PEPPER POWDERY MILDEW CONTROL
A report to the California Pepper Commission for work performed 3/31/2011 through 2/28/2012
Brenna Aegerter, UC Cooperative Extension San Joaquin County; 2101 E. Earhart Ave. Ste 200. Stockton, CA 95206; 209-953-6114; bjaegerter@ucdavis.edu
Gene Miyao, UC Cooperative Extension Yolo, Solano and Sacramento Counties, 70 Cottonwood St. Woodland, CA 95695; 530-666-8732; emmiyao@ucdavis.edu
Goal: To compare registered fungicides for powdery mildew control in bell peppers.
Two field trials were established in commercial fields of sweet bell peppers with the generous cooperation of growers. Fungicide programs were randomly assigned to plots measuring one bed by 30 to 50 feet long (length varied by trial), with each treatment being replicated four times. A non-treated buffer row separated fungicide-treated rows. Fungicides were applied prior to the onset of disease and continued on a 11-to 15-day interval (interval varied slightly due to irrigation schedules). Three applications were made at the Yolo site, four at the Stockton site. Fungicides and wettable sulfur were applied with a CO2-pressurized backpack sprayer with a hand-held boom operated at a pressure of 30-32 psi. A non-ionic surfactant was included at rate of 0.25% of spray volume, with the exception of the wettable sulfur spray. Sulfur dust was applied with a hand-crank duster. Details for each trial are presented in table 1.
Evaluations of disease control were made at regular intervals throughout the season. When disease occurred within a trial location, a subset of each plot was hand harvested just in advance of the grower-cooperators harvest. Disease severity and harvest data from the Yolo trial are presented in table 2. Disease occurred only at the Yolo trial location and even there the disease level was low and arrived late. Under those conditions, all products reduced mildew equally; we were unable to draw any conclusions about comparative efficacy of the different products. Yields were similar in all treatments.
Table 1. Trial details
Trial Leader: | Gene Miyao | Brenna Aegerter |
Cooperator: | Scott Robben, Gene Robben Farms, Dixon | Skip Foppiano, Morada Produce, Stockton |
Location: | NW corner Robben Rd x Hackman Rd. | E Mariposa Rd. between Jack Tone Rd and Van Allen Rd. |
Soil Type: | Yolo loam and Ca silty clay loam | Galt clay |
Variety: | Grande Rio | Classic |
Planting date: | 5/2/2011 as direct field seeded | 7/19/2011 transplanted |
Irrigation: | exclusively furrow | sprinkler irrigated |
Harvest: | Sept 23-24 hand harvest from 11' x 5 ' area | plots not harvested (no powdery mildew) |
Plot Design: | randomized complete block with 4 reps | same |
Sprayer: | backback style, hand held wand | same |
Nozzles: | (4) 8003 TJet flat fan nozzles including drops | two to four TXVS-18 hollow cone nozzles, depending on crop stage |
Spray Volume: | 50 gpa solution | 30 to 50 gpa, depending on crop stage |
Applications: | 3 applications on 12- to 14-day interval | 4 applications on 11- to 15-day interval |
Table 2. Effect of fungicides on mildew control and fruit yield of Grande Rio peppers, Robben Farms, DIxon, 2011.
YIELD | ||||||||
Marketable | Total fruit biomass | Small fruit | Culls | Colored | Powdery mildew | |||
Product | common name and (FRAC group #) | Rate | ||||||
Quintec | quinoxyfen (15) | 6 fl. oz | 24.7 | 28.2 | 3 | 9 | 0.1 | 0.0 |
Quadris Top | azoxystrobin (11)+ difenoconazole (3) | 14 fl. oz | 23.8 | 27.5 | 2 | 9 | 1.2 | 0.0 |
Microthiol Disperss | micronized sulfur | 10 lbs | 25.7 | 28.5 | 3 | 6 | 0.6 | 0.0 |
dusting sulfur | sulfur, 98% | 35 lbs | 26.1 | 29.5 | 3 | 9 | 0.4 | 0.0 |
Rally WSP | myclobutanil (3) | 5 oz | 25.4 | 29.9 | 5 | 10 | 0.3 | 0.0 |
Non-treated control | none | none | 23.3 | 26.3 | 3 | 8 | 0.4 | 0.8 |
LSD @ 5% | NS | NS | NS | NS | NS | - | ||
% CV | 12 | 11 | 70 | 37 | 94 | - | ||
F Value | 0.6 | 0.77 | 0.52 | 0.77 | 2.58 | - | ||
Probability | 0.07 | |||||||
y Small fruit: less than 2 5/8 inches
z Number of leaves infected out of 10 total on September 21st, one day before harvest