Effect of growth stages and moist periods on the attacking of Diplocarpon on rose

anglais. The aim of this research was to find out the effect of plant growth stages and moist periods on size of lesion and disease intensity of D. rosae on rose. The experiment was conducted at the glass-house of Segunung Ornamental Research Station from January to April 1996. The experiment consisted of two activities. The first activity was: plants were inoculated with conidium of D. rosae at six growth stages, namely; stage (st)-1 (bud until one leaf), st-2 (2-3 leaves), st-3 (4-5 leaves), st-4 (6-7 leaves), st-5 (8-9 leaves or preblooming), and st-6 (flowering). The second one, treated plants were moistened under plastic cage for: 0, 3, 6, 9, 18, 24, 30, and 48 hours after inoculation of D. rosae conidium. The randomized complete design with four replications was used in both activities. The results showed that all of growth stages were susceptible to D. rosae, with the highest susceptibility was on the first growth stage (St-1), size of lesion was 7.53 mm2 per young leaf and disease intensity was 19,18 percent. Fourty eight (48) hours moist period was more favorable for the infection, growth and development of D. rosae. This result is useful to determine the exact application time of fungicide and biological control agent for controlling D. rosae on rose

indonésien. Penelitian ini bertujuan untuk mengetahui pengaruh tingkat pertumbuhan dan periode lembab terhadap luas bercak dan intensitas penyakit D. rosae pada mawar. Penelitian dilakukan di rumah kaca Instalasi Penelitian Tanaman Hias Segunung dari bulan Januari sampai April 1996. Percobaan terdiri dari dua kegiatan yaitu pertama, tanaman mawar diinokulasi konidia D. rosae pada 6 tingkat pertumbuhan tanaman (st) yang berbeda, yaitu; tingkat (st)-1 (tunas hingga 1 daun), st-2 (2-3 daun), st-3 (4-5 daun), st-4 (6-7 daun), st-5 (8-9 daun/hampir berbunga) dan st-6 (tanaman sudah berbunga) dan kegiatan kedua, tanaman dilembabkan di bawah sungkup plastik selama; 0, 3, 6, 9, 18, 24, 30 dan 48 jam setelah inokulasi konidia D. rosae. Rancangan acak lengkap dengan 4 ulangan digunakan dalam kedua kegiatan tersebut. Hasil penelitian menunjukkan bahwa semua tingkat pertumbuhan tanaman mawar Queen Elizabeth rentan terhadap D. rosae, dengan kerentanan tertinggi pada tingkat pertumbuhan pertama (st-1). Luas bercak 7,53 mm2 per anak daun dan intensitas penyakit 19,18 persen. Empat puluh delapan (48) jam lebih baik untuk infeksi dan perkembangan D. rosae. hasil penelitian ini bermanfaat dalam menentukan waktu aplikasi fungisida pengendali hayati yang tepat pada pengendalian D. rosae pada mawar