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Bark beetle-related pine mortality in Israeli planted forests and the effect of trap trees

Authors:
  • Agricultural Research Organization - ARO

Abstract

The association of extensive mortality of pine trees and bark beetle (Scolytinae) attack is a common phenomenon in the Northern Hemisphere. Bark beetle outbreaks frequently occur in the planted pine forests in Israel and involve three species Orthotomicus erosus, Pityogenes calcaratus and Tomicus destruens. These bark beetle species undergo periods of low population density when they breed on trees stressed by drought or thinning, and on broken trees or those uprooted by wind or thinning slash. It has been suggested that high populations of these scolytids often kill trees. Assessing whether successful colonization of standing pine trees by these species is the result of direct beetle attack or a symptom of poor tree physiology is a challenge and makes it difficult to determine the required management strategy. The role of bark beetles in tree death in a wide study area was assessed by two experimental systems: (1) a study of the potential effect of drought in a layout of extensive trap trees in stands of Pinus halepensis and P. brutia, (2) examining bark beetles colonization in killed pine trees in two planted stands of P brutia. In the first experimental system, trap-trees (baited with lures attractive to both O. erosus and P calcaratus and treated with Bifenthrin) significantly reduced the number of dead trees in the trap-tree treated stands compared with similar untreated ones. O. erosus was the dominant species in these plots and tree mortality occurred in the second half of the summer (August and September). The second experimental system indicated mainly the association of P calcaratus and T destruens with the killed trees. However, in that system, the colonization was apparently mainly during autumn to early winter (October and November) and we were unable to determine the direct role of the beetles in the tree mortality. The results provided evidence that these pine bark beetles, which are usually considered secondary, are responsible for the tree death, O. erosus in particular. Both P calcaratus and T destruens are relatively more active during the low temperature periods, typical of the autumn in Israel. We suggest that the consequence of water scarcity and high temperatures due to climate change during the autumn make the pine trees more prone to beetle attack during their typical activity period. Forest (Yaar), 22/7. 71-81.
71
         
תתומתב הפילק תוישופיח לש תוברועמה
לארשיב עוטנה רעיב ןרוא יצע
4 לדנמ יבצ | 4 בוסטורפ סכלא | 1 ןורלא רואמ | 3 ,2 סאיטא םתר | 1 ןלוג רמוע
* 2 ץרוש-דוד תפקר
" ,  1
 –   ,   2
 ,   ,  ,  3
 –   ,   4
rakefetd@agri.gov.il *
ריצקת
  ,   ,  
   Scolytinae  
 .      
Orthotomicus
    
.Tomicus destruens
-
Pityogenes calcaratus
,erosus
       
      ,
 .       
        ,
     ,   
     .   
     . 
     
     ,   
   .    
       
.      
     
      
O. erosus
-     .
 ,      
       
     . 
   ,      
   .
T. destruens
-
P. calcaratus
  ,
O. erosus
 ,   
     ,   
      
    ,  .  
       
P. calcarartu
s      
.  ,   ,
T. destruens
-
 ,      
  ,    
  ,    
   ,    
.       
חתפמ תולימ
תדוכלמ יצע ,םילשורי ןרוא ,היטורב ןרוא
2022 ילוי | 22 ןויליג | רעי
72

Coleoptera:   - 
    Curculionidae, Scolytinae
       
      . 
    ,  
 Lieutier et al., 2016    
1,000    .    
        
    ,
      .
Orthotomicus erosus, Pityogenes
   
    ,
Tomicus destruens
-
calcaratus
 15-   .   
-      
Halperin     , 
Dendroctonus
  .and Holzschuh, 1984
      
 ,Lieutier et al., 2016; Seybold et al., 2016
      ,  
Mendel et al.,     
        ,1992
      
. 
 
O. erosus
   
      
     .Balachowsky, 1949
 2004- Geertsema, 19791968- 
      .Seybold et al., 2016
        . 
,
Pinus halepensis
  :  
 
P. brutia
ssp.
brutia
 
." 3.52.5-    .
P. pinaster
  
O. erosus
  
,       ,
 ,      
Carle, 1975; Mendel et al., 1985;  
 .Özkazanç et al., 1985; Ghaioule et al., 1998
      
36°C      
O. erosus
 .Mendel and Halperin, 1982
      ,  
      , 
    .1    
 ,     
     
    .(Carle, 1975; Seybold et al., 2016)
  ,   
O. erosus
     ,  
Mendel et al.,       ,
.1985; Mendel et al., 2016
 ,      
P. calcaratus

O. erosus
-      
       ,
     .Mazur et al., 2020  
      ,  
  ,  ,    
  .
P. canariensis
 
P. pinea
    ." 2.6–2.0 
      , 
 6–4  ,  
P. calcaratus
.
," 3.51.0      
.1       
       
 ,        ,
       
.Mendel et al., 2016 
  ,   
T. destruens

.Faccoli, 2007     , 
        
     ,    
       . 
 .Lieutier et al., 2016     
,       
       
Branco et al., 2010; Lieutier   
 ,  ,   .et al., 2016
–     
    .Halperin, 1978
  ,   ,  ,
    .   

T. destruens
   , 
       
   ,  . 
    .   
." 4.84.0
 ,Hylesinini    
T. destruens
    ,   
     ,  .
      
73
         
O. erosus
  Ipini   
 ,    .
P. calcaratus
-
   
T. destruens
 
    ,    
.Davi et al., 2020    

P. calcaratus
-
O. erosus
  
,     
 
T. destruens
 
      
.Lieutier et al., 2016  
       

T. destruens
;    
   ,    
.1       
 ,    
O. erosus
,    
P. calcaratus
, .    
      
,   
O. erosus ,P. calcaratus
T.
        
O. erosus
     .
destruens

P. calcaratus
     
.   
       
      .  
,       
,Leptographium
-
Ophiostoma
 
Kirisits, 2004; Dori-Bachash    
      .et al., 2015
  .       
        
1 
          
;
Orthotomicus erosus
. .Mendel et al., 1985; Mendel, 2000            
.1985
Mendel  ,        .
Tomicus destruens
. ;
Pityogenes calcaratus
.
2022 ילוי | 22 ןויליג | רעי
74
      ,  . 
   .    
 .       
P. calcaratus
      
       ,
O. erosus
-
  ,     
   ,  . 
P.
-
O. erosus
   ,  
  ,
T. destruens
   
calcaratus
 .       
Lieutier et        
.al., 2016
"      
    ,Raa et al., 1993 "
    ,     
  .     
        
  .Gaylord et al., 2010  
   ,     
       .
,       ,
   .     
    
      
  , .Lieutier et al., 2016 
     30–10   
T. destruens
 , 
P. calcaratus
-
O. erosus
    ,  
,  .2 Mendel et al., 1985  
Matsucoccus
   
"      
josephi
.Mendel, 2000
P. calcaratus
  "
      
      
  .     
      
  ,17-    
2 
2017         
  :
75
         
    
     ,
Ips typographus
      . Gmelin, 1787 
Klutsch et al.,      
   20-    .2017
      
     
  ,  .  
      
Smith et al., 1986, El-Sayed et al., 2006; Borden et
.al., 2008; Seybold et al., 2018
       
      
   ,   
   .     
      .   
       
      .  
      
        
;      .
      
.       
       
       
.    ,
P. calcaratus
-
O. erosus
      
        
        .
         
       
.  
 
  
  .      
      
   ,   
 200–100      
   . 70- 50     .
  .    , 
  ,   10–4  
,        
       3  
    .  
 ,   140–90     
.  
 :     
      
 8       . 
  Talstar®     
Bifenthrin 7.9%, Luxembourg Industries, Tel2%
Ipsowit ®       .Aviv
   ,Standard, Witasek Co, Austria
  ,     
P.
-
O. erosus
      
    .(Mendel, 1988)
calcaratus
3 
     
     
2022 ילוי | 22 ןויליג | רעי
76
  .     2.5 
    5    ,2018 
       .2018
  6      
, ,       120
        .
-      2018 
     .   
  .    
      
.      15%-  
 .        
 50        , 
.4        
      
Synergy      
.Semiochemicals LTD, British Columbia, Canada
   12-    12
Ipsowit ®     .2018
  Standard, Witasek Co, Austria
.     , 
P. calcaratus
-
O. erosus
   
.      
  
       
  .'' '' ,  
       
        
 .2022 ,'     
   27   ,  22 
    .   
 ,    
1,000–800     , 
1.3  ;      "
  . 7.5   4.5  ,
.       
        
  .      
      
.2022 ,'
 
JMP 14      
  .SAS Institute, Inc., Cary, North Carolina
       
       - 
.      
      
one-tailed       
.   Student's t-test

      
      , 
     .2.9%  
 :      
4 
,     
 ,   2017–2016 
  2018
     
.    50  
    , 
.
77
         
        
 ;   /   
  50     
    ,   
        .
 .       
        
      
P      
  .5      = 0.026
   50      
      
       
  .5      
       
.
P
=
0.0155     
P
<0.0001
  
O. erosus
    
 ,
P. calcaratus
    
.6      
      
       
 ,
T. destruens
-
P. calcaratus
  
O. erosus
      
    .1    
5 
2018 –           
                  .
   50         . .
P = 0.3389
 **- 
P = 0.0319
 *-   
   .**** 
P = 0.0155
- 
P <0.0001
 ***-         . 
.  
6 

P. calcaratus
-
O. erosus
  
      
2018 
Ipsowit ®    
   Standard, Witasek Co
    .  
.
2022 ילוי | 22 ןויליג | רעי
78
 ,   
P. calcaratus
  
  .2017       
   ,  2014  

P. calcaratus
   ,  2015
.    , ,  
,   
P. calcaratus
2016 
   ,     
    
T. destruens

    2018    .
 ,  
P. calcaratus
 
.1        

      
        
    .   
       
       ,  
        .
      
       
     , .  
  .      
     
         
   ,    
    ,  . 
   ,   
       
       
        
       .
      , ,
.       ,
 

P. calcaratusT. destruensP. calcaratusT. destruens
2018
7.5 ± 1.3 40150
05.3 ± 1.3 4015 1
07.3 ± 0.7 4014 1
2017
10.7 ± 1.9 34 118 ± 3.1 40
21 15 ± 0.7 217.3 ± 2.9 40
07.5 ± 0.4 210 ± 0 106 1
2016
10 ± 1.2 8018.9 ± 2.6 80
14.3 ± 3.1 6013.0 ± 1.3 810 1
20 ± 2.8 26.2 ± 0.4 419.0 ± 5.0 24.5 ± 0.6 3
2015
0018.3 ± 3.3 40
0013.3 ± 1.8 60
0013.0 ± 2.4 40
2014
11.3 ± 1.1 4020.8 ± 1.9 40
9.5 ± 0.3 3010.3 ± 0.1 30
007.0 ± 5.60
1 
        
T. destruens
-
P. calcaratus
  
   1.3- ,4.5 ,7.5    , ,    ." 100-    
 ± .               ,
.  
79
         
,        
       
.
      
       
   .3   

O. erosus
    
       ,4
Mendel et al., 1985; Mendel    
O. erosus
- , .et al., 1992; Lieutier et al., 2016
.       
      ,
       
.      ,
       , 
,
T. destruens
-
P. calcaratus
   
   ,    ,
O. erosus

     .
Mendel et al., 1985;
O. erosus
  
 ,Ghaioule et al., 1998; Faccoli et al., 2005
   
P. calcaratus
 
T.
-  .4     
      
destruens
       , 
         
     .– 
   
T. destruens
-
P. calcaratus

2015- 2014       .
   .1 
P. calcaratus
  
         
  
P. calcaratus
.2022 ,' 
      ,   
        ,
      . 
     
P. calcaratus

O. erosus
        .
        
      . 
   ,2016   
T. destruens
     
  .      
      
   ,    ,
  , .
O. erosus
 
 .       
        ,
P.
     
.  –
T. destruens
-
calcaratus
50%-    ,   
    ,   
.Hochman et al., 2018     56%-
       
 ,     
.      
      
 .Lieutier et al., 2016   
      
  , ;   
     
Zhou et al.,
Dendroctonus
   ,
       .2019
P.
      
  "  
ponderosa
D.
     .2015–2012  
    ,2015 
brevicomis
  .Fettig et al., 2019   
D. ponderosae
     
P. contorta
    
   (lodgepole pine)
      .Meddens et al., 2012
     , 
Bentz et al.,      
.2010
      
   .     
       
     . 
       
.    
 
       

P. calcaratus
-
O. erosus
 , 
      
      ,
     .   
       
     .  
        
    ,  . 
      , 
2022 ילוי | 22 ןויליג | רעי
80
       ,   
   .     
 ,     
    ,   
       , 
      .  
 ,     
 ,      
   .2022 ,'   
       
.    
 
  ,      
.      ,10-03-4387-18
  –     
:      
 ,   ,   
     ,  
   ,   
"   .    
 "      
.  

  .2022 .'  ,  ,  ,  ,  , 
, .-         
.70–60 ,22
,4–128 , .     .1978 . 
.28–20
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2022 ילוי | 22 ןויליג | רעי
VII
Bark beetle-related pine mortality in Israeli
planted forests and the eect of trap trees
Omer Golan 1, Rotem Attias 2' 3, Maor Elron1, Alexie
Protasov 4, Zvi Mendel 4, Rakefet David-Schwartz2*
The association of extensive mortality of pine trees
and bark beetle (Scolytinae) attack is a common
phenomenon in the Northern Hemisphere. Bark
beetle outbreaks frequently occur in the planted
pine forests in Israel and involve three species
Orthotomicus erosus, Pityogenes calcaratus
and
Tomicus destruens
. These bark beetle species
undergo periods of low population density when
they breed on trees stressed by drought or
thinning, and on broken trees or those uprooted by
wind or thinning slash. It has been suggested that
high populations of these scolytids often kill trees.
Assessing whether successful colonization of
standing pine trees by these species is the result
of direct beetle attack or a symptom of poor tree
physiology is a challenge and makes it dicult to
determine the required management strategy.
The role of bark beetles in tree death in a wide
study area was assessed by two experimental
systems: (1) a study of the potential eect of
drought in a layout of extensive trap trees in stands
1 Forest Management, KKL-JNF, Israel
2 Institute of Plant Sciences, Agricultural Research
Organization, The Volcani Center
3 Institute of Plant Sciences and Genetics in
Agriculture, The Robert H. Smith Faculty of
Agriculture, Food and Environment, The Hebrew
University of Jerusalem, Rehovot
4 Institute of Plant Protection, Agricultural Research
Organization, The Volcani Center
of
Pinus halepensis
and
P. brutia
; (2) examining
bark beetles colonization in killed pine trees in two
planted stands of
P. brutia
. In the rst experimental
system, trap-trees (baited with lures attractive to
both
O. erosus
and
P. calcaratus
and treated with
Bifenthrin) signicantly reduced the number of
dead trees in the trap-tree treated stands compared
with similar untreated ones.
O. erosus
was the
dominant species in these plots and tree mortality
occurred in the second half of the summer (August
and September). The second experimental system
indicated mainly the association of
P. calcaratus
and
T. destruens
with the killed trees. However,
in that system, the colonization was apparently
mainly during autumn to early winter (October and
November) and we were unable to determine the
direct role of the beetles in the tree mortality. The
results provided evidence that these pine bark
beetles, which are usually considered secondary,
are responsible for the tree death,
O. erosus
in
particular. Both
P. calcaratus
and
T. destruens
are
relatively more active during the low temperature
periods, typical of the autumn in Israel. We suggest
that the consequence of water scarcity and high
temperatures due to climate change during the
autumn make the pine trees more prone to beetle
attack during their typical activity period.
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The paper presents data on the occurrence and ecology of Pityogenes calcaratus (Eichh.), provides new data on the occurrence of this species in Georgia, and illustrates the beetle morphology and galleries.
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Fungi associated with the bark beetles Orthotomicus erosus, Tomicus destruens and Pityogenes calcaratus were sampled in various pine forests throughout Israel. Three ophiostomatoid fungi, Ophiostoma ips, Graphilbum rectangulosporium and Leptographium wingfieldii, and a fourth non-ophiostomatoid fungus, Geosmithia sp. 24, were identified by using morphological characteristics and molecular genetic analyses. O. ips, the most common fungus, was mainly isolated from O. erosus. The least common fungus, G. rectangulosporium, was frequently isolated from all three studied scolytids, while L. wingfieldii was almost exclusively associated with T. destruens. The fourth fungus, Geosmithia sp. 24, was isolated from both O. erosus and P. calcaratus. This is the first time that an association between O. erosus and a Geosmithia sp. has been reported. Our findings also suggest that Geosmithia sp. 24 can be separated into two distinct sub-groups by molecular analyses. Pathogenicity was demonstrated only for L. wingfieldii, both on Aleppo and brutia pine, exclusively under controlled conditions (25 ± 5 °C) but not at elevated temperatures. © 2015, Koninklijke Nederlandse Planteziektenkundige Vereniging.
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One factor that determines a tree’s resilience capacity to drought is its level of interaction with aggravating biotic factors, such as bark beetles, which in turn depends on whether insect populations are at an endemic or epidemic stage. In a Mediterranean natural forest ecosystem, we investigated the ecophysiological characteristics of trees which (i) predispose Pinus halepensis to attacks of endemic populations of bark beetles (Tomicus destruens) and (ii) that arise as a result of these attacks. The annual life cycle of Tomicus destruens features an initial dispersal phase of sexually mature adults towards pine trunks for the purposes of brood production, and a second dispersal phase of callow adults from trunks to pine shoots for sexual maturation. During a three-year survey of endemic bark beetle attacks in a stand of 178 trees, we found that trees targeted for trunk attacks showed a more aggregated distribution pattern than those targeted for shoot attacks. Moreover, shoot-attacked trees were clearly larger and taller, had lower wood density, and were less exposed to competition than non-attacked trees. No differences were found between the characteristics of trunk-attacked trees and non-attacked ones. We found crown defoliation, lower primary growth and alteration of trunk non-structural carbon in phloem in the year following trunk attacks, although this did not affect vulnerability to cavitation of the vascular system, secondary growth, wood density, and xylem starch. Conversely, the health status and physiological variables of the shoot-attacked trees were not altered, which may be explained by their initial vigor. We conclude that the distribution of Tomicus destruens attacks at the plot level was independent of the ecophysiological traits of the host trees. It was mainly determined by the dispersal strategy of the endemic bark beetle population especially during brood production as only trunk attacks significantly weakened the trees.
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Much of California, U.S. experienced a severe drought in 2012–2015 inciting a large tree mortality event in the central and southern Sierra Nevada. We assessed causal agents and rates of tree mortality, and short-term impacts to forest structure and composition based on a network of 11.3-m fixed-radius plots installed within three elevation bands on the Eldorado, Stanislaus, Sierra and Sequoia National Forests (914–1219, 1219–1524 and 1524–1829 m on the Eldorado, Stanislaus, Sierra; 1219–1524, 1524–1829, and 1829–2134 m on the Sequoia), where tree mortality was most severe. About 48.9% of trees died between 2014 and 2017. Tree mortality ranged from 46.1 ± 3.3% on the Eldorado National Forest to 58.7 ± 3.7% on the Sierra National Forest. Significantly higher levels of tree mortality occurred in the low elevation band (60.4 ± 3.0%) compared to the high elevation band (46.1 ± 2.9%). Ponderosa pine, Pinus ponderosa Dougl. ex Laws., exhibited the highest levels of tree mortality (89.6%), with 39.4% of plots losing all P. ponderosa. Mortality of P. ponderosa was highest at the lowest elevations, concentrated in larger-diameter trees, and attributed primarily to colonization by western pine beetle, Dendroctonus brevicomis LeConte. About 89% of P. ponderosa in the three largest diameter classes were killed, representing loss of an important structural component of these forests with implications to wildlife species of conservation concern. Sugar pine, P. lambertiana Dougl., exhibited the second highest levels of tree mortality (48.1%). Mortality of P. lambertiana was concentrated in the mid-diameter classes and attributed primarily to colonization by mountain pine beetle, D. ponderosae Hopkins. White fir, Abies concolor (Gord. & Glend.) Lindl. ex Hildebr., and incense cedar, Calocedrus decurrens (Torr.) Florin, exhibited 26.3% and 23.2% mortality, respectively. Only one Quercus died. Tree mortality (numbers of trees killed) was positively correlated with tree density and slope. A time lag was observed between the occurrence of drought and the majority of tree mortality. Tree regeneration (seedlings and saplings) was dominated by C. decurrens and Quercus spp., representing a potential long-term shift in composition from forests that were dominated by P. ponderosa. About 22.2% of plots contained plant species considered invasive, including cheatgrass, Bromus tectorum L., ripgut brome, Bromus diandrus Roth, bull thistle, Cirsium vulgare (Savi) Ten., and yellow star-thistle, Centaura solstitalis L. The implications of these and other results to recovery and management of drought-impacted forests in the central and southern Sierra Nevada are discussed.
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The eastern Mediterranean (EM) is expected to be influenced by climate changes that will significantly affect ecosystems, human health and socioeconomic aspects. One aspect of climate change in this vulnerable area is the length of the seasons, especially that of the rainy winter season against the warm and dry summer. Here, the synoptic seasons' definition of Alpert, Osetinsky, Ziv, and Shafir (2004a) was applied to an ensemble of eight Coupled Model Inter-Comparison Project phase 5 (CMIP5) models, under RCP8.5 and RCP4.5 scenarios, to predict the changes in the lengths of EM seasons during the 21st century. It is shown that the ensemble adequately represents the annual cycle of the main synoptic systems over the EM. The analysis further suggests that at the end of the 21st century, the duration of the synoptic summer, characterized by the occurrence of the Persian Trough, is expected to be lengthened by 49%, while the synoptic winter, characterized by the occurrence of the Cyprus Low, is expected to be shortened by 56% under the RCP8.5 scenario. This may lead to substantial changes in the hydrological regime and water resources, reduce the potential of dry farming, increase the risk of fires and air pollution and change the timing of seasonal health hazards.
Article
We summarize the status of semiochemical-based management of the major bark beetle species in western North America. The conifer forests of this region have a long history of profound impacts by phloem-feeding bark beetles, and species such as the mountain pine beetle (Dendroctonus ponderosae) and the spruce beetle (D. rufipennis) have recently undergone epic outbreaks linked to changing climate. At the same time, great strides are being made in the application of semiochemicals to the integrated pest management of bark beetles. In this review, we synthesize and interpret these recent advances in applied chemical ecology of bark beetles for scientists and land managers. Expected final online publication date for the Annual Review of Entomology Volume 63 is January 7, 2018. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
Article
Mountain pine beetle (MPB; Dendroctonus ponderosae Hopkins) has recently expanded its range into the lodgepole pine forests in Alberta, Canada. However, it is unknown whether semiochemical tools developed in the beetle’s historical range are suitable for monitoring MPB in the new environment. Thus, we conducted a 3-year study to test new MPB monitoring tools in Alberta. A field trial selected a combination of MPB pheromones and two host volatiles. Using this combination, we baited different numbers of trees in triangular, square, or rectangular formations (spatial arrangements of trees) to determine how the densities of baited trees affect MPB attraction. Three plots, each made up of three formations, were arranged in a linear transect at various distances between formation boundaries. The proportion of baited trees mass-attacked was highest in the square formation. However, the proportion of spillover trees mass-attacked (attacks on non-baited trees) was lower when formations were 1 kmapart compared with 4 or 8 kmapart. In a follow-up test of the square formation alone, there was no difference in trap tree effectiveness between distances of 8 and 12 km. We suggest that four baited trees spaced 50 m apart in a square formation at a 12 km distance can be used in the field.
Chapter
The chapter provides information on 15 species of invasive sacking insects on forest trees in the Mediterranean basin. Four Psyllids and one Thaumastocorid bug develop on Eucalyptus spp. and are native to Australia, although all of them possibly arrived in the Mediterranean area via South America. Among the five Cinara spp. those which develop on cedar trees spread inside the Mediterranean area, two of the aphids are North American species and one is probably from China. The discussed scale insects, two Matsucoccus spp. and Marchalina hellenica extent their range inside the Mediterranean basin. Finally, we report on two tingid species (Corythucha spp.) both originate from North America. We review their biology, the injury they inflect, their spread, as well as their natural enemies and the required management.
Chapter
This chapter discusses the native ranges, histories of introduction, recent research efforts, and the potential impacts of some of 22 species of invasive scolytids in California’s Mediterranean forest ecosystems. The diversity of native and ornamental tree species, the varied climatic zones, and the widespread importation of nursery stock and packaged cargo have made California a fertile location for the introduction and establishment of bark and ambrosia beetles. Eight of the twenty two taxa are ambrosia beetles; four are spermophagous (e.g., Coccotrypes and Dactylotrypes sp.); six are hardwood bark beetles (Hypothenemus eruditus, Scolytus sp., Phloeotribus liminaris, and Pityophthorus juglandis); and four are coniferophagous bark beetles (Hylurgus ligniperda, Ips calligraphus, Orthotomicus erosus, and Phloeosinus armatus). Five of the species have probable native ranges elsewhere in North America (indigenous exotic species), whereas nearly all of the remaining species have likely origins in Eurasia with at least four of those with clear roots in true Mediterranean ecosystems. Several appear to be from Africa. Many of the species were first detected in heavily urbanized southern California. Detailed overviews are provided for an ensemble of species that have had or could potentially have the most impact on California forest or orchard resources (H. ligniperda, O. erosus, P. juglandis, Scolytus multistriatus, S. rugulosus, S. schevyrewi, and Xyleborinus saxeseni). Another potentially damaging species, the polyphagous shot hole borer, Euwallacea nr. fornicatus, is treated elsewhere (Chap. 26). The introductions of these taxa range from species that may have invaded over 100–150 years ago (e.g., Hypothenemus eruditus, S. rugulosus, or X. saxeseni) to 10–15 years ago (10 of the 22 species have been detected since 2000). Dactylotrypes longicollis (a spermophage); Euwallacea nr. fornicatus; and Hylurgus ligniperda represent new generic records for California. Trends and conditions that favor future invasions by other members of this group of insects and a California watch list are presented.