PENGARUH VARIETAS DAN POLA TANAM KAPAS TERHADAP KELIMPAHAN POPULASI PREDATOR HAMA PENGISAP DAUN Amrasca biguttula (ISHIDA)

ABSTRAK Penanaman varietas tahan hama adalah salah satu cara pengendalian serangga hama pengisap daun, A. biguttula, yang telah diadopsi petani kapas di Indonesia. Penggunaan varietas tahan hama cukup efektif menekan serangan hama pengisap ini. Namun demikian, peluang adanya cara pengendalian alternatif patut dipertimbangkan, misalnya memanfaat- kan faktor mortalitas biotik A. biguttula, seperti musuh alami. Penelitian pengaruh varietas dan pola tanam kapas terhadap perkembangan populasi predator hama pengisap daun A. biguttula telah dilakukan di Kebun Percobaan Asembagus, Situbondo, dan di laboratorium Entomologi Balai Penelitian Tanaman Tembakau dan Serat di Malang, mulai Januari sampai Desember 2005. Penelitian ini bertujuan untuk mempelajari pengaruh perbedaan varietas dan pola tanam kapas terhadap perkembangan predator A. biguttula. Perlakuan terdiri atas dua faktor, yaitu faktor I adalah varietas kapas dengan tingkat ketahanan terhadap A. biguttula berbeda-beda, yaitu: (1) TAMCOT SP37 (peka), (2) Kanesia 7 (moderat), dan (3) LRA 5166 (tahan). Faktor II adalah pola tanam kapas, yaitu: (1) monokultur, dan (2) tumpangsari dengan kedelai. Setiap perlakuan disusun secara faktorial dengan rancangan petak terbagi (Split Plot) dengan tiga kali ulangan. Parameter pengamatannya adalah populasi nimfa A. biguttula dan predator. Di laboratorium dilakukan uji pemangsaan terhadap predator terpilih dengan cara memberi umpan nimfa A. biguttula untuk mengetahui kemampuannya memangsa per hari. Hasil penelitian menunjukkan bahwa perbedaan tingkat ketahanan varietas terhadap A. biguttula mempengaruhi perkembangan populasi kompleks predator. Lebih banyak predator ditemukan pada TAMCOT SP37 dan Kanesia 7 dibanding pada LRA 5166. Sedangkan perbedaan pola tanam tidak menyebabkan perbedaan populasi predator. Kapas monokultur maupun tumpangsari dapat menyediakan lingkungan ideal bagi perkembangan kompleks predator. Laba-laba dan Paederus sp. adalah predator yang populasinya lebih dominan  dibanding  predator lainnya.  Pada uji  pemangsaan di laboratorium, Paederus sp. mampu memangsa 15-25 nimfa A. biguttula instar kecil dan 10-20 instar besar, sedangkan laba-laba per hari memangsa 2-12 nimfa A. biguttula instar kecil dan besar. Kata kunci: Kapas, Gossypium hirsutum, hama, Amrasca biguttula, Paederus sp., nimfa, mortalitas biotik, varietas, pola tanam, Jawa Timur ABSTRACT Effect of variety and cropping pattern of cotton on population density of insect predator Amrasca biguttula (Ishida) Planting resistant variety of cotton is one of cultural method for controlling sucking insect pest, A. biguttula. This method has widely been applied by cotton farmers in Indonesia. Nevertheless, alternative control should also be found to obtain better control of this pest, e.g. biological control by using parasitoids and predators. Study on effect of variety and cropping pattern of cotton to population density of insect predator of A. biguttula was carried out at Asembagus Experimental Station and in Entomology Laboratory of Indonesian Tobacco and Fiber Crops Institute in Malang from January to December 2005. The objective of study was to study the effect of variety and cropping pattern of cotton to population density of insect predators. Treatment consists of two factors. The first factor was cotton variety based on resistance to A. biguttula, viz. TAMCOT SP37, Kanesia 7, and LRA 5166 known susceptible, intermediate, and resistant to A. biguttula, respectively. The second factor was cropping system with monoculture and intercropping with soybean. Each treatments was arranged in Split Plot Design with three replications. Parameter observed in field study were population of A. biguttula and its predators. While, the laboratory study was to find out the daily prey ability of selected predator by baiting nymph of A. biguttula. The result showed that difference resistance of cotton variety influenced the population density of insect predator. More insect predators were found on TAMCOT SP37 and Kanesia 7 compared to LRA 5166, while the density of insect predator was not affected by different cropping pattern and it was due to the patterns provided better environment for insect predator development. Spider and Paederus sp. were the dominant insect predators found in the field because their population higher than those other predators. Laboratory study showed that Paederus sp. preyed 15-25 younger and 10-20 older instar of nymph per day, while spider ate 2-12 nymphs of both age of A. biguttula per day. Key words: Cotton, Gossypium hirsutum, pest, Amrasca biguttula, Paederus sp., nymph, biotic mortality, variety, cropping pattern, East Java