California Pepper Commission


Bill Weir - Evaluation of Chemicals of Mechanically Harvested Red Peppers 2017



Bill Weir, Ph.D. – University of California
Seth Rossow – Rossow Farms
Nathan Sano – Director - California Pepper Commission
Bob Heisey - California Pepper Commission


To evaluate the beneficial effects of applying ethephon at two rates and comparing them with an untreated control in mechanically harvested processing red peppers.


1. Untreated Control
2. 2.0 quarts ethephon per acre
3. 4.0 quarts ethephon per acre

Site Location: Rossow Farms – Merced, California
Host Crop Variety: Processing red peppers
Plot Description and Size: 4.75 feet by 200 feet, replicated 2 times
Experimental Design: Completely randomized design

Application Conditions:

Date: August 4, 2017
Time: 7:30 a.m.
Wind: Calm
Sky: Clear
Temperature: 76 F


Yields and visual quality assessments


On August 4, 2017 areas were selected from a field of established red peppers for ethephon evaluations. Plots 6.75 feet by 200 feet were measured and staked. Ethephon was applied in three treatments replicated two times. They were: none, 2.0 quarts per acre and 4.0 quarts per acre. A fourth treatment was planned consisting of a water run application in the drip irrigation system. After much discussion regarding rates and observing the effects of the 4.0 quarts per acre foliar applied ethephon, it was decided to omit the treatment.

On August 31, 2017 the plots were mechanically harvested by the grower and resulting peppers weighed using the University of California Extension bin scales.


There were very little numerical differences among the three treatments. The untreated control was slightly lowest at 16.9 tons per acre, with the 2.0 quarts per acre and the 4.0 quarts per acre yielding 18.3 tons per acre and 17.7 tons per acre, respectively. (table 1 ). Lack of differences may be in part due to the time span between application and harvest. Although ethephon causes earliness, there was time for even maturation among the treatments.

There were noticeably more green fruits in the untreated control bins than the ethephon treated bins. The visual differences were noticed in the field also.

The 4.0 quarts per acre ethephon treatment caused the fruits to be softer and perhaps over ripe. They possibly reached maturity too soon prior to harvest.


Although trends for increasing yields were similar to earlier tests this year and prior years, actual differences were very small. Based on this year’s evaluations, there does not appear to be any measurable benefit to using ethephon on this variety of processing red peppers under these cultural practices.

Table 1 – Bin Weights of Three Treatments of Red Peppers in Tons per Acre.
Treatment -------Replication----------- Tons/Acre
  #1 #2 AVE
Untreated Control 17.0 16.6 16.8
2.0 quarts/acre 18.9 17.7 18.3
4.0 quarts/acre 17.7   17.7

August 31, 2017 Harvesting research plots

Aug 31, 2017 Bins waiting to be weighed

Arranging bins to be loaded on trucks

August 31, 2017 Loading trucks with bins of peppers

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