Use Of Ethyl Formate And Other Volatile Compounds As Environment Friendally Fumigant To Control Spotted Wing Drosophila, Drosophila Suzukii

Abstract: Spotted wing Drosophila (SWD), Drosophila suzukii (Dipetra: Drosophilidae), is an invasive pest of tender fruit crops. Unlike most other drosophila spp. It prefers to attack healthy harvestable fruit and making it unmarketable and causing loss to import/export industry. Due to nature of damage caused my SWD, quarantine and pre-shipment fumigation treatment of fruit being imported/ exported is compulsory. Methyl bromide (Mbr) has been used for many years as an effective quarantine and pre-shipment treatment to kill insect pests in fruits imported into or out of Ontario, that can otherwise be detrimental to environment and crops. However, Mbr is in the process of being phased out due to its ozone depletion properties and harmful effects to human health. As a result, there is urgent need for environment friendly fumigant approaches to meet the phytosanitary requirements of importing country and to prevent entry of harmful species to new areas. In this research, we propose a novel idea of fumigation of fruits and vegetables at individual packaging level contrary to current batch fumigation system using ethyl formate (EF) and other volatile compounds such as cinam aldehyde, allyl isothiocyanate, hexanal and benzaldehyde that possess generally-regarded-as-safe (GRAS) status, but shows synergistic insecticidal and antimicrobial properties.

Efficacy of these volatile compounds individually and in combination with EF will be tested against target insect (SWD) adults and egg stage and most effective fumigant showing highest mortality against SWD will be further investigated for stability and incorporation in electro spun fibres to use in packaging material. That proposed approach will allow the fumigation of product during transportation, thereby eliminating the static fumigation and minimizing the shipment delay and increase the product shelf life. This innovative approach of fumigation at individual packaging level using spun fibre technique would be a unique advancement in the field of fumigation that will facilitate international and interprovincial trading for Ontario fruit producers, allowing them to compete more actively in global market. Keywords: tender fruit; quarantine and pre-shipment; electro spun fibre; synergistic effect; methyl bromide, spotted wing drosophilaIntroduction: The spotted-wing drosophila (SWD), Drosophila suzukii (Diptera: Drosophilidae), is an invasive pest from Asia, that has now spread and become a key pest in Europe and North America. In contrast to other drosophila spp. It is of most economic importance as it attacks healthy fruit that is still on tree; while other spp. oviposit in overripe or already decayed fruits, D. suzukii use its serrated ovipositor to penetrate in skin of ripening fruits and these egg-laying holes acts as entry points for other pathogens to enter and cause further damage. SWD has spread to most fruit producing regions in Ontario, affecting berries, cherry, plum, peach, nectarine and grapes. Healthy fruit attacked by SWD does not show symptoms at the time of harvest but can result into economic loss in the absence of good fumigation treatment when produce is subject to transport or kept in storage for some time. To deal with this problem and post-harvest fumigation is most important treatment. Methyl bromide is most effective and extensively used fumigant due to its broad-spectrum pesticide activities against different pest of fruits, vegetables, grains and soil.

However, due to its ozone depletion properties and toxicity, it poses significant threat to human health and environment and signatories of Montreal Protocol including Canada has banned use of Mbr for all applications except quarantine and pre-shipment purpose since 2005. As, Mbr is classified number 1 substance and being phased out globally, its use for quarantine and pre-shipment purpose may not be exempted in future. As, quarantine and pre-shipment fumigation is mandatory treatment to meet the phytosanitary requirements of a country, for example in Canada CFIA (Canadian Food Inspection Agency) requires that produce being imported to Canada is fumigated and free of insect, pest and soil debris to minimize the chances of entry of any invasive pest and its establishment in Canada that can cause economic and environmental losses. Recognizing Mbr toxicity to human health, its impact on environment, it becomes need of hour to investigate alternative environment friendly post-harvest fumigant of fresh produce against insects specially SWD that would be as effective as Mbr but least toxic to human health and environment. In this research we are proposing testing of naturally occurring volatile compounds such as ethyl fromate (EF), cinam aldehyde, benzaldehyde, hexanal and allyl isothiocyanate against SWD. Ef is an FDA (Food Drug Act) approved food flavoring agent and GRAS naturally occurring in many products (e. g. , rice, beef, grapes, wine, beer and cheese). Research shows that it is effective in killing thrips, mealybugs, mites, beetles and moths. Ef hydrolyzes rapidly into formic acid and ethanol, both of which are antimicrobial in nature and do not have long residual effect as compare to Mbr which pose long term residual concerns and its chronic and acute inhalation can cause neurological respiratory problems in humans. Previous studies are also supporting insecticidal properties of Ef and cinam aldehyde against leafroller, pacific spider mite and grapes mealybug.

These low molecular weight compounds degrade rapidly into by-products that are antimicrobial in nature and do not pose long term residual concern, this is an important advantage over conventional chemical Mbr. Synergistic effects have been reported when Ef is used in combination with allyl isothiocyanate and this property of Ef will be further investigated for other compounds in this research. Post-harvest treatment of fruits with Ef and other volatile compounds can result synergistic effects to manage SWD in imported and exported produce. Objective of this study is to evaluate the toxicological response of SWD adults and eggs to Ef based formulation as fumigants. AS a result of these toxicological studies most effective formulation will be further investigated in incorporation studies in electro spun fiber to use as fumigant in active packaging material for import and export purpose. Encapsulation studies will be carried out by Food department and after successful incorporation and stabilization of most effective fumigant in electro spun fibre that material will be further tested for its effectiveness in the presence of target pest and fruit oppose to current batch fumigation. Research Methods: Considering the potential damage and significant loss pose by SWD, this is chosen as surrogate insect in this study and to carry out this research Lab reared SWD culture will be obtained from Sinclair Lab at University of Western, Ontario. Rearing of SWD will take place on cornmeal diet in a controlled chamber in Graham Hall at at 22±1°C, RH 60±5% and photoperiod of L16: D822. In this study different volatile compounds such as Ethyl formate, cinnamaldehyde, benzaldehyde, hexanal and allyl isothiocyanate individually or in combination with Ef will be tested for environment friendly fumigant. To perform the bioassays, 10 male and 10 females of mixed aged adults will be transferred to 1L glass container with modified solid lid that has hole covered with rubber to ensure the air tight conditions for fumigation. Insects in all containers will be provided with cornmeal diet in small portion cups.

All fumigation will be tested at different dose rate to have a mortality ranged from 80-100%. All fumigants will be injected into glass container using pipette through hole made in lid on the filter paper attached on underside of lid. There would be a wire mesh between insects and filter paper to keep them separate. After treatment, containers will be held in controlled environment at 22±1°C, RH 60±5% and photoperiod of L16: D8. Mortality data will be recorded 2hr, 6hr and 24hr post treatment. All the treatments will have five replications and one control. To check the efficacy of these volatile compounds against eggs diet with known number freshly laid eggs will be placed in each container and then fumigants will be provided. Data related to number of hatched eggs will be taken 24 hrs post treatment. Formulation that show promising result will be further investigated in encapsulation studies by Food department. Several approaches will be taken to solve the problem of volatility and after successful precursor development and electrospinning of these chemicals they will be tested again in the presence of fruit and SWD to evaluate stability of their precursor efficacy of volatile compounds to be used in individual packaging level as oppose to current batch fumigation. Research Significance: Canadian horticulture is a dynamic, diverse and most varied industry with almost 120 varieties of fruits and vegetables grown in every region of Canada. Total fruit and vegetable cultivated area rose 2. 3% to 235,976 hectares in 2016. The farm gate value of Canadian fruit and vegetables rose 7. 4% from 2015 to $2. 2 billion in 2016. (statistics Canada 2017). Despite that diverse horticulture industry, Canada imports its majority of fruits and vegetables from other countries to meet the market demand.

The majority of Canada’s domestic produce is grown between June and October, leaving very little in the way of fresh local produce during the cold, barren, winter months. That’s why to meet the consumer and market demand, Canada imports its majority of fruits and vegetables from other countries. But most important problem associated with export or import of fresh produce is post-harvest loss caused by different factors most importantly insects pest and reduced shelf life of these horticulture perishables. Most of the time, insects such as SWD lays eggs in healthy fruit before harvest and can cause complete decay of produce where it is held in storage or is exposed to lengthy period of transport. Sometime, quarantine insects unintentionally enter into other countries via importing fruits and vegetables. SWD is an invasive pest originated from Asia, but now spread to most part of Canada. Hence it is imperative to find solution to reduce post-harvest loss caused by SWD and maintain quality of fresh produce during import/ export and interprovincial trade and to prevent entry of quarantine pest into other destination countries. Most widely used solution of this problem is use of Mbr as quarantine and pre-shipment treatment of fruit and vegetables. However, due to its ozone depletion nature and deleterious effects on human and environment health its use is banned for most treatment though quarantine and pre-shipment use is exempted in this ban but chances are there it might not be available even for exempted use.

To maintain environmental and human health and to sustain the international and interprovincial trade of fruits and vegetables, this research for the development of environment friendly fumigant is crucial. It would result into such products that would be most effective to control SWD in fruits but least toxic to human health and environment. Moreover, as our proposed research involves encapsulation of most effective fumigant in electro spun fibre and use of that encapsulated material in at individual packaging level. Use of environment friendly fumigant in electro spun fibre at individual packaging level is an innovative idea and has not been reported so far. Firstly, it will allow fumigation at individual packaging level oppose to current batch fumigation minimizing the danger of handling large quantities of dangerous fumigant like MBr. Secondly, there would be no need to keep the produce in storage after fumigation to reduce the residual effects as these proposed volatile compounds don’t have long term residual effect and their by-products are safe. Thirdly, that will eliminate the delay in shipment allowing the fumigation during transport resulting in provision of good quality produce to market and consumer end. As, it is mentioned above these compounds show synergistic effects and have antimicrobial properties that means we would eb able to control insect and minimise the proliferation of spoilage microorganisms resulting in less use of chemicals.

Another benefit of using Ef and Ef formulation would be their increased efficacy as in the high relative humidity and fruit and vegetables are moisture rich commodities, that will help to enhance activity of Ef based formulation. Success of that project would result into unique leading-edge product that will revolutionize the market place and will benefit the consumer by providing them fresher and healthier produce. Producer will get benefitted by this product as it would make it possible for him to reduce the post-harvest loss and get more profit and most importantly environment will be safe as these are non-ozone depleting compounds. Overall this project will not only prevent the entry of unwanted insects / SWD into Ontario or export domestic species to other countries that can cause economic and environmental loss but also help to maintain product freshness during distribution. Successful development of this technology will not only facilitate the interprovincial trade but also open the doors of international markets for Canadian fruit and vegetables producers allowing them to compete in global market and increase their market share abroad.