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The Panel on Plant Health performed a pest categorisation of the great spruce bark beetle, Dendroctonus micans (Kugelann), (Coleoptera: Curculionidae, Scolytinae), for the EU. D. micans is a well-defined and distinguishable species, recognised mainly as a pest of spruce (Picea spp.) and pine (Pinus spp.) in Eurasia. Attacks on other conifers (Abies spp., Larix decidua, Pseudotsuga menziesii) are also reported. Supposedly originating from north-eastern Eurasia, D. micans has spread westward and is now distributed throughout the EU (22 Member States). It is a quarantine pest listed in Annex IIB of Council Directive 2000/29/EC for Greece, Ireland and the United Kingdom (Northern Ireland, Isle of Man and Jersey) as protected zones. Wood, wood products, bark and wood packaging material of the conifers genera listed as hosts are considered as the main pathways for the pest, which is also able to disperse several kilometres by flight. The sib-mating habits of the species allow each single female to start a new colony on her own. The pest's wide current geographic range suggests that it is able to establish anywhere in the EU where its hosts are present. The beetles attack living trees and usually complete their life cycle without killing their host, except under epidemic conditions at the limits of their distribution range, where hundreds of thousands of trees can be killed. Sitka spruce (Picea sitchensis) is particularly susceptible. Biological control using the very specific predatory beetle, Rhizophagus grandis, is a widespread and efficient option that has been implemented in all areas suffering from outbreaks. It is complemented by sanitary thinning or clear-felling. All criteria assessed by EFSA for consideration as potential protected zone quarantine pest were met. The criteria for considering D. micans as a potential regulated non-quarantine pest are not met since plants for planting are not the main pathway. [ABSTRACT FROM AUTHOR]

The Panel on Plant Health performed a pest categorisation of the eight-toothed spruce bark beetle, Ips typographus L. (Coleoptera: Curculionidae, Scolytinae), for the EU. I. typographus is a well-defined and distinguishable species, recognised mainly as a pest of spruce (Picea spp.) in Eurasia. It also attacks other conifers such as Abies spp., Larix spp., Pinus spp. and Pseudotsuga menziesii. Native to Eurasia, I. typographus has spread from the native range of spruce to new areas in Eurasia where spruce has been planted, and is now widely distributed throughout the EU (22 Member states). It is a quarantine pest listed in Annex IIB of Council Directive 2000/29/EC for Ireland and United Kingdom as protected zones. Coniferous wood, bark and wood packaging material are considered as pathways for the pest, which is also able to disperse by flight over tens of kilometres. The insects normally establish on fallen trees but can also mass-attack healthy trees, killing millions of spruces. The males produce pheromones that attract conspecifics of both sexes. Each male attracts one to four females; each female produces 2-80 offspring. The insects also inoculate pathogenic fungi to their hosts. There are one to three generations per year. The wide current geographic range of I. typographus suggests that it is able to establish anywhere in the EU where its hosts are present. Sanitary thinning or clear-felling are the major control methods. Pheromone mass trapping is presently judged unreliable because of the large dispersal capacity of the pest. Quarantine measures are implemented to prevent entry in yet uncolonised areas. All criteria assessed by EFSA for consideration as potential protected zone quarantine pest are met. The criteria for considering I. typographus as a potential regulated non- quarantine pest are not met since plants for planting are not a pathway. [ABSTRACT FROM AUTHOR]

The European Commission requested EFSA to conduct a pest categorization of Spodoptera frugiperda (Lepidoptera: Noctuidae) a pest with hosts in 27 plant families. Favoured hosts include maize, rice and sorghum (Poaceae). Hosts also include crops within the Brassicaceae, Cucurbitaceae, Solanaceae, Rutaceaea and other families. Spodoptera frugiperda is a taxonomic entity with reliable methods for identification. It is regulated in the European Union (EU) as a harmful organism whose introduction into the EU is banned. It is native to tropical and subtropical regions of the Americas and migrates to temperate regions in North and South America during the summer. Establishment in temperate areas is prevented by its inability to overwinter. Spodoptera frugiperda has been intercepted on plant produce entering the EU. Phytosanitary measures are available to impede entry via traded commodities. In 2016 S. frugiperda was reported damaging maize in Africa. Subsequent reports indicate that it continues to spread severely damaging maize and other crops. If S. frugiperda spreads into north Africa, the likelihood of adults migrating into the temperate EU increases. Within the scope and level of analysis appropriate for pest categorisation, the EFSA Plant Health Panel concludes that S. frugiperda could establish in a small area of the southern EU from where it is likely to enter more northern regions forming transient summer populations, particularly in maize growing regions where impacts on yield could occur. However, uncertainties regarding establishment remain. Considering the criteria within the remit of EFSA to assess as regards status as a potential Union quarantine pest (QP) or as a potential regulated non-quarantine pest (RNQP), S. frugiperda satisfies the criteria to be regarded a Union QP but does not meet the criteria of (i) occurring in the EU territory, and (ii) plants for planting being the principal means of spread, criteria required for RNQP status. [ABSTRACT FROM AUTHOR]

The Panel on Plant Health performed a pest categorisation of the strawberry bud weevil, Anthonomus signatus Say, (Coleoptera: Curculionidae), for the EU. A. signatus is a well-defined and distinguishable species, recognised as a pest of strawberry (Fragaria) fruit production in eastern North America where it is also a pest of Rubus. There are reports of A. signatus associated with non-rosaceous plants such as Mentha, Nepeta, Rhododendron and Solidago although whether such plants are true hosts is uncertain. This pest categorisation focuses on Fragaria and Rubus as hosts. Anthonomus signatus is not known to occur in the EU. It is listed in Annex IIAI of Council Directive 2000/29/EC. The international trade in Fragaria and Rubus plants for planting provides a potential pathway to introduce A. signatus from North America. Considering climatic similarities between North America and the EU, the thermal biology of A. signatus and host distribution in the EU, A. signatus has the potential to establish within the EU. There would be one generation per year, as in North America. As a pest of field grown Fragaria and Rubus, A. signatus would not be expected to establish in EU glasshouses. In North America, adults clip developing buds, preventing fruit development and reducing yield. Losses are variable and depend on the cultivars attacked. Severe crop losses have been reported. However, some Fragaria cultivars can compensate the loss of buds, e.g. by increasing the weight of fruits developing on remaining buds. Phytosanitary measures are available to reduce the likelihood of introduction of A. signatus from North America. All criteria assessed by EFSA for consideration as a potential Union quarantine pest are met. As A. signatus is not known to occur in the EU, this criterion assessed by EFSA to consider it as a Union regulated non-quarantine pest is not met. [ABSTRACT FROM AUTHOR]

Following a request from the European Commission, the European Food Safety Authority (EFSA) Plant Health (PLH) Panel analysed a dossier submitted by the Japanese authorities in order to clarify the host status of Citrus junos with regard to Xanthomonas citri pv. citri and Xanthomonas citri pv. aurantifolii, causal agents of citrus bacterial canker, and to indicate whether C. junos fruit could represent a pathway for the introduction of citrus bacterial canker into the European Union. In a previous opinion in the year 2014, the EFSA PLH Panel concluded that commercial fresh citrus fruit is generally pathway and that no commercially important Citrus species or variety can be considered as immune to citrus bacterial canker. In the current assessment, the EFSA PLH Panel analysed the two scientific papers provided by the Japanese authorities, as well as 16 additional papers identified through a systematic literature review. The PLH Panel considered that the conclusions of its previous opinion remain valid and that convergent lines of evidence provide sufficient demonstration that C. junos is a host of X. citri pv. citri and X. citri pv. aurantifolii. Therefore, there is no reason to consider the C. junos fruit differently from other citrus species. Consequently, the assessment of the general citrus fruit pathway from the 2014 opinion still applies. Uncertainties on these conclusions are a result of the scarce scientific evidence published on this subject in addition to the methodological and reporting limitations of the published papers. [ABSTRACT FROM AUTHOR]

Cleaner fish are commonly used as a control measure against salmon lice infestations in salmonid farms. Lumpfish (Cyclopterus lumpus) is the most common cleaner fish species used in Norwegian farms. However, little is known about how different operational, including environmental, conditions affect the salmon lice grazing efficacy by lumpfish. In this paper, we analyse salmon lice (Lepeophtheirus salmonis) in the stomach contents of a large sample of more than 20,000 lumpfish from 80 different Norwegian farms. We investigate the proportion of lumpfish with salmon lice and the mean number of salmon lice in the stomach contents of the lumpfish. We further explore how the salmon lice contents vary with different factors like lumpfish weight, weight of salmonids, salmon lice abundance in the cage, cloud cover, and sea temperature. We find that 3.1% of the 24,693 lumpfish contained salmon lice. Most of the lumpfish with salmon lice in their stomach contents contained few (one or two) lice, while there were a few lumpfish which contained many salmon lice. We find more salmon lice in the stomach contents with increasing abundance of salmon lice in the sea cage, lower weight of the salmonids, and in clear weather. Interestingly, for the relationship between lumpfish weight and salmon lice in the stomach contents, we find increased salmon lice grazing from ca. 5 g up to an optimal weight of ca. 40 g, and then a decrease from 40 g. Surprisingly, we find no relationship between sea temperature and salmon lice per lumpfish. We find more salmon lice in the stomach contents of the lumpfish with comparatively high condition. By studying the factors associated with most efficient salmon lice grazing, our paper contributes to understanding how different operational factors affect salmon lice grazing by lumpfish. For controllable factors, the results thus contribute to guiding the best practice for use of lumpfish as a salmon lice control measure. • 3.1% of the lumpfish stomach samples contained salmon lice. • We found more lice per lumpfish with increasing abundance of lice on the salmonids. • We found an optimal lumpfish weight for salmon lice grazing of ca. 40 g. • We found no relationship between sea temperature and salmon lice per lumpfish. • We found more lice per lumpfish for higher condition and in clear weather. [ABSTRACT FROM AUTHOR]

The monitoring of contaminants represents a priority to preserve the integrity of marine ecosystems, as well as to plan and to manage restoration activities in order to protect environmental and human health. In the present study, a 6-months active biomonitoring was performed to explore the levels of eighteen trace and toxic elements, including heavy metals (TEs; i.e. Al, As, Ca, Cd, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, P, Pb, Sr, Ti, and Zn), accumulated in soft tissues of blue mussel (Mytilus edulis Linnaeus, 1758) individuals transplanted at different depths (5- and 15-m depth) in five locations within the Flekkefjord fjord (Southern Norway). As this area suffered a long-lasting contamination due to both organic and inorganic contaminants, a series of restoration activities were activated to tackle and to prevent potential risks for ecosystem and local population. Our results demonstrated that the levels of TEs accumulated in edible tissues of transplanted mussels in the Flekkefjord fjord were generally low before the beginning of the restoration activities. However, location- and time-specific differences in the accumulation of TEs were noted after the implementation of such activities. Interestingly, the levels of Fe and Mn significantly increased after the beginning of the restoration activities, likely because the release of these TEs from the slag used in such operations and/or resuspension of contaminated sediments. However, assuming that native mussels can accumulate the same TEs at levels measured in transplanted individuals, our results suggest a substantial safety for human consumption of native mussels from the Flekkefjord fjord, regardless of restoration activities., (© 2022. The Author(s).)

The Panel on Plant Health performed a pest categorisation of Grapholita packardi Zeller, (Lepidoptera: Tortricidae), for the EU. G. packardi is a well-defined and distinguishable species. It is widely distributed in the USA and has a restricted distribution in Canada and Mexico. It is recognised as a pest of blueberry and cherry, and has occasionally been reported in apple, pear and plum. It is cited on quince and wild rosaceous plants such as Crataegus . Larvae feed on blueberry and cherry fruits internally and overwinter in pruned twigs. External evidence of infestation of cherries by young larvae is occasionally not detectable. In apple, fruit damage is less common; rather, the pest bores into terminal shoots of nursery stock and young orchard trees. Feeding damage spoils fruit quality and marketability and reduces crop yield. G. packardi is not known to occur in the EU and is listed in Annex IIAI of Council Directive 2000/29/EC under the synonym Enarmonia packardi . Host plants for planting and infested fruit could potentially provide a pathway into the EU. Considering the climatic similarities between North America and Europe, and that wild and commercial hosts occur widely within the EU, G. packardi has the potential to establish within the EU. There would be one to three generations per year, as in North America. Based on literature, blueberries and cherries are likely to be impacted more than apples and pears. Phytosanitary measures are available to reduce the likelihood of introduction of G. packardi . All criteria assessed by EFSA for consideration as a potential Union quarantine pest are met. As G. packardi is not known to occur in the EU, this criterion assessed by EFSA to consider it as a Union regulated non-quarantine pest is not met., (© 2018 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

The Panel on Plant Health performed a pest categorisation of the Siberian moth, Dendrolimus sibiricus Tschetverikov (Lepidoptera: Lasiocampidae). D. sibiricus is a well-defined and distinguishable species, native to Asian Russia and northern regions of Kazakhstan, Mongolia, China and North Korea, and recognised as a severe pest of Pinaceae conifers, mainly larch ( Larix spp.), fir ( Abies spp.), spruce ( Picea spp.), five-needle pines ( Pinus spp.). It has also a potential to develop on non-native Pinaceae: Cedrus, Pseudotsuga, Tsuga . It defoliates healthy trees and kills thousands of hectares of forests. It is absent from the EU and is listed as a quarantine pest in Annex IAI of Directive 2000/29/EC. Plants for planting, branches of conifers and non-squared wood from its distribution range are considered as pathways for the pest, which can also disperse by flight over tens of kilometres. The females produce sex pheromones. Adults do not feed and can survive for about 2 weeks. One female lays up to 400 eggs, attaching them to needles. One generation usually develops in 2-3 years, with larvae passing winter diapause and some undergoing facultative summer diapause. Exceptionally, 1-year generations may occur if the number of degree-days above 10°C is higher than 2,200. Larvae feed on needles through 5-6 instars and pupate in a cocoon on tree branches. Mature larvae have urticating setae on thoracic segments that protect them from enemies and may cause allergic reactions in humans and animals. The contradictory studies regarding the climatic requirements of D. sibiricus make the issue of its establishment in most of the EU territory uncertain, although its host trees are widely present. All criteria for considering D. sibiricus as a potential quarantine pest are met. The species is presently absent from the EU, and thus, the criteria for consideration as a potential regulated non-quarantine pest are not met., (© 2018 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

The Panel on Plant Health performed a pest categorisation of the non-EU Pissodes spp. (Coleoptera: Curculionidae). They constitute a well-defined taxon, with non-EU species distributed in the USA, Canada, Mexico, Guatemala, El Salvador, China, Japan, Korea, Russia and South Africa, some of which are recognised as severe pests of conifers, mainly Pinus spp. and Picea spp., or vector pathogens. The immature stages either live in the phloem and cambium of healthy, weakened or dead trees, or in the terminal shoots of living trees. They are listed as quarantine pests in Annex IAI of Directive 2000/29/EC. Plants for planting, branches of conifers and non-squared wood are considered as pathways. The pest can also disperse by hitchhiking, and fly over kilometres. The adults are long-lived (up to 4 years). They feed by puncturing the bark of stems or shoots. Females lay eggs in chewed-out cavities in the bark. The life cycle varies with species and local climatic conditions. At the end of the larval stage, the larva excavates a pupal cell between the sapwood and the bark, in the sapwood or in terminal shoots. Pissodes spp. overwinter as adults in the litter or as larvae or teneral adults in the galleries or pupal cells. The current geographic range of the non-European Pissodes spp. suggests that many of them may establish in the EU territory, where their hosts are widely present. We list some species which, if introduced to the EU, would most probably have an economic impact on plantations or may interfere with forest ecosystem processes although they are mainly abundant and damaging in intensively managed monocultures. All criteria for considering those non-EU Pissodes spp. as potential quarantine pests are met. The criteria for considering them as non-regulated quarantine pests are not met because they are absent from the EU territory., (© 2018 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of Coniferiporia sulphurascens and Coniferiporia weirii , two well-defined and distinguishable fungal species of the family Hymenochaetaceae. The pathogens are regulated in Council Directive 2000/29/EC (Annex IAI, under the previous name Inonotus weirii for both species) as a harmful organism whose introduction into the EU is banned. The two pathogens are native to North America, where C. sulphurascens causes laminated root rot primarily in Douglas fir ( Pseudotsuga menziesii ) and grand fir ( Abies grandis ), while C. weirii causes cedar laminated root and butt rot mainly in cedars ( Thuja plicata and Cupressus nootkatensis ). C. weirii has been reported from Japan and China, and C. sulphurascens from China, Russia and Turkey. Neither species has been reported from the EU. C. sulphurascens may infect all conifers, while C. weirii is reported to mainly cause disease in tree species of Thuja spp. and Cupressus spp. The two pathogens could enter the EU mainly via wood with bark, isolated bark and plants for planting (including artificially dwarfed plants) of Pinaceae and Cupressaceae. Both fungi could establish in the EU, as hosts are present and climatic conditions are favourable. The two pathogens would be able to spread following establishment by the pathways mentioned for entry and also by dissemination of basidiospores and root contact with infected root/wood. Should the pathogen be introduced in the EU, impacts can be expected on coniferous woodlands, plantations and ornamental trees, thus leading to reduced tree growth and ecosystem service provision. The key uncertainties concern (i) the distribution of the two pathogens in Asia, (ii) the level of susceptibility of conifers native to Europe and (iii) the role of plants for planting as a pathway of entry and spread. For both pathogens, the criteria assessed by the Panel for consideration as a potential quarantine pest are met. As the two pests are not present in the EU, not all the criteria for consideration as regulated non-quarantine pests are met., (© 2018 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

The Panel on Plant Health performed a pest categorisation of nematodes belonging to the genus Hirschmanniella (Nematoda: Pratylenchidae). Twenty-nine species in this genus have been considered of which five species are present in the EU ( Hirschmanniella behningi , Hirschmanniella gracilis , Hirschmanniella halophila , Hirschmanniella loofi and Hirschmanniella zostericola ). The whole genus except H. gracilis is regulated by Council Directive 2000/29/EC (Annex IAI). Hirschmanniella species are root endoparasites uniquely adapted to aquatic environments. Most species are reported from tropical regions. Monocotyledons including aquatic plants are main hosts and some Hirschmanniella species are important pests of rice. Plants for planting are potential pathways for entry. Hirschmanniella species are frequently intercepted on imported aquarium plants. Measures are available to avoid entry. Environmental conditions in greenhouses and potentially in rice production areas of the EU are suitable for establishment. The nematode may be spread with irrigation, tools or plants for planting. Hirschmanniella species were categorised into four groups. The first group includes species reported as pests of crop plants; those satisfy all the criteria that are within the remit of EFSA to assess to be regarded as Union quarantine pests. The second group includes species that are not reported to cause economic damage to crop plants; those species do not satisfy all the criteria to be regarded as Union quarantine pests. Uncertainty exists whether species in this group can cause damage once introduced into the EU. The third group includes species that are known to be present in the EU and do not cause damage; they do not satisfy the criteria to be regarded as Union quarantine pests or regulated non-quarantine pests. The fourth group consists of H. gracilis only. This worldwide occurring species is present in the EU where it does not cause economic damage. It does not satisfy all the criteria to be regarded as a Union quarantine pest., (© 2018 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

The Panel on Plant Health performed a pest categorisation of Colletotrichum gossypii , the fungal agent of anthracnose and ramulosis diseases of cotton, for the EU. The identity of the pest is well established and reliable methods exist for its detection/identification. The pest is present in most of the cotton-growing areas worldwide, including Bulgaria and Romania in the EU. Colletotrichum gossypii is listed as Glomerella gossypii in Annex IIB of Directive 2000/29/EC and is not known to occur in Greece, which is a protected zone (PZ). The only hosts are Gossypium species, with G. hirsutum and G. barbadense being the most susceptible. The pest could potentially enter the PZ on cotton seeds originating in infested third countries or EU infested areas. Entry into PZ by natural means from EU infested areas is possible, although there is uncertainty on the maximum distance the pest can travel by wind or insects. Bolls and unginned cotton are minor pathways of entry. Pest distribution and climate matching suggest that the pest could establish and spread in cotton-producing areas of northern Greece. In the infested areas, the pest causes damping-off, leaf/boll spotting, boll rot, witches' broom symptoms and stunting resulting in yield and quality losses. It affects also the lint and seeds reducing fibres quality and seed germinability. It is expected that its introduction and spread in the EU PZ would impact cotton yield and quality. The agricultural practices and control methods currently applied in Greece would not prevent pest establishment and spread. Colletotrichum gossypii meets all the criteria assessed by EFSA for consideration as potential quarantine pest for the EU PZ of Greece. The criteria for considering C. gossypii as a potential Union regulated non-quarantine pest are also met since cotton seeds are the main means of spread., (© 2018 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of Guignardia laricina , a well-defined and distinguishable fungal species of the family Phyllostictaceae. The pathogen is regulated in Council Directive 2000/29/EC (Annex IAI) as a harmful organism whose introduction into the EU is banned. G. laricina is native to East Asia and causes a shoot blight disease of Larix spp. Major hosts of G. laricina are European larch ( Larix decidua ) and two North American larch species ( Larix laricina (tamarack) and Larix occidentalis (Western larch)). Larix kaempferi (Japanese larch) is reported as susceptible. The only other host in nature is Douglas fir ( Pseudotsuga menziesii) , which is reported as an incidental host, but various other conifers have been reported as susceptible following artificial inoculation, including Picea abies . The fungus is not known to occur in the EU but could enter via plants for planting (including artificially dwarfed plants) and cut branches of Larix spp. It could establish in the EU, as hosts are present and climatic conditions are favourable. The pathogen would be able to spread following establishment by natural dissemination of ascospores and pycnospores and by human movement of infected plants for planting. Should the pathogen be introduced in the EU, impacts can be expected in larch forests, plantations and nurseries, leading to reduced tree growth and ecosystem service provision. The key uncertainties concern the current distribution and level of impacts in the native range of the pathogen. The criteria assessed by the Panel for consideration as a potential quarantine pest are met. As the pest is not present in the EU, not all criteria for consideration as a regulated non-quarantine pest are met., (© 2018 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

The EFSA Panel on Plant Health performed a pest categorisation of naturally-spreading psorosis of citrus for the European Union. Naturally-spreading psorosis is poorly defined, because the status of both the disease and its causal agent(s) is uncertain. However, Citrus psorosis virus (CPsV) is a well- characterised Ophiovirus that is systematically associated with the psorosis disease and therefore considered to be its causal agent. Efficient diagnostics are available for CPsV. It is present in at least three EU MS. Naturally-spreading psorosis is currently regulated by Directive 2000/29/EC, while CPsV is not explicitly mentioned in this Directive. CPsV has the potential to enter, establish and spread in the EU territory. However, the main pathway for entry is closed by the existing legislation so that entry is only possible through minor alternative pathways. Plants for planting are the major means of spread while there are uncertainties on the existence and efficiency of a natural spread mechanism. CPsV introduction and spread in the EU would have negative consequences on the EU citrus industry. Of the criteria evaluated by EFSA to qualify as a Union quarantine pest or as a Union regulated non-quarantine pest (RNQP), Naturally-spreading psorosis does not meet the criterion of being a well characterised pest or disease. As it is not explicitly mentioned in the legislation, it is unclear whether CPsV meets the criterion of being currently regulated or under official control. It meets, however, all the RNQP criteria. The key uncertainties of this categorisation concern: (1) the causal role of CPsV in the psorosis disease as well as elements of its biology and epidemiology, (2) the exact nature of the Naturally-spreading psorosis syndrome and the identity of its causal agent and, consequently, (3) whether CPsV should be considered as being covered by the current legislation., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

Cyclic outbreaks of forest moth pest species have long remained a puzzle for foresters and ecologists. This paper presents time-series exhibiting a strong negative relationship between sunspot numbers and population indices of autumnal and winter moths, both in a mountain birch forest in central Norway and in a mixed lowland forest in southern Norway. In the latter area, also the population level of a moth species feeding entirely on lichens was negatively related to sunspot numbers. Low sunspot activity leads to a thinner ozone layer and thus higher surface ultraviolet (UV)-B radiation. As winter moth larvae prefer leaves subjected to enhanced UV-B radiation, we suggest that the causal relationship between sunspots and moths is that the metabolic costs of producing UV-B-protective pigments during periods of low sunspot activity reduce trees' and lichens' resistance to herbivores, and thus increase the survival of moth larvae. Higher peak densities of moth cycles in mountain forests could be explained by the general higher UV-B radiation at higher altitudes.