| 1. |
- Amelia, Tudoran, et al.
(författare)
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A major forest insect pest, the pine weevil Hylobius abietis, is more susceptible to Diptera- than Coleoptera-targeted Bacillus thuringiensis strains
- 2021
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Ingår i: Pest Management Science. - : Wiley. - 1526-498X .- 1526-4998. ; 77, s. 1303-1315
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND The pine weevil (Hylobius abietis) is a major forest regeneration pest causing high levels of seedling mortality and economic losses. Current management relies on silviculture, stem coatings and insecticides. Here we evaluated for the first time the effects of Bacillus thuringiensis (Bt) strains on H. abietis adults: two producing the Coleoptera-targeted toxins Cry3Aa (Bt tenebrionis NB-176) and Cry8Da (Bt galleriae SDS-502), and one producing the Diptera-targeted Cry10A (Bt israelensis AM65-52). Choice and nonchoice assays using individual and mixtures of Bt formulations, containing these strains respectively, were conducted.RESULTS We found that Bt had toxic and lethal effects on H. abietis, but effects varied with strain and formulation concentration. The Diptera-targeted Bt israelensis had the most negative effects on weevil weight, feeding and mortality (70-82% feeding reduction, 65-82% greater mortality than control), whereas the effect was lower for the Coleoptera-specific Bt tenebrionis (38-42%; 37-42%) and Bt galleriae (11-30%; 15-32%). Reduced weevil feeding was observed after 3 days, and the highest mortality occurred 7-14 days following Bt exposure. However, we found no synergistic toxic effects, and no formulation combination was better than Bt israelensis alone at reducing consumption and survival. Also, pine weevils were not deterred by Bt, feeding equally on Bt-treated and non-Bt treated food.CONCLUSION There is potential to develop forest pest management measures against H. abietis that include Bt, but only the Diptera-targeted Bt israelensis would provide effective seedling protection. Its Diptera-specificity may need reconsideration, and evaluation of other Bt strains/toxins against H. abietis would be of interest.
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| 2. |
- Amelia, Tudoran, et al.
(författare)
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Using associational effects of European beech on Norway spruce to mitigate damage by a forest regeneration pest, the pine weevil Hylobius abietis
- 2021
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 486
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Tidskriftsartikel (refereegranskat)abstract
- Forest regeneration can be compromised by insect damage to newly-planted conifer seedlings, with the pine weevil, Hylobius abietis, being the most economically important pest in Europe. Seedling protection strategies include physical barriers, silvicultural measures and insecticides, while the potential benefits of Associational Effects (AE) have been little explored. Associational Resistance (AR) or Susceptibility (AS) arise when neighbouring plants decrease or increase, respectively, the likelihood and extent of attack on a focal plant. We investigated the potential of European beech, Fagus sylvatica, to mediate AE for Norway spruce, Picea abies, seedlings against pine weevil damage. First, we examined the effects of neighbor identity on damage to P. abies at a small scale, using choice arenas in the lab. Then, in the field, we examined these effects at a larger scale using plots containing only Norway spruce, or both species. We found that P. abies seedlings were attacked and damaged less by weevils when beech was their close neighbor, relative to having another Norway spruce as a neighbor in the lab. Yet, no difference in damage between only spruce and mixed seedling plots was found in the field. Our results indicate that the susceptibility of P. abies to H. abietis can be influenced by neighbor identity, and effects can vary with inter-plant distance. In close proximity, the presence of the non-host F. sylvatica can alter pine weevil feeding behaviour and thus, has the potential to mediate AR. However, these associational effects appear not to provide enhanced seedling protection at a larger scale.
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| 3. |
- Berggren Nieto, Kristina, et al.
(författare)
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Synergistic effects of methyl jasmonate treatment and propagation method on Norway spruce resistance against a bark-feeding insect
- 2023
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Ingår i: Frontiers in Plant Science. - 1664-462X. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- Utilizing plants with enhanced resistance traits is gaining interest in plant protection. Two strategies are especially promising for increasing resistance against a forest insect pest, the pine weevil (Hylobius abietis): exogenous application of the plant defense hormone methyl jasmonate (MeJA), and production of plants through the clonal propagation method somatic embryogenesis (SE). Here, we quantified and compared the separate and combined effects of SE and MeJA on Norway spruce resistance to pine weevil damage. Plants produced via SE (emblings) and nursery seedlings (containerized and bare-root), were treated (or not) with MeJA and exposed to pine weevils in the field (followed for 3 years) and in the lab (with a non-choice experiment). Firstly, we found that SE and MeJA independently decreased pine weevil damage to Norway spruce plants in the field by 32-33% and 53-59%, respectively, compared to untreated containerized and bare-root seedlings. Secondly, SE and MeJA together reduced damage to an even greater extent, with treated emblings receiving 86-87% less damage when compared to either untreated containerized or bare-root seedlings in the field, and by 48% in the lab. Moreover, MeJA-treated emblings experienced 98% lower mortality than untreated containerized seedlings, and this high level of survival was similar to that experienced by treated bare-root seedlings. These positive effects on survival remained for MeJA-treated emblings across the 3-year experimental period. We conclude that SE and MeJA have the potential to work synergistically to improve plants' ability to resist damage, and can thus confer a strong plant protection advantage. The mechanisms underlying these responses merit further examination.
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| 4. |
- Chen, Yayuan, et al.
(författare)
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Comparing Exogenous Methods to Induce Plant-Resistance Against a Bark-Feeding Insect
- 2021
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Ingår i: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Exogenous application of the plant hormone methyl jasmonate (MeJA) can trigger induced plant defenses against herbivores, and has been shown to provide protection against insect herbivory in conifer seedlings. Other methods, such as mechanical damage to seedlings, can also induce plant defenses, yet few have been compared to MeJA and most studies lack subsequent herbivory feeding tests. We conducted two lab experiments to: (1) compare the efficacy of MeJA to mechanical damage treatments that could also induce seedling resistance, (2) examine if subsequent insect damage differs depending on the time since induction treatments occurred, and (3) assess if these induction methods affect plant growth. We compared Scots pine (Pinus sylvestris) seedlings sprayed with MeJA (10 or 15 mM) to seedlings subjected to four different mechanical bark damage treatments (two different bark wound sizes, needle-piercing damage, root damage) and previous pine weevil (Hylobius abietis) damage as a reference treatment. The seedlings were exposed to pine weevils 12 or 32 days after treatments (early and late exposure, hereafter), and resistance was measured as the amount of damage received by plants. At early exposure, seedlings treated with needle-piercing damage received significantly more subsequent pine weevil feeding damage than those treated with MeJA. Seedlings treated with MeJA and needle-piercing damage received 84% less and 250% more pine weevil feeding, respectively, relative to control seedlings. The other treatments did not differ statistically from control or MeJA in terms of subsequent pine weevil damage. For the late exposure group, plants in all induction treatments tended to receive less pine weevil feeding (yet this was not statistically significant) compared to control seedlings. On the other hand, MeJA significantly slowed down seedling growth relative to control and all other induction treatments. Overall, the mechanical damage treatments appeared to have no or variable effects on seedling resistance. One of the treatments, needle-piercing damage, actually increased pine weevil feeding at early exposure. These results therefore suggest that mechanical damage shows little potential as a plant protection measure to reduce feeding by a bark-chewing insect.
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| 5. |
- Chen, Yayuan, et al.
(författare)
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Seasonal timing and recurrence of methyl jasmonate treatment influence pine weevil damage to Norway spruce seedlings
- 2021
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Ingår i: New Forests. - : Springer Science and Business Media LLC. - 0169-4286 .- 1573-5095. ; 52, s. 431-448
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Tidskriftsartikel (refereegranskat)abstract
- Defense can be induced in conifer seedlings to reduce pine weevil (Hylobius abietis) damage, by treatment with the plant hormone methyl jasmonate (MJ). Few studies have addressed important practical issues regarding the use of MJ such as treatment incidence and timing, seedling age and its compatibility with plant nursery practices. We examined if levels of pine weevil damage depend on seasonal timing and recurrence of MJ treatment, and if the observed effects depend on plant age. Norway spruce (Picea abies) seedlings from two age cohorts (1 year and 1.5 years old) received four MJ treatments: MJ application before winter storage in the previous year, after winter storage but before spring/summer planting, repeated MJ application (both before winter storage, and before planting) or no MJ application at all. Pine weevil damage was evaluated in a lab and field experiment. We found that the timing and recurrence of MJ treatment affected the amount of damage inflicted by pine weevils in different ways, but these effects were consistent among age cohorts. MJ application before winter storage provided the most effective protection, and this reduction in damage was comparable to that provided by a currently used physical protection method against pine weevil feeding. Our results indicated that MJ can be applied in line with nursery practices (before winter storage) and provides adequate protection for two growing seasons.
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| 6. |
- Granath, Gustaf, et al.
(författare)
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Variation in the abundance of fungal endophytes in fescue grasses along altitudinal and grazing gradients
- 2007
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Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 30:3, s. 422-430
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Tidskriftsartikel (refereegranskat)abstract
- Epichloë festucae, a common fungal symbiont of the genus Festuca (family Poaceae), can provide its host plant with protection against herbivores. However, infection might also be associated with a cost to its host plant. We examined the distribution of Epichloë festucae infection in natural populations of three fescue grasses, Festuca rubra, F. ovina and F. vivipara, on mountains in northern Sweden to determine whether infection frequency varied with reindeer Rangifertarandus grazing pressure and altitude. Two differently-scaled approaches were used: 1) infection frequency was measured at a local scale along ten elevational transects within a ca 400 km2 area and 2) infection frequency was measured on a regional scale along elevational transects on 17 mountains classified as having a history of high or low reindeer grazing pressure. Mean infection frequencies in F. rubra were 10% (vegetative tillers at a local scale), and 23% (flowering culms at a regional scale), and in F. ovina they were 13% (local scale) and 15% (regional scale). Endophyte infection frequency in F. vivipara, was, on average, 12% (local scale) and 37% (regional scale). In F. rubra, infection decreased significantly with increasing altitude at both the local and regional scale, and was positively correlated with grazing pressure. In F. ovina, an opposite trend was found at the regional scale: infection frequency increased significantly with increasing altitude, while no discernible distribution pattern was observed at the local scale. No elevational trends were observed in infection of F. vivipara. These patterns in the distribution of endophyte-infected grasses in non-agricultural ecosystems may be explained by both biotic (grazing) and abiotic factors (altitude). Differences in ecology and life history of the studied grass species may also be of importance for the different results observed among species.
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| 7. |
- Puentes, Adriana, et al.
(författare)
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A Systematic Review on the Effects of Plant-Feeding by Omnivorous Arthropods: Time to Catch-Up With the Mirid-Tomato Bias?
- 2018
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Ingår i: Frontiers in Ecology and Evolution. - : Frontiers Media SA. - 2296-701X. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Zoophytophagous (omnivorous) predators provide valuable pest control services, and offer an advantage over strict carnivores as plant-feeding enables survival during prey shortage. This putative advantage can potentially be their downside, as plant-feeding may entail damage that negatively affects plant growth/yield (i.e., the cost arising from of omnivore plant-feeding). Yet, benefits conferred by predatory services are usually thought to counterbalance any impact of plant damage. In this systematic review, our goal was to determine how often levels of omnivore damage and its consequences for plants (costs) are considered or quantified. We provide a synthesis of publication trends and findings on omnivore plant-feeding levels, plant injury variables, actual (if quantified) and potential effects on growth/yield, the type of study (lab, greenhouse) and the plants/omnivores most often examined. Our search revealed that measures of omnivore plant-feeding are occasionally reported, but seldom are the direct consequences of such damage also considered. Omnivore plant-feeding were reported in 57% of studies (53 of 93 full-text examined); within these, the majority (>80%) indicated moderate to high levels of plant-feeding. However, only 22% of reports (15 of 69) quantified the effects of omnivore-inflicted damage on plant performance. Of these 15 reports, a greater number found negative consequences for plants compared to those showing no effect (8 vs. 4; 3 with both), with consequences for yield relative to growth being more often evaluated (6 vs. 2). Overall, fruit/leaf injuries relative to stem/flower-feeding were most often examined, and lab/greenhouse experiments predominated. Tomatoes (Solanum lycopersicum) and the mirid Nesidiocoris tenuis were the most common species studied (34 and 14 reports, respectively). Our results indicate that costs to plants of omnivore-inflicted damage are often neglected. We argue that predatory benefits need to be simultaneously considered with plant-feeding effects to appropriately evaluate pest control services. Publication trends suggest that more studies are evaluating costs to plants, but a paradigm shift is still needed. Furthermore, we found that our understanding of plant-feeding and its effects is disproportionally based on studies examining tomato plants and its omnivorous biocontrol agents. To confirm the generality of findings thus far, other plant omnivore systems should be further considered.
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| 8. |
- Puentes, Adriana, 1982-, et al.
(författare)
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Additive and non-additive effects of simulated leaf and inflorescence damage on survival, growth and reproduction of the perennial herb Arabidopsis lyrata
- 2012
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 169:4, s. 1033-1042
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Tidskriftsartikel (refereegranskat)abstract
- Herbivores may damage both leaves and reproductive structures, and although such combined damage may affect plant fitness non-additively, this has received little attention. We conducted a 2-year field experiment with a factorial design to examine the effects of simulated leaf (0,12.5, 25, or 50% of leaf area removed) and inflorescence damage (0 vs. 50% of inflorescences removed) on survival, growth and reproduction in the perennial herb Arabidopsis lyrata. Leaf and inflorescence damage negatively and independently reduced flower, fruit and seed production in the year of damage; leaf damage also reduced rosette size by the end of the first season and flower production in the second year. Leaf damage alone reduced the proportion of flowers forming a fruit and fruit production per plant the second year, but when combined with inflorescence damage no such effect was observed (significant leaf × inflorescence damage interaction). Damage to leaves (sources) caused a greater reduction in future reproduction than did simultaneous damage to leaves and inflorescences (sinks). This demonstrates that a full understanding of the effects of herbivore damage on plant fitness requires that consequences of damage to vegetative and reproductive structures are evaluated over more than 1 year and that non-additive effects are considered.
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| 9. |
- Puentes, Adriana, et al.
(författare)
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Costs and benefits of omnivore-mediated plant protection: effects of plant-feeding on Salix growth more detrimental than expected
- 2017
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 184, s. 485-496
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Tidskriftsartikel (refereegranskat)abstract
- Predators can decrease herbivore damage to plants, and this is often assumed to be beneficial to plant growth/reproduction without actual quantification. Moreover, previous studies have been biased towards strict carnivores and neglected the role of omnivorous predators in prey-suppression. Here, we examined the costs (reduction in growth) and benefits (increase in growth) of enemy-mediated plant protection via the omnivorous (prey and plant-feeding) Orthotylus marginalis, relative to herbivory by a detrimental insect pest of Salix spp. plantations, the beetle Phratora vulgatissima. In a first experiment, we compared the cost of adult beetle versus omnivore nymph plant-feeding, and assessed the (non-) additive effects of the two types of damage. In a second experiment, we quantified the reduction in plant damage resulting from beetle-egg feeding by omnivorous nymphs and subsequent benefits to plants. We found that plant-feeding by omnivores negatively affected plant growth and this effect was similar to the cost imposed by beetle herbivory. Furthermore, simultaneous damage effects were additive and more detrimental than individual effects. While egg-predation by omnivore nymphs completely prevented beetle damage to plants, there was no difference in plant growth relative to only herbivore-damaged plants and growth was still reduced compared to control plants. Thus, despite herbivore suppression, there was no benefit to plant growth of omnivore-mediated plant protection and the negative effects of omnivore plant-feeding remained. These results are a first for an omnivorous enemy, and provide novel and timely insights on the underlying assumptions of tri-trophic associations and their use for biocontrol of insect pests.
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| 10. |
- Puentes, Adriana, et al.
(författare)
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Direct effects of elevated temperature on a tri-trophic system: Salix, leaf beetles and predatory bugs
- 2015
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Ingår i: Arthropod-Plant Interactions. - : Springer Science and Business Media LLC. - 1872-8855 .- 1872-8847. ; 9, s. 567-575
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Tidskriftsartikel (refereegranskat)abstract
- The net effect of climatic change on biotic interactions will depend on how each interacting species is individually affected. Elevated temperatures are predicted to have differential effects on species across trophic levels, due to asymmetric sensitivity to temperature changes. In this study, we examined the direct effects of three temperature regimes (16, 20 and 24 A degrees C) that reflect present and, potentially, future climate conditions on the response of Salix spp. plants, an important bioenergy crop, and its most damaging herbivore (Phratora vulgatissima) and an efficient natural enemy (the omnivorous predator Orthotylus marginalis). We found that plant growth, herbivore oviposition and enemy egg-foraging rate correlated positively with temperature. In the event of elevated temperatures following global climatic changes, these species could potentially respond in tandem. Still, the strength of responses varied among species, with herbivore and natural enemy exhibiting a similar and steeper rate of response relative to plants. Additionally, the herbivore's response was influenced by plant quality with altered oviposition rates depending on whether it was fed the (previously determined) resistant Salix dasyclados or susceptible S. viminalis. This indicates that host plant chemistry has the potential to mediate differential responses to temperature. Together, our results suggest that indirect effects of elevated temperatures, leading to a disruption of trophic associations, may be less likely or less severe in this tri-trophic system.
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