During 2001and 2002, 53 accessions of sweet potato (Ipomoea batatas L.) from a germ plasm collection maintained in the field at Centro Nacional de Investigaciones Agropecuarias, Maracay, Venezuela, were evaluated for diseases. Sweet potato accessions Catemaco and 2878 were symptomatic for chlorotic leaf distortion with deformation of young leaves and stunted vines. Symptomatic nodes and shoot tips were excised, surface disinfested in 0.5% sodium hypochlorite, cultured on potato dextrose agar (PDA), and incubated at 28°C. Pale pink colonies with white aerial mycelium developed from symptomatic tissues. At 20°C, pure cultures on PDA developed slow-growing, aerial, white-to-pink mycelium. Pigmentation in reverse was light orange. Conidia aggregated in false heads, and orange sporodochia were abundant. Conidiophores in aerial mycelium were prostrate, short, and sometimes branched. Sporodochial conidiophores were branched. Phialides were mostly monophialidic but occasionally polyphialidic and averaged 25.0 × 3.0 µm. Microconidia were abundant, long, oval to allantoid, and 0 to 1 septate. Macroconidia were fusiform to falcate with a beaked apical cell and a footlike basal cell, 3 to 5 sepate, and 38 to 45 × 3.6 to 4.0 µm. Chlamydospores were absent. The fungus was identified as Fusarium denticulatum Nirenberg and O'Donnell (1). Ten 25-cm-long vine-tip cuttings of accessions Catemaco and 2878 were immersed in a conidial suspension (1 × 106 conidia per ml) of F. denticulatum. As a control, vines were immersed in sterile, distilled water. After inoculation, each cutting was planted in a 13-cm plastic pot containing a soil/sand (1:1) mixture. Inoculated plants were covered with plastic bags for 48 h and grown in a greenhouse at temperatures ranging from 30 to 38°C. After 3 months, three inoculated plants of accession Catemaco and two plants of accession 2878 developed purple terminals and moderate interveinal chlorosis. Leaf distortion was not observed. F. denticulatum was recovered from both symptomatic and asymptomatic inoculated plants. To our knowledge, this is the first report of F. denticulatum from sweet potato germ plasm in Venezuela. Dried, pure cultures and slides of the fungus are being deposited in the Albert S. Muller Herbario Micologico (VIA). Reference: (1) H. I. Nirenberg and K. O'Donnell. Mycologia 90:434, 1998.

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The experiment was conducted in Centro Nacional de Investigaciones in Maracay, Aragua, Venezuela. The goal of this job was determining the efficacy of some fungicides in controlling sorghum honeydew (Sphacelia sorghi McRae). A completely block randomized with four replications was used. Three systemic triazol fungicides were used and two non triazoles were included. Each dose was subdivided in three applications: 1/4 applied at panicle pre-emergence, 1/2 applied at 50 % flowering time and 1/4 applied at postflowering time, in order to cover the whole flowering period. The variables were: incidence or infected panicles per plot, panicle infection and the total infection/ plot. According to the results there was an overall good fungicide control. There was a group constituted by Tilt and Propizole, which gave the best fungus control with 96.96 and 96.55% of effectivity in controlling of panicles’ infection and a second group was integrated by Anvil, Benlate and Plantvax which made adequate control with no significant differences among them. In conclusion, the best fungicides were Tilt and Propizole. Benlate and Plantvax gave an adequate control but they are recommended under low inoculum pressure in order to avoid resistence and for economic reasons. Anvil showed 90.43% control; however, this fungicide has low relative efficacy when it is compared with other triazol fungicides.