Electrophoretic analysis of the prey spectrum of Teretrius nigrescens (Lewis) (Col., Histeridae), a predator of Prostephanus truncatus (Horn) (Col., Bostrichidae), in Mexico, Honduras, and Benin

Abstract: Extensive collections of Teretrius nigrescens in Mexico, Honduras, and Benin, were electrophoretically analysed to elucidate the prey spectrum of the predator. Both polyacrylamide gel electrophoresis and cellulose acetate electrophoresis were used. Beetles were sampled with pheromone traps, using the synthetic aggregation pheromone of Prostephanus truncatus , and directly from farmers' maize stores. The proportion of electrophoretically detected prey protein from adult T. nigrescens in pheromone traps was low: of the 1108 specimens analysed, only in 34 cases, prey protein could be clearly identified. More frequently, prey protein was detected in adult T. nigrescens sampled in maize stores in Mexico, Honduras, and Benin, with 87 samples showing distinct prey bands of the total 1214 predators analysed. Of the 241 T. nigrescens larvae sampled in maize stores in Benin, 136 showed distinct bands of prey protein. In all samples, P. truncatus was the most frequently detected prey species. The second most often identified prey species was Sitophilus zeamais . The results are discussed with regard to various methods for prey spectrum analysis and specifically the biology of T. nigrescens .     

Biological control of the larger grain borer Prostephanus truncatus (Coleoptera: Bostrichidae) in Kenya using a predatory beetle Teretrius nigrescens(Coleoptera: Histeridae)

The establishment of the predatory histerid beetle, Teretrius nigrescens Lewis, following its field release in south eastern Kenya in 1992, and its impact on populations of the larger grain borer, Prostephanus truncatus (Horn), in woodland habitats is evaluated. Pheromone trap catch data show a single strong peak of P. truncatus from November to January, coincident with the short rains. Comparisons of P. truncatus pheromone trap catches before and after predator establishment, and in areas with and without T. nigrescens, show a sustained decline of over 80% in P. truncatus abundance over a 5-year period, following the establishment T. nigrescens. Concurrent laboratory studies of the impact of T. nigrescens on populations of P. truncatus raised on a wood substrate showed a 77% reduction in the growth of the pest population. These results are compared with published findings of the impact of T. nigrescens as a biological control agent of P. truncatus in west Africa.     

Studies on predation of Prostephanus truncatus (Horn) (Col., Bostrichidae) and Sitophilus zeamais Mots. (Col., Curculionidae) at different densities on maize by Teretriosoma nigrescens Lewis (Col., Histeridae)

Laboratory experiments using whole cobs were conducted to examine the effect of varying densities of the larger grain borer, Prostephanus truncatus and the maize weevil, Sitophilus zeamais on rate of population increase by the histerid beetle, Teretriosoma nigrescens , a predator primarily of P. truncatus . Densities of all species of insects were determined at the end of the experiment, and an electrophoretic analysis of gut content was conducted on larval and adult T. nigrescens sampled during the experiments. Results indicated that T. nigrescens has a strong preference for P. truncatus and densities of T. nigrescens were associated only with densities of P. truncatus . The maize weevil played little role as an alternative prey or in interfering with T. nigrescens reproduction.     

Flight initiation in Prostephanus truncatus: influence of population density and aggregation pheromone

The influence of population density and aggregation pheromone were investigated as possible flight initiating factors for Prostephanus truncatus (Horn) (Col.: Bostrichidae). Maize grains (175 g in glass jars) were infested with 20, 50, 150 or 300 beetles, all of which were removed after 2 weeks. Flight initiation of the progeny was observed over a period of 4 weeks, with and without the synthetic aggregation pheromone of P. truncatus. Addition of the synthetic pheromone had no influence on the number of beetles taking off. The number of beetles dispersing increased with growing initial and progeny densities. Dispersal rates (% of total progeny dispersing) rose with declining rate till they reached a maximum at ca. 33%. Of the beetles dispersing, 74% left the cultures between 18.00 and 20.00 hours. Surviving progeny per female decreased with increasing initial density. Sex ratios in the initial cultures and in the F₁ were ca. 1:1, whereas a higher proportion of females (67%) was found among the dispersing beetles.     

Infestation of maize by Prostephanus truncatus initiated by male-produced pheromone

Delta traps baited with maize cobs, which were infested each with one male Prostephanus truncatus (Horn) (Col.: Bostrichidae), were distributed in southern Benin and collected after one, two, three and four weeks. The numbers of P. truncatus caught during the different trapping periods were not significantly different. Sixty-four percent of the trapped P. truncatus were females. Females attracted during the one-week trapping period produced a mean of 6.9 progeny during the seven days. The sex ratio of the progeny was 1:1. Trap catches with the infested cobs were on average 13 times lower than catches with 2 mg of the artificial pheromone. Estimation of P. truncatus densities in a maize store at the beginning of the storage period (based on laboratory data) revealed that small initial numbers of P. truncatus, possibly attracted by a single male, sufficed to initiate high infestation rates later in the storage season.     

Factors influencing response of flying Prostephanus truncatus to its male-produced aggregation pheromone

Abstract. The effects of age, sex, mating status, pre-exposure to pheromone, resource (diet) quality, and starvation on the response of Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) to its male-produced aggregation pheromone were investigated.Age was an important factor determining the level of response to pheromone: young adults were more responsive than older adults.The suitability of the resource in which P.truncatus is present affected its dispersal tendency, but not its sensitivity to pheromone per se. Sex, mating status, brief prior exposure to pheromone, and starvation did not influence the response of the larger grain borer to pheromone.The orientation behaviour of the beetle is described, and it is proposed that the pheromone primarily functions as a 'suitable resource location and colonization signal'.     

Enantiomers of fuscumol acetate comprise the aggregation‐sex pheromone of the South American cerambycid beetle Psapharochrus maculatissimus,and likely pheromones of the cerambycids Eupromerella plaumanni and Hylettus seniculus

There is increasing evidence that pheromone chemistry within the large coleopteran family Cerambycidae is often highly conserved, with numerous related species sharing the same pheromone components. As a result, traps containing these components can attract multiple cerambycid species simultaneously. In the present study, we exploited this concept in the identification of the male‐produced aggregation‐sex pheromone of the South American species Psapharochrus maculatissimus (Bates) (Coleoptera: Cerambycidae, subfamily Lamiinae, tribe Acanthoderini). Initially, live adults of both sexes were caught using a trap baited with a lure containing a blend of known cerambycid pheromone components. Headspace volatiles were collected from live beetles and analyzed by coupled gas chromatography‐mass spectrometry. Males of P. maculatissimus sex‐specifically produced a 1:38 blend of (R)‐fuscumol acetate ([2R,5E]‐6,10‐dimethylundeca‐5,9‐dien‐2‐yl acetate) and (S)‐fuscumol acetate, which were both components of the pheromone lures to which they had been attracted. In more focused field trials, traps baited with the (S)‐enantiomer, or a blend approximating the natural 1:38 ratio of (R)‐ to (S)‐enantiomers, attracted adults of both sexes in approximately equal numbers. During bioassays, adults of the lamiine species Eupromerella plaumanni (Fuchs) (tribe Acanthoderini) and Hylettus seniculus (Germar) (Acanthocinini) also were attracted, but to different lures, with E. plaumanni being attracted to the racemic mixture of the two enantiomers of fuscumol acetate, whereas H. seniculus was attracted specifically to (R)‐fuscumol acetate. Our results suggest that differences between these sympatric species in the stereochemistry of fuscumol acetate impart species‐specificity to pheromone communication channels, similar to what has been found recently with lamiine species from other continents.     

Identification and field testing of sex pheromone components of a Korean population of the allium leafminer,Acrolepiopsis sapporensis

The allium leafminer, Acrolepiopsis sapporensis Matsumura (Lepidoptera: Acrolepiidae), is a pest of Allium species (Liliaceae) in Asia and Hawaii, USA. We identified candidate sex pheromone components in pheromone gland extracts of female moths and field tested the response of male moths to blends with different components and ratios. Gas chromatographic comparison of abdominal tip extracts from both sexes showed three female‐specific components: (Z)‐11‐hexadecenal (Z11‐16:Ald), (Z)‐11‐hexadecenyl acetate (Z11‐16:OAc), and (Z)‐11‐hexadecen‐1‐ol (Z11‐16:OH). These compounds were identified by mass spectral analysis of natural pheromone components and dimethyldisulfide adducts, and retention index comparisons with synthetic standards. The average ratio of three components, Z11‐16:Ald, Z11‐16:OAc, and Z11‐16:OH, in female extract was 33:100:14. Field trapping experiments indicated that all three components were essential for maximal attraction of male moths. Traps baited with a ternary blend mimicking the blend found in the pheromone gland extracts caught significantly more males than traps baited with caged live females. Increasing doses of the pheromone blend in the lures from 0.01 to 1.0 mg increased catches of male A. sapporensis.     

Field responses of stink bugs to the natural and synthetic pheromone of the Neotropical brown stink bug, Euschistus heros (Heteroptera: Pentatomidae)

Abstract.The synthetic racemic mixture of methyl 2,6,10‐trimethyltridecanoate, a component of the male produced pheromone of Euschistus heros (F.) (Heteroptera, Pentatomidae), was attractive to pentatomid species in a field test, using homemade pheromone trap designs. The pentatomid Piezodorus guildinii was caught in high numbers in field traps, during two field experiments, indicating a consistent response of this species to the E. heros pheromone. A correlation was found between the range of insects caught in the pheromone‐baited traps and a random sampling method. The synthetic stereoisomeric mixture of methyl 2,6,10‐trimethyldodecanoate, a minor component of E. heros pheromone, was also field tested and caught no pentatomids. Egg parasitoids were caught in traps baited with E. heros pheromone, indicating that this pheromone can be exploited as a kairomone. A synchrony in the periodicity of trap catch, between the egg parasitoids and their host, was also recorded.     

截形叶螨对胡瓜钝绥螨的吸引作用

室内测定表明,截形叶螨不同螨态对胡瓜钝绥螨均有显著的吸引作用,均达到极显著水平,而胡瓜钝绥螨对截形叶螨的排泄物没有明显的反应。截形叶螨对胡瓜钝绥螨的这种吸引作用说明胡瓜钝绥螨具有自动搜索截形叶螨的能力,表明胡瓜钝绥螨可以用于截形叶螨的生物防治。     

Phylogeographic structure of Teretrius nigrescens (Coleoptera: Histeridae) predator of the invasive post harvest pest Prostephanus truncatus (Coleoptera: Bostrichidae)

The invasive larger grain borer Prostephanus truncatus (Horn) is the most important pest of farm-stored maize in Africa. It was introduced into the continent from Mesoamerica in the late 1970s and by 2008 had spread to at least 18 countries. Classical biological control using two populations of the predator Teretrius nigrescens Lewis achieved long-term and cost effective control in warm-humid areas, but not in cool and hot-dry zones. The present study investigated the phylogenetic relationships between geographical populations of the predator. Ten populations of T. nigrescens were studied using randomly amplified polymorphic DNA polymerase chain reaction (RAPD-PCR), sequence analysis of mitochondrial Cytochrme oxydase 1 (mtCOI) gene and ribosomal internally transcribed spacers (ITS) 1, 5.8S and ITS2. The mtCOI variation revealed two clades associated with geographical regions in Central America. It also reveals a significant isolation by distance between populations and considerable genetic shifts in laboratory rearing. RAPD-PCR did not reveal any potential SCAR diagnostic markers. The ITS variation mainly involved insertions and deletions of simple sequence repeats even within individuals. This study reveals the existence of two different mitochondrial lineages of the predator, associated with the geographical origin of populations distinguishable by fixed mutations on the mtCOI gene. The populations of T. nigrescens released in Africa belonged to two different clades from Meso America, namely south (released in West Africa) and north (released in eastern Africa). However, more polymorphic markers are required to clarify the observations in demographic time scales.     

Optimizing a pheromone lure for the sugar beet root maggot fly,Tetanops myopaeformis

We previously described a putative aggregation pheromone in adults of the sugar beet root maggot, Tetanops myopaeformis (von Röder) (Diptera: Ulidiidae), comprising nine compounds identified from males. Here, we conducted a series of experiments aimed at simplifying the blend of compounds necessary to achieve attraction as well as determining the dose that maximizes captures when formulated into an attractant lure. In all experiments, females showed stronger and more consistent evidence of attraction than males. White sticky traps baited with different blends of pheromone compounds that included the major component, (R)-(−)-2-nonanol, showed significantly higher female captures relative to those baited with blends that excluded the major component. (R)-(−)-2-nonanol alone was at least as effective as any blend that included this compound with other minor pheromone components. Lures using racemic 2-nonanol were as effective as the (R) enantiomer for both females and males, with some evidence of weak attraction to the (S) enantiomer (which is not produced by males) observed as well. Maximum capture rates using racemic 2-nonanol were estimated to occur with doses of ca. 795.5 and 621.6 mg for females and males, respectively. Addition of 2-nonanol lures to standard orange sticky stake traps currently used to monitor flies increased captures of both sexes. The pheromone lure developed here could improve trapping efficiency of current monitoring programs for T. myopaeformis and may also be used to develop other management tools for this important pest of sugar beet.     

Field trials of aggregation pheromones for the stink bugs Chlorochroa uhleri and Chlorochroa sayi (Hemiptera: Pentatomidae)

In field trials, adult Chlorochroa uhleri (St?l) (Heteroptera: Pentatomidae) of both sexes were caught in significant numbers in cylindrical screen traps baited with gray rubber septum lures loaded with the main component of the male-produced pheromone, methyl (E)-6-2,3-dihydrofarnesoate. Addition of the two possible minor components of the pheromone, methyl (E)-5-2,6,10-trimethyl-5,9-undecadienoate and methyl (2E,6E)-farnesoate, did not affect attraction. Combining the pheromone with different concentrations of volatiles mimicking the odors of a known host plant, alfalfa (Medicago sativa L.), had no significant effect on attraction of adult bugs, whereas combining the pheromone with the pheromones of two sympatric stink bug species, Chlorochroa sayi (St?l) and Euschistus conspersus Uhler, decreased trap captures, suggesting interference between the pheromones. Small numbers of Chlorochroa ligata (Say) adults also were attracted, but numbers caught were too low to allow statistical comparisons between lure blends. In field trials with C. sayi, all three of the male-specific pheromone compounds [methyl geranate, methyl citronellate, and methyl (E) -6-2,3-dihydrofarnesoate] were required for optimal attraction. As with C. uhleri, adults of both sexes were attracted to pheromone lures in approximately equal numbers. Because of the decreased volatility (=release rate) of methyl (E)-6-2,3-dihydrofarnesoate in comparison with the other two, lower molecular weight pheromone components, lures needed to be loaded with a disproportionately high amount of methyl (E)-6-2,3-dihydrofarnesoate to obtain the best trap catch. There was no indication that the pheromone components of C. uhleri or E. conspersus interfered with the attractiveness of the C. sayi pheromone in lures containing a blend of all three pheromones.     

Influence of ambient and thoracic temperatures upon sexual behaviour of the gypsy moth, Lymantria dispar

ABSTRACT. In an ambient temperature ( T _a) range of 18–28°C, thoracic temperatures ( T _th) of individual male Lymantria dispar (L.), caught at flight in the field, ranged from 21 to 36.5°C, with a correlation coefficient of 0.63 between T _th and ambient temperature ( T _a). Ambient temperature (and insolation) altered the insect's body temperature and the probabilities, latencies, and durations of preflight responses to pheromone. In a wind tunnel at 16 and 20°C, quiescent males exposed to pheromone raised their T _th by sustained wing fanning from 17 and 21°C, respectively, to c. 24°C before takeoff. At 24 and 28°C ambient, T _th rose by takeoff to 28 and 31°C, respectively. The latencies of male wing fanning in response to pheromone decreased from 1.44 min at 16°C ambient, to 0.58 min at 20°C, to 0.26 min at 24°C, and to 0.16min at 28°C. The components of behaviour (antennal twitch, body jerk, step and wing tremor) that occurred between quiescence and wing fanning were more frequent at ambients of 16 and 20°C than at 24 and 28°C.     

Specificity of sex pheromones, the role of host plant odour in the olfactory attraction of males, and mate recognition in the aphid Cryptomyzus

Abstract. Choice tests in an olfactometer showed that males of the aphid Cryptomyzus galeopsidis spent more time in the odour of conspecific females than of a sibling species or a more distantly related Cryptomyzus species, which all co-occur on red currant. Analysis of the pheromone-emissions of females showed the presence of a nepetalactol and a nepetalactone, two known aphid sex pheromone components. However, no interspecific difference in the ratio of the components ( c. 30:1) was found, and this ratio did not change as the females aged. Males were only slightly attracted by a synthetic 30:1 mixture of these two components, and in a choice test preferreď the odour of conspecific females. The sex pheromone of Cryptomyzus spp. must thus consist of more than two components, the first time this has been reported for aphids. Host plant odour did not attract males or enhance the activity of the pheromone.     

Behavioral and electrophysiological responses of Tetropium fuscum (Coleoptera: Cerambycidae) to pheromone and spruce volatiles

The brown spruce longhorn beetle, Tetropium fuscum (F.), is an invasive wood-boring species in eastern Canada. Gas chromatographic/electroantennographic (GC/EAD) analyses of Norway and red spruce volatiles detected a number of consistent EAD-active responses to compounds that are known to be stress-induced in spruce. The effects of these EAD-active compounds on various aspects of adult behavior were tested. In two-choice olfactometer assays, a monoterpene spruce blend, (R)-(-)-linalool, (3Z,6E)-α-farnesene, (E)-β-farnesene and spruce essential oil were attractive to both sexes. However, when they were combined with the male-produced pheromone (fuscumol), they elicited a sex-specific response: females were significantly attracted to combinations of fuscumol plus either (3Z,6E)-α-farnesene, (E)-β-farnesene and spruce essential oil but males were not. Fuscumol alone was unattractive to either sex in the olfactometer. Males exposed to fuscumol, (3Z,6E)-α-farnesene, or a combination of both, but not (E)-β-farnesene, were more likely to engage in the pheromone calling posture relative to controls. Both the monoterpene spruce blend and spruce essential oil elicited significantly greater trap capture of both sexes of T. fuscum in the presence of fuscumol and ethanol than (3Z,6E)-α-farnesene or (R)-(-)-linalool, which did not elicit trap capture alone or in combination with fuscumol. The data support the hypothesis that stress-induced sesquiterpene components, such as (3Z,6E)-α-farnesene, are important for mediating close-range attraction and behavior in T. fuscum while the monoterpene components are important for long-range processes (trap capture).     

Longevity and pheromone output in stored-product Bostrichidae

Information on longevity and on the effect of ageing on pheromone signalling in Bostrichidae infesting stored products is important because pheromones play a crucial role in mediating aggregation by the species in storages. The longevity of starved and unstarved Prostephanus truncatus (Horn) and Rhyzopertha dominica (Fabricius) were determined at 28+/-1 degrees C, 65+/-2% RH and L12:D12 cycle. Additionally, the effects of ageing on rate of pheromone emission were investigated in R. dominica by comparing emission rates of the aggregation pheromones Dominicalure-1 (DL1) and Dominicalure-2 (DL2) released by adult males ranging from 4, 8, 12, 24 and 48 weeks of age. Mean survival time of starved male and female P. truncatus was 8.6+/-0.6 and 9.1+/-0.4 days, respectively. Starved R. dominica males lived for 5.7+/-0.2 days, and females for 4.7+/-0.1 days. However, mean survival times were not significantly different for starved males vs. females of either species. Mean survival time of unstarved male and female P. truncatus was 27.5+/-2.0 and 18.0+/-3.3 weeks, respectively, and for unstarved male and female R. dominica was 26.1+/-2.8 and 16.7+/-2.9 weeks, respectively. Difference in mean survival times of unstarved males vs. females in both P. truncatus and R. dominica were significant. Between species, no significant difference was observed in mean survival time between unstarved males of P. truncatus or R. dominica, nor between females of both species. Rate of pheromone emission in R. dominica was higher when the insects were relatively young (4, 8 and 12 weeks old), but declined by almost 55% in treatments where the insect were at about 24 or 48 weeks old, suggesting that recruitment potential of R. dominica might reduce substantially as the insects age.     

Release of sex steroids into the water by roach

Electro‐olfactogram (EOG) recordings of the olfactory epithelium of both male and female roach Rutilus rutilus demonstrated that both sexes were able to detect free and glucuronidated 17,20β‐dihydroxy‐4‐pregnen‐3‐one (17,20β‐P) with high sensitivity. Male, but not female, roach were also sensitive to androstenedione. Sexually mature female roach were shown to release free 17,20β‐P, glucuronidated 17,20β‐P and androstenedione into the water; for all three steroids, the rate of release was significantly enhanced by injection of carp pituitary extract (CPE). A series of trials was also carried out which showed that mature males, and to a lesser extent immature males and females, were able also to release free and glucuronidated 17,20β‐P, both before and after CPE treatment. Water extracts from containers that had held CPE‐treated mature male and female roach were examined for the presence of other steroids. This revealed that free and glucuronidated 17,20β‐P plus free and glucuronidated 17,20β,21‐trihydroxy‐4‐pregnen‐3‐one (17,20β, 21‐P) predominated in water extracts from both sexes. The free moieties of 17,20α‐dihydroxy‐4‐pregnen‐3‐one, 17‐hydroxyprogesterone and 11‐deoxycortisol were found at concentrations which were between four and 20 times lower than those of free 17,20β‐P. Androstenedione was found at concentrations which were 25‐fold lower than those of 17,20β‐P. Despite its apparent high rate of release by sexually mature male and female roach, free 17,20β,21‐P was found not to exhibit any EOG activity at the highest dose tested (10⁻⁷ M).     

Effects of different sex pheromone compositions and host plants on the mating behavior of two Grapholita species

The two congener species Grapholita molesta and Grapholita dimorpha share two major sex pheromone components: cis-8-dodecenyl acetate (Z8-12Ac) and trans-8-dodecenyl acetate (E8-12Ac). In fact, commercial sex pheromone lures composed of only these two major components attract the males of both species. In this study, we aimed to determine the reproductive isolation components of these two species by analyzing the effects of the minor sex pheromone components and host plants. First, different ratios of the two major sex pheromone components were greatly favored by either male species. Sex pheromone gland extracts of G. dimorpha contained a lesser proportion of Z8-12Ac than that of G. molesta. In the three (apple, pear, and peach) orchards investigated in this study, a larger number of G. molesta males were attracted to the 95:5 pheromone mixture (Z8-12Ac and E8-12Ac, respectively), while a larger number of G. dimorpha males were attracted to the 85:15 mixture. Second, there was a significant variation in male attractions in different host plants. G. molesta males were more attracted to the sex pheromone lure in the apple orchards than that in the pear and peach orchards. In contrast, G. dimorpha males were more attracted to the lures in the pear and peach orchards than that in the apple orchard. Third, the minor sex pheromone components were important for reproductive isolation. Among the four minor components tested, addition of (Z)-8-dodecenol (Z8-12OH) to the major sex pheromone components significantly suppressed male attraction in G. dimorpha and slightly elevated male attraction in G. molesta. The discriminating effect of Z8-12OH was further validated using male electroantennogram analysis. These results suggest that reproductive isolation between two congeners can be achieved by variations in the minor sex pheromone components and in the host plants, as well as by changes in the ratio of the two major components.     

Attraction of Gymnosoma rotundatum (Diptera: Tachinidae) to different amounts of Plautia stali (Hemiptera: Pentatomidae) aggregation pheromone and the effect of different pheromone dispensers

The attractiveness of different amounts of the synthetic aggregation pheromone, methyl (E,E,Z)-2,4,6-decatrienoate, of the brown-winged stink bug, Plautia stali (Hemiptera: Pentatomidae) was tested on its parasitoid, Gymnosoma rotundatum (Diptera: Tachinidae), using different types of dispensers in the field. Both sexes of G. rotundatum were attracted to the aggregation pheromone. Pheromones in rubber septum and poly-tube dispensers attracted significantly more G. rotundatum than those in PE-vial dispensers. There were no differences in the attraction of females or males when using 7 to 60 mg pheromone. However, the trap baited with 50 mg pheromone attracted significantly more G. rotundatum of both sexes than the control trap. Further research is necessary to develop an effective pheromone trap that can attract and kill P. stali and can attract G. rotundatum to increase parasitism of the host stink bugs in the field.