Kompleks artropoda predator penghuni tajuk kedelai dan peranannya dengan perhatian utama pada Paederus fuscipes (Curt.) (Coleoptera : Staphylinidae)

Abstract

Penelitian dilaksanakan pada lahan kedelai di Kecamatan Ciranjang, Kabupaten Cianjur, Jawa Barat pada musim kemarau 1997 dan 1998, dan bertujuan untuk menganalisis kompleks predator penghuni tajuk serta peranannya di pertanaman kedelai, memahami perkembangan populasi dan tingkat pemangsaan kumbang Paederus fuscipes (Curt.) (Col.: Staphylinidae), mengkaji pengaruh pemberian mulsa jerami terhadap kelimpahan populasi P. fuscipes, serta mengukur preferensi dan tanggap fungsional P. fuscipes. Hasil penelitian menunjukkan bahwa tajuk kedelai dihuni oleh lebih dari 25 spesies artropoda predator. Predator yang paling dominan adalah kumbang P. fuscipes (Curt.), cengkerik Anaxipha longipennis (Serville) dan laba-laba Pardosa pseudoannulata (Boes. & Str.) dan Atypena adelinae (Barr. & Lit.). Besarnya tekanan pemangsaan oleh predator penghuni tajuk dipengaruhi oleh kelimpahan predator dan fase pertumbuhan tanaman Tekanan pemangsaan terhadap telur mencapai 50% dari total 60 telur, dan terhadap larva mencapai 58% dari total 60 ekor larva yang diumpankan. Fase perkembangan tanaman dan kelimpahan predator mempengaruhi besarnya tekanan pemangsaan. Dengan kerapatan predator 1,47 ekor per rumpun, tekanan pemangsaan terhadap telur pada fase V4 mencapai 48% dari total 60 telur, sedangkan terhadap larva mencapai 67% dari total 60 ekor larva yang diumpankan. Tekanan pemangsaan lebih tinggi pada fase ~ (60% untuk telur, dan 68% untuk larva) yang disebabkan oleh meningkatnya kerapatan predator yang mencapai sekitar 3 ekor per rumpun.

Studies were conducted on soybean fields in the sub district of Ciranjang, Cianjur, West Java during the two growing soybean seasons of 1997 and 1998, with the objectives: to analyze the soybean canopy dwelling predatory arthropods and its roles, to analyze the population development and predation rate of Paederus fuscipes (Curt.) (Col.: Staphylinidae), to assess the effect of mulching of paddy straw on population abundance of P. fuscipes, and to determine the prey preference and functional response of P. fuscipes. Results of the studies showed that soybean canopy was inhabited by more than 25 species of predatory arthropods. The most abundant predators were P. fuscipes beetles, cricket Anaxipha longipennis (Serville) and spiders Pardosa pseudoannulata (Boes. Str. )and Atypena adelinae (Barr. & Lit.). The predation pressure varied with predator abundance and soybean growth stage. The predation pressure on eggs was 50% and on larvae 58%. During the growth stage V4, with a predator density of 1,47/hill, the predation pressure was 48% on eggs and 67% on larvae. During growth stage RJ, with a predator density of 3,39/hill, the predation pressure on eggs was 60% and on larvae 68%. P. fuscipes was present throughout the soybean growing stage, with the peak of population (1,5-2 predator/hill) occurred on 6-7 weeks after planting. Each individual beetle consumed 12-14 eggs or 12 instar-1 larvae of Helicoverpa armigera Hbn. (Lep.: Noctuidae) per day. P. fuscipes showed an adaptive searching behavior for the prey. About 32% of H. armigera eggs placed on the upper surface of the leaves were consumed, compared to 19% on the lower surface. Similarly, 53% and 41% of Etiella zinckenella Tr. (Lep. Pyralidae) eggs placed respectively on shoots and pods were consumed, whereas only 6% on eggs placed on leaves.