Incidence of Insect Pest Damage in Rice Crop in Relation to Meteorological Parameters in Punjab – A Plant Clinic Data Based Case Study

of ABSTRACT The data incidence of insect pest of rice crop received at Plant Clinic, PAU Ludhiana during 2000-2009 were used to a study to analyse the effect of various meteorological parameters. Under Punjab conditions, maximum number (percent) of insect pest damage samples received at Plant Clinic were for plant hopper (44%) followed by leaf folder (30%) and stem borer (29%). The weather conditions conducive for the build up of rice pest population were cloudy weather coupled with a well distributed rainfall received in more number of rainy days during the crop season. Such conditions were observed during the high pest infestation years (pest samples >200) a well distributed (more number of rainy days) near or above normal rainfall was received during June to October, The climatic normals alongwith the interaction of rice crop, weather and insect population dynamics and these can be used as a tool for preparation of weather based agro-advisory.

Rice is grown in area where mean monthly temperature across the growing season ranges from 23.3-27.7 o C, within a daily minimum temperatures of 15 o C and maximum temperature of 39 o C. These temperatures fall well within the favourable range for rice insect pests (Mochida et al, 1987).
During the last decade insect-pests scenario of rice has witnessed considerable changes due to changes in prevailing weather conditions in Punjab. The incidence and population build up of a pest is highly dependent on prevailing weather conditions and growth stage of the crop. The present investigation was planned to study the effect of meteorological parameters on the development of important pests of rice and formulate a tool for issuing agro-advisory for need based pesticide spraying schedule in rice.

MATERIALS AND METHODS
The Punjab Agricultural University, Ludhiana established a Plant Clinic (Agricultural Technology Information Centre (ATIC)) at the Directorate of Extension Education in April, 1999 which provides diagnostic services to the farmers and extension functionaries. In the process of providing services, Plant Clinic scientists of various disciplines i.e., entomology, plant pathology, agronomy and soils diagnose the crop disorders and devise the remedial measures to the farmers as per guidelines given by university package of practices.
From the day of establishment of Plant Clinic till date crop samples received through farmers pertaining to various disorders were regularly diagnosed and their records have been maintained. Based on receipt of farmers samples at Plant Clinic, a study was conducted to analyse the effect of various meteorological parameters on the incidence of important pests of rice crop from kharif 2000 to kharif 2009. The rice pest considered in the study were plant hoppers, leaf folder, stem borer as the major pests whereas hispa, ear-cutting caterpillar/armyworm and root weevil as the minor pests. The data on monthly meteorological parameters w.r.t. maximum and minimum temperature, maximum and minimum relative humidity, rainfall, [Vol. 14, No. 1 number of rainy days, evaporation and sunshine hours from July to October (2000 to 2009) were collected from the meteorological observatory located at Punjab Agricultural University, Ludhiana.

Activity period of rice pest population versus rice yield in Punjab
The peak activity period of rice pest considered in the study ranged from July to October in Punjab (Table 1). Amongst the various insect pests plant hoppers remained active during July to September with a peak activity during August to September. The leaf folder is also active during July to September with peak activity during August to September. The rice stem borer remained active during July to October with peak activity during August to September. During the last three years there has been considerable change in the scenario of insect pests of rice in Punjab due to change in time of sowing, cropping pattern and large scale cultivation of high yielding varieties. The rice stem borer remained pest of rice but now the leaf folder during vegetative phase and plant hoppers during re-productive phase are becoming serious on rice. The change in time of sowing in Punjab is likely to prove useful in the management of rice stem borer. The army worm and rice hispa has started causing damage to rice since 2004. Similar activity period of rice pest have been reported by Singh et al (2007)     During the high pest infestation years such as kharif 2000 (371 samples, 538 mm rainfall), kharif 2003 (200 samples, 581 mm rainfall) and kharif 2006 (300 samples, 503 mm rainfall) though a below normal rainfall was received but the rainfall was well distributed during June to October (i.e., near or slightly below normal rainfall was received), pest infestation in rice was also severe and the rice yield were adversely affected. But during other high pest infestation years such as kharif 2008 (251 samples, 906 mm rainfall) and kharif 2009 (237 samples, 858 mm rainfall) the rainfall was well distributed and above normal and as a result of which the rice yields were adversely affected.

Correlation between incidence of rice pest and meteorological parameters
The correlation worked out between monthly weather parameter insect pest population did not show significant association. However, they do indicate interactive effect.
Out of the six pests of rice considered in the study, plant hopper, armyworm and root weevil population build up is favoured under hot, dry and clear sky conditions. On the other hand, leaf folder, stem borer and rice hispa population build up is favoured under wet, humid and cloudy weather conditions. Similar results have been reported by Butter and Singh (2005) and Singh et al (2007) for rice pest scenario in the state.
The climatic normal required for major insect pest as well as susceptible crop phenological stages are presented in Table 2. Thus if the climatic conditions are favourable and the pest is present, there are chances of occurrence of the pest attack. The information will act as a scientific guiding tool for issuing agro-advisory for need based spraying of the pesticides for the benefit of farmers of the state.