non-biodegradable and can potentially pollute the environment [8]. Thus, recent trials have focused on natural insecticides (e.g., neem extracts, eucalyptus oil, maltodextrin, pyrethrin, and spinosad), natural repellents (e.g., capsicum extract, geraniol, garlic, and limonene), biological insecticides (e.g., soil fungus Metarhizium anisopliae), etc [35]. Nevertheless, when compared to synthetic insecticides, natural products individually showed weaker or temporary protection [28,35,36]. Field experiments demonstrated weak efficiency of Flexcoat repellents [37]. Neem-based oil products (NeemAzal-T/S®) have also shown weak protection, while having phytotoxic effects [35]. Maltodextrin product (Majestik®) has had very poor efficiency [35]. Essential plant oils have been estimated with considerable efficiency (temporarily) against weevils, while showing adverse effects on the seedlings [34,35,38].
Some promising results have been reported for natural cold-pressed neem oil NEEM EC [39]. Water emulsion NeemAzal has been shown to reduce feeding activity for up to 72 h [36]. Extractives of leaves and bark can effectively depress feeding activity, though the substance is unstable [36,40]. Soil bacteria enzymes (Spinosad) have shown efficiency in the field at a low pest population density [35]. Fine sand coating (Conniflex) mostly showed high efficiency and is already commercially available [32,37]. Wax coating (Norsk Wax, Kvaae® wax) has demonstrated promising effectiveness [28,35,41], which decays with time as the protective layer crumbles off [28]. Nevertheless, waxing has the potential to substitute insecticides if durability is improved [42]. Accordingly, a combination of different repellents could provide the best efficiency.
The aim of this study was to evaluate the efficiency of experimental alternative protective repellents based on plant oil epoxy and fine grit mineral particles with six biological additives for Scots pine plant protection against the damage caused by the large pine weevil in vitro.

2. Materials and Methods

The effectiveness of a biological repellent against the large pine weevil was tested in a laboratory in vitro. The tested repellent was an organic/biological mixture (base) developed and patented (patent application No. LVP2022000054, WO 2023/244098 A1) by a joint effort of LTD Jifteco (Dobele, Latvia) and Latvian State Forest Research Institute ‘Silava’ (Table 1). The repellent (base) comprises plant-based (linen) oil epoxy (20%), pine bark extractives (tannins; 10%), terpentine (7%), abrasive particles (red clay; 20%), solvent (canola oil; 20%), camphor (<10%), a viscosity agent (alkaline < 10%), and water. Two concentrations of the base (epoxy content of 20% and 50%), as well as a base with four additives (Table 1), were compared to the more widely used conventional repellent Norfort LDW 115 Exp 03 (Nordic Formulation Technology A/S, Denmark (https://www.bjorn-thorsen.com/about-us/, accessed on 21 May 2025); considered as the control). All compositions are expressed as a percentage of mass. The repellents were mixed using a laboratory mixer, IKA MINISTAR 40 digital (https://www.ika.com/en/Products-LabEq/Overhead-Stirrers-pg187/MINISTAR-40-digital-25004886/, accessed on 21 May 2025), until homogeneous consistency was achieved. The proportions are rounded as at the moment of submission of the manuscript exact proportions are proprietary information.
For the test, ten transparent Plexiglas insectariums/boxes were used. The size of the insectariums was 18 cm × 18 cm × 34 cm, and they had four ventilation holes (one 6 cm × 14 cm on the top and bottom, two 5 cm × 14 cm on the top of the opposite sides), which were sealed with a fine (0.2 mm × 0.2 mm) synthetic mesh. The insectariums were filled with coarse neutral mesotrophic mineral (sand-gravel) substrate to approximately 1/3 of the volume (Figure 1 and Figure 2). In each insectarium, four one-year-old containerised seedlings of Scots pine from a nearby nursery (Norupe, JSC, Latvia State Forest) were planted. The seedlings had already started to form the second increment. No pesticides or repellents were used when raising these plantlets, thus leaving them unprotected. Before planting, the seedlings were treated with the repellents. Depending on the repellent, 3–7 g was applied per seedling. The repellents were applied with a soft brush on the stem and needles from the root collar upwards up to 1–2 cm under the forming second-year increment.
In total, five seedlings for each alternative repellent treatment and ten seedlings (replications) for the control were prepared (Figure 1). During the application, its timing and complexity (e.g., time of treatment, dripping, and coating quality) were recorded. In each insectarium, a seedling with the control repellent and three seedlings with random though non-repeating repellent treatments were randomly planted in a non-orthogonal design (Figure 2). If the seedling was taller than the box, its top was cut to fit. Untreated seedlings were not tested as in such cases the beetles would likely feed on the untreated seedlings exclusively, overestimating the effects of other repellents. Seedlings were watered and left in the insectariums for one day to “establish” before beetles were released.
A few days (max 5) before the experiment, large pine weevil beetles were collected in a nearby sawmill (on an open dust pile) and kept in a maintenance insectarium in a laboratory. The beetles were kept in the most suitable living conditions, fed with untreated pine seedlings, and provided with water to allow the supplementation of the experiment if/when necessary. The gender (sex) of the weevils was not determined.
On the second day after the pine seedlings were planted, each insectarium was inhabited with two vigorous beetles. The insectariums were kept in a climate chamber under controlled conditions at 20 °C and a relative humidity of 60% for 20 days. The photoperiod was split equally into 12 h day and night periods. Illumination was provided by an LED, ensuring 150 µmol/m2, close to natural radiation. Seedlings were watered every 2–3 days by sprinkling while avoiding flooding the insectariums.
The extent of feeding damage of the large pine weevil on the seedlings was assessed on days 4, 6, 8, 13, 18, and 20, and recorded according to a five-grade scale from 0 (unaffected) to 4 (dead) (Table 2). The location of the damage (Table 2) was recorded for each tree as well. In addition, on the first day, repellent consistency and persistence on a plant and drying process were evaluated. It was ensured that two vigorous mobile beetles were constantly present within each insectarium, thus maintaining constant herbivore pressure on the seedlings. Immobilised or dead beetles were replaced. During the experiment, however, only eight weevils were replaced due to complete immobilisation (sticking to the repellent) and/or dying.
A mixed cumulative link model, which is a suitable method to determine the effects on ordered categorical responses for hierarchical data [43], was used to assess the effects of treatment (repellent) and day of the experiment (duration covariate) on the damage grade (as an ordered categorical variable; Table 2) and damage location (also as an ordered categorical variable with the levels ranging accordingly: no damage, untreated, untreated/treated, and treated). Box was used as the random effect. The significance of the fixed effects was estimated by the type II likelihood ratio χ2 test. Compliance of the refined model with statistical assumptions was verified using diagnostic plots. Data analysis was conducted at the significance level α = 0.05 in the program R v. 4.4.3 [44] using the library ‘ordinal’ [45].

3. Results and Discussion

Application of the tested repellents with a brush, except for the base with beeswax (No. 2) and base with hemp oil (No. 6), was convenient, although time-consuming (Table 3), suggesting the necessity for aids, e.g., an application nozzle. Both of the difficult-to-apply repellents had essential application and persistence problems; hence, the cover was heterogeneous, and the substance showed poor adhesion and/or was dripping off, which could be related to the presence of wax (No. 2) or the presence of hemp oil (No. 6; Table 2). Hence, due to poor consistency, these repellents were considered flawed, presuming mediocre efficiency (Table 3). Similarly, adhesion issues were observed for the more concentrated base (No. 4), which peeled off, had a thick consistency, and hardened slowly. These three repellents (No. 2, 4, and 6), after application, also formed the thickest layer, approximately up to 1.6 mm, while the others formed a thinner layer of <1 mm. Among the tested repellents, the best consistency and applicability were observed for the base with calcium carbonate (No. 1) and base (No. 5), while the former was superior in terms of hardening. The best applicability was, however, observed for the control repellent (C), likely because it has been optimised (as a commercial product). In general, half of the repellents did not dry completely and hence remained sticky and immobilised beetles under laboratory conditions during the experiment.
The day of the experiment as well as the repellent treatment were pronounced and significant predictors of the location and grade of browsing damage by the large pine weevil to Scots pine seedlings as indicated by the estimated pseudo R2 values (Table 4), which can be considered high for biological systems [46,47]. However, the day of the experiment, which represented accumulation of the damage, had a stronger effect compared to the treatment as indicated by the F-values, suggesting overall mediocre effectiveness of the treatments (Table 4). Although the experimental design was non-orthogonal, the box had a small effect (variance) on the results, particularly for the location of the damage, indicating sufficiency of the setup.
In all insectariums, minor (damage grade 2, Table 2) signs of feeding damage were already observed at the first observation (day 4). The statistical model (Figure 3B) indicated a significant near-linear effect of time, showing that the severity of damage steadily increased with time. Nevertheless, saplings with low damage (damage grades 1 and 2), which would likely have a moderate effect on further development [48], were common throughout the experiment (90% of observations). A high probability of considerable damage (damage grade 3), which likely hinders the development of saplings, manifested during the final part of the experiment (day 18), though for a relatively small proportion of the saplings (5%). Only 4% of saplings died by the end of the experiment, indicating good overall survival of protected saplings under intensive herbivore pressure [31,32]. No damage (grade 0) at the end of the experiment was estimated for 1% of saplings (Figure 3B), which might be related to natural defence mechanisms and resistance [49,50] or a combination of treatments with an explicitly heterogeneous repelling effect on the beetles.
The tested repellents differed in effectiveness against large pine weevil damage as indicated by the significant effect of treatment both on the location and grade of the damage to the seedling (p < 0.001; Table 4). Regarding the damage location, partial effectiveness of the tested repellents was estimated as at the beginning of the experiment, damage mostly (78% of all damaged saplings) appeared on the untreated parts of the saplings (Figure 3). However, immediate (day 4) feeding damage in the treated parts appeared for the base with hemp oil (No. 6) and the control (C), followed by the base in combination with calcium carbonate (No. 1) on the eighth day, supporting their limited effectiveness. At the end of the experiment, however, damage on the treated parts exclusively were estimated for only 4% of the cases of saplings. This might indicate an opposite effect of the repellent, or might be related to poor consistency of the repellent, thus leaving easily accessible unprotected parts of the saplings. The proportion of simultaneous damage on both untreated and treated parts at the beginning of the experiment was estimated for ~5% of the saplings; however, it increased rapidly, reaching 85% of all saplings at the end of the experiment (Figure 3). The proportion of damage exclusively on the untreated parts was similar throughout the experiment, hence likely due to the consumption of untreated needles, slightly decreasing only at the end of the experiment (Figure 4B). The probability of the seedlings remaining undamaged through the course of the experiment was low (~2%; Figure 4B), indicating limited effectiveness of repellents under high herbivore (weevil) pressure [35].
Base treatment (No. 5) appeared as the most efficient with 84% of saplings undamaged, 12% damaged at the untreated parts, and 4% damaged simultaneously on untreated/treated parts (Figure 4). Also, regarding the damage grade, the base was significantly (p < 0.001) better compared to all others, including the control repellent, which is currently applied in nurseries, i.e., the probability of undamaged saplings was considerably higher (85% vs. 10%, respectively), with none of the saplings severely damaged (Figure 3A). The efficiency of the base repellent could be explained by an already field-tested formula, which included theoretical optimisation (unpublished data). A more concentrated base (No. 4) showed similar results to the base (No. 5) in terms of damage location (Figure 4A) and showed the next highest efficiency in terms of damage grade (Figure 3A), indicating redundancy of additional epoxy.
Similar damage grade estimates (39% efficiency and less than 1% significantly affected or dead saplings) were observed for a base in combination with calcium carbonate (No. 1) (Figure 3A). The positive effect of calcium has already been proven, and it has long been added to insecticides for the successful control of pests in agriculture and forestry [51,52]. However, in this study, such an additive reduced the efficiency of the repellent, likely due to poorer consistency, and hence harder application, resulting in heterogeneous cover and unprotected parts on the sapling.
Although the addition of vanillin can increase repellent activity and protection time against mites and mosquitoes [2,53], such an additive (No. 3) failed to improve efficiency against the large pine weevil as indicated by the share of the damaged saplings (Figure 3A). The addition of beeswax (No. 2) did decrease the effectiveness of the base repellent; hence, this treatment, equally to the control (C), showed the second-lowest efficiency in terms of both damage grade and location. In other studies, the effectiveness of wax products was one of the best according to biological repellents [28,35,41]. Hence, it was effective only in the first season, after which it started to crack and fall off, and was also covered in a recommended 1.5 mm layer [28]. Probably the coating layer (>1.5 mm) was too thick, which contributed to premature peeling in this study. The low effectiveness of the control repellent probably indicates the superior efficiency of the experimental repellents or a gradual loss of its effectiveness due to adaptation of the beetles. It is difficult to compare reasons for the efficiency of the alternative and control repellents because the composition of the control repellent is confidential, and its use has recently been restricted in Germany [54]. The worst results for feeding location (Figure 4A), as well as the extent of damage on saplings (7% of saplings remained undamaged, but 4% did not survive; Figure 3A), however, were estimated for saplings treated with the base with hemp oil (No. 6). This indicates that canola oil as a liquefier (i.e., in the case of the base; No. 5) was effective and should not be substituted by hemp oil although hemp oil substances showed promising effectiveness against stored product insect pests [55]. Although some repellents showed high effectiveness in vitro, field experiments are still needed as the efficacy of alternative repellents in laboratory and field conditions can vary considerably [35].

4. Conclusions

The observed high efficiency (up to 85%) and superiority over the currently used (control) repellent indicate a high potential for alternative biological repellents against large pine weevil feeding damage in laboratory conditions. The estimated highest level of protection for a previously tested base repellent (No. 5) confirmed the effectiveness of the formula and showed no need for modification, thus indicating good potential for future research. However, considering the assessment of consistency and persistence on a plant, the drying process should be improved, probably by using and testing mechanised (nozzle) applications, as well as testing the stability and efficacy in forest environments under different large pine weevil population sizes. In general, laboratory observations provide expectations for productive forest protection using closer-to-nature-oriented products. Nevertheless, the plant-based repellent showed potential for partial applications.

Author Contributions

Conceptualisation, M.S. and R.T.; methodology, K.O., U.G., M.S., and R.T.; software, I.M.; validation, M.S. and R.T.; formal analysis, I.M.; investigation, K.O., M.S., and R.T.; resources, M.S. and R.T.; data curation, K.O., M.S., and R.T.; writing—original draft preparation, I.M.; writing—review and editing, I.M. and R.M.; visualisation, I.M.; supervision, U.G., M.S., and R.T.; project administration, U.G., M.S., and R.T.; funding acquisition, U.G., M.S., and R.T. All authors have read and agreed to the published version of the manuscript.

Funding

This study was supported by the European Fund for Agriculture and Rural Development project “Development and testing of a natural and human-friendly repellent for the protection of coniferous seedlings against damages caused by dendrophagous insects” (No. 22-00-A01612-000019).

Data Availability Statement

The data are available on request from the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Repellent treatment on Scots pine seedlings and their placement in the insectarium.
Figure 1. Repellent treatment on Scots pine seedlings and their placement in the insectarium.
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Figure 2. Schematic description of the tested combinations of the repellent-treated Scots pine seedlings in 10 insectariums. The repellent codes are shown in Table 1.
Figure 2. Schematic description of the tested combinations of the repellent-treated Scots pine seedlings in 10 insectariums. The repellent codes are shown in Table 1.
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Figure 3. The estimated effects of applied treatments (repellents, see Table 1) (A), and duration (B) of the experiment on H. abietis damage (grade, see Table 2) on first-year seedlings of Scots pine in an insectarium. Similar letters above the bars denote a lack of significant differences according to Tukey’s test (p-value < 0.05).
Figure 3. The estimated effects of applied treatments (repellents, see Table 1) (A), and duration (B) of the experiment on H. abietis damage (grade, see Table 2) on first-year seedlings of Scots pine in an insectarium. Similar letters above the bars denote a lack of significant differences according to Tukey’s test (p-value < 0.05).
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Figure 4. The estimated effects of applied treatments (repellents, see Table 1) (A), and duration (B) of the experiment on H. abietis damage location (see Table 2) on second-year seedlings of Scots pine in an insectarium. Similar letters above the bars denote a lack of significant differences according to Tukey’s test (p-value < 0.05).
Figure 4. The estimated effects of applied treatments (repellents, see Table 1) (A), and duration (B) of the experiment on H. abietis damage location (see Table 2) on second-year seedlings of Scots pine in an insectarium. Similar letters above the bars denote a lack of significant differences according to Tukey’s test (p-value < 0.05).
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Table 1. The tested alternative repellents against the damage caused by the large pine weevil Hylobius abietis.
Table 1. The tested alternative repellents against the damage caused by the large pine weevil Hylobius abietis.
Repellent No.Description
1Base * + calcium carbonate (chalk, fine flour, 20%)
2Base * + beeswax (<15%)
3Base * + vanillin (<15%)
4More concentrated base * (higher share of epoxy (50%), no water; more viscous)
5Base *
6Base * with hemp oil (20%) as a substitute for canola oil
C (control)Norfort LDW 115
* Patented organic/biological mixture comprises plant-based (linen) oil epoxy, pine bark extractives (tannins), terpentine, abrasive particles (red clay), solvent (canola oil), camphor, a viscosity agent (alkaline), and water.
Table 2. Grading of the extent and location of feeding damage of H. abietis on Scots pine seedlings.
Table 2. Grading of the extent and location of feeding damage of H. abietis on Scots pine seedlings.
The Extent of DamageLocation of Damage
GradeDescriptionDescription
0no damageno damage
11–2 small damages; growth was not affecteddamage to the untreated part
2more than damages; growth was not affecteddamage to the treated part
3significant damage, barely survivingdamage on the untreated and treated parts
4seedling is dead
Table 3. Description of the application, drying process, and persistence of the applied repellents.
Table 3. Description of the application, drying process, and persistence of the applied repellents.
Repellent No.Description
1On applying, forms a thin layer, which remains flexible but smears a little.
2Hard application. As the product dries, microcracks form, and within a week, it mostly falls off, forming uncovered areas. The residues of repellent remain sticky, partially immobilising H. abietis.
3Does not dry and remains slightly sticky, thus immobilising H. abietis.
4Repellent is layered and difficult to blend. When applied, forms a thick layer and does not dry completely.
5After applying, forms a flexible coating and does not dry completely.
6Hard application. Applies unevenly. Shortly after application, microcracks form, and the repellent appears to be dripping, thus forming uncovered areas.
C (control)Easy application. Dries and holds on well.
Table 4. Summary of the mixed cumulative link model assessing the effects of treatments (repellents) and time (day of the experiment) on H. abietis damage grade and location.
Table 4. Summary of the mixed cumulative link model assessing the effects of treatments (repellents) and time (day of the experiment) on H. abietis damage grade and location.
Damage GradeLocation of Damage
Coefficients of the fixed effects
Variableχ2p-valueχ2p-value
Treatment (repellent)64.99<0.00164.42<0.001
Day159.54<0.001129.27<0.001
Random effects
VarianceVariance
Box0.390.05
Pseudo R2 (estimated against null model)
Pseudo R2Pseudo R2
Nagelkerke (Cragg and Uhler)0.620.56
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Matisone, I.; Ozoliņš, K.; Matisons, R.; Spāde, M.; Grīnfelds, U.; Trukšs, R. Summer Cafe: In Vitro Case Study of Biological Repellents Against the Large Pine Weevil. Forests 2025, 16, 1139. https://doi.org/10.3390/f16071139

AMA Style

Matisone I, Ozoliņš K, Matisons R, Spāde M, Grīnfelds U, Trukšs R. Summer Cafe: In Vitro Case Study of Biological Repellents Against the Large Pine Weevil. Forests. 2025; 16(7):1139. https://doi.org/10.3390/f16071139

Chicago/Turabian Style

Matisone, Ilze, Kristaps Ozoliņš, Roberts Matisons, Mārtiņš Spāde, Uldis Grīnfelds, and Rinalds Trukšs. 2025. "Summer Cafe: In Vitro Case Study of Biological Repellents Against the Large Pine Weevil" Forests 16, no. 7: 1139. https://doi.org/10.3390/f16071139

APA Style

Matisone, I., Ozoliņš, K., Matisons, R., Spāde, M., Grīnfelds, U., & Trukšs, R. (2025). Summer Cafe: In Vitro Case Study of Biological Repellents Against the Large Pine Weevil. Forests, 16(7), 1139. https://doi.org/10.3390/f16071139

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