Abstract: Ips typographus is one of the major forest pests in the Italian Alps. From ... Key words: Ips typographus, damage forecast, Italy, monitoring, spruce, traps.
JEN 128(4) doi: 10.1111/j.1439-0418.2004.00848.307–311 Ó 2004 Blackwell Verlag, Berlin
Ips typographus (L.) pheromone trapping in south Alps: spring catches determine damage thresholds M. Faccoli1 and F. Stergulc2 1 Department of Environmental Agronomy and Crop Production, University of Padua, Padua, Italy; 2 1 Department of Plant Protection, University of Udine, Udine, Italy 2 Ms. received: September 16, 2003; accepted: February 11, 2004
Abstract: Ips typographus is one of the major forest pests in the Italian Alps. From 1996, populations of I. typographus in Friuli-Venezia Giulia region (NE Italy) have been permanently monitored in areas of outbreak by using pheromone traps. At the same time, damage caused by the insect was estimated annually. Preliminary analysis of the data (1996– 2002) reveals some interesting information: (i) the flight activity of I. typographus is very extended and occurs over a period of about 4 months (May to August); (ii) there is a high correlation between mean captures per trap and annual damage; (iii) there is a high correlation between spring captures (May to mid-June) and total captures (May to August), and between spring captures (May to mid-June) and annual damage. The correlation between spring captures and damage allows the determination of a reliable risk-damage threshold (about 5000 beetles/trap, in spring), reducing at the same time, the monitoring period and the general costs.
Key words: Ips typographus, damage forecast, Italy, monitoring, spruce, traps
1 Introduction The spruce bark beetle Ips typographus (L.) (Col., Scolytidae) is the most destructive scolytid attacking spruce forests (Picea abies Karsten) in Palaearctic regions (Christiansen and Bakke, 1988). In the last decades the beetle has also caused great damage to Italian spruce stands in southern Alps (Ambrosi and Angheben, 1986; Lozzia, 1993; Faccoli, 1999; Frigimelica et al., 2000; Stergulc et al., 2000). Following the identification of the pheromone for I. typographus (Bakke et al., 1977), the extensive use of traps and trap trees baited with synthetic pheromone replaced the traditional control strategies usually applied to reduce the risk of outbreaks. Traps can be set up for ÔmasstrappingÕ to catch as many flying beetles as possible (Raty et al., 1995), and to have information about beetle biology and density (Bakke, 1985). Pheromone traps could be a useful tool for monitoring I. typographus populations and for assessing the risk of tree attacks (Lindelow and Schroeder, 2001). Specifically, the relationship between the mean number of insects per trap and the damage observed in the stands allows the determination of a capture threshold, which indicates when the population density of the pest is high enough to cause serious damage (Weslien, 1992). When the capture threshold is overcome, the risk of damage is high and intensive control strategies have to be applied. Most studies that involve monitoring of populations of I. typographus have been carried out in northern Europe, where the winters are long and cold and flight
activity begins quite late in the season (June–July) (Annila, 1969; Anderbrant, 1985). Therefore, the short summer allows completion of only one generation per year (Annila, 1969) and damage to spruce stands is not always severe, as the trees are subject to only one attempt of bark colonization and vigorous spruces can survive (Krokene et al., 1999). Nevertheless, re-emerging parents are able to establish a second brood, which can account for up to 29% of the killed trees (Anderbrant, 1989). On the contrary, in southern and central European countries I. typographus attacks host trees early in spring (end of April), when the mean air temperature reaches 18°C (Ambrosi and Angheben, 1986). In this period, overwintering adults (P) emerge and look for a suitable host for the first generation. Then, at the beginning of July at low altitude (usually
