Field response of three Tephritid fruit flies to three food-based attractants and suppression of Bactrocera zonata (Saunders) using Mazoferm–Spinosad in guava ecosystem in Sudan

Fruit flies of the genus Bactrocera are the most damaging pests of horticultural crops, leading to severe economic losses hindered exportation. Bactrocera dorsalis (Hendel) and Bactrocera zonata (Saunders) were reported in Sudan in 2005 and 2011 respectively affecting most of the fruits and vegetables in Sudan threatening income of poor farmers. Only Male Annihilation Technique (MAT) is applied in Sudan to manage the two Bactrocera species. A filed experiment was conducted to evaluate the response of B. dorsalis, B. zonata and Zeugodacus cucurbitae to three food-based attractants using McPhail traps in two sites in Gezira state, Sudan. Also, other trial was undertaken to determine the effect of spray of Mazoferm and Spinosad combination to control B. zonata. The results showed that food-based attractants lured both sexes of the above mentioned fruit flies and females represented (55-86%). At the first site, B. zonata responded in high numbers to Mazoferm followed by Torula yeast and GF-120 respectively while it responded equally to the Mazoferm and Torula yeast in the second site. B. dorsalis responded positively to Mazoferm followed by Torula yeast and GF-120 while Z. cucurbitae was attracted to Mazoferm, GF-120 and Torula for each attractant respectively. Spray of Mazoferm combined with Spinosad significantly reduced population of B. zonata (FTD) population and suppressed infestation level of guava fruits (fruit flies/Kg of fruits) when compared to unsprayed orchard. Bait Application Technique is an environmentally friendly approach that reduces infestation levels, lessen contamination and safeguard produce.

Raspberry ketone diet supplement reduces attraction of sterile male Queensland fruit fly to cuelure by altering expression of chemoreceptor genes

Sterile male Queensland fruit fly, Bactrocera tryoni (Froggatt), fed as immature adults on the plant compound raspberry ketone (RK), show a reduced attraction to cuelure, a synthetic analogue of RK used as an attractant in Male Annihilation Technique. We hypothesized the reduced attraction of RK-fed adult males to cuelure may be a consequence of altered expression of chemoreception genes. A Y-tube olfactometer assay with RK-fed and RK-unfed sterile B. tryoni males tested the subsequent behavioural response to cuelure. Behavioral assays confirmed a significant decrease in attraction of RK-fed sterile males to cuelure. RK-fed, non-responders (to cue-lure) and RK-unfed, responders (to cue-lure) males were sampled and gene expression compared by de novo RNA-seq analysis. A total of 269 genes in fly heads were differentially expressed between replicated groups of RK-fed, cuelure non-responders and RK-unfed, cuelure responders. Among them, 218 genes including 4 chemoreceptor genes were up regulated and 51 genes were down regulated in RK-fed, cuelure non-responders. De novo assembly generated many genes with unknown functions and no significant BLAST hits to homologues in other species. The enriched and suppressed genes reported here, shed light on the transcriptional changes that affect the dynamics of insect responses to chemical stimuli.

Electrophysiological Responses to Cuelure of Raspberry Ketone-Fed Queensland Fruit Flies

The sterile insect technique (SIT) and male annihilation technique (MAT) are important tools for the control of Queensland fruit fly (Q-fly), Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), a major insect pest of horticultural crops in Australia. In MAT, mature Q-fly males are attracted to a toxic bait using Cuelure, a synthetic analog of raspberry ketone (RK). Substantial improvements in control could be achieved by simultaneous use of SIT and MAT, but this requires suppression of the Cuelure response in released sterile flies. Recent studies report that prerelease feeding with RK during the first 48 h after emergence can reduce the response of mature Q-fly males to Cuelure, but the mechanism underpinning this is unknown. Here, to test whether reduced sensory sensitivity to Cuelure is involved, we evaluated the effects of RK supplements, adult diet (yeast-supplemented diet throughout adult stage vs yeast-supplemented diet only for 48 h), and age on electroantennogram (EAG) and electropalpogram (EPG) responses of Q-flies to Cuelure stimuli. EAG responses did not vary with RK supplements, sex, or age of Q-flies fed yeast-supplemented diet throughout the adult stage, but the responses of Q-flies fed other diet regime decreased with age. EPG responses of both sexes of Q-flies were affected by RK supplements, age, and their interaction, but without patterns that might indicate reduced maxillary palp response of RK supplemented flies to Cuelure. Our findings do not support the hypothesis that reduced Cuelure response of male Q-flies fed RK supplements is explained by reduced electrophysiological response in antennae or maxillary palps.

Effectiveness of Selected Parapheromones for Mass Trapping of Mango Fruit Fly, Ceratitis cosyra Walker and Oriental Fruit Fly, Bactrocera dorsalis Hendel (Diptera: Tephritidae) on Mango

Mango (Mangifera indica L.) is an important fruit crop in Nigeria. It is a source of essential vitamins and is also cultivated for its nutritional, medicinal and industrial uses. Fruit flies infest various commercial fruit crops and cause economic damage. Mass trapping and male annihilation technique (MAT) has been the most useful and common means of controlling fruit flies with special focus on Bactrocera dorsalis Hendel (Diptera: Tephritidae) on mangoes. The study evaluated the effectiveness of four types of parapheromones namely, methyl eugenol (liquid and solid forms), cuelure, terpinyl acetate and trimedlure for mass trapping of fruit flies on Mango. Modified Lynfield traps containing the parapheromones were randomly set on the mango orchards in three replicates in Nigeria Horticultural Research Institute (NIHORT) orchard, Okigwe, Imo state, Southeast Nigeria. This study was conducted during the mango fruiting period of 2019 season, when the density of fruit flies peaked. Effect of parapheromones on mean number of damaged dropped fruits was also evaluated. The mean population of B. dorsalis and Ceratitis cosyra was significantly higher (P>0.05) in liquid methyl eugenol traps when compared to other parapheromones. Bactrocera dorsalis recorded more than 90% of the fruit flies that were trapped especially in the first 3 weeks of trapping. In orchard I, Liquid methyl eugenol significantly (P<0.05) trapped highest number of B. dorsalis (270.20) in week I and similar trends were observed in orchard II. There was steady decline in damaged dropped mango fruits as the study progressed (Fig. 1 and 2). Use of liquid methyl eugenol was most effective in trapping B. dorsalis and C. cosyra, and it can be incorporated in Integrated Pest Management (IPM) programmes for the control of fruit flies.

Evaluation of a Genetic Sexing Strain of the Oriental Fruit Fly as a Candidate for Simultaneous Application of Male Annihilation and Sterile Insect Techniques (Diptera: Tephritidae)

The oriental fruit fly, Bactrocera dorsalis (Hendel), is an important pest of fruits and vegetables, and many countries operate surveillance programs to detect infestations and, if needed, implement costly control efforts. The Male Annihilation Technique (MAT), which involves deployment of the male lure methyl eugenol (ME) to reduce or eliminate the male population, has been used as a stand-alone strategy or as a precursor to the Sterile Insect Technique (SIT), which involves the release of sterile males to generate sterile male by wild female crosses and the production of inviable progeny. Modeling suggests that simultaneous implementation of MAT and SIT, rather than sequential deployment, increases the probability of successful eradication. Previous research has shown that B. dorsalis males that have fed on ME show reduced tendency to re-visit ME sources. Also, males fed ME gain a mating advantage over nonfed males. The goal of the present study was to evaluate the suitability of a genetic sexing strain of B. dorsalis as a candidate for concurrent implementation of MAT and SIT. Evaluation focused on the timing of prerelease exposure to methyl eugenol to identify the male age at which feeding upon the lure both i) reduces postrelease attraction to ME-baited traps (thus allowing the operation of MAT) and ii) enhances postrelease mating competitiveness (thus increasing the effectiveness of SIT). Results indicate that prerelease ME feeding by 6-d-old males, with release the following day, would allow effective, concurrent implementation of MAT and SIT.