Khalil I. Al-Mughrabi1
Abstract: A field experiment to evaluate Bravo 500F, Quadris 250SC and Allegro 500F for control of early and late blight of potatoes was conducted in the summer of 2002 in Debec, New Brunswick, in a field planted with potatoes in the previous year. Various tank mixes of Quadris, Bravo and Allegro, and also Bravo and Allegro alone were used as treatments. In total, 32 plots (3.64m wide X 6m long each) were arranged in a randomized complete block design with 8 treatments and 4 replications. Potato (cv. Russet Norkotah) plants were sprayed using a 2.5m CO2 backpack sprayer at a spray angle of 90 degrees and spray pressure of 215 KPa. Plants were assessed for phytotoxicity, disease severity and incidence of early blight, and yield and grade out. Late blight did not occur naturally, and therefore no data were collected. Early blight was late to occur in the plots due to weather conditions that did not favour the onset of early blight. Spore suspensions of Alternaria solani were sprayed twice on the plants to initiate infection. Disease severity and incidence increased over time until the experiment was terminated. Both disease severity and incidence ratings showed that all treatments were significantly different in their effect on controlling early blight compared to the untreated check. The treatment mixture of Quadris 250SC (250 g a.i./ha) + Allegro (202 g a.i./ha) produced the best results, while Quadris 250SC (250 g a.i./ha) + Bravo 500F (1000 g a.i./ha) was the least effective treatment. No significant differences were found when yield, size and tuber weight was compared for all treatments.
1Potato Development Centre, Department of Agriculture, Fisheries and Aquaculture, 39 Barker Lane, Wicklow, New Brunswick E7L 3S5.