SORGHUM ENTOMOLOGY Progress Report-6

STUDIES ON SEPARATA AT ICRISAT

Progress Report 1980-81

H.C. Sharma, V.S. Bhatnagar and J.C. Davies

4, ICRISAT International Crops Research Institute for the Semi-Arid Tropics ICRISAT Patancheru P.O. Andhra Pradesh 502 324, India

1982 ACKNOWLEDGEMENTS

The assistance received from support staff of the sorghum

and cropping entomology is duely acknowledged. The keen

interest and tireless efforts of Mr V Venkateswara Rao need

special mention. Our thanks are also due to our co-operators

namely; Drs F R Biddinger, V Mahalakshmi, B S Talukdar,

S V R Shetty and M V Natarajan, who willingly offered their

experiments to collect observations on various aspects and

for making available their own data for purposes of comparision.

The encouragement received during the course of this work from

Dr L R House and Mr D J Andrews is gratefully acknowledged.

The authors are also thankful to Drs K Leuschner, W. Reed,

A.B. Mohamed, R P Thakur and S.L. Taneja for going through the manuscript, and making valuable suggestions. STUDIES ON AT ICRIFAT

H.C. Sharma, V.S. Bhatnagar and J.C. Davies

1 INTRODUCTION

The oriental armyworm, Mythimna (Pseudaletia)() separata

Walker is a pest of cereals in Asia and between 450N

to 450 S latitude and 60 E to beyond 170 W longitude. It has been

reported to feed in nature on 33 plant species and. some un­

specified grasses belonging to eight plant families (Sharma &

Davies, 1982). Prior to 1950 it was of minor importance in India.

In the last two decades extensive damage has been reported from

over 25 places in different parts of India. It has become a serious

pest on sorghum, millets, rice, , and wheat with the increase In

irrigated areas and the consequent changes in farming systems,

introduction of high yielding varieties, heavy fertilizer use and

continuous cultivation (Bindra and Singh, 1973, Verma and Khurana,

1971 and Gopinadhan and Kushwaha, 1978).

At ICRISAT Center, outbreak of Mythimna separata defoliating

sorghum and pearl-millet was recorded In 1977. Consequently, the biology

and population dynamics of the pest has been studied and efforts made 2

to screen pearl millet and sorghum genotypes for resistance to this

pest. The report covers the results of the studies carried out on

these and related aspects over the past several years at the ICRISAT

Center.

2 INCIDENCE AND BIOLOGY

In the period 1977-79 Mythimna damage or larval population was recorded

by selecting 100 plants (at random) diagonally across sorghum and pearl

millet fields. Usually a number of fields on two soil types (Alfisols

and Vertisols) were included in samples to determine the range of

infestation. In 197 8 ,sampling was continuous throuyhout the year.

Additional data from sole and intercropped sorghum (with pigeonpea)

were recorded in large intercropping trials between 1975 to 1980. In

these observations the number of larvae were recorded from 100 plants or

earheads.

At ICRISAT Center, Mythimna separata larvae severely damage pearl-millet

and sorghum during August-September (Table.l. In alfisols, pearl millet

sustained higher damage compared to sorghum. Extensive defoliation was

observed during 1977, when its first outbreak occured.

In intercropping trials, upto 106 larvae/100 plants were recorded

during 1977 (Table 2). The larval populations were considerable in

subsequent seasons, though far less than that of 1977. Larvae were observed

in June 7-10 days after the first few showers of monsoon rains. 3

The biology of the was studied during October 1979 and

January-February, 1980 under ambient temperature and relative humidity. 30 cm 3 The obtained from the field collected larvae were kept in

cages. The moths were provided with 10% honey solution in a cotton

swab. The eggs were laid on dry sorghum leaves or butter paper placed

at the bottom of the cage. Larvae were fed on sorghum leaves in 1 ltr.

plastic jars. Data were recorded on the development of the various stadia

and on other biological aspects such as oviposition and sex ratio,

The females laid an average of 996 eggs after a pre-oviposition

period of 2-5 days. Oviposition continued for 2-7 days after emergence

(Table 3). Egg incubation took 4-5 days. The larval instars I-VII

averaged 3.9, 3.3, 3.1, 2.7, 3.1, 2.2 & 1.8 days respectively. Pre­

pupal and pupal periods lasted for 1-2 and 8-12 days respectively. The

entire post-embryonic development was completed in 29-39 days. A third

instar larva weighed on an average O.lO-O.15g and a pupa 0.26-0.42g.

3 OUTBREAKS

Outbreaks of M. separata occured at ICRISAT Center during 1977, 1978

1980. Outbreaks at other locations have been recorded during 1980-81

at Dharwad and at Anantapur and Nandyal during 1981.

Mythimna outbreaks have occured in India and elsewhere in many

seasons (Sharma & Davies, 1982). A basic knowledge of (a) temperature

and R.H. requirements of the insect in the ecosystem, (b) availability 14 of suitable hosts, (c)migration, and (d) extent of parasitism and parasites involved, may help to understand the factors controlling the insect population. The outbreaks in India, , Japan, Bangladesh,

New Zealand, Fiji and Australia have been attributed to; (a) the owqrrenc. of drought following rains, (b) floods resulting from heavy rainfall,

(c) Induction of migrant populations into a geographic area,(d) heavy fertilizer use, (e) trash mulching, and (f) temperature and humidity regimes in the periods preceding and during the outbreaks (Butani, 1955; Puttarudriah and Usrnan, 1957; Chin, 1979; Grist and Lever, 1969; Avasthy and Chaudhary, 1965 and Koyama, 1966). High rainfall possibly leads to high humidity and more food, which are very essential for survival and development of the larvae. Prolonged periods of drought following rains may possibly restrict the activity of natural control agents (parasites, predators & diseases). Heavy manuring leads to better crop growth for insect feeding and development. Trash mulching provides a good site for oviposition and better place for the larvae to hide in.

The factors resulting in outbreaks at ICRISAT Center and other places are not fully understood. The light traps have not Indicated the arrival of migrant populations. Moreover, the phototropic behaviour of migrant moths is not fully known. Duelng 1977-78, the outbreaks possibly resulted from drought preceded by a period of normal rainfall, while during 1980, the outbreak was preceded by a period of heavy rainfall.

The build up of damaging populatlons at ICRISAT Center might have resulted from lavish crop growth and heavy use of fertilizers. Another factor may be the low parasitism and disease levels (around 30%) observed at

ICRISAT Center as against >75% in Punjab and Rajasthan (Butter, 1978 5

and Gopinadhan and Kushwaha, 1978) due to Apanteles ruficrus and Bacillus

cereus respectively. Anantapur experienced the first recorded outbreak

during 1981. It is a drought-prone area, and unusually in that year, normal

and well distributed rainfall was experienced. The arrival of migrant

populations or build of native populations in the absence of parasites

might have led to population explosion. A close examination of the case

histories of a number of outbreaks may help to elucidate the factor(s)

leadiny to ,opulation explosion.

4 POPULATION DYNAMICS

4.1 ADULTS

Activity of adult Mythimna spV was monitored daily using light traps

(Bhatnagar and Davies, 1979) installed at three locations at ICRISAT

Center. The data were converted into 4 week moving means to allow for

moon phase effects (Bhatnagar and Davies, 1978).

The site of one light trap (Site 1) on an alfisol which wa! operated

continuously between Aug. 1974 and July.1979 was subsequently changed. The

light traps at 3ite 2 (alfisol) and Site 3 (vertisol) were commissioned

In Sept. 1975 and May 1977 respectively. Light trap catches at ICRISAT

Cencer over the four /ear period (1977-80) at three locations are given In

Table.4. Most moths were caught durlng September but catches were high

In August. Very few moths were recorded in the months from December-May,

and no moths were attracted to light in June. Catches of moths were

highest in 1977. 6

The four week moving means of the trap catches are presented in Fig.l. The insect population, as indicated by trap catches, was lower

during 1974-76 and 1979-80 (Fig.l). The insect activity was higher during

August-September. The trap catches were higher during 1977 when extensive damage occured in sorghum and pearl-millet. The trap catches differed

between locations (Fig.2). The maximum number of moths were caught In the trap located in the vertisol watersheds, which is in the midst of a large

area planted to sorghum and maize. The trap catches were considerably

lower in traps located at Manmool village (tnap surrounded by off-season

nursery area, irrigated paddy fields and rainfed alfisols), Crop

Improvement Building and RA-l(near the Hyderabad-Bombay highway with trees on one side and rainfed alfisols on the other).

The light trap catches, temperature, humidity and rainfall frnom 1976

to 1980 are presented in Fig.3. The peak activity period moved ahead by

5-6 weeks from 1976 to 1980. The insect population appeared to follow the changes in weather. However, no single factor exercised marked effect on the insect populations. Generally, more moths were caught during periods of low rainfall preceded by a 2-4 week period of normal rainfall. During

1980, there was no distinct period of prolonged drought, and the trap catches declined with the decrease in the amount of rainfall. The trap catches during 1979 showed considerable insect activity up to November, when a bimodAl pattern of rainfall was experienced. The insect population was highest during 1977, when rainfall was low and erratic. The maximum activity period was also preceded by 4-5 weeks of moderate temperatures

(20-30C), higher humidity (50-95%), and smaller differences between the maximum and minimum temperatures and R.H. These conditions are highly 7

congenial for ovipositi-on, egg hatching, and larval survival and development.

During the post-rainy and summer seasons, very few or no moths were caught,

when temperatures dropped to < 200 C or went up to > 350 C and RH fell below

50%.

Populations of Mythimna lorey! Duponchel showed different patterns

of pupulation fluctuation (un-published data). The populations of

M. lore'i, as indicated by light traps, were higher than those of M.

separata though its larval population and damage on sorghum and pearl­

millet remain very low at the ICRISAT Center. Interestingly, the

population of M. loreyi during 1977 was the lowest while that of

M. separata was tne maximum, though both are closely relted.

4.2 LARVAE

The larval population was monitored at four locations at ICRISAT Center

(pesticide free alfisols and vertisols and pesticide treated alfisols

and vertisols) and at a farmer's field (4 km west of ICRISAT Center) 2 at fortnightly intervals. Three plots of 48 m were marked in each

location diagonally. The larval survey began during July when the crop

(sorghum or pearl millet) was 10-15-days old. The plant population was

recorded in each plot. Larvae were counted carefully in these plots.

The survey continued till crop maturity. In the post 3rainy season,

the surveys were conducted in fields having sorghum or millet irrespective

of location. During 1980 kharif, the pesticide treated alfisols received

one application of endosulfan (0.7 kg al/ha) on pearl millet against

Mythimna separata and Heliothis armigera on 28.8.1980. In pesticide 12 8.90a4.7. 190.ad ntMloeu p adAhrgn oc

' '' .....' ' " '0.7 *: g i/ wereap lied on pearl! milletIn the alfisols, The formen a

against Athericona Soccata on I .7.19811 and 9.7.181 an edo fan '

:::":;:,,::(@ 0.7 kg al/ha) against.. /ythimna separata: and H:el iathis armi: era, on 18.71 981 ; I I i~i iand..... 17,9,.1981: respectively on sorghum. At t e ime of.gr i iling stage, .. . carbaryl (@tI kg a[/ha0 applied againstgwas ..... uStatuson sorghu m.

Larval populations monitored during 1980-81 are given In Flg. ab.

Maximum numbers of larvae were observed cdoring August, while thepekI :- the trap catches of moths wbs recorded during September. Lavvai population as well as trap catches declined durilng October The population waslower

in pesticide free a!,fisols than in the treated fields. In vetthsols, there was little dfferee on treated and pesticide free fields. in9

insect poplations were detectd by light traps 3 5 weeks after peak larval

: , .: i-... . .po pu la t io n ...... :. i

inpete fre atsl Mthamnain the troaled tields.ain evertisols there4*

From thedforegoing account is, apparent that the l ght traps are not

rausefin Indicating the begnningof infestations, and that themode

of carryover and s of Initia infesta tions Isnot fully understod,.9 - T anr es n soterthe inttation of monsoon rains iends tag, Maimne of larvae aere os folw At, hil( eeak in The moths possibly resort to migration from one place to another depending

upon the weather conditions. The migrant behaviour of this insect has

been well established in China and Japan (Ma, 1979; Quo et al, 1963; Lin

and Chang, 1964; Li et al, 1963 & 1965; Koyama, 1970; Chen et al, 1965;

Oku and Koyani, 1976 and Nagano et al, 1972). The period before sexual maturity

has been suggested as the optimum time for long distance migration (Hwang

and How, 1966). In China moths from South China are considered to be a

source of early spring populations, which follow ascending, trans and

descending movements (Lin (Chang-Shan), 1963). The moths can fly 600-1400 km

(Grist and Lever, 1969) and have been intercepted even over the sea (Hsla et a],

1963 and Asahlna, 1968). The moths also follow the air currents (Oku and

Kobayashi, 1974 and Lin et al., 1963).

Light traps are possibly Ineffective under low population levels.

Alternatively, during unfa'ourable conditions, the moths may resort to

migration, and possibly do not respond to light traps. This point derives

support from the fact that during December, 1981, none of the 500 un-mated

moths released about 100 m away from the light trap responded to it. The

low population levels during the post rainy season, in spite of substantial

area planted to pearl-millet and sorghum, indicate the possible movement of

moths away from this place. Alternatively, decreased egg hatching and

larval survival because of lower humidity and lower or higher temperatures

(than the optimum) may be another possible causes of low population levels.

5 PARASITIZATOON

During the fortnightly surveys, samples each of 50-60 larvae were collected

from different locations. The larvae were reared in the laboratory, and 10 data were recorded on pupation, adult emergenee, the number of larvae parasitized, the parasites involved, and the natural mortality due to other factors such as fungi, viruses and bacteria. The data on parasitism were also supplemented by additional field collections.

From over 5000 field collected larvae, we recovered six hymenopterous parasites (Apanteles spp, Disophrys sp, Metopius rufus, Campoletis chloridae and Enicospilus sp.) and four dipteran parasites (Exorista xanthaspis, Carcelia spp, Palexorista solemnis and Megaselia sp.). Mermithid nematodes were also recorded as one of the important parasitic groups. Anedrallus spinidens was observed preying on the larvae at Hissar.

Larval population/unit area, their survival and parasitization are given in fig.5 ab and Table.5. Larval populations were much lower in the

Farmer's fields and the pesticide free alfisols at ICRISAT Center than In treated alfisols and vertisols, and pesticide free vertisols. In the treated alfisols and vertisols and pesticide free vertisols, the larval pupation and adult emergence were lower than in pesticide free alfisols.

The larval population and parasitism levels were higher during 1980 than those in 1981. Hymenopterans were the major parasites and their activity tended to be higher in vertisols than in alfisols. The dipteran parasites also showed higher activity in vertisols, though their incidence was much lower overall than that of hymenopteran parasites.

Pu'ation and adult emergence were higher in larvae collected from pearl-millet as compared to those collected from sorghum (Fig.6). However, the larval parasitization was much hiqher in sorghum than in pearl-millet.

Hymenopterous parasites were much more abundant in sorghum than in pearl­ millet. The dipteran parasites though less common than hymenopteran parasites, II

were also more common in sorghum than in pearl-millet (Table 5). The

sex ratio showed that there was a greater proportion of female moths in

populations collected from pearl mi!let than those from sorghum.

The pupation and adult emergence of the field collected larvae decreased considerably from June to October (Table 6). The sex ratio

(males:females) also tended to decrease from June to October. It was

higher during 1980 compared to 1981. The significance of this change,

and the factors effecting this phenomenon need to be looked into critically.

Parasitization increased considerably from June to September, and slightly

declined during October. The larval mortality due to other factors did not

show any trend across the season and generally ranged between 12.5% during

September 1980 to 48.3% during December, 1979.

Larval survival and parasitism levels did not differ substantially in

four pearl-millet cultivars having four weeding treatments (Table 7). The

parasitism by hymenopterans was very low ( < 1.7% parasitism). Mermithids

were the most important parasites (10-18/ parasitism). These parasitism

levels by mermithids were much higher than those recorded at other locations.

Forty two pzlrasites, IS predators, 4 bacteria, 5 fungi and 3 viral strains

have been reported as natural control agents of Mythimna separata (Sharma and

Davies, 1982). At ICRISAT Center, the Aoanteles ruficrus and

Exortista xanthaspis were the most important. The negligible larval parasitism

by hymenoptera in pearl millet may partially explain the heavy leaf defoliation

experienced in pearl-millet than in sorghum. On sorghum, the parasites killed

about 25-30% of the larvae. The parasite activity did not differ substantially

in protected and unprotected areas. This phenomenon need to be looked into

more intensively. At ICRISAT Center, the heavy infection and mortality due 12

to diseases (bacteria and virus) have not been observed as reported elsewhere

(Bindra and Singh,1973; Gopinadhan & Kushwaha, 1978 and Neelgund and Mathad,

1972). It is likely that ar more effective strains of parasites and

pathogens are present in other areas. Complete biological control of this

armyworm has been achieved in New Zealand by using a strain of Apanteles

ruficrus imported from Pakistan (Simmonds, 1976; Simmonds and Bonnett. 1977

and Mohyuddin and Shah, 1977). In the light of above observations, the

transfer of effective natural cnntrol agents within the country should be

actively considered.

6 HOST PLANT RESISTANCE

6.1 HOST RANGE

No directed efforts were made to study the host range of Mythimna. However,

periodical observations were made on the-plant species upon which the larvae

were found feeding. Mythimna separata has been observed feeding on pearl

millet (Pennisetum aniericanum),sorghum (Sorqhum bicolor), Maize (Zea mays),

rice () and bermuda grass (Cynodon dactylon) at ICRISAT Center,

and on Italian millet (Setaria italica) and Kodo millet (Paspalm scrobicultatum)

at Anantapur (in addition to pearl millet and sorghum). It has been reported

feeding upon 33 plant species and some unspecified grasses belonging to eight

families (Sharma & Davies, 1982). However it is a major pest of Gramineae.

The food preference, utilization and larval development varies on different

host plants (Kalode et al. 1971). During 1981, in an outbreak situation at

Anantapur, the larvae completely defoliated pearl and Italian nlillet while

there was very little damage in Kodo millet. 6.2 RESISTANCE SCREENING

A set of 40 pearl-millet genotypes (belonging to different geographical

regions) was tested using plastic pots and metal trays under free choice

test. However, the damage ratings varied conflderably in different

replications. To avoid these problems, a set of 12 genotypes was tested

under no choice situation using glass ch~mneys.

The entries were grown in plastic pots (15x15xO cm). Each pot

had five seedlings. Fifteen days after germination, 3 pairs of pots with

uniform plant growth were selected from the 10 pots raised for each genotype.

The plants in each pot were covered with a glass chimney and one pot from

each pair was infested with 3rd instar larvae @ one larva/plant.

After 24 hr the larvae were removed. The data were recorded on leaf

area, dry weight and leaf damage. The leaf area (measured by leaf area meter)

and dry weight consumed by the larvae were expressed as percentages of the control pots.

During kharif 1980, a field trial containing 36 hybrids (repllcatlons-3,

plot size 8 rows, 4M long, design RBD) was rated for Mythlmna damage on

1-5 scale (I -410% leaf area damaged, and 5 =>75% leaf area damaged)under

natural incidence of the pest.

There were significant differences in genotypic susceptibility to

leaf damage by Mythimna separata larvae (Table 8) under a no choice situation.

The genotypes, Sough Local, PIB-228, MBH-110 and D-1051-1, were less damaged 14

than SAR-57, BJ-104 and SAD-4031. Visual leaf damage rating was positively

correlated with leaf area (r=0. 85) and dry weight consumed (r=O.95). Leaf

area and dry weight consumed in different genotypes were also positively

correlated (r=0.87).

Leaf damage by Mythimna differed significantly in the hybrid trial

under field conditions. The interesting feature of these data were that

hybrids based on lilA male sterile were less damaged than those based on

5141A and 5054A. Similar indications of reduced damage of leaves in hybrids

based on IliA have also been obtained for Myllocerus damage at Hissar

(Unpublished data).

A number of reports have indicated the existence of varietal resistance

in wheat, rice, maize and sorghum under field conditions (Sharma and Davies,

1982). Under field conditions, the extent of damage is influenced by (a) the

amount of hiding space available to the larvae,(b) the plant characteristics

(height, tillering and leaf canopy), and (c) the position/location of the cultivar in the field. The insect damage tends to be higher in the center of the field and in areas with surface mulch (or any other plant material lying on the ground). The dwarf genotypes having more tillers suffer

heavier damage than tall and less tillering genotypes. In addition, the genotypic differences in susceptibility tend to narrow down with the increase

in; (a) insect pressure, and (b)exposure time. Under these situations, we must look for genotypic resistance under controlled conditions. The resistance parameters should include; (a) leaf damage, (b) larval survival and rate of development, and (c) fecundity. All cases of field resistance should be put to test for these parameters under controlled conditions. 15

7 CONTROL

7.1 AGRONOMIC PRACTICES

During kharif 1980, population of Mythimna larvae and leaf damage were

recorded in an experiment having 4 weeding treatments (weed-free, atrazine

@0.5 kg/ha + one hand weeding, one hand weeding, and weedy check) in four

pearl millet cultivars (Ex-bornu, G-73-K-77, BJ-104 and IVS-AX75). Each

treatment was replicated thrice in a split-plot design. The number of

Mythimna iarvae were counted per square meter In the center of each plot.

The treatments were also rated visuallly for leaf damage on 1-5 scale. The

larval population and leaf damage in different treatments were compared

with weed dry weight and grain yield by computing simple correlations.

The extent of Mythimna damage in two cultivars (BK-560 and ICH-118)

sown in eight plant spacings (llOxllO, 80x80, 100x40, I0Ox20, lOOxlO, 50x20,

50x1O and 50x40 cm) was evaluated for leaf damage during kharif 1981 at

Anantapur in an outbreak situation. Each treatment was replicated four times

In a split plot design with spacings as the main plots. Leaf damage in each

plot was rated on 1-5 scale. The extent of leaf damage was compared with the plant densities.

Larval population and leaf damage were greater in plots having heavy

weed population (Fig.7). Among the cultivars tested, Ex-bornu appeared

to be less damaged than GAM-75-K-77 and BJ-104. Similar indications have

also been obtained from resistance screening experiments (Table 8). The

grain yield was negatively correlated with larval population (r =-0.69),

leaf damage (r = -0.71), and weed dry weight (r =-0.94). Larval population 16

was positively correlated with weed dry weight (r = 0.67) and crop damage 6 (r=O. 3). At Anantpur, plant population was found to be positively

correlated with Mythimna damage (r=0.24). However, the correlation coefficient was

quite low, because this happened to be an outbreak situation.

Clean cultivation may be one of the important factors that would

reduce Mythimna damage. This deprives the larvae of their hiding space

during day time and possibly exposes them to a number of parasites and

predators. The weeds may also be more attractive to the larvae. We need

to look more carefully into the various apects of crop husbandry which

could be manipulated to the disadvantage of the insect without involving

additional costs.

7.2 ANTIFEEDANTS

Neem (Azadirachta indica) kernel and shell powider, and their alcoholic

extracts were evaluated for their phagodetterrent effect against Mythimna

larvae. The shell and kernel of one kg fruits were separated and

powdered in a pestle and mortair. 250g of each powder were passed through a 60 mesh

sieve and then extracted in 95 ethyl alcohol on a hot water bath for

12 hours. The alcoholic extracts were filtered through Whatman filter

paper (No.1). The filtrate was evaporated on a hot water bath. The

shell powder yiclded a reddish brown sticky material, and kernel powder

a yellowish brown oil like material.

The shell and kernel powders were suspended in 10% ethyl alcohol.

The alcoholic extracts were dissolved in 10 ml of ethyl alcohol and distilled

water was added to make up the volume to 100 m1O. In free choice test, the 17

shell powder and kernel powder were tested @ 1 and 2 g/lO0 ml and alcoholic extracts @ .5 and ig/100 ml. In no-choice test, both, powders and alcoholic extracts were tested at 1% concentration. In the free choice test, twenty-day-old

plants of BJ-104 (grown in 15x]5x]O cm plastic pots) were treated with different concentrations. Each pot had 5 plants. Twenty larvae (3rd instar) were

released in each pot. The number of larvae in each pot were counted at 24,48,72 and 96 hr after release. The plants were rated for leaf damage in each pot after 96 hr. In no-choice test, the larvae were confined to the plants using a glass chimney. The larvae were removed after 24fhr. Observations were

recorded on leaf area and dry weight of the plants. Leaf area and dry weight consumed by the larvae in treated pots was expressed as percent of the control pots. There were significant differences in larval distribution and leaf damage under free choice situation (Table 9). The number of ;arvae were minimum in pots treated with alcoholic extracts of shell and kernel powder. Under no choice conditions (Table.lO), alcoholic extracts of shell and kernel powder were most effective.

The mixing of neem leaves with grains is an age old practice in India.

Pruthl (1937) produced the first scientific data on the repellent action of neem leaves against stored grain pests. The demonstration of antifeedant properties of neem against desert locust generated tremendous interest in this plant (Pradhan et al., 1962; Sinha and Gulati, 1963 and Goyal et al.,

1971). The neem products are now known to disrupt moulting and act as antifeedants (Gill and Lewis, 1971, Leuschner, 1972; Jacobson et al,

1978; Schmutterer and Rembold, 1980 and Sharma et al, 1980). The neem components also act as oviposition suppressant (Joshi and Sitaramaiah, 1979).

In view of a number of active components isolated from neem, there seem to be 18

a great potential for its use in future pest-management systems.

8 SUMMARY

1. Mythimna separata damages sorghum and pearl-millet severely during

August-September. Larvae remain active in the field during January-

April and June-December. Over the past six years, no moths have

been trapped during June while larvae have been observed 7-10 days

after initiation of monsoon rains during June.

2. Its population can increase at a tremendous rate because of the high

fecundity of females. The entire development from egg to adult takes

around 29-39 days.

3. The maximum no. of moths were caught during 1977 when the first outbreak

was experienced. Light traps indicated peak activity during September,

and the maximum larval activity was observed in August. The trap catches

vary in different years and at different locations. The maximum activity

of moths occurred during a period of lower or no rainfall preceded by a

2-4 week period of normal/high rainfall, moderate temperatures and high

humidity.

4. Larval population was much lower in farmer's fields and unsprayed

alfisols than in sprayed alfisols and vertisols and unsprayed vertisols.

5. A number of hymenopteran, dipteran and mermithid parasites regulated

the Mythimna population to some extent. Larval parasitization increased

from June to October. 19

6. The extent of larval parasitization was much higher in sorghum than

In pearl-millet. The sex ratio tended to be more in favour of females

in pearl-millet than in sorghum. This possibly resulted in large

scale defoliation in pearl-millet as compared with sorghum.

7. A number of outbreaks have occurred at a number of places in recent

years. The problem seems to have been accentuated with an increase

in irrigated area, continuous cultivation, introduction of newer

high yielding cultivars and increased fertilizer use.

8. It is a voracious and polyphagous pest of a number of plant species.

There seem to be some indications of host preference among the plant

species it feeds upon. The insect damage also differs in different

genotypes in 6ereals. However, the extent of damage depends upon the

insect population and exposure time. Instances of field resistance need

to be varified under no-choice conditions.

9. Clean cultivation and lower plant population may help to reduce insect

damage to sortie extent.

10. Plant products from neem exhibit useful properties as phagodeterrents.

This may form an important component of our pest control armoury in

the future. 20

LOOKING AHEAD

Studies on its biology in different agroclimatic zones should

be carried out particularly in relation to seasonal activity,

maximum and minimum activity periods, mode of carryover, and

source of initial infestations,

2 A population monitoring grid should be set up in the Indian

sub-continent. The population monitoring may be carried out

through light traps, mollases and pheromone baited traps.

These data should be verified through Deriodic field observa­

tions. The data should be recorded in a manner so that it

could be used in systems modelling and pest forecasting.

3 The source of initial infestatio,-s and factors leading to outbreaks

should be studied in different aqroclimatic zones. In this, the

role of natural enemies, crops and crop combinations, and the

possibly of different cultivars need to be looked into. The

possible movement and utilizatior of efficient natural enemies

should be actively persued.

4. Population management involving host plant resistance, natural

enemies, agronomic practices (clean cultivation and lower plant

population, fe-rtilizer use ! tillage), antifeedants and

occasional u:;e of insecticidei 'Ahould be carefully investigated,

evaluated and nut up as a balanced control approach. REFERENCES

Asahina, S. (1968). Insect dispersal as observed by a weathership on the North Western Pacific. Page 106 in XIII International Congress of Entomology, Moscow. 2-9 Aug. 1968.

Avasthy, P.N. and Chaudhary, J.P. (1965). Biology and control of armyworm, Pseudaleti3 unipuncta Haw. Indian Sugarcane Journal 9:249-251.

Bhatnagar, V.S. and Davies, J.C.(1979). Insect trap studies at ICRISAT Center, Progress Report (Cropping Entomology-2) International Crops Research Institute for the Semi-Arid Tropics, ICRISAT, Hyderabad, India. 8 pp.

Bhatnagar, V.S. and Davies, J.C.(1978). Factors affecting population of gram pod borer, Heliothis armigera (Hubner) at Patancheru, Andhra Pradesh. Bulletin of Entomology. 19:52-64.

Bindra, O.S. & Singh, J.(1973). Bionomics of the armyworm, Mythimna separata (Walker). (:) at Ludhiana, Punjab. The Indian Journal of Agricultural Sciences 48:299-303.

Butani, D.K.(1955). ,ontrol of an outbreak of the armyworm (Cirphis unipuncta Haw.) on sugarcane at Pusa, Bihar, 1953. Indian Journal of Entomology 17:133-136.

Butter, N.S.(1978). Apateles ruficrus Haliday - an efficient parasite of armyworm (Mythimna seprata (Walker) on wheat. Science and Culture 44:181-182.

COen, Rui-lo; Leo, Chao-Shen; Liu, Tseng-ye; Li, Mien-chung and Sien, Nlen-ying (1965). Studies on the source of early spring generations of the armyworm Leucania separata Walker in the Kirin Province. I. Studies on the original ground of immigrant moths. Acta Phytophylacica Sinica 4:49-58.

Chin, T.S.(1979). The relations of population dynamics of the armyworm, Leucania separata Walker to relative humidity and rainfall. Acta Entomologica Sinica 22:404-412. 22

Gill, J.S. and Lewis, C.T.(197). Systematic action of an Insect feeding detterent. Nature (London) 232:4Q2-403.

Gopinadhan, P.B. and Kushwaha, K.S.(1978). Population trend of the armyworm, Mythimna separata Walker (Leoldoptera Noctuidae) under the Influence of key ablotic and biotic factors, In All India Workshop on Population Ecology in relation to of gconomic Importance, Jan 18-20, 1978, Bangalore, India.

Goyal, R.S.; Gulati, K.C; Sarup, P.; Kidwal, M.A. and Singh, D.S.(1971). Biological activity of various alcoholic extractives and isolates of neem (Azadirachta Indica) seed cake against Rhopaios. phum nympheae (Linn,) and Schistocorea gregaria Forsk. Indian Journal of Entomology 32:242-252.

Grist, D.H. and Lever, R.J.A.W.(1969). Pests of Rice, London, U.K: Longmans, Green and Co. Ltd. 520 pp.

Hsia, T.S.; Tsai, S.M. and Ten, H.S.(1963). Studies of the regularity of oatbreak of the oriental armyworm, Leucania sepgrata Walker. II. Observations on the migratory activity of moths across the Chili gulf an Yellow sea of China, Acta Entomologica Sinica 12:552-564.

Hwang, Guan-huel and How Wu-wel (1966), Studies on the flight of armyworm (Leucanla separate Walker). I. Flight duration and wing beat frequency. Acta Entomologica Slnica 15:96-104.

Jacobson, M.; Reed, O.K.; Crystal, M.M.; Moreno, D.S. and Soderstorm, E.L. (1978). Chemistry and biological activity of Insect feeding detterents from certain weed and crop plants. Entomologla Experimentalis et Applicata 24:448-457.

Joshl, B.G. and Sitaramalah, S.(1979). Neem Kernal as an ovipositional repellent for Spodoptera litura (F.) moths.Phytoparasltica 7:199-202. 23

Kalode, M.B.; Varma, A., Yadav, C.P. & Israel, P.(197). Feeding reaction of armyworm (Cirphis compta Moore) larvae fed on some cultivated and wild plants. Indian Journal of Agricultural Sciences 41:568-572.

Koyama, J.(1966). The relation between the outbreak of armyworms (Leucania separata Walker) and the richly nitrogeneous manured cultivation of rice plants. Journal of Applied Entomology and Zoology 10:123-128. Koyama, J.(0970). Some considerations on the chronological records of outbreaks of the armyworm (Leucania separata Walker). Japanese Journal of Applied Entomology and Zoology 14:57-63.

Leuschner, K.(972). Effect of an unknown plant substance on a shield bug. Naturwissenchaften 59:217-218.

Li (Kuang-po); Wong Hun; Chao (Shung-Jin); Chain (Shu-Ching) and Lin (Jung-You) (1963). Field studies on the effect of microclimate on the populatdon density of the armyworm. Acta Phytophylacica Sinica 2:57-62.

Li (Kuang-Po); Wong (Hong-hsiang) and Woo (Wen-sei)(1965). Route of the seasonal migration of the oriental armyworm moth in the eastern part of China as indicated by a three year result of releasing and recapturing marked moths. T.C.No.2 pp. 101 to 110.

Lin (Chang-Shan) (1963). Studies on the regularity of the outbreak of the oriental armyworm (Leucania separata Walker). IV. An analysis of the metereo-physlcal conditions during the descending movement of the long distance migration of the oriental armyworm moth. Acta Phytophylacica Sinica 2:111-122.

Lin (Chang-Shan) and Chang (J. Tsun-ping)(1964). Studies on the regularities of the outbreak of the oriental armyworm (Leucania separata Walker).V. A model for seasonal long distance migration of the oriental armyworm. Acta Phytophylacica Sinica 3:93-100.

Lin (Chang-Shan), Sun (Chin-ju), Chen (Rui Lo) and Chang (J. Tsun-ping)(1963). Studies on the regularity of the outbreak of the oriental armyworm, Leucania separata Walker. I. The early spring orientation of the oriental armyworm moths and its relation to winds. Acta Entomologica Sinica 12:243-261.

Ma, S.C.(1979). Insect Ecology in the People's Republic of China. Acta Entomologica Sinica 22:257-266. 24

Mohyuddln, A.I. & Shah, S.(1977). Biological control of Mythlmna separata (Lep.: Noctuldae) in New Zealand and its bearing on biological control strategy. Entomophaga 22:331-333.

Nagano, M.; Yoshioka, T.; Itayama, T.; Nishino, T. Yamaguchi, T. and Nagata, Y.(1972). Forecasting of the armyworm, Leucaiia (Mythimna) separata Walker in grassland. I. Outbreak in 1970. Proceedings of the Association for Plant Protection. Kyushu 17:88-90.

Neelgund, Y.F. and Mathad, S.B.(1972). Nuclear polyhedrosis of Pseudaletia separata (Lepidoptera: Noctuidae). Annals of the Entomological Society of America 65:763-764.

Oku, T. & Kobayashi, T.(0974). Early summer outbreaks of the oriental armyworm, Mythimna separata Walker, in the Tohoku District and possible causative factors (Lepidoptera:Noctuidae). Applied Entomology and Zoology 9:238-246.

Pradhan, S; Jotwani, M.G. and Rai, B.K. (1962), The neem seed detterent to locusts. Indian Farming. 12:7-11.

Pruthi, H.S.(1937). Report of the Imperial Entomologist. In Scientific j report of Agricultural Research Institute, New Delhi, 1935-36,

Puttarudriah, M. & Usman, S.(1957). Flood causes armyworm outbreak. Mysore Agricultural Journal 32:124-131.

Schmutterer, H. and Rembold, H.(1980). Performance of some pure fractions extracted from seed of Azadirachta indica on feeding activity and metamorphasis of Epilachna varivestis (Co. Coccinellidae). Zeitschrift fur Angewandte Entomologie 89:179-188.

Sharma, G.K.; Ch. Czoppelt and Rembold, H.(1980). Further evidence of insect growth disruption by neem seed fractions. Zeitschrift fur Angewandte Entomologie 90:439-444.

Sharma, H.C. and Davies, JC.(1982). The oriental armyworm, Mythimna separata: Distribution, biology and control - A literature review. Tropical Pest Management (submitted). 25

Simmonds, F.J.(1976). Some recent puzzles in biological control, Entomophaga 21:327-332.

Simmonds, F.J. & Bonnett, F.D.(1977). Biological control of Agriciltural pests. Proceedings of the International Congress of Entomology 15:464-472.

Sinha, N.P. and Gulati, K.C.(1963). Neem (Azadirachta indica) seed cake as a source of pest control chemicals. Bulletin of Regional Research Laboratory, Jammu, India. 176-177.

Verma, A.N. & Khurana, A.D. (1971). Incidence of armyworm Pseudaletia separata Walker in different dwarf wheat varieties. Haryana Agricultural University Journal of Research 1:20-23. Table I

Incidence of plants damaged by Mythimna separata at ICRISAT Center (1977-1979)

% plants damaged

Alfisols Vert isol s

Sorghum Pearl-Millet Sorghum Pearl-Millet

1977 1978 1979 1977 1978 1979 1977 1978 1979 1977 1978 1979

January 4.0 6.3 - 4.2 9.3 - - 0.1 - 0.2 0.5 -

February - 13.0 - - - 3.3 - - () -

March - 1.6 - - (-) - - (-) - - (-) -

April - ) - - (-) - - (-) - - (-) -

May - () - - (-) - - (-) - - (-) -

June - -) - - (-) - - (-) - - 13.7 - July - - 23.5 - 69.0 33.5 - - ­ August 98.0 66.0 - 39.7 78.0 17.3 - - 18.5 - - - September 41.5 68.0 26.0 61.1 0.5 0.2 - 0.3 - - 35.4 ­ October 43.0 0.3 - - 22.0 - - 23.4 - 0.3 - -

November 38.7 0.3 - 2.7 4.0 - - 41.3 - -

December 3.1 8.6 - 3.0 2.0 .- - 0.3 - ­

- Data not recorded

(-) Insect activity not observed Table.2

Incidence of Mythimna separata larvae on sorghum in large scale intercropping trials (1975 to 80)

No. of Mythimna larvae/lO0 plants or earheads

S.No. Year Activity Alfisols Vertisols REMARKS period Sole crop Inter crop Sold crop Inter crop

1 1975 Oct. - - 40 88 upto 7 larvae/head

2 1976 Sept. - - 7 in heads

3 1977 Sept. - 106 - 61 in vegetative phase

4 1978 Aug. 9 13 25 15 in vegatative phase

5 1979 Sept. 28 30 1 3 in heads

6 1980 Sept. 12 14 9 11 in vegetative phase

- Not recorded 28

Table 3. Observations on the biology of M. separata

October 1980 Jan.-Feb. 1981 Stage/Parameter Mean Range Mean Range

2-5 Preoviposition period (days) 3 ­ Eggs/female 996 173-1439 4-5 5 Incubation period (days) 4 5 2-7 - Oviposition period (days)

Longevity male (days) 6 1-15 12 9-19 - - Longevity female (days) 18-23 19 18-21 Larval period (days) 19 10 8-12 Pupal period (days) 10 10-11 31 29-33 Post-embryonic period (days) 33 32-39

(-) Not studied Table 4

Light trap catches of M. separata at ICRISAT Center (Total of three traps) (1977 - 1979)

Year!J F i, A M J J A S 0 N D Total Month

1977 0 0 2 0 0 0 3 780 4607 208 9 8 5617

1978 1 3 1 4 1 0 4 i0o4 1460 27 9 1 2515 1979 1 0 7 0 0 0 7 121 137 48 27 1 349 a% 1980 2 0 0 1 1 0 12 153 185 31 1 0 386

Total 4 3 10 5 2 0 26 2058 6389 314 46 10 8867 Table 5 PARASITIZATION OF MYTHIMNA SEPARATA LARVAE AT ICRISAT CENTER CIn different soil types)

Parasitization (Mortality due to factors other than parasites

S- *.­.,- Soil tu 4E typeCrop r o 4-) -0 4) x C 4 -c n )a) 0 M0 4­ * .L. Cn a. E

1980

Farmer's field Sorghum 113 84.1 79.6 1:1.6 4.4 0.9 0.0 14.1 Alfisol Un-sprayed Pearl 40 87.5 87.5 1:2.5 2.5 0.0 0.0 10.0 Alfisols Millet Unsprayed Sorghum 350 61.4 Vertisol s 50.9 1:1.2 24.3 4.9 0.0 18.8 Sprayed Pearl 623 71.1 65.8 1:1.6 10.3 9.8 0.0 13.8 Alfisols Millet Sprayed Sorghum 389 47.8 43.0 1:1.2 27.0 Verti sol s 4.4 0.0 25.5

1981

Farmer's field Sorghum 63 54.0 44.4 1:0.7 41.3 0.0 .0.0 14.3 Alfisols Unsprayed Sorghum 318 65.1 55.7 "0.8 26.7 2.5 0.3 15.1 Alfisols! P. Millet 137 83.2 70.1 1:0.9 9.5 1.5 0.0 19.0 Unsprayed Sorghum Vertisois 826 75.3 62.8 1:0.8 13.2 2.5 0.1 21.0 1: ."7 . . 2 71 . Sprayed Sorghum 678 60.5 50.9 1:0.9 27.0 3.8 2.7 15.6 Alfisols P. Millet 1084 83.2 71.2 1:0.9 5.4 1.1 0.8 21.2 Sprayed Sorghum 1720 58.7 50.5 1:0.8 28.0 18.0 0.0 19.5 Table 6 PARASITIZATION OF MYTHIMNA SEPARATA LARVAE AT ICRISAT CENTER

Parasitization (Mortality due to factors other than parasites

rQOJ S- U

Year Moth r 4 ( L

o-0 4 "a Q)o. x 4)fl0 ot) O 0 4 E

1979 Dec 236 40.7 30.5 1:1.6 48.3

1980 Jan 145 35.2 26.9 1:1.4 - - - 39.2 Jul 74 77.0 71.6 1:1.1 4.1 9.5 0.0 14.9 Aug 717 70.3 65.8 1:1.9 19.3 8.4 0.0 13.6 Sept 310 36.5 26.1 1:1.4 29.0 8.7 0.0 33.8 Oct 80 55.0 48.8 1:0.9 36.3 2.5 0.0 12.6

1981 Jun 25 92.0 80.0 1:1.5 0.0 0.1 0.0 20.0 Jul 985 86.8 71.1 1:0.9 0.4 1.1 0.5 27.0 Aug 2069 79.2 67.7 1:0.8 12.0 2.6 0.5 16.6 Sept 1264 46.7 3q.6 1:0.9 41.0 5.3 1.1 12.5 Oct 978 45.4 39.2 1:0.7 36.2 1.4 0.0 22.9 TablE 7 PARASITIZATION OF MYTHIMNA SEPARATA LARVAE AT ICRISAT CENTER (In different weeding treatments and cultivars)

Parasitization (%) Mortality due to factors other than parasites

S.No. >. 4- o D S a

4- 04- C 43 Q

l Ex.Bornu 240 60.4 40.4 1 .3 5.0 13.8 26.7

2 G-73-K-77 240 60.0 45.4 0.4 2.9 14.6 26.0

3 BJ-104 240 69.6 45.4 0.4 4.2 10.4 23.3

4 NS-AX75 240 66.3 47.5 0.4 5.9 II1.3 27.7

5 Atrazir' + 1 Hand weeding 240 65.4 44.2 0.0 4.6 10.0 26.7

6 1 Hand weeding 240 60.8 45.8 0.4 2.5 17.9 23.8

7 Weed free 240 64.2 47.5 1.7 5.9 11.3 25.0

8 Weedy

check 240 65.9 41.3 0.3- 5.0 10.8 24.2 33

Table 8

Leaf area and dry weight consumption by 3rd instar larvae of Mythimna separata (fad for 24 hours on different genotypes of pearl millet

Leaf area consumed/ Dry weight consumed/ Damage Genotypes 100 sq.cm. 100 mg. rating*

SAR-57 98.99 65.74 5 Souga-Local 4 35.09 24.73 183 PIB-228 70.22 37.82 2.5 NEP-310-5685 68.35 51.47 2.67 P-184 80.78 54.85 3.33 BJ-104 94.27 58.71 5 700112 67.5 0 34.85 2.33 MBH-110 44.38 21.91 2.33 SAD-403I 88.01 53.33 4.67 P-27511 88.09 56.11 4.0 D-1051-I 59.49 54.17 2.17 P-3081 82.23 53.33 4.0

S.Em. 8,98 7.49 0.35 C.D. 26.33 21.96 1.04

1 <10% leaf damage 2 10-20% leaf damage 3 25-40% leaf damage 4 40-60% leaf damage 5 >60 leaf damage 34

TABLE 9

Effect of neem kernal (Azadirachta indica) powder and its alcoholic extracts on leaf feeding by Mythimna spearata (Free choice test)

No. of larvae per pot at different intervals Leaf S.No. Treatment Conc.(%) Damage 24 hr 48 hr 72 hr 96 hr rating

1 Seed powder 1 20 15 11 7 5.0 2 Seed powder 2 10 6 6 4 3.6 3 Shell powder 1 14 11 4 3 3.6 4 Shell powder 2 8 7 3 4 4.2 5 Seed extract 0.5 9 7 5 3 2.4 6 Seed extract 1.0 5 4 2 2 2.2 7 Shell extract 0.5 10 5 3 3 2.6 8 1.0 10 8 4 3 2.8 9 Control 25 23 12 9 4.8

S.Em. 2.3 3.0 1.6 1.2 0.3

C.D. at 5% t 6.5 8.5 4,7 3.5 0.9 35

Table 10

EFFECT OF NEEM KERNALS AND ITS ALCOHOLIC EXTRACTS ON LEAF FEEDING BY M. SEPARATA (3rd instar larvae @ 20 larvae/5 plants released-for 24 hours)

Treatment Conc. Leaf area Dry weight consumed/100 sq..cm. consumed/100 mg.

Shell powder (1%) 48.23 28.25

Seed powder (1%) 54.93 29.50

Shell extract (1%) 33.64 37,00

Seed extract (1%) 47,07 22.25

Control 97.85 70.75

S.Em. 5.7 10.0

C.D. at 5% t 17.0 30.01 Fig.1 Light trap catches of Mythimna separata at ICRISAT Center (1974-1980)

551 1974 1975 so ... . 1976

451 1977 -- -- 1978

305 41 17

20­ __j--,-,

U 9

0

0a 7­ a

5,

4

3 -­

2­

16 10 14 1b 23 27 32 36 460q ; Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Standard weeks (1974-1980) locations at ICRISAT Center Mythimna separata at different Fig.2 Light trap catches of

40 Manmool (1975-80)

----. C.I. Building (1974-79) .. .Vertisol Watershed (1977-80)

30

0

0

3 4 4

4 2O 10 * r

32 36~ 40-5.4

Nov Dec 27 32p 36t 14 19 23 SeOcNoDc 1 6 10 Jul Aug Apr May Jun Jan Feb Mar Standard weeks 38

Walker) at ICRISAT Center (1976-80) Flg.3 Light trap catches of Mythilmna aeparata in rel - r4a t perature and R.H.

- Moth catch - rou w..ek moving amans ------Max. temp. - We kly means - in-. temp. - s (I rO1ct Min.MaXR.fl. R.H. Rainfall

- 1911 0 so- Mso 190 S0 60 30 o 40°. 20 30 0 40

| 10 1 0 2.0

0 -I40, 520

o 509 0 . . 6 . .. 350 1.$ -0 4002 aK i- 0 -.-- 9o. so . I, . .... + ..... A2 10 .0-

70_ 0 40 20. 0 b r pr -6Y 0 . A..S . O0 - 30 3 I . 1. 20 10

0.r.. 80 4 10-I -,0I-I-\ LIi -­ 0

so 30 ~--

40 50- so 1977

/A. 40 ­ 40 --.. .. .

30- '..-30 V97- +-20/" V 1 1.10-" . 0- .. .. 2-0- 70 ,o .,+,+. o+ 2.

0. Jl Il,.. _ .. + lIi-o, 10 0~~~~~~-4--" , .I lt. 0-r-... I Sep Oc t Nov e e S6 10 l ,]1 !A J Feb Mar ,Apr May "..tand~rd w-,!k3 Fig.4a Light trap catches and larval population of Mythimna separata at ICRISAT Center (1980)

O--O Trap catch/night - (weekly means) LARVAL POPULATION I Alfisols - unsprayed (Pearl millet) 20 ED Vertisols - unsprayed (Sorghum) F-40

Alfisols - sprayed (Pearl millet) ­ 20 Vertisols - sprayed (Sorghum)

12 18 '0-4J 4- 16QC a/x / x 0 4 o 312 2

60

4-4­ 66

0 z 1A-4

2

Jun Jul Aug Sept Oct Nov Fig.4b151 Light trap catches and larval population of Mythimna separata at ICRISAT Center (19b1)

0--C Trap catch per night - (weekly means) LARVAL POPULATION [] Alfisols - unsprayed (Pearl millet) EZ Vertisols - unsprayed (Sorghum) Alfisols - sprayed (Pearl millet) -10 r 1 0 ­ 10 * Vertisols - sprayed (Sorghum) 1

00 0 ,a 0J -0 0 > Ei 00

-,A - -,--i I . 0z

Jun Jul Aug Sept Oct Nov

Week intervals Fig.5a Population and extent of parasitization of the Mythimna separata larvae in different soil types at ICRISAT Center (1980)

D No. of larvae

] % Pupation

650- % Emergence

II % Parasitization

[ % Parasitizationby Hymenoptera 550­ 4% Parasitization by Diptera O 500- 100 N C.,0 450- 90

M07 to-) w -4 * 400, 80

,-4 350 EE"-- "" 5 U,­4

0-32300- " /X_ 70 /7 60' 0 7//, , ... wN. 150- -,

100- --20"

50 /1 //

f ____ l /

Farmer's Field Unsprayed Alfisols Unsprayed Vertisols Sprayed Alfisols Sprayed Vertisols Sorghum Pearl millet Sorghum Pearl millet Sorghum No. of larvae reared (113) (40) (350) (623) (389) Soil types Fig.5b Population and extent of parasitization of the Mythimna separata larvae in different soil types at ICRISAT Center (1981)

400- C No. of larvae 1 % Pupation VM % Emergence

W m % Parasitization 300 0-'-300 % Parasitization by Hymenoptera -[ % Parasitology by Diptera 0 C o 0 -A-

U)U 4 2001/

,-44

z 6

100 .1 4" 0

///

/ / /- - ..

Farmer's field Unsprayed Alfisols Unsprayed Vertisols Sprayed Alfisols Sprayed Vertisols Sorghum Pearl millet Sorghum Pearl millet Sorghum No."of larve reared (63) (137) (826) (1084) (1720) Fig. 6. Larval survival and parasitization of Mythimna separata on sorghum and pearl-millet

Sorghum

Pearl millet

Unsprayed Alfisols - Pearl millet Vertisols - Sorghum 1001 Sprayed Alfisols Unsprayped Alfisols 1980 I 1981 1981 901

80­

70 4

60

50 > II 20 I I I

10

10.

" r- C r­ o U 0 0C 0 -4 r- - . . -4 *C 0 U " " 0 r - * - * - . 0 "0 0 4j -- ~ C 4 - H - .-14 el ) - 41 4 4.4 a) 41 4j +-' cd 00 cc CUj4-j CUj wU ~ 0 4J Q 4-' ~ c c CU+l CUj c O C$ Cd 4-j CU 0. in. " P4~ N) ~~ NOp.- M In. *4 0N Q. cis LU I rq 4C ) -H4 4 LI * .- I aH) d"l w,44C -4 -4 V) En E A. CU- 0 ~4J OP C13 cUd CUd-,q 9:4 - C c dIP =.0 CU CU Cct -4 CU CU CU CU CU CU CU CU CU dP d. * dP c* d Fig.7 Effect of extent of weeding in pearl-millet on larval population and leaf damage of oriental armyworm

C.D. at 5% Weedy check 300-E ~ No. of larvae5

Damage rating S.Em. 260 LU

4 200 1 and weeding + 1 Hand weeding At razini

Weed free n 180 C­ -3

o 140 0 z

100

60­

20--1

0-- __ _ 1

C N O N C: O r- C - C N 0 N NX -41 4N- LI . 0 ~ :0 ' ~ I0 X r > - >H X N