Efficacy of chemical products for control of DMI-resistant Monilinia fructicola on peach in middle Georgia, 2007

摘要

Fungicides were evaluated for control of brown rot in a mid-ripening experimental peach variety (USDA selection 88P2251) located at the USDA Fruit and Nut Research Center (Byron, GA). With the exception of calcium chloride and Messenger STS materials,chemicals were applied with an airblast sprayer (60 gal/A spray volume) at each application date, 2 and 9 Jul (pre-harvest sprays); calcium chloride (applied on 2, 16, and 30 May, 14 and 27 Jun, and 11 Jul), and Messenger STS (applied 22 Jun) solutionswere applied with a handgun to runoff (approx= 1 gallon solution per tree to achieve the desired per acre rates). Treatments included an untreated control, PropiMax 3.6EC (propiconazole chemical standard), Pristine 38WDG (containing 25.2% boscalid and 12.8% pyraclostrobin), a Messenger STS WDG and PropiMax regimen, a Calcium and PropiMax regimen, PropiMax + Yellow Jacket Sulfur 90WP, and PropiMax + Captan 50W. The latter two treatments were added in an attempt to determine whether tank mixes would augment control of propiconazole in the presence of DMI-resistant Monilinia fructicola populations. Four replications of each treatment were applied to a randomized complete block design, with each plot consisting of four trees; the outer two trees in each plot were not utilized for ratings. Unsprayed rows were left between each spray row. All cultural practices were in keeping with peach production methods commonly observed throughout the Southeast. Earlier in the season, maintenance sprays for scab (BravoWeatherStik at 4 pt/A at shuck split and Yellow Jacket Sulfur at 9 lb/A through all cover sprays) were applied to all treatments, including the untreated control. At full maturity, 39 asymptomatic fruit were harvested from each plot for rot assessments (16 Jul). The fruit were placed on plastic produce trays and sealed in plastic for 24h to increase humidity and likelihood of brown rot development (ambient room temperatures; air-conditioned room; ~77 F). Rot incidence was recorded at four and seven days after harvest.