Assessing the quarantine potential of ethyl formate as a stand-alone phytosanitary treatment against Ceratitis capitata: A comparative study on naked condition and natural infestation in mandarin

The South African citrus industry is dependent on export of fresh fruit to many markets around the world, with approximately 70 % of South Africa’s citrus crop being exported (CGA 2013). The false codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), is recorded as a pest of citrus fruit in southern Africa (Newton 1998; Grout & Moore 2015). As a result of its endemism to sub-Saharan Africa (Moore 2002), certain export markets of importance for the South African citrus industry, such as Peoples Republic of China, U.S.A. and South Korea, regulate it as a quarantine pest. Control of the pest in the field can be highly effective, using a suite of integrated control options, applied with diligent management (Moore & Hattingh 2012). These can succeed in reducing T. leucotreta infestation by 97 % or more (Moore et al. 2015). Such an integrated system, using the sterile insect technique as the mainstay of the programme, has succeeded in reducing moth catches by 99 %, fruit infestation by 96 % and export rejections by 89 % in the Western Cape Province of South Africa, since the inception of the programme in 2007 (Barnes et al. 2015). Despite the potential efficacy of such control strategies, some export markets still require mandatory post-harvest cold treatment of citrus fruit as a phytosanitary risk mitigation measure for T. leucotreta (SA-DAFF 2014). The cold treatment developed for T. leucotreta by Myburgh (1965) entails maintenance of the fruit at temperatures below 0 °C for 22 days. Such treatment is not only costly to apply, but there is a high risk of the fruit developing chilling injury (Lafuente et al. 2003; Cronje 2007). Some citrus fruit types are able to tolerate such cold treatment, if carefully managed (Lafuente & Zacarias 2006). However, some other citrus types are highly sensitive to cold damage and this cold treatment is not a feasible risk mitigation measure for commercial export of these types (Lafuente & Zacarias 2006). Lemons are highly sensitive to cold damage and cannot withstand exposure to temperatures below 0 °C for 22 days (Underhill et al. 1999; Lafuente & Zacarias 2006). Although standalone postharvest quarantine treatments, such as cold treatment, are still the most commonly used phytosanitary risk mitigation measure (Paull & Armstrong 1994), a range of alternative options, including non-host status, are increasingly being adopted (Liquido et al. 1995; Aluja et al. 2004; Follett & Neven 2006; Follett & Hennessey 2007; Pringle et al. 2015). Pringle et al. (2015) indicated that there are no definitions of host status of fruit specifically for tortricid pests, but referred to the following definitions that Aluja & Mangan (2008) applied to host status for Tephritidae: a natural host is one that is infested under totally natural field conditions. A non-natural host (or conditional host) is not known to be infested under natural field conditions, but there is experimental evidence that it can be infested and produce reproductive adults under laboratory (artificial) conditions. A non-host is one in which development cannot be completed. Pringle et al. (2015) also applied the following definitions provided by NAPPO (2008): a conditional host may be a host or non-host depending on suitability of conditions (e.g. stage of maturity, other physiological conditions or physical conditions), whereas a natural non-host does not become infested in nature. Most importantly, Pringle et al. (2015) followed NAPPO (2008) in its guidelines on determination of host status from natural infestation by evaluating infestation during the export harvest season, as a mandatory requirement in determining host status for phytosanitary purposes, regardless of data from field cage, greenhouse or laboratory trials. This approach to establishing host status was adopted by Armstrong (1991), who declared Sharwil avocados non-hosts (when attached to the tree) for oriental fruit fly, Bactrocera dorsalis (Hendel), and Mediterranean fruit fly, Ceratitis capitata (Wiedemann), after inspection of 114 000 fruit

Simple SummaryTephritid fruit flies are among the most destructive agricultural pests of fruits and vegetables worldwide and have global significance, introducing barriers to the trade of fresh tropical commodities. The melon fly, Mediterranean fruit fly, oriental fruit fly, and Malaysian fruit fly have entered and become established in Hawaii and have been making frequent incursions into agriculturally important states of the U.S. mainland, such as California and Florida. Bait sprays containing protein food bait plus an insecticide such as spinosad have been a major control method for these fruit flies. However, resistance to bait sprays has been reported. In this study, we evaluated the potential insecticidal effects of five different non-nutritive sugars on four species of fruit flies established in Hawaii. Erythritol alone or erythritol plus sucrose formulations have a significant negative impact on their survival, suggesting a potential use of erythritol as a non-toxic management tool for the control of tropical tephritid fruit flies.Tephritid fruit flies are among the most destructive agricultural pests of fruits and vegetables worldwide and can impose trade barriers against the movement of fresh tropical commodities. Primary pre-harvest control methods for these flies rely on the spraying of conventional chemical insecticides or bait sprays. However, resistance to these control methods has been reported in fruit flies. Erythritol is a non-nutritive sugar alternative for human consumption, which has been tested and confirmed for its insecticidal properties against various insect pest species. In this study, using laboratory bioassays, we evaluated the insecticidal effect of erythritol alone or various erythritol formulations containing sucrose and/or protein on four tropical fruit fly species established in Hawaii (e.g., melon fly, Mediterranean fruit fly, oriental fruit fly, and Malaysian fruit fly). In addition, the effects of other non-nutritive hexose and pentose sugar alcohols, such as sorbitol, mannitol, and xylitol, were tested. Among the different standalone and combinatory treatments tested, 1M erythritol and a combinatory formulation of 2M erythritol + 0.5M sucrose appeared to be the most detrimental to the survival of all four species of tested flies, suggesting the potential of using erythritol as a non-toxic management tool for the control of tropical tephritid fruit flies.

Esta pesquisa teve como objetivos avaliar a dinâmica populacional e registrar a diversidade de moscas-das-frutas (Diptera: Tephritoidea) em cultivares de pessegueiro Tropical, Talismã, Aurora 2, Aurora 1, Dourado 2 e Doçura 2, enxertadas sobre os porta-enxertos 'Okinawa' e Umê, em Presidente Prudente-SP. Foram realizadas as correlações da dinâmica populacional com a temperatura e a precipitação, e também a infestação com as características químicas dos frutos, Sólidos Solúveis e Acidez Titulável. No período de julho de 2004 a dezembro de 2006, a dinâmica populacional de moscas-das-frutas foi obtida através de coletas semanais de moscas-das-frutas em armadilhas McPhail, e a incidência foi determinada através da coleta de 30 frutos/planta/cultivar. O delineamento estatístico adotado foi o inteiramente casualizado, com cinco repetições. Ceratitis capitata foi predominante nas cultivares de pessegueiros estudadas. Não foi observada correlação significativa entre população de moscas-das-frutas e as variáveis de temperatura e precipitação, e sólidos solúveis e ácidez titulável. Entre as cultivares de pêssego, Aurora 2 apresentou maior infestação por C. capitata, da ordem de 22 e 23% nos anos 2004 e 2006, respectivamente. Também foi registrada a incidência de Neosilba spp. em frutos de pêssego. Doryctobracon areolatus (Braconidae), Tetrastichus giffardianus (Eulophidae) e Pachycrepoideus vindemmiae (Pteromalidae) foram recuperados de pupários de Tephritidae.

Specific scopeThis Standard describes the conduct of trials for the efficacy evaluation of bait insecticides against Ceratitis capitata on citrus and top fruits. For foliar spray application see EPPO Standard PP 1/302. Together they replace EPPO Standard PP 1/106 Ceratitis capitata.Specific approval and amendmentFirst approved in 2017–09.Special remarksThis Standard should be used for the evaluation of insecticides applied with baits to citrus or other fruit crops, usually covering a small part of the foliage. Trials can only be carried out under natural infestations on large surface field plots.

We investigated the host status of harvest-ready green lemons, Citrus × limon (L.) Burm. F. cv. Lisbon (Rutaceae), to Oriental fruit fly (Bactrocera dorsalis), Mediterranean fruit fly (Ceratitis capitata), and melon fly (Zeugodacus cucurbitae) (Diptera: Tephritidae) in Hawaii using laboratory and field studies. In forced-infestation small-cage exposures (using 25 × 25 × 25 cm screened cages with 50 gravid females), punctured lemons were infested by Oriental fruit fly, Mediterranean fruit fly, and melon fly, whereas undamaged lemons were not infested. Field collection, packing, and incubation of approximately 58,420 mixed-grade fruit (commercial export quality and off grades) found no natural infestations and resulted in no fruit fly emergence. Field studies enclosing fruit on trees in sleeve cages that were stocked with 50 gravid females per cage resulted in no infestations. Commercial export-grade green Lisbon lemon fruit should, therefore, be considered a non-host for Oriental fruit fly, Mediterranean fruit fly, and melon fly.

We investigated the host status of harvest-ready green Persian lime, Citrus x latifolia Tan. (Rutaceae), to Oriental fruit fly (Bactrocera dorsalis [Hendel]) and Mediterranean fruit fly (Ceratitis capitata [Wiedemann]) (Diptera: Tephritidae) using laboratory and field studies. In forced-infestation small cage exposures (using 25 × 25 × 25 cm screened cages with 50 gravid females) and large olfactometer cage tests (using 2.9 × 2.9 × 2.5 m walk-in screened cages with 100 gravid females), punctured limes were infested by Oriental fruit fly and Mediterranean fruit fly at low rates compared to papaya controls, whereas undamaged intact fruit was not infested. Field collection and packing of 45,958 commercial export-grade fruit and subsequent incubation to look for natural infestation resulted in no emergence of fruit flies. Forced infestation studies in the field using sleeve cages to enclose fruit with a high density of fruit flies (50 gravid females) on the tree also showed no infestation. Commercial export-grade Persian lime fruit should be considered a conditional nonhost for Oriental fruit fly and Mediterranean fruit fly.

Parasitoids of Anastrepha fraterculus (Wiedemann) were monitored on ripe fruit of 3 native and 1 exotic, wild Myrtaceae species in the Province of Entre Rios, NE Argentina, between Jan and Mar 1993 and 1994 with the aim of identifying indigenous parasitoid species and determining natural parasitization rates and fruit infestation levels. The fruit species surveyed were Psidium guajava L. (common guava), Feijoa sellowiana (O. Berg) O. Berg (feijoa), Eugenia uniflora L. (Surinam cherry), and Myrcianthes pungens (Berg) Legrand (mato). Altogether 2,186 tephritid puparia were obtained, 95% of which were A. fraterculus and 5% of which were Ceratitis capitata (Wiedemann). Of 1,667 adult insects that emerged from these puparia, 1,378 were A. fraterculus, 89 C. capitata, and 200 larval-pupal parasitoids, representing 4 species of 2 Hymenoptera families: Doryctobracon areolatus (Szepligeti), D. brasiliensis (Szepligeti), Utetes anastrephae (Viereck) (all Braconidae, Opiinae), and Aganaspis pelleranoi (Bret...

South Africa is the 13th largest producer and second largest exporter of citrus fruit globally. The false codling moth, Thaumatotibia leucotreta, and the fruit flies, Ceratitis capitata, C. rosa and Bactrocera dorsalis, can potentially infest citrus fruit and therefore pose a phytosanitary risk for export markets. Consequently, a wide range of postharvest phytosanitary treatments for disinfestation of citrus fruit from these pests have been investigated. These include cold treatments, irradiation, fumigation, heat treatments, and combinations of some of these. Due to the potential phytotoxic effects of all these treatments, the use of a systems approach that depends on two or more independent measures for acceptable phytosanitary risk mitigation is a preferable option. To date, the only postharvest disinfestation treatments used commercially for T. leucotreta and fruit flies for South African citrus, are stand-alone cold treatments and partial cold treatments, as a component in a multi-tiered systems approach. Research on development of novel and improvement of existing postharvest measures continues as a high priority. This includes postharvest detection technologies, in addition to treatment technologies.

Mexican fruit fly, Anastrepha ludens (Loew), is a quarantine pest of several fruit, including citrus, avocados, and mangoes, from extreme southern Texas to Costa Rica. To provide information for modeling heat phytosanitary treatments, third instars were heated with an aluminum heating block between 44 and 50 degrees C for time intervals up to those causing 100% mortality. At 44 and 50 degrees C, 100% mortality was achieved at 100 and 2 min, respectively. Each 2 degrees C increase in temperature resulted in a three-fourths reduction in the amount of time required to achieve 100% mortality. Mortality was modeled using thermal death kinetics, and the most suitable reaction order was the 0.5th. The thermal death activation energy was 560.7 kJ/mol, which is very similar to the value found for Mediterranean fruit fly, Ceratitis capitata (Wiedemann), in a previous study, indicating similar modes of action for heat mortality. However, the Mexican fruit fly had a lower threshold for heat-induced mortality, resulting in less time at all temperatures studied to achieve 100% mortality compared with the Mediterranean fruit fly. This type of information being gathered for fruit flies could lead to the development of generic phytosanitary heat treatments, which are available for other major phytosanitary treatments, such as cold storage, methyl bromide fumigation, and ionizing irradiation.

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), is arguably the most significant and studied quarantine pest of fresh fruits. There is well over a century of research observations on its response to cold, first as it pertains to shipment of fruits using cold temperatures to preserve fruit quality and how that may aid the survival and distribution of the pest, and then the use of colder temperatures to kill the pest in fruit shipments. Cold tolerance at 1.1°C in three populations of C. capitata generally increased as the insect developed; therefore, the third instar is the most tolerant of the stages that are found in fruit. The three populations did not differ in cold tolerance, indicating that cold phytosanitary treatments against this pest can be harmonized regardless of country of origin of marketed fruit hosts. This study facilitated the approval of some cold treatment schedules for the International Plant Protection Convention treatment manual that were being held up by concerns of possible differences in cold tolerance among C. capitata populations from different countries and points toward the possibility of generic, broadly applicable phytosanitary cold treatments. Most larvae found alive after 9 d of cold treatment did not pupariate and fewer still emerged as adults, indicating that acute larval mortality need not always be the objective of a cold phytosanitary treatment to be efficacious in preventing the establishment of invasive species.

Ethyl formate fumigation and ethyl formate plus cold treatment combination as potential phytosanitary quarantine treatments of Drosophila suzukii in blueberries

Some phytosanitary irradiation treatment research against tephritid fruit flies (Diptera: Tephritidae) has used artificially infested fruit with the unstated and untested assumption that the method adequately simulated a natural situation. We compare grapefruit, Citrus paradisi Macfayden, naturally infested by Mexican fruit fly, Anastrepha ludens (Loew), via oviposition until larvae reached the late third instar versus insertion of diet-reared third instars into holes made in grapefruits 24 h before irradiation; the latter technique has been used in other studies. Both infestation techniques resulted in statistically indistinguishable results, indicating that insertion of diet-reared third instar Mexican fruit fly into holes bored into grapefruit and subsequently sealed 24 h before irradiation would adequately represent natural infestation and could be used to develop a radiation phytosanitary treatment of the insect in grapefruit when prevention of adult emergence is used as the measure of efficacy. Nevertheless, it may not be advisable to extend this conclusion to other fruit fly/fruit combinations without doing appropriate comparison studies. Dissection of puparia from nonirradiated control insects that failed to emerge as adults showed a relatively even distribution of mortality among the developmental stages within the puparium. In contrast, dissection of puparia from irradiated third instars that did not emerge as adults revealed a sharp attenuation in development from cryptocephalic to phanerocephalic pupae demonstrating this transition to be the developmental step most affected by radiation.

Trading partners often require phytosanitary or quarantine treatments for fresh horticultural produce to ensure no economically important pest species are moved with the imported product. When developing such treatments, it is essential that the level of treatment efficacy can be determined. This is often based on the mortality of the total number of target pests exposed to treatment, but in naturally infested products this number is not always known. In such cases, the infestation rate and subsequently an estimate of the number of pests are obtained directly from a set of untreated control samples of the host product. The International Plant Protection Convention (IPPC) Secretariat has provided 2 formulas for these situations that place an interval around the point estimate obtained from the control samples to obtain an estimate of the infestation rate. However, these formulas do not allow a confidence level to be assigned to the estimate, and there are concerns with the assumptions regarding the distribution and the measure of variability used in the formulas. In this article, we propose 2 alternative formulas. We propose that the lower one-sided confidence limit should be applied to all infestation datasets that are approximately normally distributed. As infestation data are sometimes skewed, it is proposed the lower one-sided modified Cox confidence limit is applied to data approximately log-normal distributed. These well-recognized formulas are compared to the formulas recommended by the IPPC and applied to 3 datasets involving natural infestation.

Export celery (Apium graveolens var. dulce) from Australia has been affected by a natural infestation of purple scum springtails (Hypogastrura vernalis). These insects live inside the celery head, contaminating fresh celery, but do not cause any visible damage. As a result, purple scum springtail-infested celery has led to rejection for export with an impact on market value for fresh produce. In this study, fumigation with ethyl formate (EF), phosphine (PH3), and their combination on mortality of purple scum springtails in naturally infested celery was evaluated. Laboratory experiments were conducted using concentrations of 50, 60, and 90 mg·L−1 of EF for 1, 2, and 4 hours; 1, 1.5, 2, and 2.5 mg·L−1 of PH3 for 2, 4, and 6 hours; and 20, 30, and 40 mg·L−1 of EF combined with 1 mg·L−1 of PH3, for 2 and 4 hours at the laboratory temperature 25 °C. Complete control was achieved at 90 mg·L−1 of EF for 2 hours; however, phytotoxicity was observed in celery treated by EF at all concentrations. PH3 at 2.5 mg·L−1 achieved 100% mortality within 6 hours, and no phytotoxicity was evident. Mortality of 100% was achieved also at 30 and 40 mg·L−1 EF combined with 1 mg·L−1 of PH3 for 2 and 4 hours exposure time; however, phytotoxicity occurred with EF alone treatments and with the combination. From these data, we conclude that PH3 alone has potential as a fumigant for the preshipment treatment of celery infested with purple scum springtails.

A pest management programme using the chemosterilant lufenuron against the Mediterranean fruit fly, Ceratitis capitata in Mallorca (Spain) is reported. The aim of this field trial was to monitor the reduction on C. capitata population and fruit infestation during the second and third years of an overall pest control programme. The insect growth regulator lufenuron (a phenylbenzoylurea) was placed within a Sevep device baited with the synthetic, female attractants (ammonium acetate, putrescine and amines), as well as the male attractant trimedlure (TML). A total of 7200 devices were placed on 300 ha within the municipalities of the Sóller Valley, at a density of 24 devices/ha. In order to measure the effectiveness of the chemosterilization, the C. capitata population was evaluated by Probodelt traps, baited either with the synthetic food attractants or TML, placed in three citrus orchards located at different altitudes. Fruit infestation was also evaluated. Results showed an average of 20% reduction in adult medfly population (37.2% for males vs. 2.7% for females). However, high differences were observed among the different orchards. In Site 1, where fallen oranges fruits were removed and phytosanitary treatments were applied, female captures decreased by 63.28%. Whereas at Site 2, where fallen fruits were neglected and no insecticide was applied, female captures increased by 19.90%. Ceratitis capitata population increase placed in Site 2 was probably due to the presence of unmanaged or mismanaged surrounding orchards. Summing up, it seems that the method based on lufenuron applied in the Sóller Valley was successful in decreasing medfly population, but the presence of the nearby improperly managed citrus orchards, as well as other hosts fruit trees for C. capitata, decrease the efficacy of the method.