Study on the impact of climate variability on rice pest distribution and status shift in the Northern Coast of West Java

Abstract

Every degree of earth temperature increasing will cause the life cycle of most insect pests to be speeded up. This equates to shorter time from egg hatching to full grown adult, thus creating larger pest populations. In the end, this will affect the distribution pattern and magnitude of pest invasion in the field. Brown plant hopper (BPH) and rice stem borer (RSB) are the two main types of rice pest that always gets attention from farmers due to the high damage caused by both pests. This study was aimed to analyze the impacts of climate variability on the distribution and pest status shifts of rice pests. An index of pest infestation was calculated to assest the status shift of a pest and a multiple regression technique was used to investigated the effect of climate variables on the magnitude of the pests (BPH and RSB) infestation. There was an increasing in earth temperature but a decreasing in precipitation in three districts of the Northern Coast of West Java during the period of 1990-2010. Contrary to the above two variables, the relative humidity was indicating a stable fluctuation over the period. Not all of the studied pests (Rats, BPH, RSB, and Leaffolder) indicated shifts in their status but only Rats and BPH did as the climate changed. Among the three climate variables, only the minimum temperature had a consistent effect on the infestation area of BPH and RSB. The infestation areas of BPH and RSB were increasing as the minimum temperature increased. The relative humidity had a similar but less consistent effect as the temperature effect on the pests infestation areas. The effect of precipitation on the pests infestation areas was not appearing to be significant in this study.

Perubahan nilai varian dari unsur-unsur iklim seperti suhu, curah hujan, kelembaban, dan sebagainya dalam rentang waktu tertentu merupakan salah satu fenomena terjadinya keragaman iklim. Perubahan tersebut dapat berupa kejadian iklim ekstrim pada seluruh ruang dan waktu dari masing-masing unsur iklim, sehingga menyebabkan kondisi iklim yang tidak sama untuk setiap tahunnya. Penelitian ini bertujuan untuk menganalisis hubungan antara keragaman iklim dengan distribusi dan perubahan status hama wereng batang cokelat (WBC) dan penggerek batang padi (PBP) di Pantai Utara Jawa Barat. Penelitian dilakukan melalui dua pendekatan, yaitu: 1) survei petani tentang tingkat serangan OPT padi, dan 2) pengumpulan data sekunder tentang luas serangan hama WBC dan PBP, penggunaan varietas, luas tanam padi sawah dan peubah iklim (suhu, curah hujan, dan kelembaban udara). Survei petani dilaksanakan di tiga kabupaten, yaitu: Kabupaten Karawang, Subang, dan Indramayu. Keragaman kondisi suhu, curah hujan, dan kelembaban udara selama periode 1990-2009 dianalisis menggunakan kondisi iklim per musim tanam (musim hujan/MH dan musim kemarau/MK). Besaran suhu (minimum, maksimum, dan rata-rata), curah hujan, dan kelembaban per musim tanam dihitung dari data iklim bulanan dengan kriteria seperti berikut: MH meliputi bulan Oktober-Maret dan MK meliputi bulan April-September.