Identification of attractant-derived bioactive compounds in the haemolymph of pest male carambola fruit fly, Bactrocera carambolae and melon fly, B. cucurbitae

Carambola fruit fly (CFF), Bactrocera carambolae and melon fly, B. cucurbitae are important fruit pests of economic importance. These flies are known to be strongly attracted to two different groups of male attractants- CFF to methyl eugenol (ME), and melon fly to raspberry ketone (RK) that have been successfully used in male annihilation and quarantine detection. Pharmacophagy of those attractants resulted in the biotransformation of ME to (E)-coniferyl alcohol (CF) that is a booster component of male sex pheromone in CFF whilst RK was sequestered unchanged as one of the male sex pheromone components in the melon fly. The presence of either CF or RK that sequestered in the rectal gland prior to emission during courtship period at dusk was investigated in the male circulatory system. These results and their implications in relation to that known about the oriental fruit fly, B. dorsalis will be discussed

Diurnal attraction of fruit flies (diptera: tephritidae) to methyl eugenol in a village ecosystem in Tanjung Bungah, Penang, Malaysia

Diurnal rhythm of male Bactrocera fruit fly attraction to methyl eugenol (ME) was investigated using clear traps design in a village ecosystem in Tanjung Bungah, Penang, Malaysia. The diurnal rhythm pattern studied by half-hourly sampling from 07:00 to 18:00 hr showed significant male fruit fly attraction to ME in the morning from 07:30 to 09:30 hr, with a distinct peak at 08:30-09:00 hr. The male attraction to ME was significantly lower in the afternoon and remained low approaching late afternoon. The ME-responding fruit fly species captured were B. dorsalis (86%), which dominated the local Bactrocera community, followed by B. umbrosa (5.8%) and B. carambolae (0.1%). This showed that B. dorsalis is a more dominant species than its sibling species, B. carambolae in the area studied. In addition, ca. 8.1% of Bactrocera male flies that bore intermediate morphological characteristics between B. dorsalis and B. carambolae were also captured in those traps. The present study shows that for ME-responding Bactrocera spp., male attraction to ME occurs throughout the day with peak period of attraction to ME occurring ca. 30 mins following sunrise for 2 hrs before gradually tapering off

Attraction of non-methyl eugenol-attracted males of the Oriental fruit fly to beta-caryophyllene

In controlling the highly destructive Oriental fruit fly, Bactrocera dorsalis, the use of male attractants such as methyl eugenol (ME) remains the gold standard in programmes such as the male annihilation technique (MAT). This is because ME remains the most potent attractant for this highly invasive fruit pest species. Consumption of ME by male B. dorsalis has been shown to result in result in significantly higher mating success for females compared with non-ME-fed males. Recently, work in our laboratory has been focused on developing non-ME-attracted male Oriental fruit fly lines but supplemented with semiochemical exposure. Non-ME-attracted males offer advantage that they will not be attracted to the MAT trap devices containing toxicant-laced ME. We hypothesized that non-ME-attracted males can be raised from the field, and that those males can regain mating advantage when exposed to certain semiochemicals. This follows our recent work which demonstrated that although pure isolines of non-ME-responding males were not attained, reduced responder males were obtained instead, until the 10th generation of rearing. When those males were assayed for their attraction to the sesquiterpene compound beta-caryophyllene (CP), no loss of attraction to CP was observed when compared to laboratory males that were used as controls. Males were attracted to feed on CP. Further, those CP-fed males showed that they were able to mate significantly earlier and more successfully compared with control males. This suggests that in releases of sterile male flies to compete with wild males for mating, and not getting captured in MAT devices, non-ME-attracted sterile males but supplemented with compounds such as CP can be considered for further field trials. This warrants further investigations

Response of Diaphorina citri Kuwayama (Hemiptera:Psyllidae) to volatile emmitted from leaves of two Rutaceous plants.

Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is an important worldwide pest of citrus, because of its ability to vector the three phloem-restricted bacteria in the genus Candidatus Liberibacter, that cause citrus greening or huanglungbing. Studies were conducted to examine the effects of flush growth stage and volatile compounds emitted by two rutaceae plants on oviposition and feeding site selection of D. citri. Three methods including choice, no choice and Y tube olfactometer assays were conducted using plants with only newly expanded leaves (4-6 days old), plants with all leaves completely hardened (14-21 days old) and plants without leaves (14-21 days old). The results showed that significant number of adult D. citri were attracted to plants with newly expanded leaves for oviposition and feeding in both choice and no choice assay, and when the two plants were assayed together in Y tube, significant number of the adults select Y tube arm with Citrus suhuiensis leaves and similarly in choice assay more adults select C. suhuiensis for oviposition and feeding than Murraya paniculata. The results gave an insight into response of D. citri to different plant forms and volatiles emitted by the plant which is useful in monitoring and management of the pest

Parasitism rate, host stage preference and functional response of Tamarixia radiata on Diaphorina citri

The Asian citrus psyllid Diaphorina citri (Kuwayama) (Hemiptera: Psyllidae), is a serious pest and main threat to citrus production worldwide. The present study was carried out to assess the performance of T. radiata, as biological control agent of D. citri, under insectary condition. The result shows T. radiata, to preferred late (4th and 5th) instar nymphs than early (1st, 2nd and 3rd) instar nymphs of D. citri, with mean parasitism rate of 0%, 0%, 43.3%, 76.9% and 86.0% for 1st, 2nd, 3rd, 4th and 5th instar nymphs respectively. The binomial logistic regression analysis of D. citri nymphs attacked by T. radiata, as a function of host (D. citri nymphs) density offered, shows T. radiata, to display a functional response type II with attack rate of 39.99 and 34.04, and handling time of 0.60 and 0.71 for 4th and 5th instar nymphs of D. citri respectively

Attraction and consumption of methyl eugenol by male Bactrocera umbrosa Fabricius (Diptera: Tephritidae) promotes conspecific sexual communication and mating performance

The Artocarpus fruit fly, Bactrocera umbrosa (Fabricius) (Diptera: Tephritidae), is an oligophagous fruit pest infesting Moraceae fruits, including jackfruit (Artocarpus heterophyllus Lamarck), a fruit commodity of high value in Malaysia. The scarcity of fundamental biological, physiological and ecological information on this pest, particularly in relation to behavioural response to phytochemical lures, which are instrumental to the success of many area-wide fruit fly control and management programmes, underpins the need for studies on this much-underrated pest. The positive response of B. umbrosa males to methyl eugenol (ME), a highly potent phytochemical lure, which attracts mainly males of many Bactrocera species, was shown to increase with increasing age. As early as 7 days after emergence (DAE), ca. 22% of males had responded to ME and over 50% by 10 DAE, despite no occurrence of matings (i.e. the males were still sexually immature). Male attraction to ME peaked from 10 to 27 DAE, which corresponded with the flies’ attainment of sexual maturity. In wind-tunnel assays during the dusk courtship period, ME-fed males exhibited earlier calling activity and attracted a significantly higher percentage of virgin females compared with ME-deprived males. ME-fed males enjoyed a higher mating success than ME-deprived males at 1-day post ME feeding in semi-field assays. ME consumption also promotes aggregation behaviour in B. umbrosa males, as demonstrated in wind-tunnel and semi-field assays. We suggest that ME plays a prominent role in promoting sexual communication and enhancing mating performance of the Artocarpus fruit fly, a finding that is congruent with previous reports on the consequences of ME acquisition by other economically important Bactrocera species

Dispersion pattern and sampling of Diaphorina citri Kuwayama (Hemiptera:Psylidae) populations on Citrus suhuiensis hort. ex tanaka in Padang Ipoh Terengganu, Malaysia

An understanding of the dispersion patterns of a pest is an important pre-requisite for developing an effective pest management program. In this study, fifty five (55) citrus trees were surveyed for adult Diaphorina citri once every four week for a period of ten months (March 2011 – December 2011). Analysis of spatial-distribution pattern using various indices of dispersion and regression models showed that D. citri exhibited an aggregated distribution on Citrus suhuiensis. Taylor’s power law ( a = 0.897, b = 1.267, R2 = 0.74) fitted the data better than Iwoa’s regression modal (a = 0.376, ß = 0.196, R2 = 0.409). The optimal sample sizes needed for fixed precision levels of 0.10, 0.15 and 0.25 were estimated using Taylor’s regression coefficients, and the required sample sizes increased dramatically with increased levels of precision. Therefore, these sampling-plan presented should serve as a tool for an efficient estimation of D. citri population density in citrus orchard for pest management decision

Phenylpropanoid sex pheromone component in hemolymph of male Carambola fruit fly, Bactrocera carambolae (Diptera: Tephritidae)

Males of the Carambola fruit fly, Bactrocera carambolae Drew & Hancock (Diptera: Tephritidae) are strongly attracted to, and feed on methyl eugenol (ME) that exists as a plant secondary compound in over 480 plant species worldwide. Upon feeding on this highly potent attractant, the males convert ME into a phenylpropanoid, (E)-coniferyl alcohol (ECF), that is stored in the rectal gland prior to its release as a sex pheromone component during calling and courtship. Here, using a series of chemical and behavioural assays, we provide evidence for the presence of ECF in the hemolymph and suggest the latter’s involvement in transport of ECF to the male rectal gland following consumption of ME. The greatest concentration of ECF was detected in the hemolymph at 3 h after feeding on ME and subsequently decreased, whereas accumulation of ECF in the rectal gland reached a maximum at 2 days post-feeding. Using male flies as biodetectors, fractions of 1.5–9.2 kDa from fractionated hemolymph of ME-fed males were found to be attractive and contained ECF as sex pheromone. In addition, the significant increase in the total concentration of protein in hemolymph from ME-fed males compared with that of ME-deprived males suggests a direct protein carrier involvement in hemolymph transport of the sex pheromone in B. carambolae. All these results are further discussed in comparison with previous results obtained from its sibling species, the Oriental fruit fly—B. dorsalis

Comparative sensitivity to methyl eugenol of four putative Bactrocera dorsalis complex sibling species-further evidence that they belong to one and the same species B. dorsalis

Males of certain species belonging to the Bactrocera dorsalis complex are strongly attracted to, and readily feed on methyl eugenol (ME), a plant secondary compound that is found in over 480 plant species worldwide. Amongst those species is one of the world’s most severe fruit pests the Oriental fruit fly, Bactrocera dorsalis s.s., and the former taxonomic species Bactrocera invadens, Bactrocera papayae and Bactrocera philippinensis. The latter species have been recently synonymised with Bactrocera dorsalis based on their very similar morphology, mating compatibility, molecular genetics and identical sex pheromones following consumption of ME. Previous studies have shown that male fruit fly responsiveness to lures is a unique phenomenon that is dose species-specific, besides showing a close correlation to sexual maturity attainment. This led us to use ME sensitivity as a behavioural parameter to test if Bactrocera dorsalis and the three former taxonomic species had similar sensitivity towards odours of ME. Using Probit analysis, we estimated the median dose of ME required to elicit species’ positive response in 50% of each population tested (ED50). ED50 values were compared between Bactrocera dorsalis and the former species. Our results showed no significant differences between Bactrocera dorsalis s.s., and the former Bactrocera invadens, Bactrocera papaya and Bactrocera philippinensis in their response to ME.We consider that the Bactrocera males’ sensitivity to ME may be a useful behavioural parameter for species delimitation and, in addition to other integrative taxonomic tools used, provides further supportive evidence that the four taxa belong to one and the same biological species, Bactrocera dorsalis

Characterization of Bactrocera dorsalis (fruit fly) emergence inhibitor from neem leaf-empty fruit bunch-based vermicompost using metabolomics approach

Neem (Azadirachta indica) and oil palm empty fruit bunch have been reported to contain varieties of secondary metabolites in which some possess bioactivities. Through vermicomposting of these plant materials, a useful final product which exerted inhibition activity on the emergence of Bactrocera dorsalis may be produced. This study presents the results of chemometric data analysis which describes the fruit fly emergence inhibition activity of neem leaf-empty fruit bunch-based vermicompost. The vermicompost, with neem leaf and empty fruit bunch served as controls, were analyzed by proton nuclear magnetic resonance (1H NMR)spectroscopy. The chemometric evaluation was performed by principal component analysis (PCA) and partial least square (PLS). The NMR profiles of the chemical constituents of the vermicompost were correlated to the inhibition activity of the fruit flies wherein neem leaf was shown to be the major inhibitor. Based on NMR-metabolomics approach, the metabolites of the neem leaf responsible for the activity were identified as azadirachtin and salannin