The research objective was to develop pheromone‐based monitoring of the nun moth, Lymantria monacha (L.), an important defoliator of spruce and pine forests in central Europe. In 38 spruce or pine forests in central Europe, captures of male L. monacha in nonsaturating Unitraps and saturating Delta sticky traps baited with 0.2, 2, 20, or 200 μg of the L. monacha (pheromone) volatile blend [(±)‐disparlure, (±)‐monachalure, and 2‐methyl‐Z7‐octadecene at a 20 : 20 : 1 ratio] were compared with estimates of population densities obtained by counts of larval faecal pellets, pupal cases, and adult moths resting on tree trunks. Total captures of male L. monacha throughout the flight season in both types of trap were correlated with numbers of larval faecal pellets, irrespective of pheromone dose. Nonsaturating Unitraps baited with 2 μg of the L. monacha volatile blend seem to provide a cost‐effective tool for monitoring densities of L. monacha populations. Long‐term testing of this monitoring system has been initiated to substantiate the quantitative relationship between larval populations and trap captures of male L. monacha and to determine the threshold number of captured male moths that indicates an incipient outbreak.

Abstract:The biology and population dynamics of pine sawfly Diprion pini L. are extremely complex and variable. Among other factors, climatic conditions determine the potential for mass outbreaks of the species. In this paper, we investigate this influence and describe a statistical approach to identify responsible climatic variables in floating time windows, thus identifying the factors responsible for the transition from latency to outbreak events. Analyses were built upon a data base comprising outbreak events and fine-scaled climatic data for the period 2002-2016 for a model region in the state of Brandenburg, Germany. By applying Random Forest statistic classification analyses, we isolated a set of four variables. They cover precipitation, temperature, and potential evapotranspiration in distinct periods during the current and the previous year. These periods are not fixed in their position but attached to the floating phenological date of bud burst of the host species Pinus sylvestris L. The complete set of variables was able to distinguish forests likely to be defoliated from those not threatened at high probabilities (95% true-positive rate, 98% true-negative rate). The identified climatic windows offer insights into population dynamics in the study region, support adjustments in current monitoring algorithms, and indicate starting points for further investigations covering other regions or different years.

Climate change challenges forest vitality both directly by increasing drought and heat periods and indirectly, e.g., by creating favorable conditions for mass outbreaks of phyllophagous insects. The large forests dominated by Scots pine (Pinus sylvestris L.) that cover the lowland regions in northeast Germany have already been affected regularly by cyclic mass propagations of defoliating insect species in the past with climate projections implying an even more advantageous environment for devastating outbreaks in the future. To improve predictive and responsive capacities we have investigated a wide range of ecological parameters to identify those most strongly related to past outbreak waves of three central species. In total, we analyzed 3,748 variables covering stand and neighborhood properties, site quality, and climatic conditions for an area of roughly 750,000 ha of pine forests in the period 2002–2016. To reflect sensitivity against varying climate, we computed “floating windows” in relation to critical phenological phases of the respective insects. The parameters with the highest explanatory power resulted from the variable importance measures of the Random Forest (RF) methodology and have been evaluated by a 10-fold cross-validation process. Our findings closely reflect the known specific gradation patterns and show that relative variable importance varies with species. While Lymantria monacha L. feeding was mainly dependent on the surroundings of the respective stand, Diprion pini L. proved to be almost exclusively susceptible to climatic effects in its population dynamics. Dendrolimus pini L. exhibited a mixed pattern of variable importance involving both climatic and forest structure parameters. In many cases the obtained statistical results support well-known ecological cause-effect relations and long-term population change dynamics. The RF delivered very high levels of sensitivity and specificity in the developed classifications and proved to be an excellent tool to handle the large amounts of data utilized for this study. While the presented classification approach may already support a better prognosis of the amplitude during the outbreak culmination, the obtained (most important) variables are proposed as preferable covariates for modeling population dynamics of the investigated insect species.

The research objective of this study was to develop a pheromone-based detection system for the nun moth, Lymantria monacha (Linnaeus), an important defoliator of spruce, Picea A. Dietrich, and pine, Pinus Linnaeus (Pinaceae), forests in central Europe. In northeastern Germany, comparative analyses of rubber- and polyurethane-based dispensers impregnated with a 20:20:1 blend of (±)-disparlure (cis-7,8-epoxy-2-methyloctadecane), (±)-monachalure (cis-7,8-epoxy-octadecane), and 2-methyl-Z7-octadecene revealed that polyurethane-based dispensers afforded higher captures of male L. monacha. Species specificity and optimal dose of the pheromone dispenser were tested in deciduous rather than coniferous forests in central Europe to better reflect nonhabitat settings, such as North American ports, in which detection surveys would be conducted. Baiting Unitraps with 2, 20, 200, or 2000 μg [based on (±)-disparlure] of the L. monacha volatile blend resulted in increasing, species-specific captures of male L. monacha with increasing volatile dose. (±)-Disparlure, previously used for detection of L. monacha, tested at the same four doses indiscriminately attracted male L. monacha and male Lymantria dispar (Linnaeus). Polyurethane-based dispensers loaded with at least 200 μg of the L. monacha volatile blend are recommended for sensitive detection surveys of L. monacha in North America.

The influence of SO2‐stressed host plants on the development of Bupalus piniarius L. (Lep., Geometridae) and Dendrolimus pini L. (Lep., Lasiocampidae) The influence of a SO2‐conditioned food quality alteration on the successful development of the pine needle pests pine looper (Bupalus piniarius L.) and pine spinner (Dendrolimus pini L.) was investigated under labor conditions from 1989 to 1991. After a 400‐hr sulphur dioxid application (960 μg/m3) the needles of four‐year‐old pines (Pinus sylvestris L.) show besides an increased sulphur and decreased calcium content significant higher concentrations of free aminoacids especially prolin. The concentrations of glucose and fructose are extremely reduced. Likewise the shape of procyanidins in the needles is diminished by about 24 %. The two species of lepidopters show a different sensitivity to the contaminated food. Larvae of B. piniarius, who were fed with SO2‐damaged needles, show a delay of larval development together with a diminished biomass rate increase and an increase of mortality. The deterioration of the development success of B. piniarius is attributed above all to the lower carbohydrate concentrations in the needles as well as to the nutrient imbalances. In contrast to this result the rate of biomass increase and the mortality of D. pini is insignificantly reduced. The pine spinner can tolerate the low sugar content of food. That's why the comparatively higher success of development is connected especially with a stress‐induced reduction of phenolic needle components. Zusammenfassung Der Einfluß einer schwefeldioxidbedingten Änderung der Nahrungsqualität auf den Entwicklungserfolg der Kiefernnadelschädlinge Bupalus piniarius und Dendrolimus pini wurde in den Jahren 1989 bis 1991 unter Laborbedingungen untersucht. Nach einer 400stündigen Begasung mit Schwefeldioxid (960 μg/m3) wiesen die Nadeln der vierjährigen Kiefern (Pinus sylvestris) neben erhöhten Schwefel‐ und reduzierten Kalziumgehalten signifikant höhere Konzentrationen an freien Aminosäuren, insbesondere Prolin, auf. Die Glukoseund Fruktosekonzentrationen waren drastisch vermindert. Ebenso war der Anteil der Procyanidine in den Nadeln um durchschnittlich 24 % reduziert. Die beiden Lepidopterenarten ließen eine unterschiedliche Sensitivität gegenüber der schadstoffbe‐einflußten Nahrung erkennen. Larven von B. piniarius, die mit SO2‐geschädigten Nadeln ernährt wurden, zeigten eine Verzögerung in der Larvalentwicklung, die von verminderten Biomassezuwachsraten und einer Zunahme der Mortalität begleitet wurde. Die Verschlechterung des Entwicklungserfolges des Kiefernspanners wird vor allem auf die geringeren Kohlenhydratkonzentrationen in den Nadeln sowie auf Nährstoffimbalancen zurückgeführt. Im Gegensatz dazu war die Biomassezuwachsrate und auch die Mortalität von D. pini geringfügig vermindert. Da der Kiefernspinner den niedrigeren Zuckergehalt der Nahrung besser zu tolerieren vermag, steht der vergleichsweise günstigere Entwicklungserfolg insbesondere mit einer streßbedingten Verminderun...