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Abstract Background Winter moth (Operophtera brumata) and mottled umber moth (Erannis defoliaria) are forest Lepidoptera species characterized by periodic high abundance in a 7–11 year cycle. During outbreak years they cause severe defoliation in many forest stands in Europe. In order to better understand the spatio-temporal dynamics and elucidate possible influences of weather, stand and site conditions, a generalized additive mixed model was developed. The investigated data base was derived from glue band catch monitoring stands of both species in Central and North Germany. From the glue bands only female moth individuals are counted and a hazard code is calculated. The model can be employed to predict the exceedance of a warning threshold of this hazard code which indicates a potential severe defoliation of oak stands by winter moth and mottled umber in the coming spring. Results The developed model accounts for specific temporal structured effects for three large ecoregions and random effects at stand level. During variable selection the negative model effect of pest control and the positive model effects of mean daily minimum temperature in adult stage and precipitation in early pupal stage were identified. Conclusion The developed model can be used for short-term predictions of potential defoliation risk in Central and North Germany. These predictions are sensitive to weather conditions and the population dynamics. However, a future extension of the data base comprising further outbreak years would allow for deeper investigation of the temporal and regional patterns of the cyclic dynamics and their causal influences on abundance of winter moth and mottled umber.

Climate change may facilitate shifts in the ranges and the spread of insect pests, but a warming climate may also affect herbivorous insects adversely if it disrupts the locally adapted synchrony between the phenology of insects and that of their host plant. The ability of a pest species to colonize new areas depends on its ability to adjust the timing of phenological events in its life cycle, particularly at high latitudes where there is marked seasonality in temperature and day length. Here we incubated eggs of three species of geometrid moth, Epirrita autumnata, Operophtera brumata and Erannis defoliaria from different geographical populations (E. autumnata and O. brumata from Northern Finland, E. autumnata and E. defoliaria from Southern Finland and all three species from Germany) in a climate chamber at a constant temperature to determine the relative importance of geographic origin in the timing of egg hatch measured in terms of cumulative temperature sums (degree days above 5°C, DD5); i.e. the relative importance of local adaptation versus phenotypic plasticity in the timing of egg hatch. In all three species, eggs from northern populations required a significantly lower temperature sum for hatching than eggs from southern populations, but the differences between them in temperature sum requirements varied considerably among species, with the differences being largest for the earliest hatching and northernmost species, E. autumnata, and smallest for the southern, late-hatching E. defoliaria. In addition, the difference in hatch timing between the E. autumnata eggs from Southern Finland and Germany was many times greater than the difference between the two Finnish populations of E. autumnata, despite the fact that the geographical distances between these populations is similar. We discuss how these differences in hatching time may be explained by the differences in hatch-budburst synchrony and its importance for different moth species and populations. We also briefly reflect on the significance of photoperiod, which is not affected by climate change. It is a controller that works parallel or in addition to temperature sum both for egg hatch in moths and bud burst of their host plants.

Erannis defoliaria, a spring-feeding moth, caused severe defoliation during springs 2009 and 2010. Larvae were collected from Quercus suber in northwestern forest of Tunisia: Bellif and Ain El Baya. Caterpillars of E. defoliaria were also observed feeding on Q. canariensis, Q. afares and other shrub species such as Pistacia lentiscus, Erica arborea, and E. multiflora. In this paper, we present a first report of this pest in Tunisia.

1. Winter temperatures in northern latitudes are predicted to increase markedly as a result of ongoing climate change, thus making the invasion of new insect defoliators possible. The establishment of new outbreak pest species may have major effects on northern ecosystems that are particularly sensitive to disturbances. 2. Effects of winter minimum temperatures under field and laboratory conditions were examined and limitations by minimum temperatures on future range expansion were investigated for invasive [ Operophtera brumata (Lepidoptera: Geometridae)] and potentially invasive [ Agriopis aurantiaria (Lepidoptera: Geometridae)] birch-feeding forest pests. The results for the studied invasive and potentially invasive moths were compared with the parameters of the resident moth species Epirrita autumnata (Lepidoptera: Geometridae). 3. The results showed tolerated critical temperatures of the invader ( O. brumata) and the resident ( E. autumnata) were more similar (differing only by 1 °C), whereas the potential invader ( A. aurantiaria) was much less tolerant of cold temperatures. Although describing different stages of overwintering, results were consistent between laboratory and field studies except for those at one field location, at which other abiotic conditions are suggested to have significant influence on moth egg survival. 4. Based on the present results and expected changes in winter temperatures over the next 30 years, the range expansion of an established invasive species may be predicted. No limitations were found regarding the possible future invasion of a new pest species to northern Fennoscandia. The importance of studying a species' whole overwintering period is highlighted and further studies devoted to the effects of other abiotic factors in addition to the effects of temperature are suggested. [ABSTRACT FROM AUTHOR]

1. Defoliation of oak trees and seedlings (Quercus petraea and Q. robur × Q. petraea putative hybrids) by various lepidopteran species was investigated in two upland semi-natural oakwoods (Dinnet and Ariundle National Nature Reserves) within contrasting climatic zones in the Scottish Highlands. 2. Experiments were designed to test four hypotheses: (i) the failure of oak to regenerate naturally is partly attributable to defoliation of seedlings by insects. (ii) seedling defoliation is linked to canopy density and composition: (iii) the degree of seedling defoliation is linked to the extent of canopy defoliation: and (iv) defoliation is positively correlated with insect population density in the canopy. 3. The extent of canopy defoliation of oak was significantly different between the two woods with trees at Ariundle, located within a wetter climatic zone, more defoliated than those at Dinnet which is in a drier climatic zone. Defoliation also varied significantly between individual trees and between years. 4. Defoliation was positively correlated with degree of infestation by the larvae of several lepidopteran species. Leaf samples at Dinnet were dominated by Operophtera brumata, and those at Ariundle by Erranis, defoliaria. The degree of infestation was higher at Ariundle. 5. Experimental seedlings were significantly more defoliated under oak canopy than in the open or under a Betula spp. canopy. Canopy defoliation was positively correlated with defoliation of seedlings growing directly beneath, but seedling defoliation was negatively correlated with oak canopy density. 6. Defoliation of oak seedlings by insects poses more of a threat to the natural regeneration of oak at Ariundle than at Dinnet possibly due to climatic differences between these two woods. 7. A group-felling system using coupe sizes of over 0.5 ha is recommended for encouraging oak regeneration in woods such as Ariundle. where seedlings need to be kept free from the influence of an overhead oak canopy. Shelterwood systems, where seed trees are retained after extensive thinning are not recommended. In woods similar to Dinnet both group-fell and shelterwood systems are appropriate management options. 8. Woodland managers should be aware of defoliation problems within their woods before deciding on which silvicultural option to choose. [ABSTRACT FROM AUTHOR]

Background: Winter moth (Operophtera brumata) and mottled umber moth (Erannis defoliaria) are forest Lepidoptera species characterized by periodic high abundance in a 7-11 year cycle. During outbreak years they cause severe defoliation in many forest stands in Europe. In order to better understand the spatio-temporal dynamics and elucidate possible influences of weather, stand and site conditions, a generalized additive mixed model was developed. The investigated data base was derived from glue band catch monitoring stands of both species in Central and North Germany. From the glue bands only female moth individuals are counted and a hazard code is calculated. The model can be employed to predict the exceedance of a warning threshold of this hazard code which indicates a potential severe defoliation of oak stands by winter moth and mottled umber in the coming spring.Results: The developed model accounts for specific temporal structured effects for three large ecoregions and random effects at stand level. During variable selection the negative model effect of pest control and the positive model effects of mean daily minimum temperature in adult stage and precipitation in early pupal stage were identified.Conclusion: The developed model can be used for short-term predictions of potential defoliation risk in Central and North Germany. These predictions are sensitive to weather conditions and the population dynamics. However, a future extension of the data base comprising further outbreak years would allow for deeper investigation of the temporal and regional patterns of the cyclic dynamics and their causal influences on abundance of winter moth and mottled umber. [ABSTRACT FROM AUTHOR]