Pigeon pea (Cajanus cajan) accessions from the world collection, cultivars and local advanced lines from the UPR breeding program were field screened for resistance to foliar diseases at the Isabela Research and Development Center. Uredo cajani, Colletotrichum sp., Cercospora sp. and Phoma sp. were identified as the major foliar pathogens present in the area. Forty eight of the 3286 accessions evaluated showed low incidence of foliar diseases. Of the local lines, line 64-16A showed the fewest foliar symptoms; line 8-AB-2 was the most susceptible within the group evaluated.
The effectiveness of benomyl, chlorothalonil, copper hydroxide, dinocap, sulfur and triadimefon for the control of the fungus Leveillula taurica, causal agent of the powdery mildew of peppers (Capsicum annuum), was evaluated under field conditions. Results from two experiments indicate that weekly applications of benomyl and triadimefon reduced disease incidence and increased pepper yield. In the first experiment, plots treated with triadimefon (0.35 L/ha) and benomyl (0.55 kg/ha) produced 20.2 and 17.2 kg fruit/plot, respectively, whereas the nontreated plots yielded 13,9 kg/plot. A similar trend but with higher yields was obtained in the second experiment. Treatments with triadimefon (0.70 L/ha) and benomyl (0.55 kg/ha) produced 41.0 and 41.3 kg of fruit/plot, respectively, as compared with the control treatments which yielded 29.0 kg/plot.
Fungi associated with root rot, stem canker, dieback, gummosis and leaf spots in young peach trees were isolated and identified. The most predominant fungi in the stem and root lesions were Fusarium solani and F. oxysporum. Dothiorella sp. was associated with the stem gummosis, and Mucor hiemalis was consistently found in the leaf lesions. Pathogenicity tests confirmed M. hiemalis as the cause of the foliar spots in peaches.
Greenhouse tests were conducted to evaluate the effect of iprodione (Rovral®), fosetyl-AI (Alliete®), triadimephon (Bayleton 50DF®), SoilGard® (Gliocladium virens), pentachloronitrobenzene (PCNB) (Terraclor®), copper hydroxide (Champion®), benomyl (Benlate 50WP®) and "Garlic Barrier" in the population of Rhizoctonia solani and Myrothecium roridum. The most promising fungicides were evaluated at different dosages (X/2, X and 2X) to determine seedling protection and toxicity. Pentachloronitrobenzene, benomyl and iprodione were the most effective in reducing the population of ft solant in the inoculated soil with 93, 75 and 70% of inhibition, respectively. A phytotoxicity effect was observed in coffee seedlings treated with the double dosage of PCNB. The effect of fungicides was minimal in the reduction of the propagules of M. roridum when compared to the control although benomyl and triadimephon protected the seedlings against this pathogen.
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