Curculio Nucum Research Articles

Underestimated Damage Caused by the European Hazelnut Weevil, Curculio nucum (Curculionidae)

Hazelnut is an important food resource for the larvae and adults of the hazelnut weevil, Curculio nucum. While wormy nuts reflect the impact of such weevils at harvest time, little is known about the other types of damage they cause. To establish a comprehensive list of damages, and thereby identify the period of hazelnut vulnerability, male and female weevils were collected weekly and isolated on fruiting branches for 1 week. Based on nut development, higher rates of dropped nutlets, belted nuts, and blank nuts were observed at harvest. Marks specific to weevils, including wormy nuts, riddled shells, and larvae paths on the basal scar, were recorded during nut lignification. Belted nuts and blank nuts are empty nuts and constituted the main damage. The feeding activities of both the adults and larvae, but also the oviposition punctures, are likely to be the main causes of embryo abortions. The greatest damages occurred during kernel growth and when the shell had almost reached its final size. The larvae failed to penetrate fully lignified shells, with dead larvae mainly being found on the basal scar, the later softer part of the hazelnut. In Ségorbe cultivars, the dynamic of hazelnut development is the main factor involved in its susceptibility to C. nucum, with aborted nuts being the most underestimated damage.

The Biology, Ecology, and Management of the Hazelnut-Feeding Weevils (Curculiospp.) (Coleoptera: Curculionidae) of the World

AbstractCertain species of acorn- and nut-feeding weevils, Curculio spp. (Coleoptera: Curculionidae), have become significant insect pests of cultivated hazelnuts (Corylus spp.) (Fagales: Betulaceae) worldwide. The significance of weevils that feed on and injure hazelnuts is increasing as countries such as the United States and China continue to develop hybrids of hazel plants to increase their hazelnut production. This review focuses on the ecology, impact, management, and identification of the four known species of hazelnut-injuring weevils throughout the world: Curculio dieckmanni (Faust), Curculio nucum L., Curculio obtusus Gibson (the hazelnut weevil), and Curculio occidentis (Casey) (the filbert weevil).

Sakarya İli Fındık Bahçelerinde Fındık Kurdu (Curculio nucum L.) (Coleoptera: Curculionidae) ve Fındık Yeşil Kokarcası (Palomena prasina L.) (Hemiptera: Pentatomidae)’nın Zarar Oranlarının Belirlenmesi

Bu çalışma Batı Karadeniz Bölgesi’nde yer alan Sakarya ili fındık bahçelerinde Fındık kurdu Curculio nucum L. (Colepotera: Curculionidae) ve Fındık yeşil kokarcası Palomena prasina L. (Hemiptera: Pentatomidae)’nın zarar oranlarını belirlemek amacıyla 2017-2018 yıllarında yürütülmüştür. Çalışmanın ilk yılı, Fındık kurdu’nun zararı nedeniyle oluşan delikli meyve %0.8-1.8 ve boş iç %8.2-11.5, ikinci yıl ise delikli meyve %0.0-0.2 ve boş iç %7.4-10 olarak bulunmuştur. İlk yıl, Fındık yeşil kokarcası zararı olan şekilsiz iç oluşumu %0.7-1.4 ve lekeli iç %0.5-1.1, ikinci yıl şekilsiz iç oluşumu %1.2-1.9 ve lekeli iç %0.7-1.3 olarak belirlenmiştir. Bu iki türün ortak zararı olan sarı karamuk ve kara karamuk yıllara göre sırasıyla %1.8-3.2 ve %13.5-21.9 olarak belirlenmiştir.

Antennal sensilla of male and female of the nut weevil, Curculio nucum Linnaeus, 1758 (Coleoptera: Curculionidae)

SummaryThe nut weevil, Curculio nucum (Linnaeus, 1758), is the main pest in hazelnut orchards (Corylus avellana L.). Semiochemicals are interesting bio control tools that could be used to manipulate the pest behaviour and to control pest populations. The study of the sensorial equipment of the insect antennae provides information on the importance of olfaction in the adult life for host plants and mate findings as well as on the putative other senses. Before electrophysiological investigation, the knowledge of antennae equipment is also necessary. The aim of this study is to determine the types, number and location of sensilla on the antennae of male and female adult C. nucum in order to determine their implication in seeking a sexual partner and a host plant. The 12-segmented antenna comprises a scape, a 7-segmented funicle and a 4-segmented club. Out of the nine sensillum types listed, three are present on the scape and the funicle and seven types on the club which gathers 71–73% of the total of sensilla. Tactile aporous sensilla chaetica C1, gustatory uniporous sensilla chaetica C2, olfactory multiporous sensilla basiconica B1 and B2 are found on both the dorsal and ventral surfaces of the club in both sexes. Thermo-hygroreceptive dome-shaped sensilla D, olfactory multiporous sensilla basiconica B3 and olfactory multiporous fluted sensilla basiconica F are found exclusively on the ventral surface of the club, suggesting that these sensilla are utilized in host plant acceptance during antennal tapping. The sexual dimorphism concerns only the numbers of sensilla chaetica C1 and sensilla basiconica B2.

Role of seed size, phenology, oogenesis and host distribution in the specificity and genetic structure of seed weevils (Curculio spp.) in mixed forests.

Synchrony between seed growth and oogenesis is suggested to largely shape trophic breadth of seed‐feeding insects and ultimately to contribute to their co‐existence by means of resource partitioning or in the time when infestation occurs. Here we investigated: (i) the role of seed phenology and sexual maturation of females in the host specificity of seed‐feeding weevils (Curculio spp.) predating in hazel and oak mixed forests; and (ii) the consequences that trophic breadth and host distribution have in the genetic structure of the weevil populations. DNA analyses were used to establish unequivocally host specificity and to determine the population genetic structure. We identified 4 species with different specificity, namely Curculio nucum females matured earlier and infested a unique host (hazelnuts, Corylus avellana) while 3 species (Curculio venosus, Curculio glandium and Curculio elephas) predated upon the acorns of the 2 oaks (Quercus ilex and Quercus pubescens). The high specificity of C. nucum coupled with a more discontinuous distribution of hazel trees resulted in a significant genetic structure among sites. In addition, the presence of an excess of local rare haplotypes indicated that C. nucum populations went through genetic expansion after recent bottlenecks. Conversely, these effects were not observed in the more generalist Curculio glandium predating upon oaks. Ultimately, co‐existence of weevil species in this multi‐host‐parasite system is influenced by both resource and time partitioning. To what extent the restriction in gene flow among C. nucum populations may have negative consequences for their persistence in a time of increasing disturbances (e.g. drought in Mediterranean areas) deserves further research.

Evaluation of Pathogenicity of the Fungi Metarhizium anisopliae and Beauveria bassiana in Hazelnut Weevil (Curculio nucum L., Coleoptera, Curculionidae) Larvae.

The nut weevil (Curculio nucum) is one of the most important and widespread pests in hazelnut orchards. In order to screen entomopathogenic fungal strains with high virulence against C. nucum, the growth rate, sporulation, and cumulative mortality of different Metarhizium anisopliae and Beauveria bassiana strains were investigated, and the process by which M. anisopliae CoM 02 infects C. nucum larvae was observed using scanning electron microscopy. The results indicated that the growth rate and sporulation of different fungal strains significantly differed. Thirteen days after inoculation with M. anisopliae CoM 02, the cumulative mortality of C. nucum larvae reached 100%, which was considerably higher than that of the other five strains. As the most virulent of the six test strains, the cadaver rate, LT50, and LT90 of M. anisopliae CoM 02 were 93.4%, 7.05 and 11.90days, respectively. Analysis of the infection process by scanning electron microscopy showed that the spore attachment, hyphal germination, hyphal rapid growth, and sporulation of M. anisopliae CoM 02 occurred on the 3rd, 5th, 7th, and 11th day after inoculation, respectively, indicating that the infection cycle takes approximately 11days. This finding suggests that the highly virulent M. anisopliae plays an important role in the biocontrol of C. nucum in China.

Virulence of entomopathogenic nematodes and their symbiotic bacteria against the hazelnut weevil Curculio nucum

AbstractThe virulence of different entomopathogenic nematode strains of the families Steinernematidae and Heterorhabditidae, isolates from Catalonia (NE Iberian Peninsula), and their symbiotic bacteria was assessed with regard to the larvae and adults of the hazelnut weevil, Curculio nucum L. (Coleoptera: Curculionidae). The nematode strains screened included one Steinernema affine, five Steinernema feltiae, one Steinernema carpocapsae, one Steinernema sp. (a new species not yet described) and one Heterorhabditis bacteriophora. The pathogenicity of all the strains of nematodes was tested on larvae and only four of them on adults of the hazelnut weevil. Larval mortality ranged from 10% with S. affine to 79% with Steinernema sp. Adult mortality was higher in S. carpocapsae, achieving 100% adult weevil mortality. The pathogenicity of the symbiotic bacteria Xenorhabdus bovienii, X. kozodoii, X. nematophila and Photorhabdus luminescens was studied in larvae and adults of C. nucum. In the larvae, X. kozodoii showed a LT50 of 22.7 h, and in the adults, it was 20.5 h. All nematodes species except S. affine tested against larvae showed great potential to control the insect, whereas S. carpocapsae was the most effective for controlling adults.

HAZELNUT PESTS OF SILKROAD COUNTRIES, WITH SPECIFIC EMPHASIS ON PESTS OF GEORGIA

Hazelnut is a very important crop for some silkroad countries such as Turkey, Georgia and Azerbaijan. Insect and mite pests are major detriments to hazelnut production. More than several hundreds of insect and mite species have been found in hazelnut orchards up to today. About 10 insect and mite species are serious pests for hazelnut production, with changes among countries. These pests affect the yield and kernel quality as well as the health of trees. Nearly more than 20% losses are caused by hazelnut pests in orchards, with changes in countries and years. Hazelnut is a traditional crop of Georgia and hazelnut growing is enlarging over the past few years in this country. In the current paper, two main topics are considered about hazelnut pests: 1) important hazelnut pests of silkroad countries and their management, 2) current situation of hazelnut pests of Georgia, depending on the results of large scale survey carried out in Georgian hazelnut orchards in 2013. The survey was performed in four main hazelnut growing area, including Ajara, Guria, Samegrelo and Gali, with visiting various towns of each main district on each surveying date. Four main insect and mite pests including Hyphantria cunea, Curculio nucum, Phytoptus avellana and Obera linearis were selected and surveyed, depending on previous data and observations made in previous years. As a general result; H. cunea was very common in all regions in spite of lower population level compared to previous years. C. nucum damage ratio was very high in some parts of Guria especially with some local cultivars. P. avellana was very widespread in all surveyed districts, with reaching very high populations in some towns of Guria. High population of O. linearis was observed in the Gali district. All results according to pests, locations, surveying and sampling dates were given in this study with details.

Field efficacy against the hazelnut weevil, Curculio nucum and short-term persistence of entomopathogenic nematodes

The hazelnut weevil, Curculio nucum L. (Coleoptera: Curculionidae) is a pest affecting hazelnut orchards in Europe, with an important economical repercussion. Its potential control, short-term field persistence and the vertical distribution of native entomopathogenic nematode strains were tested in Muntanyes de Prades, Tarragona (NE Iberian Peninsula) over two consecutive years. Steinernema feltiae strain D114, Steinernema sp. strain D122 and Heterorhabditis bacteriophora strain DG46 were used in summer and spring applications at a dosage of 5·105 IJs m-2. The three nematode species reduced the hazelnut weevil population, ranging from 32% to 88% efficacy, without significant differences in efficacy or between the two applications. Persistence evaluation was carried out during 9 weeks for S. feltiae (D114), Steinernema sp. (D122) and H. bacteriophora (DG46) and showed all species capable of lasting for this period. Nematodes and larval vertical distribution was assessed. Most of the hazelnut weevil stayed within the first 25 cm although some were found as deep as 40 cm. Entomopathogenic nematodes were found along all 40 cm depth. This study proves the suitability of entomopathogenic nematodes to control the hazelnut weevil.

The resistance of hazel (Corylus avellana) to hazelnut weevil (Curculio nucum L.- Coleoptera, Curculionidae). Part II. The physicochemical characteristics of the pericarp and dynamics of nut development and cultivar resistance to the pest

Significant differences were found among the 22 studied hazel cultivars (<i>Corylus avellana</i> L.) in their resistance to hazelnut weevil (<i>Curculio nucum</i> L.) which is the main pest of this crop in Europe. The study investigated the relationships between the resistance of the cultivars to the pest and the physicochemical properties of the pericarp, i.e. the lignification dynamics, changes in thickness and hardness during nut development and the rate of nutlet development. Correlation analysis showed that there was no dependence between the physicochemical properties of the pericarp and the resistance of the hazel cultivars to the hazelnut weevil. Nut development dynamics were also found to be unrelated to resistance to the pest. Laboratory feeding experiments showed that during the initial feeding phase and at the time the insect searches for an oviposition site, it seems to prefer cultivars with the largest nutlets. However, in the period of intensive oviposition, traits other than nutlet size seem to be decisive for the beetles choice of cultivar.

Isolation and virulence of entomopathogenic fungi against larvae of hazelnut weevil Curculio nucum (Coleoptera, Curculionidae) and the effects of combining Metarhizium anisopliae with entomopathogenic nematodes in the laboratory

An approach to ensure effective pest biocontrol would be to select native isolates of biological control agents (BCAs). A survey to isolate entomopathogenic fungi (EPF) from a hazelnut growing area has been carried out. EPF were recovered from 133 of the 295 soil samples. The main species isolated were Metarhizium anisopliae sensu lato (36%) and Beauveria bassiana sensu lato (42.8%). With regard to controlling abiotic factors, altitude had an effect on the distribution of B. bassiana, but not on M. anisopliae. Cropping system did not have an effect on the occurrence of these EPF, while pH appeared as a predictive variable for both. In addition, we tested the virulence of six of these isolates: three M. anisopliae and three of B. bassiana against larvae of Curculio nucum L. The highest larval mortality (reaching 80%) was due to M. anisopliae (strain 34) when applied in simultaneous combination with four entomopathogenic nematode species: Steinernema carpocapsae (strain B14), Steinernema feltiae (strain D114), Steinernema. sp. (strain D122) and Heterorhabditis bacteriophora (strain DG46). The effect of nematodes was greater and no antagonistic or synergistic effects were observed.

The resistance of hazel (Corylus avellana L.) to hazelnut weevil (Curculio nucum L., Coleoptera, Curculionidae). Part I. Evaluation of the resistance of several cultivars

In the course of 5 year investigations (1981-1985) considerable differences were found in the resistance of 24 hazel cultivars to hazelnut weevil (<i>Curculio nucum</i> L.). The resistance was determined on the basis of the percentage of nuts damaged by larvae in the total yield. Six classes of resistance were established, from class I - very resistant cultivars, to class VI - very susceptible cultivars. In feeding experiments a positive correlation, significant at the 1% and 5% level was found between the frequency of beetle feeding on hazel fruitlets during the time of oviposition (July), and the class of resistance of cultivars; a negative correlation between these parameters was found in August, i.e. during hatching and development of larvae in the nuts. In July the beetles fed more readily and more frequently on nuts of susceptible cultivars, whereas they avoided them in August, i.e. in the period when larvae developed in many fruits of these cultivars.

Entomofauna of hazelnut plantation in the north‐eastern regions of PolandEntomofauna leszczyny uprawianej w północno‐wschodniej Polsce

Summary The results of the studies on entomofauna, carried out near Lubawa on a hazelnut plantation in the fourth and fifth year of its growth, revealed that the most numerous community of phytophages was represented by aphids with the dominant species Myzocallis coryli Goeze. Other identified insects species regarded as potential threat to hazelnut belonged to the families: Agromyzidae and Cecidomyiidae with the most frequent species Contarinia coryli. Due to a lack of the presence of such economically important pest species as Curculio nucum L. or Phytoptus avellanae Nal. in the collected material, the insect population can be regarded as non‐stabilized. The assemblages of zoophagous insects were most numerously represented by the families: Chrysopidae with the species Chrysoperla perla and Chalcidoidea with Cyrtogaster vulgaris.

Ecophysiological attributes of adult overwintering in insects: insights from a field study of the nut weevil, Curculio nucum

Abstract Diapausing insect species have evolved a great diversity of life cycles, although overwintering occurs at a single development stage within most species. Understanding why diapause has evolved towards a given life stage requires investigation of both the ecological and physiological attributes. Notably, it is suggested that adult overwintering is more energy-demanding than larval overwintering but it brings fitness gains by allowing adults to be synchronized with their seasonal requisites through an early spring emergence. This hypothesis is tested in field conditions in the nut weevil Curculio nucum, whose life cycle comprises an obligate 2-year, nonfeeding underground phase, including a larval, followed by an adult, overwintering. In this species, adult wintering leads to an early spring emergence; at first glance, however, this does not enhance synchronization between weevils and their host because adults emerge more than 1 month before starting to breed. It is suggested that adult overwintering ultimately evolved in response to the phenology of the host, by allowing females to oviposit in nuts before their full sclerotinization. Adult overwintering appears to be costly because adults postpone reproduction for 1 year, incur a significant weight loss and require feeding before egg laying. Surprisingly, lipids are unaffected during diapause, lipogenesis even being likely in the summer metamorphosis. These results suggest that the lipids involved in egg production may entirely come from the larval stages, whereas the other nutrients are acquired through adult feeding but this remains to be tested.

Early nut development as a resistance factor to the attacks of Curculio nucum (Coleoptera: Curculionidae)

AbstractThe nut weevil Curculio nucum (Coleoptera: Curculionidae) is responsible for high yield losses in several hazelnut‐growing areas of Europe and Turkey, if not regularly controlled using pesticides. The resistance of hazelnut varieties to the nut weevil is known but poorly investigated so far. Thus a 2‐year study was carried out to investigate factors affecting C. nucum attacks on two cultivars [Tonda Gentile delle Langhe (TGL), Ennis] and four selections (Daria, 101, B6, L35) in a 15‐year‐old orchard of northwestern Italy. Nut developmental stages and shell characteristics, such as hardness and thickness, were measured and correlated to the biological cycle of the nut weevil and to the damage by its larvae. During the 2‐year sampling, nut weevil adults were collected on all cultivars and selections, but in greater quantities on TGL and Daria, and in lower quantities on 101 and B6. In 2005, by female dissection, mature eggs were observed from late June, when the mean temperature exceeded 18°C. Differences between cultivars and selections were found in nut and kernel development, and in shell hardening; in particular, the kernel development was directly related with the shell hardness. At harvest, the damage varied on average from 2.57% in cultivar TGL to 51.84% in selection 101 of total nuts harvested, so independently of the numbers of the collected weevil adults. These two varieties were the earliest and the latest in kernel development and shell hardening, respectively. Therefore, the susceptibility to nut weevil attacks was strictly related to shell hardening; in fact, a rapid hardening of the shell can hamper the oviposition of C. nucum females. By contrast, no correlation was found between shell thickness and damage at harvest.