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, Hyderabad 1ICRISAT, Patancheru, 502324, Andhra Pradesh 2WWF – ICRISAT campus, Patancheru, 502324, Andhra Pradesh

Introduction 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. Number of insect pest species in paddy increased during 1965-95 from 3 to >13 (Krishnaiah et al., 1999). Paddy receives 20% of total pesticides. Use is high in AP, KN, MH, Gujarat & Punjab (Shetty, 2004). 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 Pest incidence and damage recorded on ten marked hills at three stages of crop growth period viz., at maximum tillering, booting and harvest stages. 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.

Results Pest 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.

Hispa damage Leaf folder damage Stem borer damage

Mean % dead hearts at maximum tillering stage Yellow stem borer damage during rabi Mean % dead hearts at maximum tillering stage Mean % white ear heads at harvesting stage 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) 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)

Stem borer damage at flowering stage in Kharif

Defoliators damage in Kharif

Leaf mite damage in SRI method of rice cultivation S.No Variety Loss of green colouration 1 MTU 1010 < 10 % 2 Swarna 31 – 50 % 3 BPT 5204 < 10%

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

Stem borer damage in various varieties/hybrids

Effect of age of seedlings on stem borer incidence

Influence of spacing on stem borer incidence

Conclusions Future line of work 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. Among the cultivars, Shanti recorded more damage in rabi and DRRH2 in kharif seasons. Damage was more in plots of 8-day old seedlings at 20 x 10 cm compared to 25 x 25 cm spacing. Total abundance and species richness was higher in SRI as compared to conventional method. Future line of work Need for systematic assessment of damage & losses Factors responsible for the increased incidence Pest management options

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