Biology and management of oriental armyworm mythimna separata

1. Assignment on
Biology and management of Oriental Armyworm of cereals Mythimna separata
SUBMITTED BY: SUBMITTED TO:
Arjun Rayamajhi Asst. Prof. Rajendra Regmi
Class Roll No.: PLP-06M-2017 Department of Entomology
Exam Roll No.: PLP-01M-2017 Agriculture and Forestry University
MSc.Ag 3rd Semester AFU, Rampur

2. Table of Contents
1. Introduction.......................................................................................................................................3
1.1 Biology..........................................................................................................................................3
1.1.1 Systematic Position................................................................................................................3
1.1.2 Distribution: ..........................................................................................................................3
1.1.3 Host plants / species affected.................................................................................................5
1.1.3 Marks of Identification: ........................................................................................................5
1.1.4 Nature of Damage .................................................................................................................7
1.1.5 Life Cycle: .............................................................................................................................9
1.2 Management...............................................................................................................................10
1.2.1 Mechanical and Physical Control .......................................................................................10
1.2.2 Cultural Method: ................................................................................................................10
1.2.3 Biological Method: ..............................................................................................................11
1.2.4 Chemical Method:...............................................................................................................11
2. Conclusion .......................................................................................................................................11
3. References........................................................................................................................................11

3. 1. Introduction
The Oriental armyworm, Mythimna separate (Walker) is a noctuid moth whose larval (caterpillar)
stage is a serious pest of cereals, pasture and forage crops in Asia and Australia (Wright, & McNeil,
1988). Its Common names for the pest include: southern armyworm, sorghum armyworm, army
caterpillar, ear-cutting caterpillar and paddy cutworm (Sharma & Davies, 1983).It is an important
polyphagous insect with its erratic occurrence in cereal crops (Ali, Rashid, Huang, & Lei, 2016).
Armyworm attack in maize along with others crops like rice, sorghum, sugarcane, oats, wheat etc
may cause the damage of foliage parts upto 44% (Hill & Atkins, 1983).
1.1 Biology
1.1.1 Systematic Position
Phylum – Arthropoda
Class – Insecta
Order – Lepidoptera
Family – Noctuidae
Genus – Mythimna
Species – separata
1.1.2 Distribution
It has been recorded from 27 countries, territories and islands ranging from the humid tropics to
the temperate regions (Sharma & Davies, 1983). The worldwide distribution of this insect is
illustrated in the fig1.and its distribution in South east Asia in the fig 2.

4. Figure 1 Distribution of Mythimna separata in worldwide (Source:CABI Plantwise)
Figure 2 Distribution of Mythimna separata in South Asia (Source:CABI Plantwise)
In Nepal, their damages have been recorded in many parts of the country such as Palpa,
Argakhanchi and Gulmi districts (Rana & Plumb, 1973), Kavre and Sindhupalchowk districts
(Rana, 1975) and Nuwakot and Rasuwa districts (Joshi, 1978). Anonymous (1976) reported M.
separata also epidemic to maize crops in Jumla, Humla, Bajhang, Lamjung, Rasuwa, Nuwakot,
Syangja, Kaski, Nawalparasi, Chitwan, Makwanpur, Bara, Parsa, Sarlahi, Mahottari, Dhanusa,

5. Kathmandu, Bhaktapur and Lalitpur districts. In Nepal, winter maize is more susceptible to this
pest (Shivakoti & K.C., 1981).
1.1.3 Host plants / species affected
It is a polyphagous pest feeding on 33 plant species (Sharma & Davies 1983). It causes serious
damage to sorghum, pearl millet, rice, maize, wheat and sugarcane (Sharma et al. 2002).
Brassica rapa subsp. chinensis (Chinese
cabbage)
Brassica rapa subsp. oleifera (turnip rape)
Brassica rapa subsp. rapa (turnip)
Cyperus rotundus (purple nutsedge)
Echinochloa colona (junglerice)
Echinochloa crus-galli (barnyard grass)
Eleusine coracana (finger millet)
Eleusine indica (goose grass)
Hordeum vulgare (barley)
Linum usitatissimum (flax)
Nicotiana tabacum (tobacco)
Oryza sativa (rice)
Panicum antidotale (elbow grass)
Panicum miliaceum (millet)
Pennisetum glaucum (pearl millet)
Pennisetum purpureum (elephant grass)
Phaseolus (beans)
Saccharum officinarum (sugarcane)
Secale cereale (rye)
Setaria italica (foxtail millet)
Sorghum bicolor (sorghum)
Sorghum halepense (Johnson grass)
Triticum (wheat)
Triticum aestivum (wheat)
Urochloa mutica (para grass)
Zea mays (maize)
(Source: CABI plantwise)
1.1.3 Marks of Identification:
The adult moths are stoutly build and pale brown in colour. Adult is brownish white in colour.
Forewings are greyish yellow with round and reniform spots having indistinct edges (fig. 3).
External wing margin is blackened obliquely from top backwards, with dark stroke and with a row
of dark points. Hindwings are grey in colour with dark external margin. Antennae are thread-like
(Fig. 3). Mature larvae are 3–4 cm long and green to pink in colour and provided with longitudinal

6. light grey to black stripes running along the entire length of their bodies. The head is brown to
orange with an A marking (Fig. 3).
Figure 3 Adult of Mythimna separata

7. Figure 4 Army worm, Mythimna separata (a) Adult (Source:
http://www.agroatlas.ru/en/content/(b) Larvae and pupae (Source:
http://zipcodezoo.com/index.php/File:Mythimna_separata_4.jpg) (c) Eggs (Source:
http://www.slideshare.net/agp115/copy-ofpaddy- pests-11) (d) Damage (Source:
http://niphm.gov.in/IPMPackages/Wheat.pdf, http://pests.
agridata.cn/showimg3.asp?DB=5&id=162)
1.1.4 Nature of Damage
The caterpillars are damaging stage to the cereals. The primary symptom is defoliation of the plant.
In early stages, the caterpillars feed on tender leaves in central whorl of the plant. Later stages,
they are able to feed on older leaves. In case of severe attack, they defoliate leaves and the field
looks as grazed by cattle (Fig.4 d). The army worm feeds during dawn and dusk period as it is shy
of sunlight. Fourth and fifth instars larva are the major damaging stages and defoliate the maize
crop (Neupane et al., 1992). These larvae not only feed the leaves but also damage the
inflorescences, ears, growth points and finally the grains and finally caused a heavy decline in
yield (GC & Keller, 2013).The major damage to the seedlings is caused by caterpillars which move
in swarm. After destroying crop of one field, they move to the other crop. The caterpillars feed
upon the leaves of the seedlings and devour the ear heads as a result further growth of the plant
ceases.

8. M. separata's habit of severing panicles represents the greatest damage to the rice crop, and is
analogous in effect to whitehead damage caused by stem borers in that the grains are not eaten by
the pest but are removed from the plant.
1.1.5 Symptoms
During the vegetative stage of rice, M. separata damage is
evident as massive leaf removal, often including leaf veins
(Fig 6). They may also eat the lemma and palea of the
developing grains as well as the anthers of flowers (Fig 6).
Large angular notches can be cut away from young seedlings
in a seedbed, giving an irregular appearance. Damage is
often localized to one part of a field. During outbreaks many
fields can be affected at the same time.
A characteristic peculiar to M. separata occurs during the
grain filling stage when the mature larva cuts off panicles at
their base causing some to bend while others are completely
severed and fall to the ground.
Figure 5 Damage of maize cobs
by Mythimna separata

9. Figure 6 Damage of rice plants by Mythimna separata
1.1.5 Life Cycle:
Eggs:
Eggs are laid in cluster, consisting of approximately 500 eggs (fig. 3d). The young caterpillars
hatch from the eggs in 4-5 days.
Larvae:
After hatching the caterpillars starts feeding on the leaves of the seedlings. Generally the
caterpillars move in swarm from one field to the other. The caterpillars are fully grown in about
15 days and measures 3-5 cm in length.
Pupae:
It pupates in soil at a depth of 3–5 cm, but sometimes it may pupate under dry leaves or on the
stubbles or fresh tillers. The pupae are yellowish brown and shiny (Fig. 4b), and pupal period
varies from 10 to 13 days.

10. Adult:
Thus, the life cycle is completed in about 30-35 days which is repeated several times each year.
Figure 7 Lifecycle of Mythimna separata
1.2 Management
1.2.1 Mechanical and Physical Control
o Barriers can be constructed to divert migrating M. separata larvae.
o kerosene can be poured in M. separata's path.
o Egg masses or larvae can be hand-picked from seedbeds or a young crop.
1.2.2 Cultural Method:
Before planting:
o Avoid following rice after crops of maize; follow with a food or forage legume.
o Weed the field.
During growth:
o Weed crops, especially removing grass species.
o Visit fields at least once a week, to check for the number of larvae and their maturity.
o Put ducks in the fields to find and eat the larvae at the base of the plants or in the soil.
o Place perches in the fields for insect-feeding birds to use.
o Alter water levels to drown pupae, and to limit spread of larvae between plants.

11. After harvest:
o Plough the field after harvest, burying the stubble, preventing mature larvae from
pupating, and to expose the pupae buried in the soil.
1.2.3 Biological Method:
o Ducks are often raised in rice areas and can be herded into damaged fields to feed on M.
separata larvae. Ducks can locate M. separata larvae hiding in the soil or at the base of
plants. Perching in the fields can increase predation by insect-predatory birds.
o Introduction of Apanteles ruficrus, Sarcophaga orientaloides and Exorista fallax is quite
helpful in controlling the destruction caused by the caterpillars since, these insects
parasitise the caterpillars.
o Sparrows and crows act as predators of this pest.
1.2.4 Chemical Method:
Greater care should be taken in opting for selective insecticides during the early crop-growth stages
when natural enemy populations are increasing. Less care would be needed during the panicle
stage as the crop is about to be harvested.
o Spray of chlorpyriphos 20 EC @ 2.5 litres/ha or quinalphos 25 EC @2.0 litres/ha or
triazophos 40 EC @ 1.0 litres/ha or dichlorvos 76 SL 600 ml/ha on the paddy crop during
evening hours
o Dusting of chlorpyriphos 1.5 % D or endosulphan 5% D @ 30 kg/ha controls this pest.
o Spraying at early stage is very effective.
2. Conclusion
The armyworm, Mythimna separata Walker is the potential insect pest of cereals, causes a severe
damage on the vegetative and reproductive stages of these plant. Insecticides are the common
practices to manage the broad categories of the pest in a maize field. Further, these practices have
been linked to farmers health, biodiversity loss and declining of predatory arthropods. However,
pest management by adopting a tool of integrated pest management is one potential option to
reduce the pesticide in maize fields.
3. References
Ali, A., Rashid, M. A., Huang, Q. Y., & Lei, C.-L. (2016). Effect of UV-A radiation as an
environmental stress on the development, longevity, and reproduction of the oriental armyworm,
Mythimna separata (Lepidoptera: Noctuidae). Environmental Science and Pollution Research,
23(17), 17002-17007.
Anonymous. (1976). Annual report 1978. Entomology Division. Nepal Agriculture Research
Council, Khumaltar, Lalitpur, Nepal.

12. GC, Youbak Dhoj., & Keller, S. (2013). Crop pests of Nepal and their management. HELVETAS
Swiss Inter-cooperation Nepal. 171.
Hill, M. G. & Atkins, A. W. (1983). Effects of defoliation by cosmopolitan armyworm, Mythimna
separata (Walker) on maize yield, New Zealand Journal of Agricultural Research, 25:2, 251-254
Jiang, X., Zhang, L., Cheng, Y., & Luo, L. (2014). Current status and trends in research on the
oriental armyworm, Mythimna separata (Walker) in China. Chinese Journal of Applied
Entomology. 51, 881-889.
Jiang, X., Zhang, L., Yang, H., Sappington, T. W., Cheng, Y., & Luo, L. zhi. (2016). Biocontrol
of the oriental armyworm, Mythimna separata, by the tachinid fly Exorista civilis is synergized by
Cry1Ab protoxin. Scientific Reports, 6(1).doi:10.1038/srep26873. Retrived from
https://www.nature.com/articles/srep26873
Joshi, S.L. (1978). Technical Report on Epidemic of Mythimna separata in Nuwakot and Rasuwa
districts.
Neupane, F.P., Shrestha, S. M., Thapa, R. B. & Adhikari, T.B. (1992). Crop protection (In the
Nepali language). Institute of Agriculture and Animal Science, Rampur, Chitwan, Nepal.
Rana, P.N. (1975). The epidemic of Mythimna separata in Kavre and Sindhupalchowk districts.
Rana, P. N. & Plumb, G. H. (1973). Report on the Ninth session of the plant protection committee
of the South East Asia and Pacific Region, New Delhi, India.
Sharma, H. C., Davies, J. C. (1983) The oriental armyworm, Mythimna separata (Wlk.)
distribution, biology and control: a literature review. Centre for Overseas Pest Research, London,
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Sharma, H. C., Sullivan, D.J., Bhatnagar, V. S. (2002). Population dynamics and natural mortality
factors of the oriental armyworm, Mythimna separata. Crop Prot 21:721–732
Sharma, S., Bhandari, G., Neupane, S., Pathak, A., & Tiwari, S. (2018). Bio-Rational Management
of Armyworm (Mythimna separata) (Lepidoptera: Noctuidae) in Chitwan Condition of
Nepal. Journal of the Institute of Agriculture and Animal Science, 35(1), 143-150.
https://doi.org/10.3126/jiaas.v35i1.22532
Sharma, S., Bhandari, G.C., Neupane, S., Pathak, A. & Tiwari, S. (2018). Bio-rational
management of armyworm (Mythimna separata) (lepidoptera: noctuidae) in Chitwan condition of
Nepal. Journal of Institute of Agriculture and Animal Science. 35:143-150.
Shivakoti, G. P. & KC, B. (1981). Screening of maize germination against maize borer Chilo
partellus, Swinhoe, pp. 95-98. Ninth Summer Crops Workshop. National Maize Development
Program, Rampur, Chitwan, Nepal

13. Shrestha, A., Pandey, A., & Sapkota, R. (2018). Damage Assessment and Management of
Armyworm [Mythimna separata, Walker] in Winter Maize at Rampur, Chitwan. Journal of the
Institute of Agriculture and Animal Science, 35(1), 161-166.
https://doi.org/10.3126/jiaas.v35i1.22535
Wright, I.T.J. & McNeil, J. (1988). A Bibliography of the Oriental armyworm, Mythimna separata
(Walker). Overseas Development Natural Resources Institute Bulletin No. 3, iii + 30.
http://niphm.gov.in/IPMPackages/Wheat.pdf, http://pests.
agridata.cn/showimg3.asp?DB=5&id=162
http://www.agroatlas.ru/en/content/
http://www.keyunnpv.com/Mythimna-separata/6350.html#.XPSX6TFubIU
http://www.slideshare.net/agp115/copy-ofpaddy- pests-11
http://www.yourarticlelibrary.com/zoology/army-worm-mythimna-separata-walk-distribution-in-
india-life-cycle-and-control/23905
http://zipcodezoo.com/index.php/File:Mythimna_separata_4.jpg
https://www.plantwise.org/knowledgebank/datasheet/45093#