Click beetles and pheromones – an overview
Miklós Tóth
Plant Protection Institute, HAS, Budapest, Hungary Wireworms, the larvae of click beetles (Coleoptera: Elateridae) are important soil-dwelling polyphagous pests all over the world.
www.photoshelter.com www.naturamediterraneo.com Traditional forecast and monitoring involves labour-intensive soil sampling methods,
Photo L. Furlan and to obtain wireworms from soil samples collected is time-consuming (several days or more). Photo L. Furlan Pheromone-baited traps are much easier and simpler to use.
However, the pheromone composition should be identified first!
Photo M. Tóth
On the picture: the YF trap design specifically developed for pheromone trapping of click beetles (Furlan Inform. Fitopat. 10:49. (2004) Pheromone structures - first identifications The very first chemical structures elucidated from click beetles (female- produced pheromone) were organic acids
O O
OH OH
valeric acid (pentanoic caproic acid (hexanoic acid) acid) Limonius californicus Limonius canus
Jacobson Science 159:208 Butler Environ. Entomol. 4:229 (1968) (1975) Limonius californicus www.bugguide.net Pheromone structures - geranyl/farnesyl esters Starting from the eighties, a number of geranyl and farnesyl esters were identified mainly by scientists from the Soviet Union. Example structures:
O
O O O
geranyl butyrate (E,E)-farnesyl acetate [(E)-3,7)-dimethyl-2,6- [(E)-3,7,11)-trimethyl-2,6,10- octadienyl butyrate] dodecatrienyl acetate]
i.e. A. sputator i.e. A. ustulatus
First report on similar structures from: Oleschenko, 1979, cited in Kamm, Coleopt. Bull. 37:16 (1983) Pheromone structures - geranyl/farnesyl esters Permutations and combinations of such compounds are present in the pheromones of several Agriotes spp. ger.hex. farn.acet. ger.oct. ger.i-val. farn.but. ger.but.
IS ustulatus IS obscurus IS sordidus IS litigiosus IS lineatus brevis IS sputator
46 81012141618202224 min GC analysis of pheromone gland extracts of Agriotes spp. (after Tóth J. Chem. Ecol.. 28:1641 (2002) and Pest Manag. Sci. 59:1 (2003) Pheromone structures - geranyl/farnesyl esters Structures for many spp. were reported, however, a great part of these compounds showed no behavioral activity.
I = compound identified but no behavioral activity shown
I P = compound identified, P found attractive A A = synthetic compound attractive, but not known Total: 24 spp. whether present in female
Data from
oviduct ovary
(After Ivaschenko Zool. Zh. 59: 225 supposed (1980). pheromone glands / reservoirs Gland extract vs. volatile collection (example No. 1) In A. sordidus, in gland extracts large amounts of (E,E)-farnesyl hexanoate were present,Agriotes with only sordidus traces in volatile collections. glands E,E-farnesyl ratio ger:farn =1:1 hexanoate geranyl hexanoate int. std.
volatiles ratio ger:farn =1:<0.1 A. sordidus ? Photo J. Vuts
15 20 25 30 35 40 45 50 50 min Gland extract vs. volatile collection (example No. 1) In field tests on A. sordidus, no influence of the addition of the farnesyl compoundAgriotes could sordidusbe observed. glands E,E-farnesyl ratio ger:farn =1:1 hexanoate geranyl Eraclea, Italy, 20 hexanoate 1998 int. std. Total caught in test: 10 535 beetles volatiles ratio a ger:farn =1:<0.1 a bbb average catch/trap/inspection 0 -- 3 30 30 30 geran. hex. ? 30 30 30 3 -- E,E-farn. hex. (mg) 15 20 25 30 35 40 45 50 50 min (after Tóth M, et al., unpublished) Gland extract vs. volatile collection (example No. 1) Consequently, by definition, only geranyl hexanoate can be termed a pheromoneAgriotes component sordidus in this species. glands E,E-farnesyl ratio ger:farn =1:1 hexanoate geranyl Eraclea, Italy, 20 hexanoate 1998 int. std. Total caught in test: 10 535 beetles volatiles ratio a ger:farn =1:<0.1 a bbb average catch/trap/inspection 0 -- 3 30 30 30 geran. hex. ? 30 30 30 3 -- E,E-farn. hex. (mg) 15 20 25 30 35 40 45 50 50 min (after Tóth M, et al., unpublished) Gland extract vs. volatile collection (example No. 2) Gland extracts of A. lineatus were dominated by a single very large peak of geranyl octanoate, geranyl butyrate was hardly detectable (ratio of octanoate:butyrate = 100:<0.01)
geranyl octanoate
retention region of int. std. geranyl butyrate
4681012 14 16 18 20 22 24 min Gland extract vs. volatile collection (example No. 2) In volatile collections the butyrate was well visible (ratio of mV octanoate:butyrate = 100:10) 10
geranyl- octanoate
5 int. std.
geranyl- butyrate
0
24681012 14 16 18 20 22 24 min
(After Vuts J. et al., in preparation) (After Tóth(After Pest Manag. Sci. 59:417 (2003) Gland extractvs. volatilecollection In thefieldpresence of thebutyratewasabsolutelynecessaryfor Total caught 1997 August 14, May 23 - Rümlang, beetles in test: 279 0 - - - 100 0 - -0 1 2 - - 1 - - - - 1 - - - - - 1 - - 10 - 10 10 10 0 - - - - - 30 10 10 Geranyl octanoate
1 Geranyl butanoate attraction.
- E,E-farnesyl acetate 1 1 - - 2 0 - - 0 - Geraniol
- Geranyl hexanoate Neryl isovalerate (example No.2) 273 A.lineatus (After Tóth(After Pest Manag. Sci. 59:417 (2003) Gland extractvs. volatilecollection It appearsthatvolatilecollections reflectbetterthetruepheromone Total caught 1997 August 14, May 23 - Rümlang, composition ofagivenspecies thanglandextractsdo. beetles in test: 279 0 - - - 100 0 - -0 1 2 - - 1 - - - - 1 - - - - - 1 - - 10 - 10 10 10 0 - - - - - 30 10 10 Geranyl octanoate
1 Geranyl butanoate
- E,E-farnesyl acetate 1 1 - - 2 0 - - 0 - Geraniol
- Geranyl hexanoate Neryl isovalerate (example No.2) 273 A.lineatus Geometrical isomers Another reason for inactivity of identified structures may be that in some cases geometrical purity of synthetic compounds is crucial - as commonly found also in moth pheromones.
It is well known that Agriotes ustulatus responds only to synthetic (E,E)- O farnesyl acetate batches which have >95% (E,E) O geometric purity.
Presence of higher (E,E)-farnesyl acetate percentages of the other isomers inhibits catches. Agriotes ustulatus www.elateridae.com
(After Tóth et al., unpublished) Geometrical isomers A recent report described the first neryl ester (nerol is the geometrical isomer of geraniol) as a pheromone component in Agriotes acuminatus also suggesting the importance of geometrical isomerism in click beetles.
“Good” isomer “Wrong” isomer
O O O
O
neryl butyrate geranyl butyrate [(Z)-3,7)-dimethyl-2,6- [(E)-3,7)-dimethyl-2,6- octadienyl butyrate] octadienyl butyrate]
After Tolasch J. Chem. Ecol. 36:314 (2010) Geometrical isomers The full pheromone composition in A. acuminatus contained also another ester with an unusual structure, which was necessary for field activity.
“Good” isomer second component
O O O O O O
neryl butyrate (Z,E)-2,6-dimethyl- [(Z)-3,7)-dimethyl-2,6- 2,6-octadien-1,8-diyl octadienyl butyrate] dihexanoate]
After Tolasch J. Chem. Ecol. 36:314 (2010) Other structures Some Melanotus spp. from the far east appear to use dodecenyl compounds (structurally similar to moth pheromones)
O O
O O dodecyl acetate (E)-9,11-dodecadienyl acetate Melanotus okinawensis Melanotus sakishimensis, M. tamsuyensis Tamaki Jpn KokaiTokyo Koho JP 61:12601 (1986) Iwanaga, Appl. Ent. Zool. 35:283 (2000) Yen, Syn. Comm. 28:4561 (1998) Other structures As new structure, a methyloctanolAmi ester kell) has been identified from the non- pest Ectinus aterrimus click beetle.
O
O
7-methyloctyl 9- methyldecanoate
Ectinus aterrimus www.biolib.cz
Tolasch Chemoecology 18:177 (2008) Other structures Four similar esters were recentlyAmi shown kell) out from E. ferrugineus, an endangered click beetle.
O O
O O O 7-methyloctyl 5- 7-methyloctyl O methylhexanoate octanoate 7-methyloctyl 7- methyloctanoate Elater ferrugineus
O
Tolasch J. Chem. Ecol. O 33:2156 (2007) 7-methyloctyl www.nhmus.hu (Z)-4-decenoate Other structures
Kairomonal effect: www.hvlfoto.cz E. ferrugineus also is attracted to the pheromone of its prey, Osmoderma eremita (Scarabaeidae).
Osmoderma eremita Elater ferrugineus O
O
(R)-gamma-decalactone
www.nhmus.hu Svensson J. Chem. Ecol. 30:353 (2004) Pheromone information in click beetle genera At present we have some information on chemical structures in 34 spp. Information on the genus Agriotes predominates.
Agriotes Athous Cidnopus Ectinus Elater Limonius Melanotus Synaptus Total: 33 spp.
Data from
2.5 (total caught: 2 109 beetles)
1.5
1 Catches of male and female
mean / trap (+SE) 0.5 A. sordidus in traps baited abcc with different doses of the 01030100 mg pheromone (Italy, Veneto, May 1 - 26, 2001, Furlan et abbcc 2 al., unpubl.) 4 6 8 10 mean / trap (+SE) 12 (total caught: 14 709 beetles) Females responding to the pheromone However, L. Furlan observed that in traps of A. sordidus baited with synthetic pheromone, sizeable catches of females (besides large catches of males) were recorded 2.5 (total caught: 2 109 beetles)
1.5
1 Catches of male and female
mean / trap (+SE) 0.5 A. sordidus in traps baited abcc with different doses of the 01030100 mg pheromone (Italy, Veneto, May 1 - 26, 2001, Furlan et abbcc 2 al., unpubl.) 4 6 8 10 mean / trap (+SE) 12 (total caught: 14 709 beetles) Females responding to the pheromone Female catches also showed a dose response, suggesting that the pheromone showed true attraction in female A. sordidus.
2.5 (total caught: 2 109 beetles)
1.5
1 Catches of male and female mean / trap (+SE) 0.5 A. sordidus in traps baited abcc with different doses of the 01030100 mg pheromone (Italy, Veneto, May 1 - 26, 2001, Furlan et abbcc 2 al., unpubl.) 4 6 8 10 mean / trap (+SE) 12 (total caught: 14 709 beetles) Females responding to the pheromone Attraction of females to the respective synthetic pheromone has been confirmed in several species, so the case of A. sordidus is not unique. A. brevis A. ustulatus A. sordidus pheromone components: pheromone component: pheromone component: (E,E)-farnesyl butyrate + (E,E)-farnesyl acetate geranyl hexanoate geranyl butyrate Eraclea, Italy, 2000 Berton-Greggio,www.elateridae.com Italy, 2001 Eraclea, Italy, 2000 Total caught: 20 beetles Total caught: 42 beetles Total caught: 194 beetles
2 16 1.8
1.8 1.6 14 P= 0.0002 P= 0.0001 1.6
1.4 12 P= 0.0011 1.4
1.2
10 1.2
1
8 1
0.8
0.8 6
0.6
0.6
4
0.4 0.4 Mean catches (+SE)
2 0.2 0.2
0 0 BREVbait unbaited 0 transpbait transpUNBAITED mg30 unb(test) pheromone bait Females responding to the pheromone What is more, female antennae responded well to the pheromone and gave similar response spectra in EAG to that of male antennae. % pheromone 800 700 600 500 standard control 400 300 200 100 Agriotes 0 air sordidus )-farnesol )-farnesyl )-farnesyl geranyl acetate geranyl geranyl geranyl geranyl butyrate butyrate geraniol octanoate isovalerate hexanoate E,E propionate ( E,E E,E ( ( 0 50 mean normalized responses (+SE) 100 150 200 250 300 350 (after Vuts J. et al., unpublished) Females responding to the pheromone This again was true to a number of species, and strongly suggested that females are capable to perceive their respective pheromone components. % pheromone
400 350 pheromone 300 250 standard control 200 150 100 50 Agriotes 0 air brevis )-farnesol )-farnesyl )-farnesyl geranyl acetate geranyl geranyl geranyl geranyl butyrate butyrate geraniol octanoate isovalerate hexanoate propionate E,E E,E E,E ( ( ( 0 50 mean normalized responses (+SE) 100 150 200 250 300 350 (after Vuts J. et al., unpublished) Females responding to the pheromone This brings up the possibility that the pheromones of click beetles are wrongly classified into the “classical” sex pheromone cathegory. % pheromone
400 350 pheromone 300 250 standard control 200 150 100 50 Agriotes 0 air brevis )-farnesol )-farnesyl )-farnesyl geranyl acetate geranyl geranyl geranyl geranyl butyrate butyrate geraniol octanoate isovalerate hexanoate propionate E,E E,E E,E ( ( ( 0 50 mean normalized responses (+SE) 100 150 200 250 300 350 (after Vuts J. et al., unpublished) Sex pheromone vs. aggregation pheromone? In A. ustulatus, a floral lure has been discovered, which attracts females. (White colour as attractive visual cue showed negligible influence) Debrecen, 2008 Eraclea, 2008
d c c
30 b 30 b a a 25 25
20 20 15 f 15 f (total caught: (total caught: 10 10 mean catch +SE 4814 beetles) 2532 beetles)
5 5
0 0 floral lure
pheromone white colour (After Tóth M. et al., in preparation) Sex pheromone vs. aggregation pheromone? The addition of the pheromone to the floral lure in the same trap increases catches of females! Debrecen, 2008 Eraclea, 2008
d c c
30 b 30 b a a 25 25
20 20 15 f 15 f (total caught: (total caught: 10 10 mean catch +SE 4814 beetles) 2532 beetles)
5 5
0 0 floral lure
pheromone white colour (After Tóth M. et al., in preparation) Sex pheromone vs. aggregation pheromone? Most female specimens are caught in traps with both floral AND pheromonal baits
Debrecen, 2008 Eraclea, 2008 (total caught: 34325 beetles) (total caught: 6123 beetles) c
140 b 60 b 130 a 55 a m 120 50 110 45 100 90 40 80 35 70 30 60 25 50 20 mean catch +SE 40 15 30 10 20 10 5 f 0 floral lure
pheromone white colour (After Tóth M. et al., in preparation) Sex pheromone vs. aggregation pheromone? A similar phenomenon (that the presence of the pheromone increases the effect of floral bait on females) is unusual with sex pheromones
Debrecen, 2008 Eraclea, 2008 (total caught: 34325 beetles) (total caught: 6123 beetles) c
140 b 60 b 130 a 55 a m 120 50 110 45 100 90 40 80 35 70 30 60 25 50 20 mean catch +SE 40 15 30 10 20 10 5 f 0 floral lure
pheromone white colour (After Tóth M. et al., in preparation) Sex pheromone vs. aggregation pheromone? However, it is frequently reported with aggregation pheromones
Debrecen, 2008 Eraclea, 2008 (total caught: 34325 beetles) (total caught: 6123 beetles) c
140 b 60 b 130 a 55 a m 120 50 110 45 100 90 40 80 35 70 30 60 25 50 20 mean catch +SE 40 15 30 10 20 10 5 f 0 floral lure
pheromone white colour (After Tóth M. et al., in preparation) Sex pheromone vs. aggregation pheromone? This again suggests that the pheromone of Agriotes click beetles is not a “classical” sex pheromone
Debrecen, 2008 Eraclea, 2008 (total caught: 34325 beetles) (total caught: 6123 beetles) c
140 b 60 b 130 a 55 a m 120 50 110 45 100 90 40 80 35 70 30 60 25 50 20 mean catch +SE 40 15 30 10 20 10 5 f 0 floral lure
pheromone white colour (After Tóth M. et al., in preparation) Acknowledgements
Scientists cooperating in unpublished results shown:
Bálintné Csonka, É. (Hungary) Francke, W. (Germany) Furlan, L. (Italy) Subchev, M. (Bulgaria) Szarukán, I. (Hungary) Tolasch, T. (Germany) Toshova, T. (Bulgaria) Vuts, J. (Hungary) Yatsynin, V.G. (Russia)