AREA WIDE SUPPRESSION OF BACTROCERA FRUIT FLIES IN DRAGON FRUIT IN BINH THUAN, VIET NAM
In Viet Nam, fruit flies (Bactrocera dorsalis Hendel and Bactrocera correcta Bezzi) are among the most economically important pests attacking fruits including dragon fruits (Hylocereus undatus and Hylocereus spp.), which have high economic value for domestic consumption and exportation. The total cultivated area for dragon fruit in Viet Nam is about 42 000 ha; among that, Binh Thuan is the largest dragon fruit producer with about 29 447 ha. The Area-wide Integrated Pest Management (AW-IPM) has been implemented in Ham Hiep village (Ham Thuan Bac district, Binh Thuan province, Viet Nam) since October 2016 under structure of core zone (581 ha) and buffer zone (986 ha). Management strategies included field sanitation and male annihilation techniques (MAT) were applied in both zones. Additionally, in the core zone, protein bait spray was applied while a contiguous area under farmer practice was used as the control. The results showed the highest number of fruit flies per trap per day (FTD) with 2.2 and 4.11 FTD in core zone and buffer zones, respectively in comparison with 28.93 FTD in the farmers practice area. The results clearly indicated the advantage of integrating of several methods in an AW-IPM approach to build up the model with low prevalence of fruit flies for the dragon fruit production region.
Hien, N.T.T.¹; Hoat T.X1.; Liem N.V1.; Thanh.M.H.1; Pereira R.²; Trang V.T.T.¹; Lien, H.K.¹; Thang, D.D.¹; Thanh, V.V.¹ and Xuyen, L.T.¹
¹ Entomology Division, Plant Protection Research Institute, Viet Nam
² Insect Pest Control Section, Join FAO/IAEA Division of Nuclear Techniques in Food and Agriculture, Vienna, Austria.
Keywords: Area-wide Integrated Pest Management (AW-IPM), bactrocera dorsalis, bactrocera correcta, guava fruit fly, male annihilation technique (MAT), methyl eugenol, oriental fruit fly, protein bait spray, sanitation.
Total exporting value of fruit and vegetables in Viet Nam reached US$3.8 million in 2018 and increased 47.3% compared with of the 2017 figures (Department of Rural and Development Agricultural Binh Thuan, 2019). The leading fruit is Dragon fruit (Hylocereus sp.) which contributes US$1.1 million and are grown in many regions in Viet Nam such as Ha Noi, Long An and Binh Thuan, where the production area is the largest.
Binh Thuan is located in the tropical monsoon climate with hot and dry weather in South Central Coast, in which there is no winter. The province is also the driest place in Viet Nam with two distinctive seasons: rainy season occurs from May to October, while the dry one starts in November and ends in April. The average temperature in the province is 26-27°C, humidity is 75-85%; and rainfall is 800–2000 mm per year. The total hours of sunshine are 2 459 hours per year (Department of Rural and Development Agricultural Binh Thuan, 2019). Therefore, Binh Thuan province is the most appropriate location to produce dragon fruit in Viet Nam.
The total areas used to grow dragon fruit (Hylocereus sp.) in Binh Thuan has increased within 10 year, up to 308% since until January 2019, the province has about 29 447 ha of dragon fruit, bringing in 591 965 tons of yield, 80% of which is for export to China, Korea, Japan, South East Asia, the Middle East, Europe, USA (Department of Rural and Development Agricultural Binh Thuan, 2019). The dragon fruit procedure systems are joined by thousands of families, 23 cooperatives and two unions. In addition, 10 073 ha of the dragon fruit growing areas adheres to the Vietnamese Good Agricultural Practices (VietGAP) and 262 ha to the Global Good Agricultural Practices (GlobalGAP) standards (Department of Rural and Development Agricultural Binh Thuan, 2019). Additionally, some products made from dragon fruit such as wine, dried, candy, and fresh juice which can be major to sell.
Although the areas are increasing but the average yield per hectare area is not growing higher, which is a result of the overexploitation to reduce the self-protection under the attack from diseases and pests. These major diseases in both the pre-harvest and post-harvest stages are: Colletotrichum gloeosporioides, Erwinia spp., Fusarium spp., Botryosphaeria sp., and Curvularia spp. (Phan et al., 2014; Hieu and Hoa, 2015), Some pests occur during the plant growth and flowering stages, such as ants, thrips, aphids, and beetle pests, and others occur during the fruit stage, such as ants, fruit flies, mealybugs, stink bugs, beetles, snails and slugs (Binh Thuan Sub-Department of Plant Protection, 2009).
The objective of this article is to provide the information fruit flies identified and studied in Viet Nam as well as the Area-wide Integrated Pest Management (AW-IPM) methods developed on dragon fruit production.
FRUIT FLY MANAGEMENT
Fruit fly species
Both Bactrocera dorsalis and Bacrocera correcta, are listed in the quarantine pest group, have been recorded to attack dragon fruit, of which B. dorsalis is the major pests (Hien et al., 2011; 2012).
Distribution, dynamic and host status
Bactrocera on fruit flies occurs all the time in the entire Binh Thuan province. The number of fruit fly in methyl eugenol traps increased rapidly in April until it reached it peak in May. Thereafter, the number of captured adults reduced gradually until November and December.
Studies had recorded 13 and 11 host fruit species for B. dorsalis and B. correcta, respectively, including pomelo (Citrus grandis L.), star fruit (Averrhoa carambola L.), mango (Mangifera indica L.), papaya (Carica papaya L.), guava (Psidium guajava L.), rose apple (Eugenia malaccensis L.), jujube (Ziziphus mauritiana L.), rambutan (Nephelium lappacum L.), Barbados cherry (Malpighia glabra L.), whose harvest season had a strong impact on population dynamic in both B. dorsalis and B. correcta (Hien et.al., 2011, 2016).
Although it is not easy to determine the early symptoms of fruit fly infestation, after 3-7 days, depending on the fruit stage, it will be seen clearly (Fig, 1).
|Figure 1. Red-fleshed dragon fruit (Hylocereus spp.) infested by fruit fly under natural field conditions
(Photo credit: Hien N.T.T, 2013)
Some pilots on fruit fly management have been previously conducted (Khanh et. al., 2003; Dien et al, 2011; Hien et. al., 2011; Khanh et al, 2012; Khanh et al, 2016) in Viet Nam. Lesson taken determined that the AW-IPM model was the best choice on fruit fly control, especially for the wide production areas like Binh Thuan province.
The pilot project area (1 567 ha) consists of a 581 ha core zone where the full suite of available IPM control measures was implemented. The core zone is surrounded by a 986 ha buffer zone, which separated the core zone from the farmer zone (Fig. 2). This farmer zone used the existing farmer practices such as spraying insecticide applications and/or lure traps, which served as a control of our suppression trial.
Figure 2. Map of fruit fly suppression in the dragon fruit production area of Binh Thuan province, 2016-2019. The core zone of 581 ha is inside the orange line, and the 986 ha between the orange and green line is the buffer zone. The area outside the green line is the farmer zone used as a control.
Three suppression methods were applied in the core zone. These included: (i) Field sanitation; (ii) Male Annihilation Technique (MAT); and (iii) Protein bait spray.
(i) Activities of field sanitation method: Fallen and infested fruits were regularly collected and sealed into plastic bags which were exposed to direct sunlight for 3 days to kill larvae in the fruit. Collected fruits were also burned or buried under the ground, at least 30 cm deep. Sanitation focused on dragon fruit plus fruits collected from backyards, such as mango, guava and star fruit;
(ii) Male Annihilation Technique (MAT): attracts and kills blocks. Blocks are made of wood about 1 cm thick (5 cm by 5 cm). A small hole in the corner of wooden block is created for a wire nylon to pass through. This wooden block is soaked in the mixture of 4 ml of fipronil or malathion and 1 litre of methyl eugenol for 4 days. The MAT blocks were placed at 50 m interval across the field, replaced after 2-3 months (depending on the wet season) and maintained continuously throughout the year in the field to suppress the population of males of both B. dorsalis and B. correcta (Hien et al., 2011, 2016).
(iii) Protein bait spray application targeting female fruit flies: Bait mixture (1 000 ml+ 1g of fipronil/malathion + 9 liter of water) was applied every seven days from fruit maturation until harvest (Hien et al., 2012). Bait mixture is sprayed as spots (50 ml) under leaves or bushes or bait station (not applied directly on the fruits).
Field sanitation and MAT block methods were applied in combination in the buffer zone.
All information on host fruit maturation and infestation was recorded weekly during the implementation of the pilot project to obtain the status of the host (Khanh et al., 2016). Additionally, public information and training on AW-IPM for the farmers was conducted.
Adult populations were monitored during the full period of the pilot project (October 2016 to date) by using Methyl eugenol (ME) traps (FAO/IAEA 2014, 2018) inspected every 10 days and serviced every two months.
To evaluate the impact of the suppression measures on the different zones and the control, weekly visual observations were conducted for tephritid damage on dragon fruits (FAO/IAEA, 2019). As of April 2017, a total of 300 dragon fruits in each zone were collected and observed for damage at the harvesting stage every month. They were then kept individually to allow larvae within the fruits to pupae and be counted, thus obtaining a percentage of fruit infestation.
Our preliminary research indicated the higher fruit fly per trap per day (FTD) in the wet periods, from March to August/September, and with the peak in May/June. In dry season (October to March), fewer flies were caught (Hien et. al., 2009, 2011, 2016). However, in 2018 during the period of January 2018 to December 2018., instead of the seasonal difference, the result showed a stability in the number of flies caught from traps placed at two zones (see Table 1).
Table 1. The result of fruit fly suppression in Dragon fruit production (Binh Thuan, 2018).
|Average number of flies per trap per day (FTD)
|Damaged dragon fruit (%)
||0 - 4.67
||0,4 - 7.67
||1.2 - 24.67
Area-wide suppression methods using MAT with protein bait sprays and field sanitation were effective in controlling fruit fly populations in dragon fruit farms in the AW-IPM pilot trial in Binh Thuan province, which appears to be promising to build up areas of fruit fly low pest prevalence. However, for maintenance of the AW-IPM model, a good knowledge base on alternative hosts and effect of climate change, education for farmers and stakeholders is also necessary and should be continued.
We wish to thank Binh Thuan province, Vietnamese Ministry of Agricultural Rural and Development, Vietnamese Ministry of Science and Technology, and the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture for their support to implement activities of the fruit fly management, this workshop organizers for us to present this to you all.
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