Insect-Pest Dynamics and Arthropod Diversity in SRI and Conventional Methods

of Rice Cultivation

Ch. Padmavathi, R. Mahender Kumar, K. Surekha, P.C. Latha, L.V. Subba Rao,

M. S. Prasad, V. Ravindra Babu, J.S. Prasad, O.P. Rupela1, Vinod Goud2, I.C.Pasalu

and B.C.Viraktamath

Directorate of Rice Research, Rajendranagar, Hyderabad1ICRISAT, Patancheru, 502324, Andhra Pradesh

2WWF – ICRISAT campus, Patancheru, 502324, Andhra Pradesh

Introduction

o In India, rapid increase in area under HYV of rice accompanied by high use of fertilizers has led to increased incidences of pests and diseases. o Number of insect pest species in paddy increased during 1965-95 from 3 to >13 (Krishnaiah et al., 1999).

o Paddy receives 20% of total pesticides. Use is high in AP, KN, MH, Gujarat & Punjab (Shetty, 2004).

o Earlier reports indicated that rice plants in SRI are more resistant to insect-pests and diseases due to their healthy growth.

Methodology

Field Experiments – DRR Ramachandrapuram farm, ICRISAT campus

Soil - sandy clay loam Seasons - rabi and kharif in 2006 Design - split-plot design

Main plots - MTU 1010, Shanti & DRRH2 in rabi BPT 5204, Swarna & DRRH2 in kharif

Sub-plots - methods of crop husbandry (SRI, Eco-SRI and conventional)

Replications - four SRI and conventional method - same inputs applied Eco-SRI - total nutrients through organic source only

Pest dynamics

o Pest incidence and damage recorded on ten marked hills at three stages of crop growth period viz., at maximum tillering, booting and harvest stages.

o Damage symptoms recorded by counting number of damaged leaves by each pest species, total tillers & dead hearts at vegetative stage, and panicle-bearing tillers and white ear heads at reproductive stage.

Arthropod diversity - Insects were collected using standard sweep net. Each plot was swept thrice, and insects collected were sorted separately. For plots with conventional method (flooded soil), water samples were collected for aquatic insects.

ResultsPest dynamics

Five insect pests, viz., whorl maggot, hispa, yellow stem borer, leaf folder and green leaf hoppers, were observed at different stages of crop growth period.

Among these pests, incidence of yellow stem borer was high in various treatments followed by leaf folder. Others pests occurred at low level.

In Rabi 2006, the mean per cent of dead hearts was significantly different at maximum tillering stage for the alternative methods of rice cultivation and also among the varieties.

Leaf folder damage

Stem borer damage

Hispa damage

Mean % dead hearts at maximum tillering stage

Mean % white ear heads at harvesting stage

MTU 1010

Shanti DRRH2 Mean MTU 1010

Shanti DRRH2 Mean

ECO-SRI

0.98 (1.18)

2.03(1.51)

0.69(0.98)

1.24(1.23)

1.49 (1.29)

13.83 (3.51)

3.40 (1.97)

6.24 (2.26)

SRI 3.59(1.92)

6.99(2.73)

2.71(1.61)

4.43(2.08)

3.62 (1.92)

28.34 (5.14)

5.62 (2.34)

12.53(3.13)

CON 8.31(2.94)

11.36(3.42)

8.26(2.88)

9.31(3.07)

3.33 (1.83)

21.17(4.18)

2.25 (1.56)

8.92(2.52)

Mean 4.29(2.01)

6.79(2.55)

3.89(1.82)

2.82 (1.68)

21.11 (4.27)

3.76 (1.96)

CD Methods (M) = 0.62 Varieties (V) = 0.54 Interaction = NS

CD Methods (M) = 0.54 Varieties (V) = 0.78 Interaction = NS

Figures in parentheses are square root transformations (√ X+0.5)

Yellow stem borer damage during rabi

0

0.5

1

1.5

2

2.5

3

3.5

4

BPT 5204 DRRH2 Swarna

Pe

r c

en

t w

hit

eh

ea

ds

Eco-SRI

SRI

Conv

Stem borer damage at flowering stage in Kharif

0

0.5

1

1.5

2

2.5

3

BPT 5204 DRRH2 Swarna

Pe

r c

en

t d

am

ag

ed

lea

ve

s

Eco-SRI

SRI

Conv

Defoliators damage in Kharif

S.No Variety Loss of green colouration

1 MTU 1010 < 10 %

2 Swarna 31 – 50 %

3 BPT 5204 < 10%

Leaf mite damage in SRI method of rice cultivation

Diversity indices

SRI Conventional

Total abundance 263.34 ± 32.19 210.67 ± 27.90

Number of species 20.34 ± 0.67 18.67 ± 2.03

Shannon’s index (H) 1.92 ± 0.05 1.91 ± 0.04

Evenness (E) 0.33 ± 0.02 0.37 ± 0.04

Simpson’s index 0.76 ± 0.02 0.78 ± 0.005

Berger Parker index 0.38 ± 0.04 0.35 ± 0.02

Menhinick index 1.27 ± 0.10 1.28 ± 0.05

Margalef index 3.48 ± 0.16 3.29 ± 0.29

0

5

10

15

20

25

DRRH1 KRH2 PHB 71 KH Rasi Tulasi Jaya PB1

Per c

ent w

hite

ear

s

Varieties / Hybrids

SRI 10 day old seedlings SRI 25 day old seedlings

Stem borer damage in various varieties/hybrids

0

1

2

3

4

5

6

7

8

9

SRI Normal

8 day

18day

28day

Effect of age of seedlings on stem borer incidence

0

1

2

3

4

5

6

7

8

9

10

SRI Normal

25x25 cm

20x10 cm

Influence of spacing on stem borer incidence

Conclusionso Among various pests, stem borer damage was high. Dead hearts were low in SRI as compared to conventional method. White ear heads were high in SRI.

o Among the cultivars, Shanti recorded more damage in rabi and DRRH2 in kharif seasons.

o Damage was more in plots of 8-day old seedlings at 20 x 10 cm compared to 25 x 25 cm spacing.

o Total abundance and species richness was higher in SRI as compared to conventional method.

Future line of work

o Need for systematic assessment of damage & losseso Factors responsible for the increased incidenceo Pest management options