Vietnam Demonstration Project

Demonstration models in the management of Fall Armyworms in maize crops

Background

This project was led by the Plant Protection Research Institute (PPRI) of Vietnam in conjunction with the ASEAN FAW Action Plan. Demonstration trials were employed to provide a learning space for researchers, policymakers, and farmers to develop and refine practices and test solutions to ensure that they can be deployed correctly and efficiently in the field. Cost-benefit analysis was also a feature of this project.

Maize is Vietnam's second most important staple crop, essential for food security and rural livelihoods, particularly in regions such as Vinh Phuc province, where this study was undertaken. In this location, maize is grown in three cropping seasons: Spring-Summer, Summer-Autumn, and Autumn-Winter, with Fall armyworm present across all seasons, so pest pressure remains high.

The project

A small set of demonstration trials using proven scouting approaches combined with a focus on good agricultural practices and the use of lower-toxicity pesticides and biocontrol options was conducted during the Summer–Autumn and Autumn–Winter seasons (from April to December) of 2023 to evaluate the effectiveness of different FAW management strategies under local farming conditions.

General Methodology

Selection of study site

The project was situated in the corn cultivation area of the Red River Delta region of Northern Vietnam, which is about 100 km North of Hanoi. In this location, crops are regularly affected by Fall Armyworm all year round, causing significant damage to production, especially during the spring-summer season.

Figure 1. Demonstration sites in the Red River Delta in the Lowlands Agroecological Zone.

Scouting and decision to treat

Scouting, involving the systematic assessment of FAW infestation in each plot, was undertaken every 3 days from germination to the V9 stage and every 7 days from flowering to the seed setting stage (figure 2) to determine the percent (%) infestation (%IP).

Monitoring

Pheromone traps were used for monitoring, and the traps were monitored as advised by expert opinion at the Vietnam Plant Protection Research Institute (PRRI) and the Vietnam National University of Agriculture (VNUA) to assess the number of adults trapped. This includes using traps in test fields to understand the performance of treatments and to ensure timely intervention of solutions in the field.

Training and Workshop

Figure 2. The Maize growth stages (Alam et al., 2021)

Figure 3. A) Pheromones trap in the field, B) Lure from VNUA

All farmers participating in the demonstration model and growing maize in the area participated in a training course as part of the demonstration (Fig. 4). The training course focused on helping farmers distinguish FAW from other insect pests and to better understand FAW behaviors and characteristics. The growers were provided training on Integrated Pest Management (IPM) solutions. 62 maize growers participated in the training course.

Figure 4. Training course on IPM solution for the local farmers

Figure 5. The leader of the People's Committee of the commune where the project is implemented

PPRI, the Vietnam Ministry of Natural Resources and the Environment, and the ASEAN FAW Action Plan organized an international workshop in Hanoi on December 4, 2023. Seventeen participants from nine South and Southeast Asian countries, along with local agricultural experts and industry representatives from Vietnam, attended the event.

Demonstration Phase 1 Methodology: June to September 2023

The demonstration trial was divided into two separate phases with the first phase in the Summer-Autumn season and the second phase implemented in the Autumn-Winter season of 2023. Phase I included a single treatment trial, and a combined solutions demonstration trial conducted from June to September 2023 during the Summer-Autumn season.

Phase 1: Single treatment trial

The trial included eleven (11) treatments and one control with each treatment replicated three times for a total of 36 plots using a Randomized Complete Block Design (RCBD).

Table 1: Selected Treatments in Single Treatment Trials

Phase 1: Combined Solutions Demonstration Trial

The Phase 1 combined solutions demonstration trial was planted on 8 June 2023 and harvested on 3 September 2023.

A total of five (5) solutions were applied. Core solutions in the Combined Solution Trial included:

1. Seed treatment with Cyantraniliprole + Thiamethoxam (Fortenza® Duo 480 FS).

2. Intercropping with soybean

3. Fertilizer use + pH adjustment (avoiding excessive use of Urea application)

4. Use of Bacillus thuringiensis var. Kurstaki (Aztron WG) in one-third and Spinetoram (Radiant® 60SC) in the other one-third.

5. NPV (Fawligen) just after the initial infestation was used in R1&R2.

Demonstration Phase 2 Methodology: September to December 2023

Phase 2 included another Combined Solutions Trial as well as three Pheromone trials carried out in the Autumn –Winter season from September to December 2023 in the same location as Phase 1. In addition, a small EPN trial was implemented following up on work from Phase 1 applying nematodes in a gel. Another small trial of Fawligen was undertaken, with three applications of Fawligen applied when the %IP was >20%.

Phase 2: Combined Solutions Trial

A total of four (4) core solutions were selected from Phase I to apply in 0.6ha (R2).

Core solutions in the Phase 2 Combined Solutions Trial included:

1. Seed treatment with Cyantraniliprole + Thiamethoxam (Fortenza® Duo 480 FS)

2. Use of a Hybrid maize variety (CP512)

3. Use of Bt pesticide (Aztron WG) for one time, if necessary

4. Use of Spinetoram (Radiant® 60SC) for one time, if necessary.

Phase 2: Pheromone Demonstrations

Three pheromone technologies were selected for this demonstration project.

Pheromone A: Demonstration (A1)

The trial was carried out on two (2) ha of farmer’s land for the purpose of mating disruption. The A1 pheromone was used from the beginning of the trial and installed just after planting. The dispensers were placed following the manufacturer’s protocol. Installation involved attaching the dispensers to a bamboo stake in the field within a row of corn at a height of 0.6m. 88 stakes were placed at 15m x 15m spacing and remained in place for the whole season. Two (2) times applications of Aztron WG were used during the season when the %IP exceeded 20%.

Pheromone B: Demonstration (B1)

This trial was carried out on two (2) ha of farmer’s land for the purpose of mating disruption. The B1 pheromone was used from the beginning of the trial immediately after planting. The dispensers were placed following the manufacturer’s protocol. The dispensers were attached to the bamboo stake in the field within a row of corn. 250 stakes at 9m x 9m spacing were installed and remained in place for the whole season. Two (2) times application of Aztron WG were used throughout the season when the %IP exceeded 20%.

Pheromone C: Demonstration (C1)

The C1 pheromone solution was carried out on one (1) ha of farmer’s land for the purpose of mating disruption. C1 was used two weeks after planting. The lures were attached inside the plastic trap and hung at a height of 1.2m. The number of traps was 30 per ha at 15m x 20m spacing, and the lure was changed every 20 days, not exceeding three times for the season. Two (2) times application of Biopesticides Bt (Aztron WG) was used when %IP exceeded 20%.

Key findings

Maize is always under very high pressure from FAW in the study locations. Without the early application of a control measure, maize is typically heavily damaged as early as the emergence stage (V3). The percentage of infested plants (% IP) without prompt management increases up to 100% during the V5-V9 stages, leading to a potential yield reduction of up to 50%, compared to effectively managed fields.

Moth counts were extremely high in the summer season but decreased sharply in the autumn season. However, even the lower counts were still considered high and one can expect FAW to be a permanent and serious pest that farmers must proactively manage in this region. At these FAW population levels, a package of IPM solutions is needed to manage FAW effectively and sustainably and maintain good yields.

The results clearly showed the importance of good agricultural practices. Proper field preparation and plant health management make a big difference in yield and income. Farmers were provided with some training as part of this project, and they responded positively to the training and were curious about new solutions. Follow-up training is important.

Soil pH test results show that most soils have a pH ranging from 4 to <6, which is considered low. The optimal pH range for maize cultivation is between 6 and 7. Currently, fertilizer application for maize is still based on traditional practices or personal experience, relying on observations of plant colour and growth to determine the timing and dosage of fertilizer. The dosage of fertilizer is therefore often very different between households. In future, soil testing would be beneficial to understand nutrient levels, pH, and other factors to arrive at prescriptive rates of fertilizer or lime that may be needed. Not only can this support more resilient maize crops it can also have economic advantages in the form of cost savings through more efficient fertilizer applications.

Farmers generally do not scout often enough; consequently, they miss opportunities to effectively control FAW early.

Further investigation of the plants affected by FAW during the vegetative stage across the 12 treatments in Phase 1 indicated that larvae began to appear 7 days after planting. Subsequently, the %IP increased rapidly from stages V3-V5. One recommendation might be to focus on the importance of increased scouting intensity from the V3-V5 stage to ensure better timing of any control measure.

There is potential to make large pesticide use production, even reducing pesticide use by 50%, with better timing of pesticide applications alone. Combined with good agricultural practices and biocontrol solutions, there is a significant opportunity to drive more sustainable and effective management of FAW. More farmer training beyond this project is particularly important in scouting and understanding best practices on when to apply rescue treatments.

The results of this demonstration project showed that an early biopesticide spray, timed correctly and at an action threshold of 20% infestation, was very effective.

GM maize showed good tolerance to FAW in the experiments, especially the DK6919S variety, which recorded minimal damaged plants. In contrast, the NK7328 Bt/Gt variety had the highest %IP of approximately 33% at the V7-V9 stage but performed well under conditions without pesticides.

The results of the trials showed that the farmers could realize higher yields of around 20-30% compared with local farmers' practices, leading to an increase in income of around US500-800 per ha.

Some biocontrol options were not particularly effective (e.g., earwigs), while others did show promise (e.g., nematodes), but it is unclear if these are scaleable options. Nematode solutions and Fawligen (NPV) were less convincing in phase 1 when the FAW population was extremely high, but they showed good results in phase 2 when population levels were lower, and temperatures were cooler.

More trials are recommended to investigate more efficient applications and scale-up of both biocontrol approaches.

The new pheromone-based solutions for FAW management combined with biopesticides and as part of an IPM package showed much promise. They will likely be a good fit for an area-wide FAW control program, especially as maize is grown year-round and the pest is endemic. These solutions need further testing in the field in Vietnam to refine their use and effectiveness. In addition, the registration process for these solutions needs further development to ensure such approaches can be used and scaled in Vietnam.

An insecticide seed treatment before planting did not appear as effective as expected in the single-treatment trials. However, it showed better results in the Combined Treatment Package of Phase One. However, neonicotinoid pesticides in seed treatments pose risks to animals, especially pollinators. Developing lower toxicity or alternative seed treatments could be beneficial due to the early pest pressure on maize in this location where FAW population levels are high across all maize growing seasons.

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ACKNOWLEDGEMENTS

This research could not have been conducted without the crucial support of the local government in the Yenlac district of Vinhphuc province, as well as the men and women farmers who provided their land, valuable time and input to the project. Ongoing support from experts from the Vietnam Ministry of the Environment and Agriculture is also acknowledged.

The project also received assistance from crop protection and plant health companies that supplied important expertise and solutions for use in the trials. We gratefully acknowledge the support of: AgBiTech, Ngan Anh Limited Company, M2i Biocontrol, Provivi, Valent BioSciences and the Vietnam National University of Agriculture.

We would also like to acknowledge the help of Dr Joseph Huesing from Huesing Agricultural and Educational Consulting; Dr Patrick Fallet, an entomopathogenic nematode specialist from the University of Neuchatel, Switzerland; and Dr Tran Thi Thu Phuong from Vietnam National University of Agriculture.

The project involved many staff across teams within PPRI. A special thanks is made to Dr Nguyen Van Liem, Director of the Plant Protection Research Institute (PPRI), for his leadership and Dr Le Xuan Vi, Head of the Pest Diagnosis & Identification Division at PPRI, for his work as the Project Lead.

Thanks to the Australian Department of Foreign Affairs and Trade for their crucial support of the ASEAN FAW Action Plan.

Photos of the project activities

Land preparation for the field trial

Combined solution demonstration trail (phase I)

Dr. Nguyen Van Liem (Director of PPRI), Dr Le Xuan Vi (Project Lead, PPRI) and Dr. Alison Watson (Head of ASEAN FAW Secretariat) visiting the IPM model field trials