Edi A. Malo

Antennal Sensilla and Electrophysiological Response of Male and Female Spodoptera frugiperda (Lepidoptera: Noctuidae) to Conspecific Sex Pheromone and Plant Odors

Abstract The olfactory system of male and female Spodoptera frugiperda (J. E. Smith) was studied by examining the morphology and distribution of antennal sensilla and determining the responses of both sexes to conspecific female sex pheromone components and plant volatiles using electroantennography (EAG). Seven types of sensilla were observed on the flagellum of the antennae: trichodea, chaetica, coeloconica, styloconica, auricilica, squamiformia, and basiconica. Only one type of trichodea sensilla was found on the antennae of both sexes, but these sensilla were more abundant on male than on female. EAG records of both sexes to 10-μg stimulus loads of six pheromone components showed that (Z)-7-dodecenyl acetate (Z7–12: Ac) and (Z)-9-dodecenyl acetate (Z9–12: Ac) elicited larger responses than those evoked by (Z)-11-hexadecenyl acetate (Z11–16: Ac), (Z, E)-9,11-tetradecadienyl acetate (Z9, E11–14: Ac), (Z, E)-9,12-tetradecadienyl acetate (Z9, E12–14: Ac), and hexane in female antennae. In the case of male antennae, (Z)-9-tetradecenyl acetate (Z9–14: Ac) and Z9, E12–14: Ac evoked larger EAG responses than those elicited by Z7–12: Ac, Z11–16: Ac, Z9, E11–14: Ac, and hexane. The compounds that selectively evoked larger EAG responses from males than females were Z9, E12–14: Ac, and Z9–14: Ac. Dose-response experiments showed that, at the lowest dose tested, Z9–14: Ac and Z9, E12–14: Ac elicited larger EAG responses than Z9–12: Ac and Z7–12: Ac in male antennae. At the highest doses tested, the diene elicited the largest EAG responses. In the case of female antennae, the dose, but not the pheromone component, had a significant effect. Male and female responses to 10-μg stimulus loads of 16 plant volatiles showed that hexan-1-ol evoked larger EAG responses in comparison with those elicited by hexanal, (E)-3-hexenol, 2-carene, phellandrene, limonene, β-pinene, and hexane. The response of male antennae was significantly stronger than the female. Dose-response experiments showed that both sexes appeared to be most sensitive to alcohols, particularly at the highest dose tested.

A New Potential Attractant for Anastrepha obliqua from Spondias mombin Fruits

Nonirradiated males and females of Anastrepha obliqua (Macquart) were attracted to and landed more frequently on ripe fruits of Spondias mombin L. than on artificial fruit in wind tunnel bioassays. Porapak Q volatile extracts of S. mombin were also attractive and elicited landing on artificial fruit for both sexes. Combined gas chromatographic–electroantennographic detection (GC-EAD) analysis of volatile extracts showed that nine volatile compounds elicited repeatable antennal responses from females and males. The EAD-active compounds were identified by GC–mass spectrometry (MS) as follows: ethyl butyrate, isopropyl butyrate, hexan-1-ol, propyl butyrate, isobutyl butyrate, ethyl hexanoate, isopentyl butyrate, ethyl benzoate, and ethyl octanoate. In wind tunnel bioassays, males and females were attracted and landed more frequently on lures containing the nine-component blend of synthetic compounds than on unscented controls. Field cage bioassays showed that multilure traps baited with the nine-synthetic blend captured significantly more A. obliqua than traps baited with hydrolyzed protein or water.

Response of Cranberry Weevil (Coleoptera: Curculionidae) to Host Plant Volatiles

ABSTRACT The oligophagous cranberry weevil, Anthonomus musculus Say, causes economic losses to blueberry growers in New Jersey because females deposit eggs into developing flower buds and subsequent larval feeding damages buds, which fail to produce fruit. A cost-effective and reliable method is needed for monitoring this pest to correctly time insecticide applications. We studied the behavioral and antennal responses of adult A. musculus to its host plant volatiles to determine their potential for monitoring this pest. We evaluated A. musculus response to intact and damaged host plant parts, such as buds and flowers in Y-tube bioassays. We also collected and identified host plant volatiles from blueberry buds and open flowers and performed electroantennograms with identified compounds to determine the specific chemicals eliciting antennal responses. Male weevils were more attracted to blueberry flower buds and were repelled by conspecific-damaged buds compared with clean air. In contrast, females were more attracted to open flowers compared with flower buds. Nineteen volatiles were identified from blueberry buds; 10 of these were also emitted from blueberry flowers. Four of the volatiles emitted from both blueberry buds and flowers [hexanol, (Z)-S-hexenyl acetate, hexyl acetate, and (Z)-3-hexenyl butyrate] elicited strong antennal responses from A. musculus. Future laboratory and field testing of the identified compounds in combination with various trap designs is planned to develop a reliable monitoring trap for A. musculus.

A Reinvestigation of Brindley’s Gland Exocrine Compounds of Rhodnius prolixus (Hemiptera: Reduviidae)

Abstract A chemical, electrophysiological and behavioral study was carried out to analyze the volatile compounds of the Brindley’s gland of Rhodnius prolixus Stål. Six compounds were found in the Brindley’s gland of males and females: acetic, isobutyric, caproic acids and three compounds not identified. The mass spectra of the unidentified compounds have the appearance of a propionate ester, a butyrate ester and a valerate ester. There was no difference in the concentration of these compounds in the glands of males and females. The major component was isobutyric acid. The electroantennographic (EAG) evaluation of isobutyric, acetic, and caproic acids elicited weak responses. With both sexes, the EAG responses for the acids were no different from the control response at any of the doses evaluated (1, 10, 100, and 500 μg). The behavioral response of males and females to acetic, isobutyric, and caproic acids at 1, 5, and 10 μg and binary and tertiary mixtures of the three compounds was evaluated in a Y-olfactometer. Males showed preference for acetic acid at a dose of 1 μg, but not at 5 or 10 μg. Females showed preference for this compound at the dose of 5 μg. Males showed preference for isobutyric acid at 1 and 5 μg, but not at 10 μg. Females did not show any preference for isobutyric acid. Males were attracted to caproic acid at the dose of 1 and 10 μg. Females were attracted to the caproic acid. Males, but not females, preferred the mixture of acetic and isobutyric acids over control. Neither males nor females showed preference for the mixture of acetic and caproic acids or hexane control. Females, but not males, were attracted to the mixture of the isobutyric and caproic acids. Only males showed a positive response for the tertiary mixture of the acids.

BEHAVIORAL AND ELECTROPHYSIOLOGICAL RESPONSES OF THE MEXICAN FRUIT FLY (DIPTERA: TEPHRITIDAE) TO GUAVA VOLATILES

Abstract The behavioral and electrophysiological responses of males and females of the Mexican fruit fly Anastrepha ludens (Loew) to guava (Psidium guajava L.) volatiles were investigated in laboratory tests. Males and females were significantly more attracted and landed more often on guava fruits than yellow spheres used as control in the wind tunnel. Also, both sexes were more attracted to Porapak Q extracts of guava than to solvent controls. Gas chromatography-electroantennographic detection (GC-EAD) analysis of the behaviorally active extracts showed that consistently eight and seven compounds elicited antennal response from male and female, respectively. The compounds were identified by gas chromatography-mass spectrometry (GC-MS) as ethyl butyrate, (E)-3-hexenol, (Z)-3-hexenol, hexanol, ethyl hexanoate, hexyl acetate, (Z)-3-hexenyl butyrate and ethyl octanoate. The electrophysiological activity of the identified compounds at three different doses was evaluated with electroantennography (EAG). An analysis of covariance of the EAG amplitude revealed that synthetic chemicals, sex, dose, and the synthetic chemical × dose interaction significantly influence the antennal response of A. ludens. Males and females were significantly more attracted to septa loaded with the eight-component synthetic blend compared to solvent controls in the wind tunnel.

Aggregation pheromone of the agave weevil, Scyphophorus acupunctatus

The agave weevil, Scyphophorus acupunctatus Gyllenhal (Coleoptera: Curculionidae), is the most important insect pest of wild and cultivated agaves in the world. Combined gas chromatography‐electroantennography (GC‐EAD) analysis of male volatile extracts showed that four peaks elicited antennal responses from males and females. The peaks were identified by GC‐mass spectrometry (GC‐MS) as 2‐methyl‐4‐heptanol (1), 2‐methyl‐4‐octanol (2), 2‐methyl‐4‐heptanone (3), and 2‐methyl‐4‐octanone (4). Electroantennogram (EAG) recordings of both sexes to 0.01‐, 0.1‐, 1‐, and 10‐µg stimulus load of synthetic compounds showed that the dose of the tested compounds and weevil sex significantly influenced the antennal response of S. acupunctatus. However, there was no sexual dimorphism in the antennal responses to the four synthetic compounds evaluated because the EAG profiles revealed no interaction between doses by sex. Antennae of S. acupunctatus were most sensitive to compounds 2 and 4, reaching the threshold at a 0.01‐µg stimulus load. Weevil antennae were less sensitive to compounds 1 and 3, and the threshold response to these compounds was 0.1 µg. Behavioural evaluation of the synthetic compounds showed them to be attractive to both males and females in a Y‐tube olfactometer. Field experiments confirmed the laboratory results, showing that all components, singly or in blends, were attractive to the weevils. In general, traps baited with the quaternary blend of compounds 1–4 captured significantly more weevils than traps baited with males. However, compounds 3 and 4 were sufficient to obtain captures equivalent to those by the quaternary blend. The potential use of the aggregation pheromone in the development of a mass‐trapping programme as a viable pest management alternative for S. acupunctatus is discussed.

Aggregation pheromone in five species of Triatominae (Hemiptera: Reduviidae)

An aggregation pheromone found in the faeces of 5th instar nymphs and adults of Triatoma mazzottii Usinger, Triatoma longipennis Usinger, Triatoma pallidipennis (Stal), Triatoma barberi Usinger and Rhodnius prolixus (Stal) was studied under laboratory conditions. Bioassays were performed using a 30 cm-diameter arena and wind tunnel. T. longipennis nymphs showed a stronger response than the other triatomine nymphs tested. There were no significant differences in faecal attractiveness to nymphs, but the faeces of T. longipennis and T. pallidipennis were most active. The responses of all species to male and female faeces of T. mazzottii was significantly different, but there was no significant difference in the responses of the development stages to male and female faeces of T. mazzottii. However, male faeces were more active than female faeces. The feeding status of nymphs did not affect the response.

Mandibular Gland Secretion of Melipona beecheii : Chemistry and Behavior

The mandibular gland secretion of Melipona beecheii contains a rich mixture of terpenoid and oxygenated compounds and unsaturated and saturated hydrocarbons. However, it differs markedly from the 11 other Brazilian species examined in previous studies, both by the absence of 2-heptanol and the presence of rose oxides. The most abundant compound was geranyl hexanoate, whereas the most volatile compounds were cis- and trans-rose oxide and geraniol. The complete blend and five individual components found in the gland secretion were tested by electroantennography (EAG) and behavioral assays. The complete mandibular gland extract and geraniol elicited the strongest EAG responses, whereas these and farnesyl acetate induced the strongest attack response from workers. The role of the rose oxides remains to be elucidated, as they do not appear to play a major role as an alarm pheromone of this species.

Attraction of the West Indian fruit fly to mango fruit volatiles

In this study, we investigated the attraction of West Indian fruit fly, Anastrepha obliqua (Macquart) (Diptera: Tephritidae), to volatiles of three mango [Mangifera indica L. (Anacardiaceae)] cultivars in field cage tests. The number of flies captured with Multilure traps baited with Amate mature green mangoes was significantly higher than that captured in traps baited with Coche and Ataulfo fruits. There was no significant difference between the number of flies captured in traps baited with Coche or Ataulfo mangoes. Gas chromatography‐mass spectrometry analysis of mango fruit volatiles identified 24, 22, and 19 compounds for Amate, Ataulfo, and Coche mango cultivars, respectively. A principal component analysis of the volatiles revealed that the Amate mango was more distant from the Ataulfo mango, and the latter cultivar was closer to the Coche mango. The compounds myrcene, α‐pinene, β‐selinene, and trans‐β‐ocimene were the most abundant in Amate mangoes, whereas 3‐carene, β‐selinene, terpinolene, and α‐pinene were the predominant compounds of Ataulfo cultivars. In the Coche mango, the predominant compounds were 3‐carene, β‐selinene, terpinolene, and limonene. Traps baited with a blend of myrcene, α‐pinene, and trans‐β‐ocimene captured more A. obliqua females and males than control traps. Flies were more attracted to the Super Q volatile extracts of Amate mango than to the three‐component blend formulated in a ratio of 1:1:1. However, there was no significant difference between the number of flies caught by traps baited with Amate mango extracts and that caught by traps baited with the three‐blend component when this was formulated according to the relative proportions in the mango extracts. Traps baited with myrcene, the major component, caught fewer flies than traps baited with Amate mango extracts.

SEASONAL AND NOCTURNAL FLIGHT ACTIVITY OF SPODOPTERA FRUGIPERDA MALES (LEPIDOPTERA: NOCTUIDAE) MONITORED BY PHEROMONE TRAPS IN THE COAST OF CHIAPAS, MEXICO

Abstract We determined seasonal and nocturnal flight activity of Spodoptera frugiperda (J. E. Smith) males with traps baited with pheromone in the coast of Chiapas, Mexico. A total of 3015, 3065, and 838 males were captured in 2000, 2001, and 2002, respectively. Pheromone trap catches decreased approximately 72% during 2002 with respect to 2000 and 2001. One of five experimental sites caught 90% of the total captured. The pattern of trap captures was quite variable among years and sites. In general, the flight activity of S. frugiperda males was seasonal, with two distinctive peaks in trap captures during the year. Males were caught during all hours of scotophase, however, most males were captured during the first 7 h. Highest peak capture was between 1900-2000 h. Trap captures were positively correlated with wind speed and temperature, and negatively correlated with relative humidity. Significantly more males were captured at wind speeds of 100-200 and >200 m/min than at wind speeds of 0-100 m/min.