The False codling moth (FCM), Thaumatotibia leucotreta is a major quarantine pest that hampers Capsicum production and trade in sub-Saharan Africa (SSA) and may need a postharvest treatment to meet ...quarantine standards of lucrative overseas markets. In this study, we evaluated the efficacy of hot water treatment (HWT) as a potential nonchemical quarantine control option against T. leucotreta in bell pepper and its effect on the quality parameters of the peppers. Infested bell pepper harboring different immature stages of T. leucotreta were subjected to a hot water treatment of 50 ± 0.2 °C for eight different time-points to determine heat susceptibility of immature stages of T. leucotreta. The third-instar was the least heat susceptible, followed by second-and first-instar larva and the egg stage, respectively. The immersion time of 44.23 min (95% CL 43.22 – 45.24) was estimated to be the minimum time required to attain 99.9968% control level. In the large scale confirmatory experiment, there were no survivors from the 20,325 third instar individuals treated in bell pepper (180 – 220 g). Additionally, none of the 25,384 third instars exposed to 50 ± 0.2 °C for 32 min survived. The impact of the HWT schedule on bell pepper fruit quality parameters was assessed and there were no significant effects on weight loss, moisture content, total soluble solids, titratable acidity, dry matter and pH post treatment. These results provide strong evidence that the HWT schedule is an effective phytosanitary treatment for control of T. leucotreta, and may be adopted to facilitate access to overcome the phytosanitary barriers imposed by importing countries to capsicum from SSA.
•Bell pepper is a suitable host of false codling moth (FCM).•Third instar larva (L3) is the heat tolerant stage of FCM.•Minimum time required to achieve probit-9 control of the L3 is 44.23 min.•The HWT schedule does not affect bell pepper quality.
The use of protective netting is becoming an increasingly popular practice in the citrus industry in South Africa. However, data on its effects on biotic factors, particularly insect pests, are ...limited. This study focused on the effect nets have on key citrus pests in the Eastern Cape province. Orchards under nets and open orchards, of similar cultivars, ages and management practices, were monitored at several sites over two seasons for pest infestation and damage. Weekly monitoring was conducted for Thaumatotibia leucotreta infestation. Other pests were monitored either monthly or once a season. During the first season, T. leucotreta infestation was higher in orchards under nets, probably because, unlike the open orchards, the nets provided protection for the existing high levels of T. leucotreta. No T. leucotreta infestation was recorded in both orchard types in 2019. This was due to generally lower than usual pest abundance and dramatically improved area-wide management of T. leucotreta. Pheromone traps were used to monitor T. leucotreta males, including sterile moths used in a sterile insect technique programme. Although higher catches of wild T. leucotreta moths were recorded in orchards under nets, so too were there higher numbers of sterile moths and a higher ratio of sterile to wild moths, indicating the potential for better pest suppression for orchards under nets. Various other key pests were monitored during this time, with variable results for each species. Pests that were elevated under nets include Planococcus citri and Aonidiella aurantii. Pests that seemed to be lower under nets were Ceratitis capitata and Scirtothrips aurantii. Nets had no effect on Empoasca distinguenda, Penthimiola bella and Eriophyes sheldoni. These differences in pest levels in netted and open orchards trigger an important debate on whether nets are beneficial for or detrimental to the successful implementation of an integrated pest management programme.
Abstract Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) is a quarantine pest for certain export markets due to its phytosanitary status in affected crops in sub‐Saharan Africa, ...including citrus. Consequently, there is a zero‐tolerance policy for T. leucotreta in export markets. In South Africa, an integrated pest management strategy, incorporating a systems approach is used to achieve complete control of T. leucotreta . Preharvest management is multi‐faceted, including reliance on sex pheromone tools such as monitoring, attract‐and‐kill, mating disruptions, and sterile insect technique (SIT). Geographically isolated populations of T. leucotreta occur in South Africa, and there is speculation concerning the possible loss of sexual communication between these isolated populations, thereby compromising the efficiency of sex pheromone tools. To investigate this possibility, we collected samples from five geographically isolated populations of T. leucotreta and a population used for SIT in South Africa. These were subjected to sexual attraction trials under choice and no‐choice scenarios in a semi‐natural environment. Results of the choice tests revealed that males of each population preferred their corresponding population females, except irradiated males. However, when we deprived males of their preferred females, these preferences dissipated, and they were equally attracted to females from all populations. These results indicate that local adaptation and other selection forces in contrasting environments are important in sexual communication and selection in T. leucotreta but do not necessarily prevent recognition of sexual signals and attraction between geographically isolated populations. These findings are crucial for area‐wide IPM and precision control of T. leucotreta .
In insects, glutathione S-transferases (GSTs) are enzymes involved in detoxification of insecticides. However, few data are available for the codling moth, Cydia pomonella (L.). In this study, we ...cloned a delta class GST gene CpGSTdl from C. pomonella. Real-time quantitative PCR shows that CpGSTdl was up-regulated with aging, and the mRNA level of CpGSTdl was higher in the fat body and silk glands than in other tissues. The expression level of CpGSTdl exposure to insecticide suggests that CpGSTdl is up-regulated after chlorpyrifos-methyl and lambda-cyhalothrin treatments. Both lambda-cyhalothrin and chlorpyrifos-methyl altered GST activity in vivo. The purified CpGSTdl protein exhibits a high catalytic efficiency with CDNB and was inhibited by lambda-cyhalothrin and chlorpyrifos-methyl in vitro. Metabolism assays indicate that lambda-cyhalothrin was significantly metabolized while chlorpyrifos-methyl was not metabolized by CpGSTdl. Binding free energy analysis suggests that CpGSTdl binding is tighter with lambda-cyhalothrin than with chlorpyrifos-methyl. Our study suggests that CpGSTdl plays a key role in the metabolism of insecticides in C. pomonella. Keywords Cydia pomonella * Glutathione S-transferases * Metabolism * Insecticides * Molecular docking * Binding free energy
•Phenological model based on development rate functions versus demographic model.•Age distribution of the individuals in the overwintering stage.•Introduction of temperature- and age-dependent ...fecundity rate functions.•Introduction of temperature-dependent mortality rate functions.•Application to the codling moth.
Pest phenological models describe the cumulative flux of the individuals into each stage of the life cycle of a stage-structured population. Phenological models are widely used tools in pest control decision making. Despite the fact that these models do not provide information on population abundance, they share some advantages with respect to the more sophisticated and complex physiologically-based demographic models. The main advantage is that they do not require data collection to define the initial conditions of model simulation, reducing the effort for field sampling and the high uncertainty affecting sample estimates. Phenological models are often built considering the developmental rate function only. To the aim of adding more realism to phenological models, in this paper we explore the consequences of taking three additional elements into account: the age distribution of individuals which exit from the overwintering phase, the age- and temperature-dependent profile of the fecundity rate function and the consideration of a temperature-dependent mortality rate function. Numerical simulations are performed to investigate the effects of these elements with respect to phenological models considering development rate functions only. To further test the implications of different models formulation, we compare results obtained from different phenological models to the case study of the codling moth (Cydia pomonella) a primary pest of the apple orchard. The results obtained from model comparison are discussed in view of their potential application in pest control decision support.
Since its humble beginnings in the late 1990s, use of the sterile insect technique (SIT) in South African crop agriculture evolved from an underfunded ‘rag and bones’ operation in Stellenbosch for a ...single pest, Mediterranean fruit fly (Medfly), Ceratitis capitata (Wiedemann), on deciduous fruit and table grapes, to privatized programmes for three fruit pests, viz. Medfly, false codling moth (Thaumatotibia leucotreta (Meyrick)) on citrus, and codling moth (Cydia pomonella (Linnaeus)) on apples and pears.Afourth SIT programme, for the sugarcane stalkborers, Eldana saccharina Walker and Chilo sacchariphagus Bojer, is well under development. This review focuses mainly on the Medfly SIT programme, but gives brief summaries of the development and current status of SIT for the other pests mentioned. However, many of the hardships experienced by the Medfly SIT programme have also been experienced by those people that developed, or are still developing SIT for the other pests. During the last 15 years the Medfly programme has passed through many phases and evoked many emotions, including hope, despair, misunderstanding and mistrust; but it also bred perseverance, determination, empowerment and, later, confidence. It has also included an international DNA investigation to identify the origin of a Medfly outbreak in the SIT area. The Medfly SIT programme started at Agricultural Research Council (ARC) Infruitec-Nietvoorbij in Stellenbosch in the Western Cape Province with a feasibility study over some 5000 ha of table grapes in theHex RiverValley area, releasing by air 5 million sterile male Medflies per week, produced in a run-down outbuilding with questionable equipment. Fungal rot, ant invasions, severe rust, lack of funding, inexperience and ignorance were among the challenges. The feasibility project subsequently metamorphosed into a fully-fledged, privatized programme which now produces 25 million sterile male Medflies per week in a modern, state-of-the-art facility with high-specification equipment and highly qualified technicians, distributed weekly to three different production areas and released on the ground. The current objective of the Medfly SIT programme is population suppression, but this is merely a means to an end. Medfly is regarded as a pest of international quarantine importance, and a number of countries impose strict phytosanitary measures against this pest. The ultimate goal, therefore, is the creation of Medfly-free areas, leading to sustained and expanded international fruit markets without trade restrictions due to Medfly. Many challenges still remain, but there is a fierce determination by those involved that it will succeed. In the meantime, the false codling moth SIT programme, based in Citrusdal in the Western Cape Province, is very successful and has improved and expanded significantly. The pilot release phase of the sugarcane borer SIT programme is expected to be fast-tracked after the likely procurement of an irradiator in KwaZulu-Natal in 2015. However, for economic and other reasons the codling moth SIT programme had to be terminated in 2014. ‘Will SIT in South Africa fly?’ It is already flying, but it needs to fly much higher. With the necessity to export fruit from pest-free areas, to minimize crop losses of commercial and small-scale farmers, and considering the large investments already made in SIT in South Africa, there should be no going back.
Postharvest vacuum fumigation with methyl bromide (MB) was approved by Animal and Plant Quarantine Agency (APQA), Republic of Korea, to control codling moth, Cydia pomonella (Lepidoptera, ...Tortricidae), infesting 23-kg bags of in-shell walnuts (Juglans regia). Consistent with the approved parameters, in-shell walnuts with nut meat temperature (T) of 15.4 ± 0.2 °C (grand mean ± 2 SD; x‾GM± 2spooled) were packaged in sealed fiberboard cartons, loaded to 53% (v/v) chamber capacity, and fumigated in triplicate trials involving a single 63-carton pallet, with each lasting 4 h following the application of 56 mg L−1 MB at ca. 13.3 KPa (100 mmHg). MB concentrations were measured at four different locations over the course of each fumigation, respective Ct exposures were calculated, and the relative distribution of fumigant was evaluated. Exposures were maintained ≥ ca. 75 mg L−1 h in all cases, resulting in Ct exposures sufficient to control codling moth. A single 18-pallet confirmatory trial involving sealed fiberboard cartons was then conducted at a commercial facility, gas measurements were taken as above, and a minimum Ct of 117 mg L−1 h was observed. A kinetic model of MB sorption was used to demonstrate congruence across all trials, thereby supporting the reproducibility, scalability, and efficacy of this treatment, regardless if the in-shell walnuts are packaged in 23-kg bags or sealed fiberboard cartons.
•Certain countries require control of codling moth in California walnuts.•Postharvest methyl bromide vacuum fumigation of walnuts packaged in bags is approved by Korea.•The approved fumigation results in a Ct exposure adequate to control codling moth.•Packaging in fiberboard cartons versus bags did not affect sorption, and in turn, the Ct exposure.
The codling moth Cydia pomonella (L.) (Lepidoptera: Tortricidae) is one of the key pests of pome fruit and walnut in almost all growing regions of the world and has developed resistance to several ...insecticides. In this study, the susceptibilities of 15 codling moth populations to emamectin benzoate and 9 populations to lambda cyhalothrin collected in five European countries were measured by standard diet incorporation bioassays. Variation in susceptibility was observed among populations, with LC50 values ranging from 0.0017 to 0.0119 mg a.i./kg diet for emamectin benzoate and from 0.033 to 0.292 mg a.i./kg diet for lambda cyhalothrin. Our results revealed only small variations in emamectin benzoate susceptibility between populations, indicating no selection of resistance to this active ingredient. Even though a wider range of responses was detected for lambda cyhalothrin, our results also suggest that populations remain susceptible to this insecticide. Based on pooled LC95 evaluations, we propose the use of concentrations 0.02 mg a.i./kg of diet for emamectin benzoate and 0.60 mg a.i./kg of diet for lambda cyhalothrin in order to discriminate between resistant and susceptible individuals.
The susceptibility of wild populations of the codling moth Cydia pomonella (L.) to emamectin benzoate and lambda-cyhalothrin, was tested by diet incorporation bioassays. Results revealed small variations in emamectin benzoate susceptibility between all the populations, while a wider range of responses was detected for lambda cyhalothrin. Display omitted
•The susceptibility to two insecticides was tested in many codling moth populations.•Small range of responses and no resistant strains were found for emamectin benzoate.•A wider variability and a resistant population were detected for lambda cyhalothrin.•0.021 mg a.i./kg is suggested as discriminant concentration for emamectin benzoate.•A discriminant concentration of 0.60 mg a.i./kg is proposed for lambda cyhalothrin.
Male Cydia pomonella (L.) (Lepidoptera:Tortricidae) dispersion has largely been studied in nonmating disrupted orchards due to synthetic pheromone interference with capture in monitoring traps. ...Little is known about female dispersion. This study aimed to characterize male and female dispersion in mating disrupted commercial apple orchards. Sterile C. pomonella recapture data from single-trap multiple-release experiments using PHEROCON CM-DA COMBO + AA Lure-baited orange Pherocon VI delta traps was interpreted to determine pheromone–kairomone lure-baited trap effective area, trap deployment density for effective monitoring, and absolute male and female C. pomonella density in mating disrupted Washington commercial apple orchards. The maximum plume reach of the pheromone–kairomone lure in mating disrupted orchards was <5 m from the baited trap for both sexes. Maximum dispersive distances for 95% of the released C. pomonella in mating disrupted orchards were 106 and 135 m for males and females, yielding trapping areas of 3.87 and 6.16 ha, respectively. Estimates were consistent across 3 growing seasons and represent the first records of male and female dispersal distance and monitoring trap efficacy from commercial C. pomonella mating disrupted apple orchards. With relevance to commercial monitoring programs and economic thresholds in mating disrupted orchards, traps should be deployed at a density of 1 per 3–6 ha. Capture of a single male or female C. pomonella corresponds to at least 82–104 C. pomonella within the 3–6 ha trapping area. This refined C. pomonella capture interpretation in pheromone–kairomone baited traps in mating disrupted commercial apple orchards yields more precise damage estimates and assists in insecticide-use decision making.
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