Synthetic Aggregation Pheromone Research Articles

Semiochemicals produced by fungal bark beetle symbiont Endoconidiophora rufipennis and the discovery of an anti-attractant for Ips typographus.

Bark beetles vector symbiotic fungal species into their host trees during mass attacks. The symbiotic relationship with blue stain fungi of the Ascomycetes, including genera of Endoconidiophora (syn. = Ceratocystis), promotes successful establishment whereby the microbes help to overcome the host trees' defence and degrade toxic resins. This is the first study to evaluate both the volatile emissions from an insect-associated blue stain fungus over time and the insect response in a field trapping experiment. Volatile emissions from isolates of Endoconidiophora rufipennis (ER) were collected by solid-phase microextraction (SPME) and analysed by gas chromatography-mass spectroscopy (GC-MS) over a period of 30 days. This virulent North American fungus is closely related to E. polonica, a symbiotic fungus known from Eurasian spruce bark beetle Ips typographus.Nine volatiles were emitted by ER in substantial amounts: isoamyl acetate, sulcatone, 2-phenethyl acetate, geranyl acetone, geranyl acetate, citronellyl acetate, (R)- and (S)-sulcatol, and (R)-sulcatol acetate. A late peaking compound was geranyl acetone. In the field trapping experiment, three of the fungal volatiles (geranyl acetone, 2-phenethyl acetate and sulcatone) were tested in combination with a synthetic aggregation pheromone for I. typographus. Traps with geranyl acetone attracted lower numbers of I. typographus compared to traps with 2-phenethyl acetate, sulcatone or the pheromone alone as a control. The results showed that geranyl acetone acts as an anti-attractant and may act naturally on I. typographus as a cue from an associated fungus to signal an overexploited host.

Improved Captures of the Invasive Brown Marmorated Stink Bug, Halyomorpha halys, Using a Novel Multimodal Trap.

Simple SummaryPest monitoring using traps is a key component of integrated pest management. For several insects, trapping is achieved using visual or olfactory stimuli. Although the combination of both is supposed to provide higher efficacy, this has often been overlooked in trap design. Through laboratory bioassays and field experiments we evaluated the use of UV-A and visible light in combination with olfactory stimuli to improve trapping of the invasive brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae). Our results may be useful for the improvement of monitoring strategies for early pest detection. Additionally, the higher efficacy of the multimodal traps would allow their use in attract-and-kill or push–pull strategies within integrated pest management.Capture strategies for the brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae), are challenging. Here we developed and evaluated a multimodal trap which combines visual and olfactory stimuli. Visual stimuli consisted of LEDs emitting UV-A and visible light. Olfactory stimuli were comprised of the synthetic aggregation pheromone and odours from trapped H. halys individuals. Stink bug attraction at different wavelengths was evaluated in laboratory two-choice bioassays, and different prototypes of the trap were tested in 2021 in natural, agricultural, and urban settings. Traps with a combination of UV-A and blue or green visible wavelengths provided higher H. halys attraction (up to ~8-fold) compared to traditional sticky or small pyramidal traps. The concurrent presence of synthetic pheromone and LED had a synergistic effect on H. halys positive phototaxis. Further development and implementation of the multimodal trap is discussed for prospective use in attract-and-kill or push–pull strategies.

COMPOUNDS FROM PEPPER FLOWERS AND FRUITS AS POTENTIAL ATTRACTANTS FOR THE CAPTURE OF PEPPER WEEVIL

Two field experiments were conducted to evaluate synthetic attractants derived from pepper flowers, flower buds and fruits, alone or in combination with the aggregation pheromone. The evaluation was carried out with the release and recapture of Anthonomus eugenii adults at different distances from the four cardinal points in separate trials. The volatility of the synthetic mixture and aggregation pheromone was determined by gas chromatographic analysis of the volatiles captured by dynamic headspace. The traps with synthetic mixture and essential oil captured insects at 10 m, while the aggregation pheromone trapped up to 60 m. The combination of synthetic mixture or essential oil with the aggregation pheromone did not increase the number of recaptures compared to the single pheromone. The synthetic mixture together with geranic acid recaptured adults up to 15 m, although they were not significantly different from the control. The exclusion of geranic acid from the aggregation pheromone significantly reduced the number of recaptured insects (P<0.05), while geranic acid alone failed to capture weevils. The results could be improved by increasing the concentrations of the compounds or by adding other compounds released during the reproductive stages of pepper. These results could guide future efforts for the development of tools based on synthetic plant volatiles for the monitoring of this pest.

Disparity of Phoresy in Mesostigmatid Mites upon Their Specific Carrier Ips typographus (Coleoptera: Scolytinae).

Simple SummaryThis study investigated the phoretic relationship between mites and one of the most aggressive spruce bark beetles from Eurasia. During one season (April–September), bark beetles Ips typographus were collected with a specific synthetic aggregation pheromone. In the lab, we investigated the diversity of mites associated with I. typographus, mite preferences concerning the body parts of the beetles and how phoretic relationships change during the bark beetle’s flight season. Six phoretic mites species were found and 20% of beetles carried mites. Phoretic mite loads and the percent of beetles with mites were highest during the spring flight period. Phoretic mite species had specific preferences regarding their location on the body of the carrier.Ips typographus Linnaeus, 1758, the most important pest of Norway spruce (Picea abies Linnaeus, 1753) from Eurasia has damaged, in the last decades, a large area of forest in Romania. Associations between beetles and their symbiotic fungi are well known compared to beetle-mite relationships. The objectives of the study are to determine: (i) the diversity of mites species associated with I. typographus in a local outbreak from Central Romania; (ii) the mite’s preferences concerning the body parts of their carriers; and (iii) how phoresy changes during seasonal flight activity of the host. A total of 7896 adult I. typographus were analyzed and six mite species (both adults and immature stages) were found: Dendrolaelaps quadrisetus Berlese,1920, Proctolaelaps fiseri Samsinak, 1960, Trichouropoda polytricha Vitzthum, 1923, Histiostoma piceae Scheucher, 1957, Uroobovella ipidis Vitzthum, 1923, and Uroobovella vinicolora Vitzthum, 1926. Most mites were observed under the carriers’ elytra (46.8%), while 26.7% and 25.8% were seen on the thorax and elytral declivities, respectively. Mite phoresy peaked in the spring corresponding to the dispersal flight of the carrier. A smaller peak in phoresy occurred in the summer during the second beetle generation.

Abundance of Scyphophorus acupunctatus Gyllenhal (Coleoptera: Dryophthoridae) in Agave tequilana Weber (Asparagaceae) Fields of Different Age and Agronomic Management

One of the most important pests that affect the blue agave, Agave tequilana is Scyphophorus acupunctatus Gyllenhal which as larvae bore into and make galleries in the plant and also damage plant tissues as adults. In the present study, the abundance of S. acupunctatus was analyzed in plantations of A. tequilana of ages of 2, 3 and 4 years through monthly samples from May to November of 2016 in nine plantations distributed in the municipalities of Tequila, Magdalena and Arandas in the state of Jalisco, Mexico. In each plantation, nine traps were placed with synthetic aggregation pheromone (2-methyl-4-octanone 950 g/L y 2-methyl-4- octanol 5g/L), placed 50 m apart and arranged as follows: three within the A. tequilana plantings, three on the crop edges, and three in adjacent non-cultivated areas, for a total of 81 traps which were checked monthly. The temperature and humidity of each plantation was registered with dataloggers and the precipitation from data from NASA, as well as historical data of these variables were obtained from 1951 to 2016. A total of 4,390 individuals were trapped, consisting of 3,289 females and 1,101 males. We found significant differences among the weevil abundance in A. tequilana plots of different age and agronomic management. There was less abundance of weevils in plantations where no agrochemicals were used and where natural vegetation was allowed within rows suggesting that natural habitat complexity is an important factor in reducing the abundance of the weevil.

Development of pull and push–pull systems for management of lesser mealworm, Alphitobius diaperinus, in poultry houses using alarm and aggregation pheromones

The lesser mealworm, Alphitobius diaperinus (Coleoptera: Tenebrionidae), is the most important insect pest affecting poultry production around the world, with all life stages being susceptible to infection by bacteria, viruses and fungi. Control of A. diaperinus in poultry houses using intensive insecticide application is not effective due to the cryptic behaviour of this pest. Here, we evaluated the potential of recently identified A. diaperinus alarm (1,4-benzoquinone, 2-methyl-1,4-benzoquinone and 2-ethyl-1,4-benzoquinone) and aggregation [(R)-limonene, 2-nonanone, (E)-ocimene, (S)-linalool, (R)-daucene and (E,E)-α-farnesene] pheromones as tools for the management of this pest in poultry houses in Brazil. Laboratory arena assays with synthetic alarm pheromone confirmed A. diaperinus repellency. In an initial field assay, traps baited with synthetic aggregation pheromone captured significantly more insects than control traps. In further field assays that compared a pull (aggregation pheromone) and a push-pull (simultaneous alarm/aggregation pheromone deployment) system, a higher number of A. diaperinus were captured in aggregation pheromone-baited traps in the push-pull system. Our results suggest that alarm and aggregation pheromones can be deployed in poultry houses to trap significant numbers of adult A. diaperinus. Studies are underway to determine the potential for using these components as part of an integrated A. diaperinus management strategy. © 2018 Society of Chemical Industry.

Tree resin flow dynamics during an experimentally induced attack by Ips avulsus, I. calligraphus, and I. grandicollis

The success of tree colonization by bark beetles depends on their ability to overcome host tree defenses, including resin exudation and toxic chemicals, which deter bark beetle colonization. Resin defenses during insect outbreaks are challenging to study in situ, as outbreaks are stochastic events that progress quickly and thus preclude the establishment of baseline observations of non-infested controls. We use synthetic aggregation pheromones to demonstrate that confined Ips bark beetle herbivory can be successfully initiated to provide opportunities for studying interactions between bark beetles and their hosts, including the dynamics of constitutive and induced resin exudation. In Pinus taeda L. plantations between 12 and 19 years old in North and South Carolina, U.S., trees were affixed with pheromone lures, monitored for evidence of bark beetle attacks, and resin samples were collected throughout the growing season. Baiting increased beetle herbivory to an extent sufficient to produce an induced resin response. Attacked trees exuded about three times more resin at some time than control trees. This supports previous work that demonstrated that information on constitutive resin dynamics alone provides an incomplete view of a host tree’s resistance to bark beetle attack.

Factors Influencing Mating Behavior and Success in the Red Palm Weevil, Rhynchophorus ferrugineus Olivier (Coleoptera: Dryophthoridae).

The effects of body size, age, feeding and mating status, conspecific volatiles from live adults, synthetic aggregation pheromone, and a pheromone synergist, ethyl acetate, on the mating behavior of red palm weevil, Rhynchophorus ferrugineus Olivier, were investigated. To evaluate these factors, variables such as mating latency, frequency and duration, and refractory period were assessed. While both, body size and age, influenced the mating behavior, the latter showed a stronger effect. The large males recorded frequent and longer matings, whereas the young males outperformed the old weevils in all the studied variables. The difference in body size or age of females showed a limited effect. After 72h without food, the males showed a significant decline in mating frequency and duration, and refractory period. Mating status showed comparatively stronger effects on mating variables. In the case of females, mating status emerged as the most important factor affecting four out of five variables. The volatiles from the males, grouped males and females, and synthetic aggregation pheromone both alone and in combination with ethyl acetate triggered mating initiation, propelled mating frequency, prolonged total mating duration, and reduced the refractory period. However, the presence of females or ethyl acetate alone was a weak mating stimulator.

Evaluation of Semiochemical-Baited Traps for Monitoring the Pea Leaf Weevil, Sitona lineatus (Coleoptera: Curculionidae) in Field Pea Crops.

The pea leaf weevil (PLW), Sitona lineatus L., is a pest of field pea (Pisum sativum L.) and faba bean (Vicia faba L.) that recently invaded the Canadian Prairie Provinces. Although most damage is done by larvae that feed on root nodules, adults are easier to monitor than larvae. Both male and female weevils respond to a male-produced aggregation pheromone and to volatiles released by host plants. The current study tests the attractiveness of synthetic aggregation pheromone, 4-methyl-3,5-heptanedione, and host plant volatiles linalool, (Z)-3-hexenol, and (Z)-3-hexenyl acetate to PLWs in spring when weevils are reproductively active and in fall when weevils seek overwintering sites. Different combinations of semiochemical lures at various doses, released from a variety of devices were tested in pitfall traps. Semiochemical-baited traps captured both male and female weevils in both seasons but the sex ratio varied with season. Weevils did not respond in a dose-dependent manner to pheromone, as all pheromone lures were equally attractive. Pheromone release rate was determined by the release device and not the pheromone dose in the lure. The addition of plant volatiles sometimes increased weevil captures but plant volatiles alone were not attractive to PLW adults. An additional study tested the effect of trap type on weevil capture. Of the 12 different trap types tested, pheromone-baited pitfall traps were most successful in attracting and retaining weevils. Bycatch of other Sitona species was limited to a few specimens of the sweet clover weevil, Sitona cylindricollis Fahraeus.

Food Attractants to Increase Pheromone-Baited Trap Performance forScyphophorus acupunctatus(Coleoptera: Dryophthoridae) in Mezcal Maguey

The agave weevil, Scyphophorus acupunctatus Gyllenhal (Coleoptera: Dryophthoridae), is the main insect pest on maguey grown for mezcal beverage production in Guerrero, Mexico. We studied the effectiveness of several food attractants in pheromone-baited traps for capturing S. acupunctatus in mezcal maguey plantations. All of the tested food attractants synergized the response of the agave weevil to synthetic aggregation pheromone traps. Adding papalote maguey tissue, ripe banana, or ripe pineapple fruit increased the number of captured weevils in pheromone-baited traps. However, it is easier, cheaper, and more practical to use ripe banana or pineapple fruit as the bait attractant than using the agave tissue.

Females of Riptortus pedestris (Hemiptera: Alydidae) in Reproductive Diapause are More Responsive to Synthetic Aggregation Pheromone.

Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) enters reproductive diapause under short-day length (< 13.5 h) conditions. As an apparent increase of field populations of R. pedestris has been observed during the fall when aggregation pheromone traps are placed in soybean fields, we tested the hypothesis that R. pedestris becomes more responsive to the aggregation pheromone during fall as it enters its reproductive diapause. The response of R. pedestris females-either ones collected seasonally from fields or reared in the laboratory under short-day length (10:14 [L:D] h) conditions-to the aggregation pheromone was examined using a Y-tube olfactometer. Riptortus pedestris collected in fall showed a higher response to the aggregation pheromone (74-80%) than those collected in July (40%). Females in which diapause was induced in the laboratory also showed a higher response to the pheromone than those not in diapause. In a wind tunnel assay, female bugs in laboratory-induced diapause also responded positively to the aggregation pheromone. In addition, we assessed the reproduction of females to verify their diapausing status. Diapausing females never mated with either short- or long-day-reared males, nor did they reproduce, but non-diapausing females mated with short-day-reared males at a rate of 13%. Females collected from fields during fall never mated. In a soybean field evaluation, the number of adult female R. pedestris was higher in the presence of an aggregation pheromone trap than in the absence of one. This is the first confirmation of higher response to the aggregation pheromone of both field-collected and laboratory-reared R. pedestris in reproductive diapause.

Evaluating Predators and Competitors in Wisconsin Red Pine Forests for Attraction to Mountain Pine Beetle Pheromones for Anticipatory Biological Control.

Mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae), is an irruptive tree-killing species native to pine forests of western North America. Two potential pathways of spread to eastern forests have recently been identified. First, warming temperatures have driven range expansion from British Columbia into Albertan jack pine forests that are contiguous with the Great Lakes region. Second, high temperatures and drought have fostered largescale outbreaks within the historical range, creating economic incentives to salvage killed timber by transporting logs to midwestern markets, which risks accidental introduction. We evaluated the extent to which local predators and competitors that exploit bark beetle semiochemicals would respond to D. ponderosae in Wisconsin. We emulated D. ponderosae attack by deploying lures containing synthetic aggregation pheromones with and without host tree compounds and blank control traps in six red pine plantations over 2 yr. Predator populations were high in these stands, as evidenced by catches in positive control traps, baited with pheromones of local bark beetles and were deployed distant from behavioral choice plots. Only one predator, Thanasimus dubius F. (Coleoptera: Cleridae) was attracted to D. ponderosae's aggregation pheromones relative to blank controls, and its attraction was relatively weak. The most common bark beetles attracted to these pheromones were lower stem and root colonizers, which likely would facilitate rather than compete with D. ponderosae. There was some, but weak, attraction of potentially competing Ips species. Other factors that might influence natural enemy impacts on D. ponderosae in midwestern forests, such as phenological synchrony and exploitation of male-produced pheromones, are discussed.

Attractiveness of an Aggregation Pheromone Lure and Chicken Droppings to Adults and Larvae of &lt;I&gt;Alphitobius diaperinus&lt;/I&gt; (Coleoptera: Tenebrionidae)

The chemical cues by which lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae) beetles find each other are still unknown. Laboratory two-choice pitfall bioassays were conducted to evaluate the attractiveness of synthetic aggregation pheromone lure to lesser mealworm adults and larvae. All components of this synthetic aggregation pheromone lure, including: (R)-(+)-limonene, (E)-β-ocimene, (S)-(+)-linalool, (R)-(+)-daucene, and 2-nonanone were also tested singly. Chicken dropping volatile compounds and fresh chicken droppings (CD) were evaluated singly or in combination with the pheromone lure. In Arkansas, trapping experiments were conducted in different poultry houses with low, moderate, and high lesser mealworm populations to evaluate the attraction of pheromone lure. Laboratory two-choice pitfall bioassay was found to be a useful and convenient tool for evaluating the attractants before testing them in the poultry house. Greater attraction of adults and larvae to a dose of 20–30 μg pheromone lure was identified in laboratory two-choice pitfall bioassays. Adults and larvae were highly attractive to a combination of fresh CD and pheromone lure, whereas, a combination of chicken dropping volatile and pheromone lure was not significantly attractive. The low attraction of limonene and linalool in the laboratory two-choice pitfall bioassays suggest that either they are nonattractive or attractive only at a narrow range of concentrations. Higher numbers of lesser mealworm adults and larvae were found in traps treated with pheromone lure as compared with untreated controls in field experiments. Results indicate a potential for combining the pheromone lure with the attractive CD compounds to enhance trap efficacy.

Using an Electronic Nose to Rapidly Assess Grandlure Content in Boll Weevil Pheromone Lures

Samples of pheromone lures used in boll weevil, Anthonomus grandis (Boheman), eradication programs are routinely analyzed by Gas Chromatography (GC) to ensure lures are adequately dosed with grandlure, the synthetic aggregation pheromone produced by male weevils. However, preparation of GC samples is tedious, time consuming, and requires a moderate level of experience. We examined the use of a commercially-available electronic nose (e-nose) for rapidly assessing the grandlure contents of lures. The e-nose was trained to recognize headspace collections of grandlure emitted from new lures and after lures were aged under field conditions for 4 d, 7 d, 10 d, and 14 d. Based on cross-validation of the training set, the e-nose was 82% accurate in discriminating among the different age classes of lures. Upon sampling headspace collections of pheromone from a different set of field-aged lures, the e-nose was <50% accurate in discriminating 4 d, 7 d, and 10 d aged lures from the other age classes of lures. However, the e-nose identified new and 14 d aged lure samples with 100% accuracy. In light of these findings, e-nose technology shows considerable promise as an alternative approach for rapidly assessing the initial grandlure contents of lures used in boll weevil eradication programs.

Response of a parasitoid fly, Gymnosoma rotundatum (Linnaeus) (Diptera: Tachinidae) to the aggregation pheromone of Plautia stali Scott (Hemiptera: Pentatomidae) and its parasitism of hosts under field conditions

We studied the attraction of a tachinid fly, Gymnosoma rotundatum (Linnaeus) to the male-produced aggregation pheromone of the brown-winged green bug, Plautia stali Scott, its parasitism on the bug, and its seasonal occurrence in the field. The tachinid fly was continuously attracted to the aggregation pheromone from spring to autumn and utilized the bugs as hosts. Our field experiment to clarify the effect of the pheromone on parasitism demonstrated that parasitism occurred only in female bugs baited with synthetic aggregation pheromone and did not occur in females without the pheromone. The parasitoid flies therefore appeared to use the bug’s pheromone as a host-finding kairomone. The pheromone attracted not only female flies but also males. Male flies may increase their chance of encountering pheromone-attracted females by waiting near pheromone sources. The tachinid develops multiple generations in active hosts from spring to autumn and overwinters in dormant hosts. Thus, G. rotundatum seems to be highly adapted to using P. stali as its host, and it is a potentially important biological control agent of P. stali populations in the field.

Possible use of synthetic aggregation pheromones to control stinkbug Plautia stali in kaki persimmon orchards

1 The brown-winged green stinkbug Plautia stali Scott (Hemiptera: Pentatomidae) is the most serious pest of all noxious stinkbugs in various orchards in Japan. An area-wide integrated pest management programme using the species-specific aggregation pheromone is desirable to control P. stali because nonspecific insecticides may kill arthropod natural enemies and induce the resurgence of other endemic pests. 2 The traditional mass-trapping method is not expected to be effective as a result of huge migrations from cypress forests. Therefore, we chose an ‘attract-and-kill’ strategy of intensively installing poisonous eggplants with a synthetic aggregation pheromone lure as enclosures for the target orchards. 3 We found no overall control effect of the installation of poisonous eggplants, although regional differences were observed, which might originate from topological configurations or the distance from the source population in cypress forests. 4 The poisonous eggplants with an aggregation-pheromone lure, however, changed the spatial distribution of fruit damage, appearing to induce the majority of the damage within a 100-m range of the poisonous eggplants. Some damage, although at a low level, was found in regions 100–200 m away from the poisonous eggplants. 5 We postulate that such low-damage regions were created because the majority of the bugs dispersed from the centre of the orchards to the areas with poisonous eggplants. The present study, in which the spatial scale of the damage spillover was estimated at approximately 150 m, has important implications for future strategies of attract-and-kill and possibly push–pull.

Effects of humidity on the response of the bark beetle Ips grandicollis (Eichhoff) (Coleoptera: Curculionidae: Scolytinae) to synthetic aggregation pheromone

AbstractEnvironmental factors may affect chemical communication between individuals by limiting their ability to detect and respond to these signals. One such factor, high humidity, has been shown to interfere with the normal response of some invertebrate species to their attractant pheromones. The effect of humidity on the response of the five‐spined bark beetle, Ips grandicollis, to a synthetic form of the aggregation pheromone component ipsenol, was tested in an experimental chamber in the laboratory. The response was measured as both the number of beetles to reach the pheromone source and the time taken, and was tested under high (&gt;80% relative humidity) and low (30–40% relative humidity) conditions of humidity. There was no significant difference in response of beetles between the two treatments although there was a reduction in response in the high‐humidity treatment when relative humidity levels were in excess of 90%. These findings suggest that atmospheric humidity does not influence bark beetles response to synthetic pheromone, except perhaps in unlikely conditions of excessive humidity.

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.

Adaptive Traits of Riptortus pedestris Nymphs (Heteroptera: Alydidae) for Locating Host Plants

Abstract Riptortus pedestris (F.) (Heteroptera: Alydidae) females oviposit not only on host plants but also on nonhosts, which may impose high costs on nymphs in terms of locomotion energy and time searching for host plants. Therefore, we hypothesized that second-instar nymphs have developed adaptive traits that help them access host plants, because the first feeding stage occurs during the second instar in this bug. We compared responses to the aggregation pheromone, relative leg lengths, and locomotion performance using a servosphere locomotion compensator as tests of physiological, morphometric, and behavioral traits, respectively, among the instars. We also investigated the effects of delayed feeding in the second instar on subsequent survival and development. Our results indicated that second-instar nymphs might have responded more sensitively to synthetic aggregation pheromone than other instars. Morphological measurements showed that second-instar nymphs had the longest relative leg length compared with other instars. The experiment using the servosphere revealed that second-instar nymphs had higher locomotion performance than did older nymphs, which may allow second-instar nymphs to walk a distance comparable to older nymphs, although their body size is much smaller. However, we did find that more than a 48-h delay in feeding after the first-instar molt decreased subsequent survival rates and that a later first-feeding led to a longer developmental period during the second instar. We concluded that R. pedestris nymphs have evolved various adaptive traits to enhance the probability of accessing host plants in response to the costly oviposition habit of adult females that lay eggs on nonhosts.

Sitona Weevils (Coleoptera: Curculionidae) Caught by Traps in Alfalfa Fields in Bulgaria

ABSTRACTModified sticky Delta traps and PAL CSALOMON® traps, unbaited or baited with synthetic aggregation pheromone of Sitona lineatus (L., 1758), 4-methyl-3,5-heptanedione, were used for studying the species spectrum of Sitona (Coleoptera: Curculionidae) weevils in alfalfa fields in the regions of Sofia, Plovdiv and Pazardzhik in 2007 and 2008. Several Sitona species, all known as pests on leguminous crops in Bulgaria, were caught. Modified sticky Delta traps baited with 4-methyl- 3,5-heptanedione caught significantly higher number of Sitona weevils than the unbaited traps.