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Indian Journal of Entomology 82(4): 842-845 (2020) DoI No.: 10.5958/0974-8172.2020.00108.X
SPODOPTERA EXIGUA (HÜBNER), A NEWLY EMERGING PEST OF
POTATO IN HIMACHAL PRADESH
RAHUL KUMAR, R S CHANDEL*, ANIL1, VASU MEHTA AND KALPANA H S
Department of Entomology, CSK Himachal Pradesh Krishi Vishvavidyalaya,
Palampur 176062, Himachal Pradesh
1Department of Genetics and Plant Breeding (Cotton Section),
CCS Haryana Agricultural University, Hisar 125004, Haryana
*Email: visitrvchandel@yahoo.com (corresponding author)
ABSTRACT
The beet army worm Spodoptera exigua (Hubner) was found to infest the foliage and tubers of potato in
Himachal Pradesh. Initially the larvae made large irregular holes on the leaves, and with severity, led
to complete defoliation, and stems were also injured. After defoliating, the larvae entered the soil and
made numerous circular holes in the tubers causing considerable damage. Its biology was studied under
laboratory conditions. It was observed that the egg, larva, pupa and adult periods last for 2.2± 0.13, 9.7±
0.45, 4.3± 0.15, and 9.3± 0.15 days, respectively. Pupation occurred in soil. The total life cycle (egg to
adult emergence) was completed in 18.9± 0.62 days, with fecundity being 450.2± 31.08 eggs/ female. This
S. exigua
Key words: Potato, Spodoptera exigua, Himachal Pradesh, biology, tuber damage, emerging pest, defoliation,
Potato is a major crop grown in 2.15 million ha
in India during 2018 (FAO, 2020), and in Himachal
Pradesh, it is a main cash crop (Anonymous, 2017).
In India, potato tubers worth 60 billion rupees are
lost annually due to pest damage, which accounts for
10-20% of total production (Chandel et al., 2013).
The potato pests are grouped into soil pests, sap
feeders, foliage feeders, and storage pests (Chandel et
al., 2013). Leaf defoliators are either coleopteran or
lepidopteran insects causing variable damage (Trivedi
and Rajagopal, 1999). The beet army worm Spodoptera
exigua (Hübner) (Lepidoptera: Noctuidae), a generalist
herbivore occurs worldwide attacking over 170 plant
species. In Korea, S. exigua had been reported as an
important pest of potato (Ahn et al., 1989). Since the
mid-1980s, its infestations have become increasingly
serious in China on many crucifers (e.g., broccoli,
potato, chilli pepper, tomato, eggplant, and tobacco)
and Fabaceae (beans, peas, peanuts, and soybeans). In
crops and cotton. In India, S. exigua had been reported
as a serious pest of jute, indigo and a minor pest of
chillies, onion, brinjal, sweet potato, lentil, cabbage,
David and Ramamurthy, 2012). Larvae can also
complete development on a number of common weeds
such as lambs quarters, mullein, pigweed, purslane,
Russian thistle, parthenium, and tidestromia (Smits et
al.,
that the young larvae feed gregariously and skeletonize
foliage. As they mature, larvae become solitary and eat
large irregular holes in foliage (Capinera, 1999). This
study reports on the damage caused by S. exigua larvae
and explains its biology.
MATERIALS AND METHODS
The survey was conducted in major potato growing
areas of Himachal Pradesh during different seasons
to collect and identify the insect pests associated. In
in Kangra valley representing mid-hills, spring crop
was surveyed from January to May. Potato is grown
in summer season under high-hills of Shimla district.
In low hill areas like Una, autumn season crop is
grown. Data on the infestation of S. exigua in potato
plants each were chosen at each location. Observations
on number of larvae/ plant, % plant incidence and tuber
infestation were made. Larvae were collected, carried
to the laboratory in plastic containers, and their culture
maintained on potato tubers. These pupated in soil
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Spodoptera exigua (Hübner), a newly emerging pest of potato in Himachal Pradesh 843
Rahul Kumar et al.
within one week after collection, which were removed
from soil after about 2-3 days and kept in glass jars for
adult emergence.
Adult moths were maintained in glass jars covered
with a double layer of black muslin cloth. A crumpled
paper was placed in each glass jar for providing resting
sites. A cotton swab dipped in 10% honey provided in
each jar served as food. The eggs laid on the muslin
cloths were removed with a moist camel hair brush.
Newly emerged larvae were released singly on fresh
potato leaves. The culture was further maintained on
fresh leaves and tubers, and larvae reared individually.
Observations on egg hatching, larval instars, pre-
pupa, pupa, pre-oviposition, oviposition and adult
longevity were made. Length of eggs, larval instars,
pupa and adult wingspan were also measured (n=10).
The mean weekly temperature and RH during these
observations varied from 21.84- 25.17°C and 66.1-
S. exigua
was done by Dr. P. R. Shashank, Scientist, Division
of Entomology, ICAR-Indian Agricultural Research
Institute, New Delhi.
RESULTS AND DISCUSSION
The field surveys revealed that there was no
incidence of S. exigua on potato in Una and Shimla
districts, but in Kangra, an outbreak occurred on spring
of larvae on foliage and tubers at the time of harvesting
was observed during May, 2015. The larvae caused
complete defoliation of the plants (Fig. 1), after which
these migrated to the soil and seen damaging the tubers
to be infested with larvae/ plant varying from 28.34
to 45.67/ 100 plants, and the plant incidence ranged
infestation was also very high, from 30.00 to 51.25%
consumption. Chandel et al. (2011) had reported S.
exigua as serious defoliator of potato in India, but
record of S. exigua larvae feeding on potato tubers in
lepidopterous pests, cut worms and potato tuber moth
had been observed earlier causing damage to potato
tubers in India. The occurrence of S. exigua on tubers
larvae of Spodoptera
are known to develop resistance to insecticides.
The observations on the biology of S. exigua under
laboratory conditions made during May, 2015 and
presented in Table 1 reveal the following: female
moths laid eggs in clusters (Fig. 3). With a fecundity
of 450.2± 31.08 eggs, with 35-75 eggs/ mass. Eggs
were usually deposited on the lower surface of the leaf,
covered with a layer of dirty white scales. Chandel et
al. (2011) reported that a female lays up to 1300 eggs
in batches of 50-200 on the ventral surface of leaves.
Capinera (1999) also reported that female lays 300-600
eggs in clusters, with 50-150 eggs/ mass. The eggs were
greenish to white, and hatched in 2-3 days. Gill et al.
(2015) reported this as 2.4± 0.55 days and Azidah and
instar pale green or yellow, but acquired pale stripes
pink or yellow coloured ventrally and a lateral white
stripe, with a series of dark spots on the dorsal and
dorsoventral surface (Fig. 3). Wilson (1932) reported
that Laphygma exigua larvae normally pass through
five instars. Fye and McAda (1972) observed five
Fig. 1. Defoliation in potato by S. exigua
Fig. 2. Larvae of S. exigua and infested tubers
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844 Indian Journal of Entomology 82(4) 2020
a b
c d
Fig. 3. Stages of S. exigua;
Table 1. Infestation (plant, tuber basis) and biology (on leaves) of S. exigua in potato (Palampur)
Location No. of larvae/ 100 plants % plant incidence % tuber infestation
1 45.67 52.25 50.00
2 39.71 45.81 51.25
3 28.34 34.41 45.00
4 29.83 36.39 30.00
5 35.18 43.02 36.67
Mean 35.75 42.38 42.50
Stage Duration (Days) n=10 Length (mm) n=10
Range Mean ± SE Range Mean ± SE
Egg 2.0- 3.0 2.2± 0.13 0.48- 0.53 0.51± 0.01
Larva I 2.0- 3.0 2.5± 0.17 2.2- 2.8 2.42± 0.06
II 1.0- 2.0 1.5± 0.17 5.5- 6.4 5.91± 0.08
III 1.0- 2.0 1.2± 0.13 8.5- 9.8 9.05± 0.13
IV 1.0- 2.0 1.5± 0.17 14.0- 16.0 14.92± 0.22
V 3.0 3.0± 0.15 24.0- 26.4 25.52± 0.29
Total larval period 8.0- 11.0 9.7± 0.45 - -
Pre-pupa 2.0- 3.0 2.7± 0.15 - -
Pupa 4.0- 5.0 4.3± 0.15 15.0- 20.0 17± 0.58
Preoviposition period 2.0- 3.0 2.4± 0.16 - -
Oviposition period 4.0- 8.0 5.5± 0.52 - -
Adult 9.0- 10.0 9.3± 0.15 25.0- 28.0
(wingspan)
26.55± 0.38
Total life cycle
(egg-adult emergence)
16.0- 22.0 18.9± 0.62 - -
instars. Gill et al. (2015) reported that full grown larvae
measured 26.20 ± 2.21 mm in length. Chandel et al.
(2011) reported that larvae of S. exigua grow 3.8 cm
long. Duration of the instars I-V was 2.0-3.0, 1.0-2.0,
1.0-2.0, 1.0-2.0, and 3.0 days, respectively (Table 2),
with total larval period being 8-11 days. Berdegue
et al. (1998) observed this to be 16 days on shallot,
10 to 24 days on cotton and 21.3 days on common
weed (Chenopodium murale) and 16.5 days on celery,
respectively. However, Gill et al. (2015) observed this as
16 to 20 days. Initially, the larvae gregarious, feeding in
a group, causing complete skeletonization of leaves. As
they matured, larvae became solitary and mobile. Under
the tubers. The larvae made deep holes in the tubers and
in case of heavy infestation, 5-8 holes were observed
on a single tuber. Several larvae were observed to feed
on a single tuber.
Pupation occurred in the soil in an earthen cell, pupa
was pale brown, measured 15.0- 20.0 mm long (Fig. 3).
Shankar et al. (2014) observed this a obtect, turning
reddish brown. Gill et al. (2015) reported its pupation
in a thin, loose cocoon, as a light brown one, becoming
reddish brown. The duration of the pupal stage was
recorded to be 4-5 days, and in contrast, Chandel et al.
(2011) observed larval and pupal duration of 15 and
16-17 days, respectively. Adults were moderate in size,
grey and brown having irregular banding patterns and
greyish white and had a dark line along the margin. The
oviposition began within 2-3 days after the emergence,
oviposition period extending over 4-8 days. Adult
longevity was 9-10 days, and total life cycle from egg
to adult emergence was 16.0-22.0 days. Capinera (1999)
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Spodoptera exigua (Hübner), a newly emerging pest of potato in Himachal Pradesh 845
Rahul Kumar et al.
reported that moths are having a wingspan of 25-30
mm and oviposition period extend over 3 to7 days and
moths usually perish within 9-10 days of emergence.
Pupal period varied from 4 to 10 days in summer and 6
to 20 days in winter, and 7.5 days on celery (Berdegue
et al., 1998). Adult longevity ranges from 9-10 days.
According to Gill et al. (2015), adult longevity ranged
from 6 to 8 and 7 to 9 days, in case of males and females,
respectively.
ACKNOWLEDGEMENTS
The authors thank Dr. P. R. Shashank, Scientist,
Division of Entomology, Indian Agricultural Research
S. exigua.
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