Insect pest incidence in SRI method of rice cultivation

Insect pest incidence in SRI m= ethod of rice cultivation

Ch. Padma= vathi, R. Mahendra Kumar and I.C. Pasalu

Directorate of Rice Research, Rajendranagar, Hyderabad 500 030, AP

System of rice intensification (SRI) developed in = Madagascar in late 1980’s by Father Henri de Laulanie has now spread to many parts of the world including = India. = The increased attention by the government, NGOs and farmers to popularize and implement SRI method of rice cultivation has brought a momentum in its adoption. Earlier reports indicate that the incidence of pests and diseases= was generally low in SRI. Hence the present study was contemplated to assess the insect pest incidence in SRI vs conventio= nal method of rice cultivation. F= ield experiments were conducted in kharif and rabi seasons in 2004= and 2005 at Directorate of Rice Research to evaluate the response of various popular varieties and hybrids to SRI practices.

Insect pest incidence was observed starting from one month after planting. Differe= nt insect pests found were, (i) whorl maggot – Hydrelia philippina Fe= rino (Diptera: Ephydridae), (ii) rice hispa - Dicladispa= armigera (Olivier)) (Coleoptera: Chrysomelidae= ), (iii) yellow stemborer - Scirpophaga incertulas (Walker) (Lepidoptera: = Pyralidae), (iv) leaffolder - Cnaphalocrocis medinalis (Guenee) (Lepidoptera: Pyralidae) (v) green leafhoppers = - Nephotettix spp. (Hemiptera: Cicadellidae) and leaf mite – Oligonychus oryzae (Hirst= ) (Acarina: Tetranychidae).

Stem borer incidence was found at low to medium level, in both vegetative and flowering stages in both the seasons. Maximum per cent white ears were reco= rded in Pusa Basmati 1 (20.27%) followed by KRH2 (17= .68%) and Rasi (14.23%). Minimum damage was recorded = in PHB 71 (2.09%) and Jaya (5.97%). Stem borer damage was found more in SRI as compared to conventional method. When different aged seedlings were used in SRI, maximum damage by stem borer was found in plots sown with 8-day old seedlings (8.57%) as compared to 18 and 28-day old seedlings. Stem borer incidence was more at 20 x 10 cm (7.4 % white ears) spacing as compared to = 25 x 25cm spacing (5.5% white ears). Low incidence of leaf folder, whorl maggot,= hispa and green leaf hoppers was seen at tillering stage. Incidence of leaf mite was severe in Swarna variety grown under SRI method.

Though healthy plants in SRI method were reported to be more resistant to pests and diseases, some of the SRI practices like wider spacing, weed free condition= and absence of stagnant water make the micro-environment of this method of rice cultivation non conducive for some of the major pests of rice like BPH and = Gall midge. However a need for systematic monitoring is advised to be cautious a= bout some of the pests like leaf mite, leaf folder and soil nematodes.

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