# Current Problems of Forest Protection (25-27 October 2022, Katowice Poland)
## 11 **Intermediate-Term Forecasting Nun Meth Outbreaks**
The body length of 80 randomly selected males and females was measured from each forest district. In 2020, in the Kolumina forest district, the culmination of the flight of females occurred between 8-12 April, and a year later on 20 April. In 2020, in the Lubliniec forest district, the culmination of the flight of females occurred on 20 April, and a year later on 24 April. In 2020, in the Przedborow forest district, the culmination of the flight of females occurred on 18 April, and a year later on 22 April. In all forest districts, the temperature had a noticeable effect on the number of males and females in the initial period, up to flight culmination. Compared to 2020, a later appearance of the _Acantholyda posticalis_ and a clearly shorter period of activity, as well as the subsequent culmination of the flight, were observed. In order to check whether the air temperature in both years could have had an impact on the flight dynamics, the significance of the differences during the period from 20 March to 30 April was checked. In the Kolumina and Lublinice forest districts, the temperatures in 2021 were lower than the temperatures recorded in 2020, and these differences turned out to be statistically significant. In the Przedborow forest district, these differences were insignificant. Research on the influence of tree location in the stand on the number of _Acantholyda posticalis_ showed no statistically significant differences. The location of the tree with the trap did not significantly affect the accuracy of the monitoring. In the Lubliniec forest district, males and females were significantly smaller than in other forest districts. **Keywords:**_Acantholyda posticalis_; flight dynamics; air temperature; monitoring  
**Amount and Dynamics of the Foliage Consumption Caused by Great Web-Spinning Sawfly _Acantholyda posticalis_ (Mats.) Marek Slawski and Malgorzata Slawska  
Warsaw University of Life Sciences, Warsaw, Poland  
\({}^{\star}\) Correspondence: marek_slawski@sggw.edu.pl  
**Abstract:** Under field conditions, measurement of the amount of foliage eaten by primary pests faces some methodological difficulties. In forestry practice, it is often limited to estimation of the foliage loss as a percentage compared to healthy stands. The research presented is an attempt to determine the magnitude of needle consumption caused by the_Acantolyda posticalis_ based on the weight of frass drop on the forest floor. The weight of collected feces was converted to consumption based on a laboratory-determined factor. The conversion factor was determined based on the rearing of larvae fed with a known weight of needles and measurement of the excrements produced. The average conversion factor was 1.32 (\(\pm\)0.02), which means that 1 g of mass represents 1.32 g of needles eaten. Additionally, the correction factor for the loss of fecal weight due to leaching by precipitation was determined to be 1.23. Frass traps were placed in four outbreak and four control stands, with six traps in each stand. The traps were emptied every week during the feeding activity of _A. posticalis_, i.e., from the beginning of May to the end of July in 2021 and 2022. The frass was sorted, dried and weighed, and then consumption was calculated. The average level of needle consumption in the outbreak stands reached 745 kg/ha, while in the control plots it was 70 kg/ha. Consumption in 2021 was twofold greater than in 2022, with 678 kg/ha and 304 kg/ha needles eaten, respectively. The highest consumption in both years studied was measured in the two first weeks of June in both years. The studies allowed us to find differences between the consumption levels of the studied stands. The highest level of consumption in the outbreak stands amounted to 1300 kg/ha, while the lowest was 500 kg/ha. In the control stands, the highest consumption amount was about 100 kg/ha and the lowest was 50 kg/ha. The method used was relatively simple and allowed us to objectively estimate pest consumption in the canopy of pine stands.