INTRODUCTION
Introduction
The fall armyworm (FAW), Spodoptera frugiperda (J E Smith, 1797)
The Lepidoptera family, specifically the Noctuidae, is identified as a significant pest of noctuid moths in both North and South America Recently, this pest has also expanded its range to Africa and has been detected in Europe (Montezano et al., 2018).
In Ethiopia, the 2017 cropping season saw the Fall Armyworm (FAW) infest over 24% of the 2.9 million hectares of maize, resulting in a loss exceeding 134,000 tons, valued at nearly $30 million (Beemer, 2018) Similarly, in Brazil, significant quantities of insecticidal active ingredients were utilized annually for FAW control, with estimated maize losses ranging from 19% to 100% (Montezano et al., 2018).
FAW (Fall Armyworm) was first identified in Vietnam in 2019, with the Ministry of Agriculture and Rural Development (MARD) reporting on August 16 that 15,000 hectares of maize across 40 provinces were affected Notably, over 2,000 hectares experienced severe infestations, with more than eight larvae per square meter (USDA, 2019).
A pheromone trap is an insect trap designed to attract primarily male insects using female sex pheromones, which are chemicals secreted by females to lure males for mating The most commonly utilized pheromones are sex and aggregation pheromones Currently, various pheromone lures and trap types are being evaluated for effectiveness While many of these options may be effective, some pheromone lures can also attract a limited number of non-Fall Armyworm (FAW) moths, potentially leading to confusion in pest management strategies (Prasanna et al., 2018).
The female S frugiperda emits a sex pheromone to attract male counterparts for mating The primary component of this pheromone, identified as (Z)-9-tetradecenyl acetate (Z9-14:Ac), was first discovered by Sekul and Sparks in 1967.
The compound's attractiveness appeared inadequate, prompting extensive research and field testing for improved formulations, as summarized by Tumlinson et al (1986) They identified two key components of the S frugiperda sex pheromone in a Florida population: Z9-14:Ac and (Z)-7-dodecenyl acetate (Z7-12:Ac) Additionally, a third component, (E)-7-dodecenyl acetate (E7-12:Ac), was discovered in a Brazilian population in São Paulo (Batista-Pereira et al., 2006).
The recent rise of the fall armyworm (FAW) on maize in Vietnam has made the use of pheromone traps for its management and prevention increasingly urgent In response to this situation, and under the guidance of Dr Tran Thi Thu Phuong from the Department of Entomology at the Faculty of Agronomy, I am conducting a research project titled "Research on pheromone lures and traps for monitoring and management of the fall armyworm Spodoptera frugiperda (J E Smith) on maize in Vinh Phuc, Vietnam 2020."
Objective and Requirement
This study focuses on identifying effective pheromone lures and trap types for monitoring and managing fall armyworm (FAW) in maize fields in Vietnam The research evaluates the efficacy of pheromone traps as a method for controlling FAW populations.
- Determining morphological and biological of fall armyworm on maize
- Determining specific pheromone lures, trap types for fall armyworm in Vinh Phuc, Vietnam
- Identification of pheromone method for FAW in Vinh Phuc, Vietnam
- Determining the evolution of the FAW density on maize in the Autumn-Winter crop in 2020 in Yen Lac, Vinh Phuc.
LITERATURE REVIEW
Research over the World
Domain: Eukaryota Kingdom: Metazoa Phylum: Arthropoda Subphylum: Uniramia Class: Insecta Order: Lepidoptera Family: Noctuidae Genus: Spodoptera Species: Spodoptera frugiperda
The fall armyworm (FAW) is native to tropical and subtropical regions of the Americas, with its presence noted in North America, including Bermuda, Canada, the United States, and Mexico In South America, FAW is found in 12 countries, such as Brazil, Argentina, Chile, Colombia, Ecuador, French Guiana, Guyana, Paraguay, and Peru.
The fall armyworm has been reported in Europe, specifically in Germany, the Netherlands, and Slovenia In Africa, it was first documented in Central and West Africa in 2016, with notable occurrences in Nigeria, São Tomé, Benin, and Togo (Goergen et al.).
2016) In 2019, it harm the yield of 47 African nations as Nigeria, Nambia, Kenya, Ghana, Ethiopia, Congo, Egypt, Sudan, Zambia, Zimbabwe, etc (Kuate et al.,
The Fall Armyworm (FAW) was first identified in Asia in India and Yemen in 2018, but by 2019, it had spread to over 12 countries, including Bangladesh, China, Korea, Japan, Laos, Malaysia, Myanmar, Nepal, the Philippines, Sri Lanka, Thailand, and Vietnam.
FAW has spread to over 180 countries worldwide, causing significant damage to crops, particularly maize Its presence from the USA to Asia poses a serious threat to various host plants, leading to substantial economic losses in a short period.
The adult female lays eggs in masses throughout the crop, with hatching occurring within 2-3 days during the summer Newly hatched larvae begin feeding on the softest plant tissues, typically consuming the green tissue from one side of the leaf while leaving the epidermis intact As they mature, older instars create holes in the leaves, and by the fourth to sixth instar stages, they can completely devastate small plants and strip larger ones (Cruz et al., 1999).
Seedlings are vulnerable to feeding within the whorl, while larger larvae can sever the plant's base, leading to significant damage to mature plants, particularly their reproductive structures Maize leaves exhibit extensive damage, characterized by holes, ragged edges, and larval frass, with young larvae causing 'window-pane' damage that is often confused with other stem borers Typically, multiple young larvae inhabit a single plant, but older larvae tend to migrate to neighboring plants As they grow, they create larger holes and produce sawdust-like droppings, resulting in a severely infested field resembling hailstorm damage Fall armyworms can also damage silks and tassels, hindering ear fertilization, while larvae may bore into cobs, risking fungal infections and aflatoxin contamination, ultimately compromising grain quality In high densities, large larvae may swarm like armyworms but often remain localized on available wild grasses.
Larvae damage maize plants by consuming foliage, resulting in characteristic shot holes on the leaves (Sisodiya et al., 2018) Initially, young larvae feed on one side of the leaf, leaving the opposite epidermal layer intact, but as they progress to the second or third instar, they create holes and consume leaves from the edges inward Feeding in the whorl of corn leads to a distinct row of perforations, and larval densities typically decrease to one or two per plant due to cannibalism Older larvae can cause severe defoliation, often leaving only the ribs and stalks of the plants Research by Marenco et al (1992) indicated that the early whorl stage of sweet corn is least sensitive to fall armyworm injury, while the late whorl stage is most affected, with mean densities of 0.2 to 0.8 larvae per plant during this stage potentially reducing yield by 5 to 20 percent (Capinera, 2020).
Larvae can damage plants by burrowing into growth points or clipping leaves, with fall armyworm larvae specifically feeding on corn kernels by entering through the husk Unlike corn earworms, which feed through the silk, fall armyworms prefer the ear zone and silk tissues, although these are not ideal for growth Young leaf tissue supports larval survival, but mature plants are less suitable, leading larvae to focus on the ear area While closed tassels can support survival, they do not promote optimal growth, indicating that initial feeding on tassel tissue is suboptimal until larvae find the silk and ears (Capinera, 2020).
The life cycle of the fall armyworm varies significantly with the seasons, completing in approximately 30 days during summer, 60 days in spring and autumn, and 80 to 90 days in winter The number of generations in a given area is influenced by the emergence of dispersing adults, with reports indicating one to two generations in Kansas, three in South Carolina, and four in Louisiana In regions like Minnesota and New York, where moths appear later in the season, only a single generation may occur Coastal areas of north Florida see moths from April to December, with some present even in winter months (Capinera, 2020).
The egg is dome-shaped with a flattened base and a rounded apex, measuring approximately 0.4 mm in diameter and 0.3 mm in height A female typically produces between 100 to 200 eggs per mass, averaging around 1500 eggs, with a maximum of over 2000 Eggs are usually spread over a single layer attached to foliage, sometimes deposited in layers, and are covered with a layer of grayish scales that give them a furry or moldy appearance The egg stage lasts only two to three days during the summer months (Capinera, 2020).
Larvae: There usually are six instars in fall armyworm Head capsule widths are about 0.35, 0.45, 0.75, 1.3, 2.0, and 2.6 mm, respectively, for instars 1 to
6 Larvae attain lengths of about 1.7, 3.5, 6.4, 10.0, 17.2, and 34.2 mm, respectively, during these instars Young larvae are greenish with a black head, the head turning orangish in the second instar In the second, but particularly the third instar, the dorsal surface of the body becomes brownish, and lateral white lines begin to form In the fourth to the sixth instars the head is reddish brown, mottled with white, and the brownish body bears white subdorsal and lateral lines Elevated spots occur dorsally on the body; they are usually dark in color, and bear spines The face of the mature larva is also marked with a white inverted "Y" and the epidermis of the larva is rough or granular in texture when examined closely However, this larva does not feel rough to the touch, as does corn earworm, Helicoverpa zea (Boddie), because it lacks the microspines found on the similar- appearing corn earworm In addition to the typical brownish form of the fall armyworm larva, the larva may be mostly green dorsally In the green form, the dorsal elevated spots are pale rather than dark Larvae tend to conceal themselves during the brightest time of the day Duration of the larval stage tends to be about
14 days during the summer and 30 days during cool weather Mean development time was determined to be 3.3, 1.7, 1.5, 1.5, 2.0, and 3.7 days for instars 1 to 6, respectively, when larvae were reared at 25ºC (Capinera, 2020)
Pupation typically occurs in the soil at depths of 2 to 8 cm, where the larva creates a loose, oval cocoon measuring 20 to 30 mm by binding soil particles with silk In harder soil, larvae may use leaf debris to form a cocoon on the surface The pupa, which is reddish brown, measures 14 to 18 mm in length and about 4.5 mm in width The duration of the pupal stage lasts approximately eight to nine days in summer but can extend to 20 to 30 days in winter in Florida Notably, the pupal stage of the fall armyworm is sensitive to cold, with survival rates varying significantly across Florida: 51% in southern Florida, 27.5% in central Florida, and only 11.6% in northern Florida (Capinera, 2020).
Adult moths have a wingspan of 32 to 40 mm, with males displaying gray and brown forewings featuring triangular white spots, while females exhibit less distinct markings, ranging from uniform grayish brown to mottled patterns Both sexes possess iridescent silver-white hindwings with a narrow dark border Nocturnal in nature, these moths are most active during warm, humid evenings After a preoviposition period of three to four days, females typically lay most of their eggs within the first four to five days, although some oviposition can continue for up to three weeks The average lifespan of adult moths is about 10 days, with a range of seven to 21 days (Capinera, 2020).
The FAW (Fall Armyworm) has a broad host range, favoring grasses, with over 80 recorded plant species, including field maize, sweet maize, sorghum, and various grass weeds like crabgrass When larvae populations surge, they exhibit an "armyworm" behavior, defoliating preferred plants and consuming nearly all vegetation in their vicinity While many host records indicate periods of abundance, they do not accurately reflect typical oviposition and feeding behaviors Field crops such as alfalfa, barley, cotton, and wheat often suffer damage, with sweet maize being the most consistently affected vegetable crop Other occasionally attacked crops include apple, grape, and peach, while various weeds like crabgrass and morning glory also serve as hosts.
Research on host plants for S frugiperda has identified a total of 353 larval host plant records across 76 plant families The majority of these records belong to the Poaceae family, with 106 instances, followed by Asteraceae.
Research in Vietnam
In Vietnam, maize (Zea mays L.) ranks as the second most important food crop following rice, with an estimated cultivation area of 1.1 million hectares The productivity of maize is approximately 46.7 quintals per hectare, resulting in a total output of 5.13 million tons, according to the Crop Industry Report.
In recent years, state policies and advancements in agricultural technology, such as the introduction of high-yield hybrid maize varieties, have significantly boosted maize production However, the shift towards intensive farming and the alteration of maize variety structures have led to an increase in harmful pests, including the corn borer, corn leaf borer, thorn worm, and gray worm, which adversely affect productivity Notably, the fall armyworm, Spodoptera frugiperda (FAW), which has recently invaded Vietnam, poses a serious threat to maize cultivation across the country.
In mid-March 2019, the MARD Plant Protection Department (PPD) alerted all provinces about the threat of Fall Armyworm (FAW), with reports of corn damage, especially in young plants, emerging from Nghe An, Thanh Hoa, Quang Binh, and Hanoi Following positive genetic analysis results from the Centre for Agriculture and Bioscience International in the UK, PPD confirmed the presence of FAW in Vietnam on April 17, 2019, and officially reported it on April 24.
2019, MARD issued official announcement 2827/BNN-BVTV about FAW prevention and control in Vietnam
Recent estimates indicate that the total area affected by Fall Armyworm (FAW) is approximately 35,000 hectares of corn, primarily concentrated in the northwest and central highlands, which represent 65 percent of the country's corn production As of August 16, 2019, the Ministry of Agriculture and Rural Development (MARD) reported that 15,000 hectares of the current corn crop across 40 provinces have been impacted by FAW, with over 2,000 hectares classified as heavily infested, exhibiting more than eight larvae per square meter (USDA, 2019).
As of May 15, 2020, the total planted corn area in Vietnam decreased by three percent compared to the previous year, totaling 435 thousand hectares Data from PPD weekly pest status updates indicates a significant reduction in areas heavily infected by Fall Armyworm (FAW) during the cooler months, dropping from 664 hectares in November to just 9 hectares in March However, by late May 2020, heavily infected areas rose to 196 hectares, compared to 547 hectares in May 2019 Despite efforts by plant protection and agricultural extension agencies to mitigate the impact of FAW, industry experts anticipate continued spread and damage to the upcoming corn planting season in 2020.
Table 2.1 Vietnam corn planted and FAW infected area from October 2019 to May 2020
Oct 10 Nov 29 Dec 29 Jan 28 Feb 21 Mar 28 April 30 May 21
Total FAW infected area (hectares)
Sources: MARD’s Plant Protection Department Weekly Pests Status Update
As of July 25, 2019, the fall armyworm (FAW) affected 16,467 hectares of maize in Vietnam, with 2,741 hectares experiencing severe infestation This pest has impacted all six provinces within the Regional Plant Protection Center Zone 4, damaging over 1,223 hectares of maize, including 339.4 hectares with significant damage and 10 hectares suffering yield losses exceeding 70% Being an invasive species newly introduced to Vietnam, there is a lack of research on its biological characteristics, ecology, and effective control measures (Vu Quang Con et al., 2020).
A new pest has been identified in Gialam, Hanoi, causing significant damage to maize crops, as reported by Tran Thi Thu Phuong et al (2019) The larvae appear 20 to 30 days after maize germination, initially feeding on leaf tissues and primarily targeting the young parts of the plant By the third instar stage, the larvae inflict damage on all plant parts, including leaf tops, baby corn, and young seeds The symptoms observed in Hanoi are consistent with those of the fall armyworm (Spodoptera frugiperda), as described by Cruz et al (1999).
2.2.3 Morphological and biological of fall armyworm
According to Tran Thi Thu Phuong et al (2019), the fall armyworm undergoes four developmental stages: Egg, Larvae, Pupa, and Adult In the field, female adults typically lay their eggs on both sides of maize leaves during the night, depositing them in clusters on the upper surface These egg masses are covered with a white cream-like substance, and each egg measures approximately 0.4-0.5 mm in diameter.
The sixth instar larvae of the fall armyworm (Spodoptera frugiperda) exhibit a color range from light green to yellow-brown and dark brown, featuring a distinctive yellow reverse "Y" on the head and a grid pattern on the sides The head diameter of fully grown larvae measures approximately 2.5 to 2.7 mm, with a total length of 32 to 35 mm The pupae are shiny brown, measuring between 1.6 to 1.8 cm in length, with females typically being longer than males Adult moths range from 1.3 to 1.5 cm in body length and have a wingspan of 3 to 3.3 cm, displaying brown to dark brown front wings and white-yellow hind wings, with distinct wing patterns between the sexes.
Eggs are laid in nests containing approximately 150 to 300 eggs, which are globally shaped and initially white or light blue, darkening as they approach hatching Newly hatched larvae are white, transitioning to light green, brown, dark brown, and light black, characterized by a distinctive reverse "Y" shape on their heads and four spots on their backs The pupa is shiny brown, while male adults have a wingspan of 10 to 15 mm, compared to 11 to 17 mm for females Males exhibit more decorative features than females.
As recommended by the Plant Protection Department, the fall armyworm control include cultivation methods, baits, manual and chemical methods
Effective farming methods include enhancing soil quality and employing techniques such as drying soil to eliminate larvae and pupae, which can be easily managed by natural predators Implementing crop rotation, such as planting wet rice immediately after corn, helps to disrupt the life cycle of soil-dwelling pests.
Method of traps and baits: Use sweet and sour baits, pheromone traps to kill adults
Manual measures: Regularly check the field to collect old stage caterpillar, remove eggs (especially in the stage of 3-6 leaves to detect eggs, break and destroy them)
The Plant Protection Department advises farmers to employ chemical methods to prevent acacia fall during the critical early 1-3 years, specifically at the corn stage of 3-6 leaves It is recommended to spray these treatments in the early morning or late afternoon Farmers should utilize plant protection products that contain active ingredients or microorganisms such as Bacillus thuringiensis, Spinetoram, Indoxacard, and Lufenuron.
2.2.5 Sex pheromone application in Vietnam
The pheromone application in Vietnam is not popular And Fall armyworm is a new pest, so there is not many research about sex pheromone of this pest
In August 2019, the Maize Research Institute conducted tests on a pheromone trap purchased from China to manage Fall Armyworm infestations in maize The findings revealed that the commercial pheromone lures effectively attracted a high density of male adult Fall Armyworms.
PART III: MATERIAL AND METHOD 3.1 Objectives and Materials
- Objective: Fall armyworm Spodoptera frugiperda
Maize serves as an essential food source for nurturing growth, while a variety of laboratory equipment is necessary for effective experimentation Key items include rackets, plastic trays, pots, mesh cages, quill pens, and magnifying glasses Additional tools such as cotton, scissors, drawers, and bottles of different sizes, along with iron wire, curtains, pliers, and an electric welding pen, are also vital To support documentation and organization, A4 paper and notebooks are included in the list of necessary supplies.
+ Pheromone trap with 4 main components: Z9-14: OAc; Z7-12: OAc; Z9-12: OAc; Z11-16: OAc.
Location and Time
+ Room 108 and D08 of Entomology Department, Faculty of Agronomy, Vietnam National University of Agriculture
+ Maize field at Trung Kien commune, Yen Lac district, Vinh Phuc province, Vietnam
Target
- Determine specific pheromone lures, trap types for fall armyworm in Vinh Phuc, Vietnam
- Evaluate the ability to attract and capture the FAW of pheromone bait and trap in the field
- Identification of pheromone method for FAW in Vinh Phuc, Vietnam
- Determining the evolution of the FAW density on maize in the Autumn-Winter crop in 2020 in Yen Lac, Vinh Phuc
- Identification of biological and ecological characteristics of the fall armyworm Spodoptera frugiperda on maize.
Methods
- Investigation of pests on crops in the field is conducted according to QCVN 01-38: 2010 / BNNPTNT National technical regulations on methods of investigation and detection of plant pests
- Investigate pests on maize pests according to QCVN 01- 167:2014/BNNPTNT National technical regulation on methods for investigation and detection of pests of maize
- Periodic survey: every day in the first month and every 7 days in the next month
+ Based on the principle of selecting the investigated area as the field representing the investigated factors such as topography, variety, season, soil layer
+ The selected field is maize cultivation area of Vinh Phuc province
+ Selection of fields to investigate: Investigate on maize varieties popularly grown in winter-spring maize crop 2020
- Select survey points: Each element investigates 10 random distributed points on the diagonal of the investigation area The survey point must be at least 2 meters from the shore
Figure 3.1 Sample scouting pattern for maize (Marr, 2009)
- Number of survey samples per point: 1m² / point
To conduct an effective investigation, observe the environment both from a distance and up close Count the number of worms at each developmental stage on each tree at the survey point, and ensure to preserve the samples in insect containers for further analysis.
3.4.2 Method of rearing insect in experiments of biological characteristic of S frugiperda
Fall armyworm larvae, S frugiperda, are collected in large quantities from the field in Phu Dong, Gia Lam, Hanoi, and transported to the laboratory, where they are maintained on maize plants in 45 ml plastic cups until they pupate The pupae are then separated by sex, with 10 females and 10 males placed in mating cages (20x20x20 cm) and provided with a diet of 10% honey Eggs are collected and stored in plastic boxes until they hatch into larvae The adult mating pairs are isolated, and the newly hatched larvae are used for experiments to study their biological and ecological characteristics.
Figure 3.2 Rearing fall armyworm eggs in plastic box
Eggs collected on the same date are stored in a plastic box at 30°C to monitor their development time A minimum of 120 eggs is used for each experiment, allowing for accurate tracking of the hatching rate and development duration.
Larvae are monitored every two hours, seven times a day, starting from the egg mass stage After hatching, first instar larvae are placed in individual plastic boxes and reared in a controlled laboratory environment at 30°C They are fed maize plants, with food being replaced daily The development time and mortality rates of the larvae from the first instar to the sixth phase are meticulously recorded, with a minimum number of larvae per experiment ensured.
After the larva of S frugiperda ceases feeding and enters the pre-pupae stage, it is transferred to a plastic box with moist soil or wet tissue The pupae are maintained at a temperature of 30°C until they mature into adults, with males and females being separated for monitoring The size and weight of the pupae are measured two days post-pupation, while tracking the development time and mortality rates of the pupae is essential for effective management.
In this study, 10 male and 10 female adults are placed in mating cages to observe their mating behavior The selected mating pairs are then transferred to plastic cages with maize plants for egg-laying Key metrics such as pre-reproduction time, reproduction time, and the longevity of both sexes are meticulously recorded Additionally, the body length and wingspan of the males and females are measured The experiment focuses on monitoring the development times associated with pre-reproduction, mating, reproduction, and adult longevity.
Figure 3.3 Mating cage (A); Plastic cage for mating pairs (B)
3.4.3 Method of investigation the method applied pheromone lures and traps on the field a Pheromone lure types
Pheromone lures will be prepared by the same method of (Meagher et al.,
* Pheromone lures have 9 treatments of compositions:
+ TM1: Four component (4C) contained Z9-14:OAc, Z11-16:OAc, Z7- 12:OAc and Z9-12:OAc;
+ TM2: Three component (3C) contained Z9-14:Oac, Z11-16:OAc and Z7- 12:OAc
+ TM3: Two component (2C1) contained Z9-14:OAc and Z7-12:OAc; + TM4: Two component (2C2) contained Z9-14:OAc and Z9-12:OAc; + TM5: Two component (2C3) contained Z9-14:OAc and Z11-16:OAc
+ TM6: Four component (4C) contained Z9-14:Ac (78.3%), Z11-16:Ac (3.6%), Z7-12:Ac (11.2%), and Z9-12:Ac (7.0%) (Meagher et al., 2019)
+ TM7: two- component lure (2C) contained Z9-14:Ac (90.5%) and Z7- 12:Ac (9.5%) (Meagher et al., 2019)
+ TM8: Three-component lure (3C) contained Z9-14:Ac (66.1%), Z11- 16:Ac (4.7%), and Z7-12: Ac (29.3%) (Meagher et al., 2019)
Pheromone traps are strategically placed in a straight line at the center of the maize field, with each trap positioned 20 meters apart and 1.5 meters above the ground Over a period of 30 days, the number of male moths entering each trap is observed and recorded daily, with three repetitions for accuracy.
Diagram 3.1 Pheromone lure types experiment
* Trap type: Bucket funnel trap (commercial trap)
Figure 3.4 Bucket funnel trap b Pheromone trap types
Three kinds of trap will be used in this study:
Figure 3.5 Hand-made trap (funnel) (A); Hand-made trap (window) (B);
* The colors used are blue, green, yellow, colorless (white), and commercial trap (control)
The experiment will utilize a treatment comprising three components: Z9-14:OAc, Z11-16:OAc, and Z7-12:OAc Pheromone traps will be strategically placed in a straight line at the center of the maize field, with each trap positioned 20 meters apart and 1.5 meters above the ground The number of male moths entering each trap will be observed and recorded daily over a period of 30 days, with three repetitions for accuracy.
Blue White Green Control Yellow Yellow White Green Control Blue Green Yellow
Diagram 3.2 Pheromone trap colour (windown) experiment
Green Blue Yellow Control White
White Control Yellow Green Blue
Yellow Green White Blue Control
Diagram 3.3 Pheromone trap colour (funnel) experiment c Distance between traps: 20, 30, 40, 50 m
The experiment will utilize a treatment comprising three components: Z9-14:OAc, Z11-16:OAc, and Z7-12:OAc Pheromone traps will be strategically placed in a straight line at the center of the maize field, with a spacing of 20 units between each trap.
The study involved monitoring the number of male moths entering traps positioned at various heights of 1.0 m, 1.2 m, 1.5 m, 1.7 m, and 2.0 m above the ground Over a period of 30 days, data was collected daily from traps located 30 m, 40 m, and 50 m away, with each trap being observed three times The height of the traps was consistently set at 1.5 m from the ground to ensure uniformity in the experiment.
The experiment will utilize a treatment comprising three components: Z9-14:OAc, Z11-16:OAc, and Z7-12:OAc Pheromone traps will be strategically placed in a straight line at the center of the maize field, with a distance of 20 meters between each trap The traps will be positioned at varying heights of 1.0, 1.2, 1.5, 1.7, and 2.0 meters above the ground Over a period of 30 days, the number of male moths entering each trap will be observed and recorded daily, with three repetitions for accuracy.
3.4.4 Calculation methods a Average phase time
X i : Phase time of objective n in day i
N i : The number of objectives change phase in day i
N : Sum of the observed objectives b Average living time
Combined: : Average living time ai: Living time of objective until day i ni: Number of objectives are still alive in day i
N: Sum of the observed objectives c Mortality rate:
Data were subjected to analysis of variance (ANOVA) using IBM SPSS Statistics 20, to test the significance of differences among different treatments tested based on F-test at P = 0.05.
RESULTS AND DISCUSSION
Harmful symptoms of fall armyworm in Vinh Phuc, Hanoi
In Vinh Phuc, Hanoi, we identified detrimental effects of Fall armyworm on maize, specifically in the CP 512 variety The first and second instar larvae consume leaf tissue from one side, while preserving the opposite epidermal layer.
By the second or third instar, larvae create holes in leaves, feeding from the edges inward, which results in a distinctive row of perforations in corn leaves When larvae feed near each other, their densities typically decrease to one or two per plant due to cannibalism Older larvae can cause significant defoliation, often leaving only the ribs and stalks of corn plants, resulting in a ragged and torn appearance.
Figure 4.2 Second to sixth instar’s symptom
Morphological characteristic of fall armyworm
Eggs are typically laid in clusters of 20 to 300, covered by a protective layer of grey-pink scales from the female's abdomen These egg masses are usually found on both sides of leaves, and occasionally on stems Each egg measures approximately 0.5 to 0.7 mm in width, initially appearing pale yellow or creamish at oviposition, and turning light brown just before hatching.
Figure 4.3 Egg masses of Fall armyworm
The larvae undergo six instars, separated by five molting stages We observed and described the morphological characteristics of the larvae from the first to the sixth instar, noting features such as head capsule color and size, body color, body spots, and variations in coloration throughout each instar stage.
Head capsule was back and about 0.3 mm in width The body was white or white green and smaller than the head The spots were not clear
The body coloration ranged from white to light green and green, with a smaller head compared to the body As the larvae grew to about double their size, the trunk darkened The head capsule measured approximately 0.5 mm in width and was black, with distinct spots that were easily observable.
Figure 4.4 First instar larvae Figure 4.5 Second instar larvae
The third instar larvae were molted form second instar larvae Head capsule was about 0.8 to 0.9 mm The body had green or white green color and clearly black spot
Figure 4.6 Third instar larvae Figure 4.7 Fourth instar larvae
The larvae exhibited a dark green or brown coloration, featuring distinct black spots, with four prominent black spots located at the end of the body The head capsule measured approximately 1.5 to 1.7 mm in width.
Fifth instar larvae exhibit a color range from green to dark brown, featuring a distinctive yellow reverse "Y" shape on the top of their heads and a grid pattern on the sides Their head capsules measure between 1.9 to 2.2 mm in width, and white hairs are prominently visible.
At the final instar stage, fall armyworm larvae exhibit a dark green to black-brown coloration, with some presenting a predominantly green dorsal appearance In this green form, the elevated dorsal spots are pale instead of dark The head capsule width measures between 2.6 to 2.7 mm The larvae enter the pre-pupation stage when they cease feeding and moving.
Figure 4.8 Fifth instar larvae Figure 4.9 Sixth instar larvae
Larvae typically undergo pupation in the soil, where pre-pupae construct cocoons using leaf webs, soil, and other materials Initially, the pupae are white-green in color, transitioning to a shiny brown or dark brown as they mature Notably, male pupae are larger than their female counterparts.
Figure 4.10 Pupa of fall armyworm
Figure 4.11 Female adult (A); Male adult (B)
The male moth features forewings that range from gray to dark gray, adorned with white spots and distinct triangular white markings at the tip and center In contrast, the hindwings are light silver with a brown edge The female moth, however, is less decorated, primarily exhibiting a grayish hue.
Biological characteristic of fall armyworm
Our research focused on measuring the size of fall armyworm, specifically examining the head capsule width of larvae, as well as the length, width, and weight of pupae Additionally, we assessed the wingspan of adult fall armyworms under conditions of 30°C temperature and 80% humidity.
Table 4.1 Head capsule width of larvae fall armyworm Spodoptera frugiperda
Stages Head capsule width of larvae (mm)
The data presented indicates that the head capsule width of FAW larvae increases with each developmental stage Specifically, the average head capsule widths from the 1st to the 6th instar are 0.30 mm, 0.51 mm, 0.89 mm, 1.56 mm, 2.06 mm, and 2.62 mm, respectively Notably, there is no significant difference in head capsule width among larvae during the 1st instar; however, from the 2nd instar onward, variations in head capsule width become evident at each stage.
Length (cm) Width (cm) Weight (mg)
Min Max Mean±SE Min Max Mean±SE Min Max Mean±SE
The data presented indicates the dimensions and weight of both male and female fall armyworm (FAW) pupae, as well as their wingspan Female pupae measure between 1.3 to 1.6 cm in length, averaging 1.45 cm, with a width ranging from 0.4 to 0.5 cm and an average of 0.44 cm Their weight varies from 109 to 228 mg, averaging 162.74 mg In comparison, male pupae also range from 1.3 to 1.6 cm in length, with an average of 1.49 cm, and a width of 0.4 to 0.5 cm, averaging 0.43 cm The weight of male pupae fluctuates between 119 to 198 mg, with an average of 159.97 mg Notably, male FAW pupae are longer than their female counterparts, while female pupae are wider and heavier than male pupae.
The adult female fall armyworm (FAW) measures between 1.4 and 1.6 cm in length, with an average of 1.48 cm, and has a wingspan ranging from 3.0 to 3.4 cm, averaging 3.13 cm In contrast, the adult male FAW is larger, with a length varying from 1.5 to 1.7 cm and an average of 1.63 cm, while its wingspan ranges from 3.2 to 3.5 cm, averaging 3.32 cm.
We conducted research to determine development time of fall armyworm in temperatures of 30°C and humidity 80% Our results are shown in the table 4.3
The table provides insights into the development time of male and female adult Fall Armyworm (FAW) For females, the average duration of the egg stage and larval instars ranges from 2.00 to 2.87 days, while the pupal stage lasts between 7 to 9 days Additionally, the pre-oviposition period varies from 1 to 2 days In summary, the life cycle of female adult FAW spans approximately 20 to 21 days, with a total lifespan of 26 to 30 days.
The average development time for male insects from the egg stage through the first to sixth larval instars is 2.00, 2.13, 1.33, 1.67, 1.60, 2.27, and 2.73 days, respectively The pupal duration varies between 7 to 10 days, resulting in a total lifespan of 23 to 29 days.
Table 4.3 The development time of male and female adult fall armyworm
Range Mean ± SE Range Mean ± SE
We conducted research to determine food consuming ability of fall armyworm in temperatures of 30°C and humidity 80% Our results are shown in the table 4.4
Table 4.4 Food consuming ability of larvae fall armyworm Spodoptera frugiperda on maize
Food consumpsion (mg/day/larvae) Min Max Mean ± SE
Food plays a crucial role in the growth of all organisms, including the Fall Armyworm (FAW) Our research aimed to assess the food consumption capabilities of FAW on maize to evaluate their potential harmfulness.
3 rd instar because from 3 rd instar to 6 th Instar, the food consuming ability of larvae FAW increased The food consuming ability of FAW results were presented in table 4.4
Research indicates that the food consumption of larvae increased at each developmental stage, peaking before a decline in the final stage Specifically, larvae exhibited food consumption rates of 28.95 mg/day in the 3rd instar, 124.47 mg/day in the 4th instar, 610.93 mg/day in the 5th instar, and 770.63 mg/day in the 6th instar, with a notable decrease occurring as they prepared to pupate.
We conducted research to determine mortality and sex ratio of fall armyworm when rearing on maize in temperatures of 30°C and humidity 80% Our results are shown in the table 4.5
Table 4.5 Mortality of fall armyworm in laboratory
The laboratory study on fall armyworm mortality indicated a fluctuation in the number of deceased individuals, with an overall mortality rate of 5.83% Additionally, the sex ratio of fall armyworms reared on maize under laboratory conditions was found to be 1:1.35.
Pheromone lure types experiment in Vinh Phuc
In 2020, we conducted research in Vinh Phuc to evaluate the effectiveness of pheromone traps and lures in controlling fall armyworm The findings of our study are presented in Tables 4.6 and 4.7.
Table 4.6 shown the density of fall armyworm on the maize fields applied pheromone traps and no applied pheromone traps
Table 4.6 The density of fall armyworm on the maize field of pheromone experiment in Vinh Phuc 2020
Survey date Maize growth stages
Density of larvae Mean ± SE (larvae/m 2 ) Pheromone traps
Table 4.6 showed that the density of FAW larvae decreased along the development stages of maize in Vinh Phuc 2020 for pheromone traps and fluctuate for
In a study comparing the effects of pheromone traps on fall armyworm (FAW) larvae density, it was found that the highest density of larvae with pheromone traps occurred at the 2-4 leaf stage, measuring 3.2 larvae/m², while the lowest density recorded was 0 larvae/m² Conversely, in fields without pheromone traps, the peak density was observed at the 9-12 leaf stage, reaching 3.3 larvae/m², with a minimum of 0 larvae/m² Overall, the presence of pheromone traps resulted in a consistently lower density of FAW larvae throughout all maize growth stages compared to fields without traps.
In summary, the use of pheromone traps significantly reduced the average density of FAW larvae in the field compared to areas without these traps, demonstrating their effectiveness in pest management.
In 2020, a study conducted in Vinh Phuc revealed significant differences in the number of male adults captured using various types of pheromone lures in maize fields, as illustrated in Table 4.7.
The highest capture of male adult Fall Armyworm (FAW) was recorded with TM3, which utilized the two-component blend of Z9-14:OAc and Z7-12:OAc, resulting in 159 moths per trap per day and a total of 1,933 moths Following closely were TM1 and TM2, with total captures of 1,730 and 1,748 moths, respectively, using their respective pheromone blends In contrast, the lowest capture was observed with TM9, which extracted pheromones from 20 moths, yielding only 9 moths.
Table 4.7 Number of male adult captured in different pheromone lure types in
Number of male adult captured
Min Max Total Mean ± SE
The highest average capture of male adult FAW was observed in TM3, which contained the pheromones Z9-14:OAc and Z7-12:OAc, yielding 20.78 moths per trap per day TM1 and TM2 followed closely with averages of 18.6 and 18.8 moths per trap per day, respectively, featuring a combination of various pheromones In contrast, TM9, which utilized pheromones extracted from 20 FAW moths, recorded the lowest average at just 0.1 moth per trap per day Notably, Z7-12:OAc emerged as a crucial component influencing the efficacy of each treatment.
In our study, we compared the capture rates of male adult fall armyworm (FAW) using different lures to those reported by Meagher et al (2019) The TM6 (4C) lure captured an average of 11.16 moths per trap per day, closely matching Meagher's four-component lure, which captured 11 moths The TM7 (2C) lure showed a higher capture rate of 13.3 moths per trap per day, equivalent to Meagher's two-component lure at 13 moths However, the TM8 (3C) lure captured only 8.72 moths per trap per day, significantly lower than Meagher's three-component lure, which captured 15 moths Overall, TM6 and TM7 demonstrated effectiveness similar to Meagher's findings, while TM8 was less effective in Vinh Phuc.
Our treatments (TM1, TM2, TM3) significantly outperformed the lures developed by Meagher et al (2019) (TM6, TM7, TM8) This demonstrates that our four-component lure (4C), three-component lure (3C), and two-component lure (2C) with varying component concentrations effectively increased the capture rate of male adults compared to Meagher's lures.
Pheromone trap types experiment in Vinh Phuc
In 2020, we conducted research in Vinh Phuc to evaluate the effectiveness of different pheromone trap types for controlling fall armyworm in the field The findings are presented in Tables 4.8, 4.9, and 4.10.
Table 4.8 reveals significant differences in larval density among various pheromone trap types The funnel-shaped pheromone trap exhibited the lowest average larval density at 1.13 larvae/m², while the control group recorded the highest density, averaging 2.8 larvae/m².
45 three pheromone trap types trap colour (window), trap colour (funnel), chinese trap were lower than control (commercial bucket trap)
Table 4.8 The density of fall armyworm on the maize field of pheromone trap colour and Chinese trap experiment compare to control in Vinh Phuc 2020
Density of larvae Mean ± SE (larvae/m 2 ) Trap colour (window)
Table 4.9 indicates that the TM5 trap captured the highest number of male adult FAW, with 28 moths per trap per day and a total of 221 moths In contrast, TM1 recorded the lowest total with 94 moths and an average of 1.08 moths per trap per day TM5 also had the highest average capture rate at 2.54 moths per trap per day Notably, TM2 captured double the total number of male adult FAW compared to TM1, TM3, and TM4, suggesting that color significantly influences the capture rates of male adult FAW.
46 captured in pheromone traps colour (window) experiment and yellow was the most effective colour
Table 4.9 Number of male adult captured in different pheromone traps colour
(window) in Vinh Phuc 2020 Treatments
Number of male adult captured
Min Max Total Mean ± SE
Table 4.10 indicates that the TM5 trap captured the highest number of male adult FAW, with 31 moths per trap per day and a total of 333 moths In contrast, the TM3 trap recorded the lowest total, with only 17 moths, and the lowest average capture rate of 0.2 moths per trap per day While there were differences in capture rates among the color treatments, these differences were not statistically significant.
Table 4.10 Number of male adult captured in different pheromone traps colour
Number of male adult captured
Min Max Total Mean ± SE
Mitchell et al (1989) found that a standard multicolored bucket trap, featuring a forest green canopy, yellow funnel, and white bucket, captured significantly more male FAW moths compared to a monochromatic forest green bucket trap This indicates that the multicolored commercial trap is more effective in attracting male adult FAW than homemade monochrome traps Similarly, Malo et al (2018) evaluated various colors for homemade traps, including blue, green, yellow, black, red, and white, and discovered that yellow traps were the most effective in capturing male adult FAW These findings align with the results of both Mitchell et al (1989) and Malo et al (2018), reinforcing the effectiveness of color in trapping male FAW moths.
Pheromone trap height experiment in Vinh Phuc
In 2020, we conducted research in Vinh Phuc to evaluate the effectiveness of pheromone trap height in controlling fall armyworm in the field The findings are presented in Tables 4.11 and 4.12.
Table 4.11 The density of fall armyworm on the maize field of pheromone trap height experiment in Vinh Phuc 2020 Survey date Maize growth stages
Density of larvae Mean ± SE (larvae/m 2 )
Table 4.11 indicates significant differences in larval density across various treatments, with the lowest density recorded at 1.2m, averaging 1.1 larvae/m² Conversely, the highest density was observed at 1.5m, averaging 1.5 larvae/m² In conclusion, traps positioned at a height of 1.5m demonstrated the most effective performance.
Table 4.12 indicates that the peak capture of male adult Fall Armyworm (FAW) reached 1.5 million, averaging 46 moths per trap per day The overall highest total capture was 1.2 million, totaling 185 moths, while the lowest total recorded was 2.0 million, with 113 moths captured.
A total of 49 male adult Fall Armyworms (FAW) were captured, with an average of 1.2 moths per trap per day The lowest average recorded was 2.0 moths, yielding a value of 1.3 moths per trap per day In conclusion, both the 1.2m and 1.5m captures demonstrated strong performance.
Table 4.12 Number of male adult captured in different pheromone traps height experiment in Vinh Phuc 2020 Height of traps
Number of male adult captured
Min Max Total Mean ± SE
Pheromone trap distance experiment in Vinh Phuc
In 2020, we conducted research in Vinh Phuc to evaluate the effectiveness of pheromone traps at varying distances for controlling fall armyworm in the field The findings are detailed in Tables 4.13 and 4.14.
Table 4.13 indicates significant differences in larval density across treatments, with the lowest density recorded at 20m, averaging 1.15 larvae/m², while the highest density was observed at 50m, averaging 1.88 larvae/m² In conclusion, traps placed at a distance of 50m demonstrated superior performance compared to other distances.
Table 4.13 The density of fall armyworm on the maize field of distance pheromone trap experiment in Vinh Phuc 2020
Density of larvae Mean ± SE (larvae/m 2 )
Table 4.14 Number of male adult captured in different pheromone traps distance experiment in Vinh Phuc 2020
Number of male adult captured
Min Max Total Mean ± SE
Table 4.14 indicates that the peak capture of male adult Fall Armyworm (FAW) occurred at 30 meters, with a rate of 27 moths per trap per day The overall highest capture was recorded at 40 meters, totaling 234 moths.
In a study of adult Fall Armyworm (FAW) capture, a total of 51 moths were collected at a distance of 20 meters, yielding a value of 185 moths The highest average capture rate of male adult FAW was observed at 40 meters, with an impressive rate of 2.69 moths per trap per day Conversely, the lowest average capture rate occurred at 20 meters, recording 2.13 moths per trap per day Overall, traps positioned at 40 meters demonstrated the most effective performance in capturing adult FAW.
CONCLUSION
Conclusion
- The average life-time of female and male adults FAW were 27.43 and 25.30 days, respectively The food consuming of larvae FAW was the highest in 6 th instar 770.63 mg/day/larvae
In a study examining various pheromone types, treatments TM1, TM2, and TM3 demonstrated a greater attraction to fall armyworm moths compared to treatments TM4 and TM5, as well as the USA pheromone lures (TM6, TM7, TM8) Notably, treatment TM3 achieved the highest capture rate, with an average of 20.78 male adult FAW moths per trap per day, significantly surpassing the USA pheromone lure (TM7), which recorded 13.30±1.81 moths per trap per day.
In a study comparing different types of pheromone traps, the yellow hand-made (window) traps captured an average of 2.40 moths per trap per day, closely rivaling the commercial bucket traps, which caught 2.54 moths per trap per day The research identified that the optimal height for pheromone traps was 1.2 meters, yielding 2.13 moths per trap per day, while the most effective distance was found to be 40 meters, resulting in 2.69 moths per trap per day.
The application of pheromone traps in maize fields led to a significant reduction in the density of Fall Armyworm (FAW) larvae, decreasing to 0.50±0.22 larvae/m² over four weeks In contrast, maize fields without pheromone traps experienced an increase in FAW larvae density, rising to 3.30±0.76 larvae/m² This demonstrates the effectiveness of pheromone traps in controlling FAW larvae populations in maize crops.
Recommendation
Pheromone lures and traps may apply to control fall armyworm on the maize fields in Vietnam
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1 Cục Bảo Vệ Thực Vật (2010) Quy chuẩn kĩ thuật quốc gia về nghiên cứu và điều tra dịch hại trên cây trồng (QCVN 01-38:2010/BNNPTNT), Bộ Nông nghiệp và Phát triển nông thôn ban hành tại Thông tư số 72/2010/TT- BNNPTNT ngày 10 tháng 12 năm 2010
2 Cục Bảo Vệ Thực Vật (2014) Quy chuẩn kĩ thuật quốc gia về nghiên cứu và điều tra dịch hại trên ngô (QCVN 01-167:2014/BNNPTNT), Bộ Nông nghiệp
& PTNT ban hành tại Thông tư số 16/TT-BNNPTNT ngày 05 tháng 6 năm
3 Đào Thị Hằng, Nguyễn Văn Liêm, Phạm Văn Lầm, Nguyễn Thị Thủy, Trần Thị Thúy Hằng, Phạm Duy Trọng & Nguyễn Đức Việt (2019) Đặc điểm hình thái, giải phẩu và sinh học phân tử của sâu keo mùa thu hại cây ngô ở Việt Nam Tạp chí Bảo vệ thực vật số 2 (283), trang 50- 56
4 Trần Thị Thu Phương, Đỗ Nguyên Hạnh, Hồ Thị Thu Giang & Hà Viết Cường
(2019) Xác định loài xâm lấn sâu keo mùa thu Spodoptera frugiperda (L.E
Smith) (Lepidoptera: Noctuidae) trên cây ngô tại Hà Nội vụ xuân năm 2019 Tạp chí Bảo vệ thực vật số 2 (283), trang 56- 68
5 Vũ Quang Côn, Phạm Văn Lầm, Nguyễn Viết Tùng, Trương Quang Học, Nguyễn Văn Đĩnh, Bùi Công Hiển, Nguyễn Thế Nhã, Nguyễn Quốc Huy, Trần Đức Hinh, Khuất Đăng Long, Lê Xuân Hợi, Trương Xuân Lam, Nguyễn Văn Liêm, Vũ Văn Liên, Trịnh Văn Hạnh, Trần Ngọc Lân, Trần Văn Hai, Phạm Văn Lầm, Nguyễn Thúy Hiền, Trần Thị Thu Huyền, 2020 BÁO CÁO KHOA HỌC HỘI NGHỊ CÔN TRÙNG HỌC QUỐC GIA LẦN THỨ 10 HỘI CÔN TRÙNG HỌC VIỆT NAM
Length, width and weight of pupa Female Male
Head capsule width of larvae in different stages Minimum Maximum Mean
Length, width and weight of pupa
Sum of Squares df Mean Square F Sig
Length and wingspan ranged of male and female adult Female Male
Length and wingspan ranged of male and female adult
Sum of Squares df Mean Square F Sig
The development time of male and female adult fall armyworm Female Male
The development time of male and female adult fall armyworm
Sum of Squares df Mean Square F Sig
Food consuming ability Minimum Maximum Mean Std Error of
Tukey HSD Food consuming ability N Subset for alpha = 0.05
The density of fall armyworm in control field Mean Std Error of Mean
Control Mean Std Error of Mean
The density of fall armyworm of pheromone lure types experiment Mean Std Error of Mean
The density of fall armyworm on the maize field of pheromone experiment in Vinh Phuc 2020
Sum of Squares df Mean Square F Sig
\ Pheromone lure types experiment Minimum Maximum Sum Mean Std Error of Mean % of Total Sum
The density of fall armyworm of pheromone trap colour experiment TM1 TM2
The density of fall armyworm of Chinese trap experiment Mean Std Error of Mean
Pheromone trap colour (windown) experiment Sum Mean
Pheromone trap colour (windown) experiment
Pheromone trap colour (funnel) experiment Minimum Maximum Sum Mean Std Error of
Pheromone trap colour (funnel) experiment
\ Chinese trap experiment Sum Mean
Density of fall armyworm on the maize field of pheromone trap colour and Chinese trap
Density of fall armyworm on the maize field of pheromone trap colour and Chinese trap
Density of fall armyworm on the maize field of pheromone trap colour and Chinese trap
Density of fall armyworm on the maize field of pheromone trap colour and Chinese trap
The density of fall armyworm in pheromone trap height experiment TM1 TM2 TM3 TM4
Density of fall armyworm on the maize field of pheromone trap height experiment
Density of fall armyworm on the maize field of pheromone trap height experiment
Density of fall armyworm on the maize field of pheromone trap height experiment
Density of fall armyworm on the maize field of pheromone trap height experiment
Pheromone trap height experiment Sum Mean
The density of fall armyworm on the maize field of distance pheromone trap experiment TM1 TM2 TM3 TM4
Density of fall armyworm on the maize field of distance pheromone trap experiment
Density of fall armyworm on the maize field of distance pheromone trap experiment
Density of fall armyworm on the maize field of distance pheromone trap experiment
Density of fall armyworm on the maize field of distance pheromone trap experiment
Pheromone trap distance experiment Minimum Maximum Sum Mean