Improved Envirosol fumigation methods for disinfesting export cut flowers and foliage crops

Transcription

1 Improved Envirosol fumigation methods for disinfesting export cut flowers and foliage crops Z Zhang & C W van Epenhuijsen September 2004 A report prepared for MAF Sustainable Farming Fund, Central Flower Growers Association, Westbay Waratahs Ltd, Katikati Revised 19/10/05 Copy 1 of 6 New Zealand Institute for Crop & Food Research Limited Private Bag , Palmerston North, New Zealand

2 2004 New Zealand Institute for Crop & Food Research Limited

3 Contents 1 Executive summary 1 2 Introduction 1 3 Experimental methods and materials Fumigation facilities Vacuum/Floragas trials VaporMate trials Pests and life stages for mortality assessment Western flower thrips Two-spotted spider mites Phytotoxicity assessment Cut flowers and foliage crops assessed Phytotoxicity assessment procedures Experimental design and treatments Vacuum/Floragas treatments VaporMate treatments 4 4 Results Floragas/vacuum treatments Floragas/vacuum treatments of western flower thrips Floragas/vacuum treatments of two-spotted spider mites Phytotoxicity VaporMate treatments Western flower thrips Two-spotted spider mites Phytotoxicity 6 5 Discussion 10 6 Recommendations 10 7 Acknowledgements 10 8 References 11 I:\Zhang\ImpEnvirosol FINRpt 1240.doc

4 1 Executive summary Two pre-shipment treatments were applied to cut flowers and foliage to determine their ability to control key quarantine pests such as western flower thrips (Frankliniella occidentalis) and two-spotted spider mites (Tetranychus urticae). The treatments were: 1) a combination of vacuum conditions with Floragas and 2) VaporMate TM alone. Combinations of vacuum conditions and Floragas reduced the number of insect pests on cut flowers, but did not guarantee that the material was pestfree. The new Envirosol product, VaporMate TM, was effective against the two major insects tested in this study. However, it had severe phytotoxic effects on some cut flowers and on most of the foliage to which it was applied. Longer periods of fumigation with lower VaporMate TM concentrations may be worth testing. New approaches, tested overseas recently by Crop & Food Research, may also help to reduce phytotoxic effects of ethyl formate. 2 Introduction In recent years cut flower growers have found it increasingly difficult to export product. Consignments are being rejected when they arrive at international ports following the discovery of live insects in the consignments. These crops are being refumigated on arrival, which is costly and, in the case of methyl bromide, can shorten vase-life because of phytotoxic effects. Growers and exporters sending high value cut flowers and foliage to Japan and other markets must ensure that all insects are killed in their shipments before the product is exported, even the highly resistant egg stages. Growers are moving away from using methyl bromide as a postharvest fumigant because it is an ozone-depleting substance and can damage cut flowers and foliage. Floragas (active ingredients permethrin and pyrethrin) is the most popular alternative to methyl bromide for postharvest control of insect pests on export flowers. However, growers are finding that Floragas is not completely effective against some pests. Various methods of application have been tested and not all have been successful. For example, higher fumigant application rates damage the flowers or foliage (phytotoxicity) or leave visible deposits. Research has shown that a vacuum (conditions of lowered pressure) increases the efficacy of fumigants (Zettler et al. 1998) by increasing their insecticidal activity and improving their penetration amongst packaged produce. Such conditions are already used successfully to control pests on export sweet corn (Eder 2002) and show potential for application to cut flowers. Improved Envirosol fumigation methods for disinfesting export cut flowers and foliage crops Z Zhang & C W van Epenhuijsen, September 2004 New Zealand Institute for Crop & Food Research Limited Page 1

5 VaporMate is a new Envirosol formulation. It contains 16.7% ethyl formate with 83.3% liquid carbon dioxide to reduce its flammability. Ethyl formate is a fumigant with a long history of use on stored products such as dried fruits. It is flammable when applied without water. The US FDA has reviewed the use of ethyl formate and characterised it as generally recognised as safe (GRAS). Ethyl formate is also a widely used food additive. Studies at the Stored Grain Research Laboratory, Australia, and elsewhere have shown that it can be a very effective and rapidly acting grain fumigant (Williams 1998; Tipping 2002). However, relatively high concentrations of ethyl formate are required. Recent research has shown that the ability of ethyl formate to rapidly disinfest products is an advantage in some situations where it is not possible or practical to maintain gas concentrations for long periods e.g. in poorly sealed shipping containers. These studies have also shown that ethyl formate can have phytotoxic effects on fresh produce, including some varieties of cut flowers. The objective of this project was to improve the efficacy of two fumigants for use on New Zealand export cut flowers and foliage to ensure these products reach markets pest-free. Any methods developed could also be applied to imports. Phytotoxic effects were also assessed in order to understand the impact of fumigation on cut flower vase-life. The project explored the potential for flower growers to use VaporMate and vacuum fumigation in combination with Floragas to improve postharvest insect pest control on premium quality New Zealand export cut flowers and selected foliage crops. 3 Experimental methods and materials This project consisted of two tasks. Firstly, vacuum fumigation with Floragas was tested for its potential to control all life stages of western flower thrips (WFT). Secondly, experiments with VaporMate were carried out to assess the potential of this new fumigant to control pests on export cut flowers. The treatments were applied to two major New Zealand export cupflower crops (calla and sandersonia) and one export foliage crop. 3.1 Fumigation facilities Vacuum/Floragas trials Vacuum fumigation trials using Floragas were carried out in two Crop & Food Research vacuum fumigators that were depressurised to at least 7.5 kpa absolute pressure VaporMate trials VaporMate trials were carried out in 200 L well-sealed fumigation chambers. Page 2

6 3.2 Pests and life stages for mortality assessment Two major quarantine pests were selected for this study: western flower thrips (WFT) and two-spotted spider mites (TSM). Both adult and egg stages were tested Western flower thrips Chrysanthemum plants are a good host for WFT and were used for rearing WFT to the required population for mortality assessment. Potted chrysanthemum plants were placed between infested plants in the CFR insect rearing room in order for WFT populations to become established on them. Potted chrysanthemums infested with WFT were then chosen at random for the fumigation trials and placed among the flower stems for the phytotoxicity assessment (see Section 3.3). Plants were removed from fumigation and the efficacy of each treatment was assessed 24 hours later. Plant were held upside down and flowers were tapped 10 times over a bench. Live and dead WFT adults were counted Two-spotted spider mites Two-spotted spider mites were established on dwarf bean plants and carnation seedlings using similar techniques as described above. Infested plants were chosen at random for the fumigation trials. Twenty-four hours after fumigation adult insect mortality rates was assessed. TSM eggs were placed in Petri dishes for treatment. After fumigation the dishes were placed in an insect rearing room for hatching. Hatch rates were assessed a number of days later. 3.3 Phytotoxicity assessment Cut flowers and foliage crops assessed We selected calla lily and sandersonia cut flowers and pittosporum foliage for phytotoxicity assessment. The crops were stored at 12 C before the experiment. During the experiment, stems of each species were hold in buckets of water Phytotoxicity assessment procedures The phytotoxicity of VaporMate was assessed after treatment. Flower stems from each treatment were put in a 3 L bucket with 500 ml distilled water. The flowers were stored at 20 C for two weeks. Phytotoxicity was assessed by observing the extent of browning on petals and leaves on the fumigated material. We developed a damage index, from 0 to 10, based on an assessment of the percentage as well as the severity of damage on each flower or other plant tissues. Phytotoxic effects caused by fumigants generally occurred within 24 hours after fumigation treatment. However, we examined the stems over a period of two weeks to assess the effects of treatments on shelf life. Page 3

7 3.4 Experimental design and treatments Vacuum/Floragas treatments The commercial recommended application rate of Floragas is 50 g/m 3. We selected three levels of Floragas (0, 25, 50 g/m 3 ) and three vacuum levels (absolute pressure kpa or 0 mmhg, 10 kpa or 680 mmhg and 5 kpa or 720 mmhg). The lowest vacuum pressure of 5 kpa or 720 mmhg is commercially achievable. All nine combinations of treatments were replicated three times. Quality assessment of all three crops was carried out for the 5 kpa vacuum treatment only VaporMate treatments Four VaporMate concentrations, 0, 30, 60, 120 g/m 3, were applied. Each treatment was replicated three times. Cut flower stems were placed with potted chrysanthemums infested with WFT for mortality assessment. Pittosporum stems were treated with TSM collected from dwarf bean and carnation leaves. The leaves or TSM which were placed in 70 ml plastic containers while TSM eggs were placed on Petri dishes during the treatment. 4 Results 4.1 Floragas/vacuum treatments Floragas/vacuum treatments of western flower thrips Mortality rates of WFT adults and hatch rates of WFT eggs treated with vacuum and Floragas are shown in Fig. 1. Vacuum increased the mortality of WFT adults, especially when combined with Floragas. Mortality rates were higher than 40%. However, Floragas lowered WFT egg emergence, but there was no effect of vacuum. % Adult Mortality Least Sig Difference Pressure mmhg 50 g/m3 25 g/m3 0 g/m3 % Egg Emergence Least Sig Difference Pressure mmhg 0 g/m3 25 g/m3 50 g/m3 Figure 1: Mortality rates of WFT adults and hatch rates of WFT eggs in vacuum and Floragas treatments. Page 4

8 4.1.2 Floragas/vacuum treatments of two-spotted spider mites Mortality rates of TSM adults and hatch rates of eggs after Floragas and vacuum treatments are shown in Fig. 2. % Adult Mortality Least Sig Difference 25g Pressure mmhg 50g/m3 25g/m3 0g/m3 % Egg Emergence 0 g/m3 Least Sig Difference 25 g/m3 50 g/m Pressure mmhg Figure 2: Mortality rates of TSM adults and hatch rates of TSM eggs in vacuum and Floragas treatments. TSM mortality was increased by a combination of Floragas and vacuum. Mortality rates were low, however, and did not exceed 35%. TSM egg emergence was close to zero following the combined treatments Phytotoxicity The Floragas/vacuum treatments did not damage any of the crops tested, nor did they affect potential vase-life. 4.2 VaporMate treatments Western flower thrips VaporMate was very effective at controlling WFT adults. Mortality rates were 100% (Fig. 3). Even at the lowest rate (30 g/m 3 ) VaporMate reduced WFT egg hatch. Page 5

9 Figure 3: Emergence of WFT eggs after VaporMate treatment. VaporMate TM reduced the frequency of WFT egg emergence significantly, but none of the selected levels of concentrations achieved 100% mortality or 0% emergence for treated WFT eggs Two-spotted spider mites Mortality rates of TSM in VaporMate TM treatments are shown in Fig. 4. VaporMate TM killed 90% of TSM at 60 g/m 3 and 100% at 120 g/m 3. Eggs were controlled at 30 g/m 3. Figure 4: Mortality of two-spotted spider adult mites and egg hatch rates in VaporMate TM treatments Phytotoxicity Phytotoxicity assessment of the effects of VaporMate TM on sandersonia is shown in Table 1. Plate 1 shows the damage caused to this crop. Even at the lowest rate, some damage was apparent. Page 6

10 Table 1: Phytotoxicity effects on sandersonia. Phytotoxicity damage Flower Leaves Stem Shoot Damage index Untreated control no No No No 0 Untreated control no No No No 0 Untreated control no No No No 0 VaporMate TM 15 g spot spot No Yes 4 VaporMate TM 15 g spot spot No Yes 3 VaporMate TM 15g yes No Yes Yes 3 VaporMate TM 30 g yes yes No Yes 10 VaporMate TM 30 g yes yes No Yes 10 VaporMate TM 30 g yes No Yes Yes 10 VaporMate TM 60 g yes yes Yes Yes 10 VaporMate TM 60 g yes yes Yes Yes 10 VaporMate TM 60 g yes yes Yes Yes 10 VaporMate TM 120 g yes yes Yes Yes 10 VaporMate TM 120 g yes yes Yes Yes 10 VaporMate TM 120 g yes yes Yes Yes 10 Plate 1: Phytotoxic effects on sandersonia cut flowers at 30 g/m 3. Phytotoxic effects of VaporMate TM on calla stems are shown in Table 2 and Plate 2. Callas showed some tolerance of VaporMate. Page 7

11 Table 2: Phytotoxicity effects on callas. Phytotoxicity damage Flower Leaves Stem Shoot Damage index Untreated control no na no na 0 Untreated control no na no na 0 Untreated control no na no na 0 VaporMate TM 15 g no na no na 0 VaporMate TM 15 g no na no na 0 VaporMate TM 15 g no na no na 0 VaporMate TM 30 g no na no na 0 VaporMate TM 30 g no na no na 0 VaporMate TM 30 g no na no na 0 VaporMate TM 60 g yes na no na 4 VaporMate TM 60 g yes na no na 4 VaporMate TM 60 g yes na no na 3 VaporMate TM 120 g yes na no na 10 VaporMate TM 120 g yes na no na 5 VaporMate TM 120 g yes na no na 2 Plate 2: Effects on treated calla cut flower stems at 120 g/m 3. Page 8

12 Table 3 shows the phytotoxic effects of VaporMate TM on pittosporum and Plate 3 shows the damage to the foliage crop. VaporMate TM damages pittosporum foliage at the lowest rate (15 g/m 3 ). Table 3: Phytotoxic effects of VaporMate treatments on pittosporum. Phytotoxicity damage Leaves Stem Shoot Damage index Untreated control no no no 0 Untreated control no no no 0 Untreated control no no no 0 VaporMate 15 g spot no yes 4 VaporMate 15 g spot no yes 3 VaporMate 15 g no no yes 3 VaporMate 30 g yes no yes 10 VaporMate 30g yes no yes 10 VaporMate 30 g no no yes 10 VaporMate 60 g yes no yes 10 VaporMate 60 g yes no yes 10 VaporMate 60 g yes no yes 10 VaporMate 120 g yes no yes 10 VaporMate 120 g yes no yes 10 VaporMate 120 g yes no yes 10 Plate 3: Phytotoxic effects on pittosporum stems at 15 g/m 3. Page 9

13 5 Discussion One of the objectives of this study was to determine if vacuum conditions improved the effectiveness of Floragas when used to disinfest export cut flower and foliage crops. The efficacy of Floragas improved in a high vacuum as determined by mortality rates of both adult insects and eggs in this study. However, the results were unsatisfactory adult mortality rates were lower than 40%. The low mortality rates may be due to the fact that insects were kept within a container or hidden inside chrysanthemum flowers so they were less exposed to the fumigant than if they were on flower stems. VaporMate TM was very effective against both WFT and TSM. However, it is also very damaging to some flower crops and especially to foliage. Alternative fumigants should be investigated for use on those leafy crops. 6 Recommendations If vacuum facilities are available, the combination of vacuum and fumigation can improve pre-shipment treatment results if a pressure of below 7.5 kpa can be reached in the fumigation chamber. This combination is safe to apply and in our trials were not phytotoxic. Phytotoxicity is a major disadvantage of using VaporMate TM on cut flowers and foliage. Phytotoxicity trials on a range of other cut flower crops, including lisianthus and orchids, are recommended. Longer periods of fumigation with lower VaporMate TM concentrations may be worth testing in the future. New approaches, tested overseas recently by Crop & Food Research, may also help to reduce phytotoxic effects of ethyl formate. 7 Acknowledgements We thank the MAF Sustainable Farming Fund for supporting this project. We also thank the Central Flower Grower Association and Westbay Waratahs Ltd (Katikati) for providing cut flowers and leafy foliage for use in this project. We thank David and Andrew Pugh, Tony and Lucille Lett, and Michelle Wallis for their interest and assistance in this work. Page 10

14 8 References Eder 2002 Personal communications. Macdonald, O. C.; Mills, K. A Phosphine/carbon dioxide combinations as alternatives to methyl bromide in structural and commodity fumigation. Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions. San Diego, CA. 95 p. Tipping, C Further exploration of ethyl formate as a fumigant for arthropod pests associated with table grapes. UCDAVIS website, CA, USA. Villers, P Advanced vacuum fumigation and its applications. Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions. San Diego, CA. 95 p. Williams, P Improved fumigation for export wildflowers. RIRDC, Canberra. Zettler, J. L.; Leesch, J. G.; Gill, R. F.; Tebbets, J. C. Chemical alternatives for methyl bromide and phosphine treatments for dried fruits and nuts. Proceedings of the 7 th International Working Conference on Stored Product Protocol. October 15-18, Beijing, China. Page 11

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