Chemical Composition of Essential Oils from Leaves and Fruits of Juniperus foetidissima and Their Attractancy and Toxicity to Two Economically Important Tephritid Fruit Fly Species, Ceratitis capitata and Anastrepha suspensa

The present study analyzed the chemical composition of Juniperus foetidissima Willd. essential oils (EOs) and evaluated their attractancy and toxicity to two agriculturally important tephritid fruit flies. The composition of hydrodistilled EOs obtained from leaves (JFLEO) and fruits (JFFEO) of J. foetidissima was analyzed by GC–FID and GC–MS. The main compounds were α-pinene (45%) and cedrol (18%) in the JFLEO and α-pinene (42%), α-thujone (12%), and β-thujone (25%) in the JFFEO. In behavioral bioassays of the male Mediterranean fruit fly, Ceratitis capitata (Wiedemann), both JFLEO and JFFEO showed strong attraction comparable to that observed with two positive controls, Melaleuca alternifolia and Tetradenia riparia EOs. In topical bioassays of the female Caribbean fruit fly, Anastrepha suspensa (Loew), the toxicity of JFFEO was two-fold higher than that of JFLEO, with the LD50 values being 10.46 and 22.07 µg/µL, respectively. This could be due to differences in chemical components between JFLEO and JFFEO. The JFFEO was dominated by 48% monoterpene hydrocarbons (MH) and 46% oxygenated monoterpenes (OM), while JFLEO consisted of 57% MH, 18% OM, and 20% oxygenated sesquiterpenes (OS). This is the first study to evaluate the attractancy and toxicity of J. foetidissima EOs to tephritid fruit flies. Our results indicate that JFFEO has the potential for application to the management of pest tephritid species, and further investigation is warranted.

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.

Toxics or Lures? Biological and Behavioral Effects of Plant Essential Oils on Tephritidae Fruit Flies

The family Tephritidae (Diptera) includes species that are highly invasive and harmful to crops. Due to globalization, international trade, and human displacement, their spread is continuously increasing. Unfortunately, the control of tephritid flies is still closely linked to the use of synthetic insecticides, which are responsible for detrimental effects on the environment and human health. Recently, research is looking for alternative and more eco-friendly tools to be adopted in Integrated Pest Management (IPM) programs. In this regard, essential oils (EOs) and their main compounds represent a promising alternative to chemical insecticides. EOs are made up of phytoconstituents formed from the secondary metabolism of many plants and can act as attractants or toxics, depending on the dose. Because of this unique characteristic, EOs and their main constituents are promising tools that can be used both in Sterile Insect Technique (SIT) programs and in the “lure and kill” technique, exploiting the attractiveness of the product in the former case and its toxicity in the latter. In this article, current knowledge on the biological and behavioral effects of EOs and their main constituents on tephritid fruit flies is reviewed, mainly focusing on species belonging to the Anastrepha, Bactrocera, Ceratitis, and Zeugodacus genera. The mechanisms of action of EOs, their real-world applications, and challenges related to their use in IPM are critically discussed.

Parental RNAi Silencing of the transformer-2 Gene in a Species of the Anastrepha fraterculus Complex of Cryptic Species (Diptera, Tephritidae)

In genera Anastrepha, Bactrocera and Ceratitis of the tephritid fruit flies the auto-regulatory function of gene transformer is assumed to be activated by maternal derived mRNA or the proteins of the gene transformer (tra-2 mat) and transformer-2 (tra-2mat). However, this maternal effect was not yet been demonstrated. The objective of the present study was to test the effect of absence of tra-2mat in the eggs on the sex determination of A. sp.1 affinis fraterculus. This was achieved by silencing gene tra-2 in the parental females via the pRNA interference. The data showed that tra-2 was transiently silenced in the female for three weeks period. The progenies sex ratio produced by these females during the silencing of tra-2 depart from 1:1 in favor of males. The excess of males was due to the transformation of a fraction of genotypical female XX embryos into XX males, the so-called pseudomales, Individual F1 males from the offspring of treated females crossed to females from the stock, revealed that majority of them showed regular mating behavior and were fertile. However, no offspring was produced in the crosses by a fraction of males that have produced sperms, showed regular mating behavior but did not transfer sperms to the females. The data allow the conclusion that the absence of tra-2mat in the eggs had impaired the self-regulation of the embryonic gene tra resulting in the transformation of XX embryos into pseudomales and also that these pseudomales are sterile. This effect may be useful improve more sustainable technologies for fruit fly control such as SIT.

Climate Change and Invasion Expansion Jointly Reshape Geographic Ranges of Invasive Tephritid Fruit Flies

Human-mediated species introductions have greatly contributed significantly to the current global alteration of the biosphere, with many invasive species rapidly expanding their geographic ranges, leading to changes in biodiversity and disruptions of ecosystem functioning. With a modified SDM that considers both extensive data coverage and the distance to previously already occupied areas, we show continued shifts and expansions of geographic ranges of two globally invasive tephritid pest species Bactrocera dorsalis and Ceratitis capitata). Both tephritid pests are still expanding globally, with their geographic ranges estimated to have expanded by 65% and 22% in the past three decades. The potential future geographic distributions of B. dorsalis and C. capitata under four scenarios of Representative Concentration Pathways (RCPs) for 2050 highlighted some key changes when compared to their current occurrences. Under all four RCPs by 2050, the potential geographic distribution of C. capitata was predicted to shrink by 5-14%, while the distribution of B. dorsalis was predicted to increase by 12-15%. Under different climate scenarios for 2050, B. dorsalis could experience a notable poleward expansion with increasing connectivity in its future geographic distribution. The two tephritids will continue to co-occur in Africa, with B. dorsalis experiencing higher suitability in most regions where they overlap. Climate changes were estimated to contribute more, than non-equilibrial invasion expansion, to changes in the geographic ranges of the two tephritid pests. The forecasted potential geographic distributions could enhance regional biosecurity preparedness in future climates and mitigate proactively the economic loss from these fruit fly pests.

Establishing criteria for the management of tephritid fruit fly outbreaks

Tephritid fruit flies (Diptera; Tephritidae) represent a group of insects that include some of the most economically important pests in horticulture. Because of their economic importance, the financial impacts of an incursion of tephritid fruit flies into a new area can often result in restrictions to trade. The economic impacts of any trade restrictions imposed by importing countries are confounded by the current absence of consistent and accepted criteria for the strength and extent of any trade restrictions and declaring the end of an incursion. The author has developed models that can be used to establish criteria for the management of tephritid fruit fly outbreaks as outlined in international standards. A model enables criteria on when to recognise an incursion has occurred and establish export restrictions. Another model determines what area or radius an export restriction zone (ERZ) should cover. And a third model establishes criteria for the conditions required to enable an ERZ to be rescinded and the area’s pest free status reinstated. The models rely primarily on fruit fly biology and the effectiveness of surveillance trapping systems. The adoption of these proposed criteria internationally for establishing a control system and responding to fruit fly outbreaks would provide considerable economic benefits to international trade. Additionally, these criteria would enable countries to make more informed cost–benefit decisions on the level of investment in fruit fly control systems that better reflects the economic risks fruit flies represent to their economy.