The Panel on Plant health performed a pest categorisation of the larch web‐spinning sawfly Cephalcia lariciphila (Hymenoptera: Pamphiliidae) for the EU. The insect has been reported in 11 EU Member ...States (MSs). It is a quarantine pest listed in Annex IIB of Council Directive 2000/29/EC. Protected zones are in place in Ireland and the UK (Northern Ireland, Isle of Man and Jersey). C. lariciphila can feed on all species of the genus Larix. There have been reported outbreaks in the Czech Republic, Germany, the Netherlands and the UK (England and Wales) in plantations of European larch (Larix decidua) and Japanese larch (Larix kaempferi = Larix leptolepis). C. lariciphila is absent in the protected zones. The pest can enter the protected zones by human‐assisted spread or by natural spread from EU areas where the pest is present. Plants for planting are considered the most important pathway for the pest. The pest can establish in the protected zones because the climatic conditions are similar to those of the 11 MSs where C. lariciphila is established, and the pest's main host plants are present. The prepupae overwinter in the litter, the adults emerge during May–June, and each female lays 30–40 eggs in slits in mature needles. The larvae feed on the needles through four instars. There is one generation per year; some of the prepupae undergo prolonged diapause for more than 1 year. The impact where the pest occurs is mainly related to the loss of tree growth following defoliation, while tree mortality was locally observed only after repeated defoliation. However, impact is likely to be mitigated by local biological control agents. All criteria assessed by EFSA above for consideration as a potential protected zone quarantine pest and as a potential regulated non‐quarantine pest were met.
The cedar web-spinning sawfly, Cephalcia tannourinensis (Hymenoptera: Pamphiliidae) is considered a major defoliator of the cedar forests in Lebanon. In the early 1990's, a severe damage of the ...Tannourine Hadath El-Jebbeh cedar forest was caused by the sudden outbreak of this insect. The insect has a complex life cycle with two types of diapause: annual diapause and multiple years diapause. The present study aimed at studying soil characteristics and their influence on the survival and diapausing cycles of C. tannourinensis prepupae. Different soil samples collected from three different cedars forests in Lebanon were incubated with prepupae of C. tannourinensis under laboratory conditions. The effect of soil origins and properties on prepupal mortality, annual diapause and multiple years diapause cycles were analyzed. The influence of soil moisture and soil temperature on prepupal development was studied separately through two constant temperatures and three constant soil moisture levels. Prepupal mortality was found to be highly correlated with soil properties and types. Prepupae survived well in soil coming from Tannourine and Bcharry followed by Chouf. However mortality was almost 100% in the two reference soils sand and peat. Diapause cycle was strongly correlated with temperature, while the effect of moisture was mainly on the prepupal survival.
Larvae of the cedar web-spinning sawfly, Cephalcia tannourinensis Chevin (Hymenoptera: Pamphiliidae), infected with a white fungus were collected from the Tannourine-Hadath El-Jebbeh cedar forest. ...Macro- and micro-morphological data based on the examination of colonies, conidiophores, and conidial shape of the fungus suggested a Beauveria species. Sequence analysis of the internal transcribed spacer regions of the isolated fungus showed that it is most closely related to isolates of B. bassiana Clade C. The present study showed that the isolated B. bassiana is a naturally occurring entomopathogenic fungus parasitizing the larvae of C. tannourinensis in Lebanon. Laboratory bioassays showed that B. bassiana caused high mortality of eggs and larvae. The infected eggs turned brownish in color, while larvae of the first instar ceased feeding and showed immobility and rigidity within 5 days and before sporulating conidial mat appeared on their cuticle. Second and third larval instars took longer time to show fungal sporulation: mortalities ranged between 85 and 100% within 7 days when treated with different conidial concentrations. The efficacy of control of C. tannourinensis using B. bassiana was higher or equal to the reference insect growth regulator, diflubenzuron, suggesting the possibility of its success as a biological control agent.
Adults of Cephalcia lariciphila emerge and start their activity at Vetrny Jenikov village (Czech Republic) during mid-April. First specimens were collected from Malaise traps at the same time as from ...emergence traps. Last specimens flew at the beginning of May or even the beginning of June. Adult occurrence typically lasted about 20 (-30) days. One Malaise trap and five yellow sticky boards were placed on three plots, and sawflies were collected at 1 hour intervals in two two-day periods. The variables with the best explanatory power for activity of imagos were temperature in interaction with humidity. Sawflies were most active at 16°C with 20% air humidity and numbers caught decreased steeply up to 0°C and 80% air humidity. The daily flight activity began at 10 a.m. and ended after 5 p.m. Both methods, the Malaise traps and the yellow sticky boards, should be used in forest practices from the middle of April.
The web-spinning sawfly
Cephalcia arvensis is a defoliator of the Norway spruce (
Picea abies) in Northern Eurasia. Four outbreaks have been recorded in the last 15 years in Czech Republic and in ...Italy. A comparative analysis of the involved populations revealed noticeable differences in phenology, leading to a strong variation in life cycle and voltinism. A population already known as `spring form' for the early emergence of adults, and morphologically distinguishable at the prepupal stage, has been found to be genetically different from populations emerging later, as far as allozymes and chromosomes are concerned. The high biological and genetic variability observed among populations of
C. arvensis allows these sawflies to become adapted to a wide range of local conditions, contributing in this way to the differentiation of local races and species. In spite of this variability, all the outbreaks occurred in Norway spruce plantations characterized by about the same silvicultural parameters (50-to-100-year-old, high density and medium to high quality), located outside or on the border of the natural range of the host plant, and thus undergoing various environmental stresses. As the silvicultural conditions of the stressed stands may determine the risk of outbreak, the integration of cultural methods (selection of planting areas and of regeneration material, selective cutting of mature stands to increase diversity) in pest management seems to be very important. The management of the pest would also benefit from extending monitoring to cover all the phenological variants, because an early detection of the outbreak is essential for a successful application of the biocontrol techniques presently available.
The web‐spinning sawflies of the genus Cephalcia Panzer (Hymenoptera, Pamphiliidae) are usually monitored by sampling prepupae in soil and by catching adults with visual traps, including yellow ...sticky traps. However, adult catches have never been compared with the actual density of prepupae. In this paper, a relationship is presented between the catches of Cephalcia arvensis Panzer adults (mostly males) and the number of prepupae ready to emerge (pronymphs) in an outbreak area of spruce forest (Picea abies Karsten) in the Southern Alps (Asiago, Italy). A significant linear relationship between the logarithmic estimates of the two variables was found. The model includes a spatial autoregressive parameter because adult catches were spatially correlated. The relationship allows to know whether or not the defoliation threshold of 20 pronymphs/m2 in spring samples is being exceeded, based on the number of adults caught on yellow sticky traps (defoliation threshold of 14.26 adults/trap). The variance not explained by the model is probably due to the flight behaviour of adult males, to the low precision of the estimated pronymph density at low population levels, and to the attraction of males by few females that are trapped and remain alive. The model was validated in a large monitoring programme of undamaged alpine spruce forests and allowed detection of two newly infested stands out of six that were considered at risk of defoliation, because of adult catch exceeded the threshold. Low adult catches were always associated with absence of defoliation. Our conclusion is that trapping of adult sawflies is a cheaper and easier monitoring method than prepupae sampling in the soil. This makes earlier detection of outbreaks possible, and consequently more efficient control.
The paper describes the population dynamics of the spruce false webworm Cephalcia abietis L. in an 80-year-old spruce stand in the forest area of Erolzheim near Ulm (Germany) between 1986 and 1996. ...Emerging sawflies and adult parasitoids were trapped in groundphotoeclectors and the descending host larvae in funnel-traps. About 7000 host larvae and prepupae were dissected to evaluate the degree of parasitism. The emergence pattern of the sawfly was determined as well as the duration of the feeding period. The development of the majority of the sawfly individuals lasted 3 years; during the warm summer of 1994 univoltinism was observed in 36% of the population. Temperature was ascertained as the key factor for the variable duration of the dormancy and for the population dynamics of the forest pest. Since 1986, the year of heavy feeding, the density of emerging females, of descending larvae, and of prepupa in the soil decreased finally to a subepidemic level in 1996. The sex ratio (SI) of different host stages averaged from 0.37 to 0.54. In the yellow prepupae - amounting to 11% of the total population - males were predominating (SI=0.16). The annual average number of full-grown and developing eggs per female varied between 21 and 53, the total number of all oocytes between 46 and 112 (average 79). The complex of parasitoids of Cephalcia abietis consists of the egg parasitoid Trichogramma cephalciae, nine primary larval parasitoids (eight ichneumonids, one tachinid), and the hyperparasitoid Mesochorus nov. sp. Within 5 years the average of the total (effective) parasitism of descending larvae amounted to 74%, of prepupae in October to 45%, and of emerging adults to 40%. The possible reasons for the discrepancies are discussed, taking into account the effects of a single parasitoid species.
The first outbreaks of three species of larch web-spinning sawflies (
Cephalcia lariciphila japonica Shinohara,
Cephalcia koebelei (Rohwer) and
Acantholyda nipponica Yano and Sato (Hymenoptera: ...Pamphiliidae) that occurred in 1993 in non-native larch (
Larix leptolepis Gordon) plantations in Hokkaido, northern Japan, were examined in two distinct areas 500
km apart. We also examined annual changes in prepupal densities in the soil in seven larch stands chosen across a defoliated region in central Hokkaido. The influence of stand structure on sawfly density were examined in 30 larch stands. Defoliation by
C. lariciphila, which took place in eastern Hokkaido, were restricted to a small area for 4 years, then increased rapidly from 1997 and reached 15,000
ha in 2000. Defoliation in central Hokkaido, which was caused by
C. koebelei and
A. nipponica, increased to 2600
ha in the next year after initiation of the outbreak, continued at this level for 4 years and diminished in 1999. In central and eastern Hokkaido, outbreaks were preceded by three consecutive years of high yearly average temperature, which occurred 2–4 years before the outbreaks. However, yearly precipitation did not change noticeably prior to the outbreaks. Annual changes in prepupal densities in central Hokkaido revealed that the density peaked earlier near the stands where the outbreak was first observed and peaked later in peripheral areas. This suggests that the outbreaks began in local epicenters and expanded to surrounding areas. Neither larch density (trees/area), tree size (height and diameter at breast height (DBH)) nor proportion of larch stems correlate with the prepupal densities although these factors varied considerably. Thus, after canopy closure, sawfly density does not seem to be influenced by the stand factors.
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