Effect of fungicides sprays intervals on potato late blight control in Argentina, 2005-2006.

摘要

During 2005 and 2006 seasons, field trials were carried out in a Brunizen soil with 4.8% organic matter at the INTA Balcarce Experimental Station, Argentina. Uncut potato seed tubers were machine planted at 0.20 m intervals in rows spaced 0.8 m apart.Artificial inoculation at planting time was done by seeding blighted tubers. Plots were four rows wide and 5 m long spaced 0.8 m apart and were bordered on all sides by 2 m wide plantedand unsprayed guard rows . Evaluated treatments were set up in a randomized complete block design with four replications. The crop was irrigated as needed with sprinklers for increased disease expansion with a total of 150 mm in 2005 season and 210 mm in2006 season. Both seasons fungicide sprays were applied from 4 January to 10 March, for a total of 9 applications on weekly intervals and 5 applications on biweekly intervals. Fungicide treatments were compared with an untreated check and standard program with propineb (as Antracol 70WP) applied weekly at a rate of 2.5 kg ha-1. Sprays were applied in water with a CO2 backpack boom pressure sprayer equipped with four ceramic disc-type nozzles. Applications were made at 344.2 kPa pressure and a rate of 250 lha-1. Disease severity was rated using a disease index (0 = no infection; 5 = maximum defoliation). The two center rows were harvested from each plot and then potatoes were graded into two categories, commercially acceptable tubers (+60g) and "seed" tubers (-60g) and weighed for total yield. Data were subjected to analysis of variance.Means were compared by LSD at P=0.05.