Mass outbreak prognosis of the most significant pests to Latvia up to 2020.
Reasons of insect mass outbreaks are crucial to understand right forestry options (Allard et al., 2003; Barbosa et al., 2012). There are almost countless factors affecting propagations of denrophagous pests - such as inner concurrence, dynamics of natural enemies, host plant quality and availability, etc. Lot of those still remains unknown (Allard et al., 2003; Roques et al., 2006; Barbosa et al., 2012). This review study serves as summary of 25 aggressive dendrophagous pests (Lymantria dispar, Lymantria monacha, Ips typographus, Ips acuminatus, Hylobius abietis, Bupalus piniarius, Neodiprion sertifer, Phymatodes testaceus, Scolytus ratzeburgi, Euproctis chrysorrhoea, Aradus cinnamomeus, Xyleborus dispar, Cryphalus piceae, Archips crataegana, Melasoma populi, Phalera bucephala, Diprion pini, Rhyacionia buoliana, Saperda carcharias, Panolis flammea, Melolontha melolontha, Dendrolimus pini, Pityogenes chalcographus, Tomicus piniperda, Tomicus minor) outbreak history in West and Central Europe with aim to modeling and determine differences in outbreak trends in future. To set predictions we reviewed outbreaks from 1950 to 2013 years. Information was collected from EFI(European Forest Institute), GISD (Global Invasive Species Database), EPPO (European and Mediterranean Plant Protection Organization), FED (Fauna Europaea Database) and scientific publications to make outbreak prognoses. Historical data have been analyzed by generalized additive model (GAM) in R program by use of "Rmgcf " package to derive outbreak projections till 2020. As at beginning diagnostics of model residuals showed high autocorrelation values between time series, models appended with autocorrelation structure. GAM analysis were applied to time series of outbreak area volumes and total outbreak number per year by using Poisson distribution and a log link. It was concluded that, volume of pest outbreak territories will increasing in the course of time. Rapid projected the increase of outbreak area observed in 8 selected pest species. Although outbreak activity of 3 reviewed coniferous pest species will decrease in course of time. In addition, more than half of reviewed species show clear outbreak tendencies in future.